Categorization of Silent Intervals in Parkinsonian Speech: a Study of Pause

CATEGORIZATION OF SILENT INTERVALS IN PARKINSONIAN SPEECH: A STUDY OF PAUSE

Anna C. Gravelin

A Thesis

Submitted to the Graduate College of Bowling Green State University in partial fulfillment of the requirements for the degree of

MASTER OF SCIENCE

August 2017

Committee:

Jason A. Whitfield, Advisor

Ronald Scherer

Anna C. Gravelin

Jason A. Whitfield, Advisor

Parkinson Disease (PD) is a neurodegenerative disease that affects the function of the basal ganglia, which affects both speech and non-speech movements. Examining silent intervals may be an important diagnostic feature of speech impairment severity, because a number of studies indicate individuals with PD exhibit differences in the proportion, frequency, and duration of pause as compared to control speakers. The goal of the current investigation was to determine the extent to which silent intervals in the speech of individuals with PD differ from healthy controls relative to linguistic and phonemic contexts. Silent intervals as short as 15 ms in duration were identified in speech samples of speakers with and without PD. Each interval was categorized relative to the surrounding syntactic and phonemic environment. Compared to control speakers, individuals with PD exhibited significantly longer silent intervals between words at locations that were syntactically unrelated. Additionally, silent intervals that were preceded by a stop or followed by a fricative or sonorant were significantly longer for speakers with PD than controls. Finally, speakers with PD produced significantly fewer stop gaps than controls. The results of this study indicate that individuals with PD exhibit differences in the distribution of silent intervals related to phonemic, rather than linguistic boundaries, likely reflecting deficits in speech motor timing associated with PD. iv

This thesis is dedicated in memory of my grandparents, Walter and Roberta Bolthouse. v ACKNOWLEDGMENTS

There are many individuals I would like to acknowledge for their support during the completion of this project. First and foremost, I must sincerely thank my parents, Nancy and

Craig Gravelin, without whom this project would not have been possible. Their unwavering love, support, and guidance has instilled in me a confidence and tenacity I carry with me every day.

Thank you to my sister, Kristen, and brother, Nick, for their love and support at every point in my educational career. I also acknowledge my grandma, Laura Gravelin, and my aunts, uncles, and cousins for their encouragement.

To my dearest friends, Megan Andrews and Hannah Geiger: your friendship the past two years has been remarkable. I am overwhelmingly grateful for the support and care you both so generously showed me throughout my Master’s career and in the completion of this project. To my close friend and colleague, Zoe Kriegel: thank you for your abundant encouragement and belief in my capacity to learn and grow as a person, mentor, student, and professional. To my dear friend, Ashlei Castillo: I cherish our nearly 20 years of friendship and thank you for your continual support at every step in my journey. I thank my friends Mike and Natalie Trent and my fellow classmates Christina Dick, Courtney Wrentmore, Lisa Raab, Rachel Rutherford, Jake

Baker, Sarah Starcher, Nicole Moore, Ashleigh Stanfield, Alexa Wiebusch, and Sadie Sneider for their encouragement and helping hands along the way.

Lastly, my sincerest thanks to those individuals who assisted me in the completion of this project. To my advisor and mentor, Dr. Jason Whitfield: Thank you for your integral guidance, patience, support, and investment in my success as a student and professional over the past two years. Thank you to Tarynn Clune and Cassidy Quinlan, who assisted me in calculating reliability. I also acknowledge and thank my committee members, Drs. Ronald Scherer and Brent

Archer for their input and guidance in the completion of this project. vi

TABLE OF CONTENTS

Page

CHAPTER I: INTRODUCTION ...... 1

Speech Production ...... 1

Pause ...... 2

Short silent intervals in speech ...... 3

Stop gaps ...... 3

Longer silent intervals in speech...... 4

Parkinson Disease ...... 5

Speech Production in Parkinson Disease ...... 6

Articulation in Parkinson Disease ...... 6

Prosody in Parkinson Disease ...... 8

Measurement of Pause: Methodological Considerations ...... 8

Silent intervals in the speech of individuals with Parkinson Disease ...... 9

Aims of the Current Paper ...... 13

CHAPTER II: METHOD ...... 14

Participants ...... 14

Protocol ...... 16

Measures ...... 18

Syntactic boundaries ...... 19

Phonemic boundaries ...... 22

Reliability ...... 22

Statistics ...... 23 vii

CHAPTER III: RESULTS ...... 24

Overall Measures of Speech Rate and Percent Pause ...... 24

Effect of Syntactic Boundary Type...... 25

Comparison of Between-Word and Within-Word Intervals ...... 31

Effect of Preceding Phoneme Manner ...... 32

Effect of Subsequent Phoneme Manner ...... 35

CHAPTER IV: DISCUSSION ...... 42

Silent Intervals Associated with Syntactic Boundaries ...... 42

Between- and Within-Word Intervals ...... 43

Effect of Preceding Phoneme Manner on Silent Interval Duration ...... 45

Effect of Subsequent Phoneme Manner on Silent Intervals: Stop Gaps ...... 45

Methodological Notes ...... 46

Limitations ...... 46

REFERENCES ...... 48

APPENDIX A. HUMAN SUBJECTS REVIEW BOARD APPROVAL LETTER ...... 56

APPENDIX B. CATERPILLAR PASSAGE: BETWEEN-WORD SYNTACTIC

BOUNDARIES ...... 57

APPENDIX C. OCCURRENCE OF PRECEDING PHONEME MANNER CATEGORIES BY

PARTICIPANT...... 58

APPENDIX D. OCCURRENCE OF SUBSEQUENT PHONEME MANNER CATEGORIES

BY PARTICIPANT ...... 59 viii

LIST OF FIGURES

Figures Page

1 Histogram of log-transformed duration of identified silent intervals for the

control and Parkinson Disease groups, Adapted from Whitfield et al., 2015 ...... 13

2 Annotated waveform and spectrogram of an example of a silent interval

associated with a major syntactic boundary ...... 21

3 Distribution of between-word silent intervals before and after log

transformation for the control and Parkinson Disease groups ...... 27

4 Distribution of silent intervals by syntactic boundary type for the control and

Parkinson Disease groups ...... 28

5 Fixed effect estimates and standard error for the duration of short silent intervals

preceded by stops, fricatives, and sonorants for the control and Parkinson

Disease groups ...... 35

6 Fixed effect estimates and standard error for the duration of short silent intervals

that were followed by continuants and stops for the control and Parkinson

Disease groups ...... 37

7 Fixed effect estimates and standard error for the number of short silent intervals

that were followed by continuants and stops for the control and Parkinson

Disease groups ...... 39

8 Histogram of voiceless stop gap interval duration for the control and Parkinson

Disease groups ...... 40

9 Histogram of voiceless stop gap interval duration by place of articulation for

the control and Parkinson Disease groups ...... 41 ix

LIST OF TABLES

Tables Page

1 Demographic information for participants with Parkinson Disease ...... 16

2 Demographic information for participants in the control group ...... 17

3 Between-word silent interval categories ...... 20

4 Number of boundaries by type in the Caterpillar passage ...... 21

5 Comparisons of average speech rate, percent pause, and articulation rate

measures for the control and Parkinson Disease groups ...... 24

6 Number and duration of inaudible fixed posture disfluencies in the Parkinson

Disease group ...... 25

7 Mean and standard deviation for the duration and number of silent intervals by

boundary type for the control and Parkinson Disease groups...... 26

8 Fixed effect estimates of log-transformed silent interval duration by group and

boundary type ...... 28

9 Fixed effect estimates for the duration of between- and within-word silent

intervals ...... 31

10 Fixed effect estimates for the number of between- and within-word silent

intervals ...... 32

11 Average number and duration of intervals for each preceding phoneme manner

for the control and Parkinson Disease groups...... 33

12 Fixed effect estimates for the duration of short silent intervals by preceding

phoneme manner ...... 34 x

13 Average number and duration of intervals for each subsequent phoneme manner

for the control and Parkinson Disease groups...... 36

14 Fixed effect estimates for the silent interval duration by subsequent phoneme

manner...... 37

15 Fixed effect estimates for the number of silent intervals by subsequent phoneme

manner...... 38

16 Number of voiceless stop gaps by place in the “Caterpillar” passage...... 40 1

CHAPTER I: INTRODUCTION Speech Production

Speech production involves coordinating the respiratory, laryngeal, and articulatory

systems to generate pressures and airflows that create the sounds of speech. The resulting

acoustic signal propagates through the air and is perceived by the listener (e.g., Stevens, 2000;

Kent & Read, 2002). Speech includes individual phonemes that are concatenated together to form meaningful units of language. Phonemes are the smallest units of a language system that

distinguish meaning, and are characterized as vowels or consonants (e.g., Pulgram, 1951).

Vowels are produced with a relatively open vocal tract and are typically voiced (Johnson,

Ladefoged, & Lindau, 1993; Laver, 1994; Ashby & Maidment, 2005). Consonants, by contrast,

are produced with varying degrees of vocal tract constriction and may be voiced or voiceless

(e.g., Raphael, Borden, & Harris, 2011). Because vowels form the nuclei of the syllables in

English, they are typically longer in duration than any consonant segments in connected speech

(e.g., Cairns & Feinstein, 1982).

Temporally, speech contains an alternating sequence of sounded and silent intervals,

which are characterized by the presence and absence of acoustic energy, respectively (e.g.,

Goldman-Eisler, 1968). Both sound production and silence contain pertinent perceptual

information that contribute to the intelligibility of the message. Descriptive data on the temporal

aspects of speech segments suggest that vowel durations range, on average, between 50 and 130

ms, while consonant durations range from 55 to 80 ms (Crystal & House, 1982, 1988). Many

factors affect the duration of speech segments. For example, vowels and consonants contained

within stressed syllables are approximately 66 ms and 25 ms longer in duration, respectively, than vowels and consonants contained within unstressed syllables (Crystal & House, 1988;

Wagner & Watson, 2010). 2

Furthermore, speaking style affects temporal aspects of speech production. For example, speech segments produced using clear speech are longer than segments produced using a habitual or conversational speech style (Picheny, Durlach, & Braida, 1986). Additionally, clear speech contains a greater number of silent intervals that are less than 250 ms than habitual speech (Picheny et al., 1986; Krause & Braida, 2004; Smiljanić & Bradlow, 2009). Classic studies suggest that a clear speech style yields a seventeen percent increase in listener intelligibility (e.g., Picheny, Durlach, & Braida, 1985), though these effects may differ slightly between individual speakers (e.g., Krause & Braida, 2004; Searl & Evitts, 2013).

Pause. A pause is operationally defined as a silent interval between sounded speech segments in speech lasting an unspecified duration. Silent intervals may result from different processes which underlie speech production, including articulatory, prosodic, linguistic, and / or cognitive processes. The durational criterion used to define pause is often determined by the process under investigation. Silent intervals associated with articulatory processes might result from a brief cessation or local minima in the velocity of articulatory movement that coincides with the cessation of vocal fold vibration and the absence of airflow. For example, production of a voiceless stop consonant involves a closing gesture at the place of articulation, resulting in a brief silent interval due to the abrupt shutoff in airflow and the cessation of phonation. Silent intervals that result from such articulatory processes are typically 50 to 150 ms, but may be as short as 10 to 15 ms.

Silent intervals that are prosodic or linguistic in nature often coincide with inhalation, and typically range from 130 to 500 ms (Solomon & Hixon, 1993; Huber, Darling, Francis, & Zhang,

2012). They reflect the time course of language production and inhalation (e.g., Hieke, Kowal, &

O'Connell, 1983). Silent intervals that are cognitive in nature are associated with revision or 3 formulation of the thought process, and are often 250 ms or longer (e.g., Goldman-Eisler, 1968).

Other pauses in this temporal range may include stuttering-like disfluencies, which can last one second or longer (Love & Jeffress, 1971; Hänni, 2014). Due to the wide range of silent interval durations, categorization of silent intervals in connected speech is needed to determine the extent to which the abovementioned processes are affected in clinical populations.

Short silent intervals in speech. Short silent intervals, resulting from articulatory processes, reflect phoneme-to-phoneme transitions (Jardine, 2003). Studies examining these short silent intervals have previously defined pause as a silent interval with a minimum duration of 15 ms (e.g., Rosen et al., 2010), while others have used a minimum duration of 10 ms as a criterion (e.g., Picheny et al., 1986). This range encompasses most pauses associated with the phonemic level, including stop gaps, which have been reported to range from 50 to 150 ms (Kent

& Read, 2002; Rosen et al., 2010).

Stop gaps. A stop gap is a silent interval of complete vocal tract occlusion that occurs before the release burst of a stop consonant (Kent & Read, 2002). A stop gap is the first element in the sequence of acoustic events associated with the production of a stop consonant. A stop gap occurs before the burst. The burst is produced at the initiation of the release of the articulators, the sound being produced by the sudden release of airflow passing by the just separated articulators, and is generally less than 30 ms in duration (Kent & Read, 2002). Stop consonants may be aspirated or unaspirated and have a spectral pattern that theoretically varies with place of articulation (Halle, Hughes, & Radley, 1957; Kewley-Port, 1983). A transient burst of acoustic energy marks the release of the stop consonant. This is followed by a period of frication, during which noise is generated by airflow through the small constriction created as the articulators separate. Finally, a period of aspiration follows, which is generated from turbulent airflow 4

through the glottis (or between the tongue and palate), and occurs immediately prior to the onset of voicing. Stop gaps mark the complete obstruction of the vocal tract during the production of

the voiceless stop consonants /p/, /t/, and /k/ prior to the burse release. Stop gaps associated with

the voiced stop consonants /b/, /d/, and /g/ may exhibit acoustic energy if there is voicing during the closure, and are, therefore, not identified as silent intervals. That is, a silent interval for

voiced stops may occur after articulatory closure, but may be relatively short depending upon the

initiation of phonation prior to or just after the burst (articulator separation).

Longer silent intervals in speech. Silent intervals lasting longer than 150 ms may be

associated with inspiration at major syntactic or prosodic boundaries (e.g., Huber et al., 2012).

These pauses occur during reading as well as spontaneous connected speech (e.g., Huber &

Darling, 2011). Pauses associated with normal prosody or linguistic processes typically range

from 130 to 250 ms in duration, but may be longer (e.g., Rosen et al., 2010). These pauses often

aid in the communication of a thought, idea, or meaning of a sentence. For example, when

reading, these pauses occur at punctuation markers, such as a period or comma, which indicates

syntax or prosody. A portion of these brief cessations do not coincide with inspiration, but still

likely reflect the prosodic marking of syntactic boundaries (e.g., Huber et al., 2012). Conversely,

pauses may also occur at optional, yet appropriate, locations as a stylistic device to help the listener anticipate the linguistic message (e.g., Mukherjee, 2001).

Pauses associated with cognitive-linguistic processing typically range from 250 to 500

ms, though may be as long as 2000-2500 ms in duration (e.g., Goldman-Eisler, 1968; Hänni,

2014). These pauses result from cognitive processes that temporarily interrupt the forward flow

of speech. For example, during a formulation pause, a linguistic message is formulated, encoded,

and programmed (e.g., Rochester, 1973; Postma, 2000). Conversational discourse is associated 5 with a greater cognitive load related to linguistic formulation than during reading (e.g., Howell &

Kadi-Hanifi, 1991). Therefore, these types of long pauses are more prevalent in conversational speech and are rarely found in a reading context. Moreover, a greater occurrence of formulation pauses might reflect neurological deficits within linguistic planning, motor planning, or motor programming.

Parkinson Disease

Parkinson Disease (PD) is a neurodegenerative disease that affects the function of the basal ganglia secondary to degeneration of the dopamine-producing neurons. Over time, breakdown in these structures cause a movement disorder (Samii, 2008). Additional functional differences in neural structures such as the prefrontal cortex and cerebellum and neurochemicals such as serotonin, glutamate, and acetylcholine have also been implicated in PD (Moustafa,

Chakravarthy, Phillips, Gupta, Keri, Polner, & Jahanshahi, 2016).

The cardinal motor symptoms of PD include tremor, rigidity, bradykinesia (slowness), and postural instability. Parkinsonian tremor is characterized as a “pill-rolling” tremor with a frequency of 4 to 6 Hz that is observed at rest (Deuschel & Bain, 1998). The etiology of tremor is unknown and most pharmacological and medical interventions are ineffective at treating tremor (Carr, 2002). Tremor may worsen with disease progression and may affect other limb and axial muscles (Elizan, Sroka, Maker, Smith, & Yarr, 1986). Rigidity is increased resistance to passive stretch, which results in stiffness in the limbs as well as decreased range of motion.

Bradykinesia is an overall slowness of volitional movement that often worsens and impacts activities of daily living, such as buttoning a shirt or cutting food at mealtimes (Berardelli,

Rothwell, Thompson, & Hallett, 2001). Another movement deficit associated with PD is hypokinesia, which is a decrement in the amplitude of movement and has also been described as 6

poverty of movement associated with decreased expression of automatic and rhythmic

movement. For example, hypokinesia during ambulation often manifests as shorter stride length

and decreased arm swing (e.g., Giladi, Shabtai, Rozenburg, & Shabtai, 2001). Akinesia, which is

difficulty with the initiation of volitional movement, may present as a hesitation before an initial

movement or as a motor block when switching between motor tasks (e.g., Giladi, McMahon,

Przedborski, Flaster, Guillory, Kostic, & Fahn, 1992). These deficits can affect all movement,

including movements of the speech musculature (Moustafa et al., 2016).

Speech Production in Parkinson Disease

Individuals with PD often exhibit a motor speech disorder termed hypokinetic dysarthria.

This dysarthria type results from rigidity, bradykinesia, akinesia, and hypokinesia in the speech

motor system and manifests as decreased force, velocity, and range of speech movements

(Ackermann & Ziegler, 1991; Adler, 2011). Perceptual characteristics associated with

hypokinetic dysarthria include reduced vocal loudness, reduced utterance length, rapid,

“blurred,” or imprecise articulation, reduced stress, monopitch, monoloudness, inappropriate

silences, and short rushes of speech with variable, and often accelerating rate (Dromey, 2003).

All of these deficits negatively affect overall loudness, intelligibility, fluency, and prosody of

speech.

Articulation in Parkinson Disease. When present, a primary articulatory deficit in hypokinetic dysarthria is consonant imprecision resulting from articulatory undershoot and

leading to a “blurring” of speech sound boundaries (e.g., Ackermann & Ziegler, 1991; Mcauliffe,

Ward, & Murdoch, 2006). For example, individuals with PD may produce bilabial fricatives in

place of bilabial plosive consonants (Parveen & Goberman, 2014) or may devoice voiced

phonemes during connected speech (Walsh & Smith, 2012). Additionally, PD affects segmental 7

aspects of speech timing related to voice onset time of stop consonants. Specifically, participants

with PD exhibit significantly smaller differences between voice onset time of voiced and

voiceless stop consonants compared to older adult controls (Lieberman, Kako, Friedman,

Tajchman, Feldman, & Jiminez, 1992; Hochstadt, Nakano, Lieberman, & Friedman, 2006).

Skodda, Rinsche, and Schlegel (2009) concluded that articulatory undershoot associated with PD

affects the overall speech clarity and intelligibility and may worsen with disease progression.

Speech rate in PD may be affected by multiple factors including bradykinesia and

hypokinesia. Bradykinesia, or the slowness of movement, may lead to slower rate of speech

production. For instance, Goberman, Coehlo, and Robb (2005) reported an overall slower speech

rate for individuals with PD compared with older adult control speakers. Another common

characteristic of speech rate in PD is festination, or short rushes of speech, often accompanied by

an acceleration in speech rate near the end of an utterance (Skodda, Lorenz, & Schlegel, 2013).

These deficits in speech timing are comparable to the deficits observed in the gait and limb

movement systems of individuals with PD.

In addition to articulation and speech rate differences, recent work has found that

individuals with PD exhibit stuttering-like disfluencies during speech production. Goberman and

Blomgren (2003) reported that individuals with PD, both on and off medication, had a greater

percent disfluency than controls both within and between words during a monologue task.

Within-word disfluencies were described as sound and syllable repetitions, audible and inaudible

sound prolongations, and monosyllabic whole-word repetitions, while between-word disfluencies

were identified as multisyllabic whole-word repetitions, phrase repetitions, and revisions.

Additionally, in a reading passage, individuals with PD exhibited a higher frequency of

disfluency than control speakers. The majority of disfluencies were characterized as within- 8 word, inaudible fixed postures and incomplete syllable repetitions (Goberman, Blomgren, &

Metzger, 2010).

Prosody in Parkinson Disease. Prosodic deficits in the speech of individuals with PD are often prominent. These can include abnormal variations in speech rate, pause timing, monopitch, and monoloudness. Monopitch and monoloudness are characterized by little-to-no fluctuation in fundamental frequency and intensity, respectively, during connected speech

(Goberman et al., 2005; Tykalova, Rusz, Cmejla, Ruzickova, & Ruzicka, 2014; Rigaldie,

Nespoulous, & Vigouroux, 2006). These deficits, in combination with changes in articulation and speech rate, have a large effect on the intelligibility of speech production and may worsen as the disease progresses (Skodda et al, 2009).

Measurement of Pause: Methodological Considerations

Though a number of studies have examined pause, there is little consistency in the minimum pause duration used to operationally define the presence of a pause. For example, some researchers defined pause to be a silent interval as short as 10 ms in duration (e.g., Picheny et al., 1986; Krause & Braida, 2004), while others have defined pause to be a silent interval that is at least 250 ms in duration (Solomon & Hixon, 1993; Nishio & Niimi, 2001). Therefore, a review of these methodological options is needed in order to formulate an informed and accurate interpretation of the current literature on pause in PD.

The methodological decisions made by an author should be informed by the specific process under investigation. For instance, researchers studying the effects of clear speech and investigating differences in motoric aspects of pause, have used a minimum duration criterion of

10 ms to examine pause (e.g., Picheny et al., 1986). Other researchers examining cognitive- linguistic pauses have frequently examined silent intervals that are of at least 250 ms in duration 9

(Goldman-Eisler, 1968; Riggenbach, 1991). Findings of studies that have examined pause in parkinsonian speech may, therefore, differ based on the criteria that are used to define a pause.

The measurement of short pauses has usually been excluded from pause research, with many researchers adopting a minimum duration of 250 ms (e.g., Solomon & Hixon, 1993; Nishio

& Niimi, 2001). This criterion is often used based on a recommendation by Goldman-Eisler

(1968) for the study of hesitation pauses in connected speech. In her classic text, she indicates that defining pause as a silent interval greater than 250 ms ensures that only hesitation pauses are included in the pause measurement and that the measurement is unrelated to motoric or articulatory processes (e.g., Goldman-Eisler, 1968).

Silent intervals in the speech of individuals with Parkinson Disease. The measurement of silent intervals may be an important diagnostic feature of dysarthria severity because a number of studies indicate individuals with PD exhibit differences in the proportion, frequency, and duration of pauses compared to control speakers. Data suggest that individuals with PD typically exhibit longer pause durations and greater proportion of pause than control speakers (Quek et al., 2002; Goberman et al., 2005; Goberman & Elmer, 2005). These findings may be associated with delay in the initiation of speech, stuttering-like disfluencies, more frequent inspiratory breaths, or abnormal language production. Individuals with PD exhibit fewer silent intervals within polysyllabic words than control speakers (Skodda et al., 2008; 2009;

2013). Abnormal within-word pauses may be associated with articulatory imprecision, festinating rate, or articulatory undershoot. Still, other work suggests that individuals with PD exhibit more inspiratory pauses at between-word boundaries that are unrelated to syntax than control speakers do, potentially suggesting deficits in speech motor or linguistic planning

(Ludlow, Connor, & Bassich, 1987; Huber & Darling, 2011; Huber et al., 2012). 10

Using a reading passage, Skodda and Schlegel (2008) investigated articulation rate and percent pause time in 121 participants with PD and 70 control participants. Pauses were defined as silent intervals lasting at least 10 ms in duration. While no significant difference in articulation rate was reported between the groups, participants with PD exhibited an overall lower percent pause time and fewer pauses within polysyllabic words than control participants. Additionally, participants with PD exhibited fewer pauses that were longer in duration at the ends of words.

The findings of this study suggest that speech rhythm and overall organization of timing is impaired in individuals with PD (Skodda & Schlegel, 2008).

Quek et al. (2002) compared pauses with a duration of at least 150 ms in a study of two individuals with idiopathic PD before and after receiving Lee Silverman Voice Treatment

(LSVT). Before treatment, both participants exhibited more pauses within utterances, fewer pauses between utterances, and more silent intervals associated with revisions. Based on this pre- treatment finding, the authors suggested that the participants exhibited more hesitations during speech production as well as difficulty with normal phrasing. Following LSVT, the participants exhibited fewer within-utterance pauses and more between-utterance pauses, as well as fewer revisions. The authors suggested that this result indicated an improvement in speech prosody and phrasing, as the pause distribution more closely aligned with the patterns observed in healthy control speakers (Quek et al., 2002).

Goberman et al. (2005) examined prosodic characteristics in nine participants with idiopathic PD before morning levodopa-based medication, one hour after morning medication, and two hours after morning medication and compared them with age-matched controls. When examining articulation rate and percent pause, the researchers defined a pause as a silent interval that lasted at least 50 ms in duration and was not associated with a stop gap. Participants with PD 11

in the OFF medication state exhibited a greater proportion of pause and a slower rate than

controls. Percent pause time decreased for the ON medication state and was more similar to the

percent pause time of control speakers. Results suggest that for some patients speech prosody

deficits may normalize following the administration of levodopa-based medication (Goberman et

al., 2005).

Goberman and Elmer (2005) studied differences between clear and habitual speech in both a reading and monologue task in twelve participants with idiopathic PD. The researchers

investigated percent pause time and operationally defined a pause as a silent interval lasting at

least 50 ms. The participants with PD exhibited 16% pause during the habitual reading task and

30% during the monologue task. Results indicated that less than half of the participants with PD

increased percent pause in the clear monologue task, but a majority increased percent pause in

the clear reading task. The authors suggest that this finding may result from a greater frequency

of prosodically inappropriate pauses, stuttering-like disfluencies, the use of a compensatory clear

speech strategy, or other disturbances in speech motor timing (Goberman & Elmer, 2005).

Huber et al. (2012) investigated the impact of typical aging and PD on the relationships

between pausing for inspiration, syntax, and punctuation. Pauses associated with inspiration were

defined using a Respitrace and microphone signal. The authors defined a major syntactic

boundary as a boundary associated with ending punctuation such as a period, a minor syntactic boundary as a boundary associated with a comma or clause boundary, and other pauses as unrelated, as they did not coincide with a syntactic boundary. Older adults and individuals with

PD produced shorter utterances between breaths, had a smaller percentage of breaths at major

syntactic boundaries, and a larger percentage of breaths at minor syntactic boundaries than did 12

younger adults. Adults with PD had a larger percentage of breaths at locations unrelated to

syntactic boundaries than older adult controls (Huber et al., 2012).

A previous study presented by Whitfield, Fields, Giachetti, Giardina, Holubeck, and

Siesel (2015), which motivated the current study, examined the distribution of silent intervals in the speech of individuals with PD and healthy controls. Silent intervals as short as 15 ms were

extracted from a connected speech sample (reading passage). As expected, there was significant

negative skew in the data, because there are more opportunities for short silent intervals than

long intervals. Log transformation of the data resulted in a bimodal distribution, with the first

mode centered around 50 ms and the second mode centered around 400 ms, as shown in Figure

1. The large degree of temporal separation between the modes indicated that the two modes were

likely governed by different speech-language processes. Gaussian mixture model analysis was

used to differentiate Mode 1 (i.e., short) from Mode 2 (i.e., long) intervals for each speaker. The

analysis revealed that the frequency count and duration of Mode 1 pauses differed significantly

between speakers with PD and healthy controls. Specifically, the Mode 1 (i.e., short) intervals

were significantly longer and less frequent in the speech of individuals with PD than healthy

controls (Whitfield et al., 2015). 13

Figure 1. Histogram of log-transformed duration of identified silent intervals for the Parkinson Disease (PD; orange) and control (CN; blue) groups adapted from Whitfield et al., 2015.

Aims of the Current Paper

Though previous authors have reported longer and more frequent silent intervals in parkinsonian speech (e.g. Quek et al., 2002; Goberman et al., 2005; Goberman & Elmer, 2005), other studies have found that parkinsonian speech is characterized by fewer silent intervals (e.g.

Skodda et al., 2008; 2009; 2013) compared to neurotypical individuals. Discrepancies between studies may be due to differences in the operational criteria used to define pause. Therefore, in order to more accurately determine how the profile of silent intervals differ between speakers with and without PD, a wide range of silent interval durations must be described relative to the surrounding phonemic and linguistic context. By examining silent intervals in relation to the phonemic and linguistic context, the extent to which syntactic, prosodic, and articulatory processes contribute to pause abnormalities in the speech of individuals with PD can be more clearly defined. The goal of the current investigation was to determine the extent to which silent intervals in the speech of individuals with PD differ from healthy controls relative to linguistic and phonemic contexts. 14

CHAPTER II: METHOD

Participants

Previously collected reading samples (Whitfield, 2014) were used to investigate the

extent to which silent intervals in the speech of individuals with PD differ from healthy controls

relative to linguistic and phonemic contexts. Recorded speech samples from ten individuals with

PD, five males (Mean age = 70 years; Range: 65-76 years) and five females (Mean age = 64 years; Range: 60-77 years), and ten older adult control speakers, five males (Mean age = 68

years; Range: 64-72 years) and five females (Mean age = 70 years; Range: 64-76 years) were

used for the current study. All participants were from the Midwest and spoke English as their

first language. Because the current study involved previously collected, de-identified data, the

Human Subjects Review Board determined it was exempt from board review, see Appendix A.

All participants with PD reported a diagnosis of idiopathic PD that was received from a

neurologist with specialized training in movement disorders. The time since receiving the

diagnosis ranged from 2 to 11 years and no participant had received speech or voice therapy in

the two years prior to data collection.

As part of the earlier data collection protocol, standard hearing, cognitive, and motor speech screenings were administered by an investigator who held a clinical Master’s degree in

Speech-Language Pathology and had experience in motor speech disorders. All participants

passed a hearing screening protocol or had been fit with hearing aids by an audiologist in the past

year and were considered to be aided to normal hearing. Participants over the age of 65 were

screened at 40 dB while participants under 65 were screened at 25 dB at 500, 1000, 2000, and

4000 Hz. Table 1 provides descriptive demographic data for participants in the PD group and

Table 2 provides demographic information for the Control Group. 15

The Dementia Rating Scale-2 (DRS-2; Mattis, 2004) was administered to ensure that the

cognitive abilities of all participants were within normal limits. All participants in both groups

exhibited scores above the 123 cut-off score that indicates cognitive impairment.

Relative to the motor speech screening, participants in the control group exhibited speech

and voice production that was considered to be within normal limits for the age range. All

participants in the PD group presented with hypokinetic dysarthria as the primary dysarthria

type. Three of the ten participants presented with a mixed hypokinetic-hyperkinetic dysarthria.

For these three participants, all hyperkinetic symptoms were restricted to voice quality and did not affect speech timing. Dysarthria severity ranged from mild to severe, with the majority of

participants (7 of 10) falling in the mild to moderate range.

For the individuals in the PD group, the third section of the Unified Parkinson Disease

Rating Scale (UPDRS) was used to assess motor function. The UPDRS examines all cardinal

deficits in PD including freezing, bradykinesia of limb movements, gait, balance, and tremor and indicates disease severity. 16

Table 1.

Demographic information for participants with Parkinson Disease (PD)

ID Sex Age DRS-2 Time since UPDRS Dysarthria Characteristics Diagnosis PD01 M 65 144 9 years 57 Moderate-to-Severe Hypokinetic PD02 M 76 136 5 years 34 Mild Hypokinetic + Hyperkinetic PD03 F 57 140 5 years 20 Moderate Hypokinetic PD04 F 63 142 2 years 37 Mild-to-Moderate Hypokinetic PD05 M 74 170 11 years 55 Severe Hypokinetic PD06 F 60 138 2 years 40 Mild Hypokinetc + Hyperkinetic PD07 F 65 142 2 years 21 Mild Hypokinetic PD08 F 77 136 9 years 56 Moderate Hypokinetic + Hyperkinetic PD09 M 67 136 6 years 27 Mild Hypokinetic PD10 M 69 137 11 years 22 Mild-to-Moderate Hypokinetic Note: Columns include Participant Identification (ID), Sex (F=female; M=male), Age (years), Dementia Rating Scale Score (DRS-2), Time since Parkinson Disease Diagnosis in years, Unified Parkinson Disease Rating Scale (UPDRS), severity and type of dysarthria

Protocol

As per the previous data collection protocol (Whitfield, 2014), participants read the

“Caterpillar Passage” (Patel et al., 2013). The speech samples were recorded using a portable digital audio recorder (Marantz PMD661; sampling rate=44.1 kHz) and a tabletop microphone

(Shure SM-58) in a quiet room. The “Caterpillar Passage” is a phonemically balanced reading passage that was developed for use with adults with motor speech disorders. It contains all

English phonemes in varied locations. The passage includes 197 words with a mean length of utterance of 13.4 words (SD = 6.6 words), ranging from 4-28 words. This passage was designed to build from the Grandfather Passage (Van Riper, 1963) by examining speech motor skills. To ensure the testing of speech motor skills instead of cognitive, linguistic, or reading skills, 64% of the words in the passage are high frequency words. Additionally, it includes word pairs of increasing length, complex words, and repeated words. (Patel et al., 2013). 17

Table 2. Demographic information for participants in the control group (CN)

ID Sex Age DRS-2 CN01 F 71 136 CN02 F 53 142 CN03 F 65 141 CN04 F 64 143 CN05 F 63 140 CN06 M 67 138 CN07 M 66 144 CN08 M 69 141 CN09 M 64 140 CN10 M 72 141 Note: Columns include Participant Identification (ID), Sex (F=female; M=male), Age (years), Dementia Rating Scale Score (DRS-2)

As part of a previous study (Whitfield et al., 2015), acoustic analyses were performed on

the recorded passage using PRAAT (Boersma & Weenink, 2015). First, an automated silent interval detection script was used to identify silent intervals that were at least 15 ms in length.

Next, the automatic analysis was manually corrected using spectrographic and waveform

displays as a visual guide. Inspiratory breaths that were perceptually audible, and thus visually

identifiable on the spectrographic and waveform displays, were also identified as a silent interval. Other perceptually audible noises that were not speech-related, such as a tongue click or

lip smack that occurred during a silent interval, were included within the silent interval. For the

current investigation, all previously identified silent intervals were inspected and corrected when

necessary to ensure validity of the previous work (Whitfield et al., 2015). As outlined below,

each silent interval was categorized relative to the surrounding linguistic and phonemic context. 18

Measures

Prior to analyzing the silent interval characteristics, average measures of speech rate, percent pause, and articulation rate were calculated for each participant’s speech sample and the number of stuttering-like disfluencies were recorded. Speech rate was calculated as number of syllables divided by the total speaking time, including all pause. Percent pause was calculated by dividing the sum of all pause durations by the total speaking time. Three different minimum duration criteria were used to define a pause, thus yielding three measures of percent pause. The three minimum silent interval durations used to define a pause were 50, 150, and 250 ms.

Articulation rate was calculated number of syllables per second of the total speaking time less the total pause duration. Again, three measures of articulation rate were calculated based on the three criteria used to define a pause. Finally, stuttering-like disfluencies associated with silent intervals (i.e. inaudible fixed postures) were categorized using the system outlined by Teesson,

Packman, and Onslow (2003) because individuals with PD exhibit disfluencies during speech

(Goberman & Blomgren, 2003; Goberman et al., 2010).

For the main analysis, each silent interval was categorized relative to the characteristics of the surrounding linguistic and phonemic context. Each identified pause was first labeled as either a between-word or within-word interval. Between-word intervals were further categorized by syntactic boundary type (i.e., Major, Minor, Optional, Unrelated; defined below in text and in

Table 3). The presence of an inspiratory breath was also noted. Additionally, aspects of the surrounding phonemic context (i.e., preceding and subsequent phoneme manner) of each short pause was noted. This categorization system allowed for a detailed characterization of silent intervals in connected speech that ranged from 15 to 1200 ms. 19

Syntactic boundaries. Between-word silent intervals were categorized relative to

syntactic boundary. Syntactic boundaries were determined based on the text of the Caterpillar

Passage and, therefore, correspond to written rather than spoken syntactic conventions. Similar

to Huber et al. (2012), a major syntactic boundaries, minor syntactic boundaries, optional pauses,

or syntactically unrelated silent intervals were categorized. A major syntactic boundary was

defined as a punctuation marker occurring at the end of a sentence, such as a period, exclamation point, or question mark (Huber et al., 2012). A minor syntactic boundary was defined as other

punctuation occurring within a sentence, such as a comma (Huber et al., 2012). An optional

boundary was defined as a clause or phrase boundary that is not associated with a major or minor

syntactic boundary, but that is prosodically appropriate (Goldman-Eisler, 1968; Hawkins, 1971;

Winkworth, Davis, Ellis, & Adams, 1994). Pauses at these junctures are considered optional

because their absence does not affect the clarity of the spoken message. Clauses and phrases

were identified using guidelines from Justice and Ezell (2002). Syntactically unrelated

boundaries were all other between-word boundaries that did not meet the criteria for the major,

minor, or optional boundary designations. For example, a silent interval between words

occurring in the middle of a noun or prepositional phrase is unrelated to a syntactic boundary or

prosodic process (Goldman-Eisler, 1968; Hawkins, 1971; Winkworth, et al., 1994). Table 4

provides the total number of syntactic boundaries by type in the “Caterpillar Passage” and Figure

2 shows an annotated spectrogram and waveform of a major syntactic boundary. Appendix B

provides a detailed marking of every boundary in the passage. 20

Table 3.

Between-word silent interval categories.

Boundary Type Description Sentence Examples Major Syntactic Boundary a A boundary coinciding with an ending punctuation (a) Boy was I marker (i.e. period, question mark, or exclamation point) SCARED[!] (b) As quickly as it started, the Caterpillar came to a stop[.] Minor Syntactic Boundary a A boundary coinciding with any other punctuation (a) Well[,] I sure do. marker (i.e. comma) (b) To amuse myself[,] I went twice last spring. Optional Pause Boundary b A boundary: (a) It went SO high [ ] I preceding linking coordinating and subordinating could see the parking lot. conjunctions (b) That night [ ] I dreamt of the wild ride preceding relative and interrogative pronouns on the Caterpillar. between adverbial phrases and noun or verb phrases between adjective phrases and noun or verb phrases between prepositional phrases and noun or verb phrases

Syntactically Unrelated b,c A boundary occurring within a: (a) I gave the man my [ ] noun phrase coins, asked for change, verb phrase and jumped on the cart. adjective phrase (b) It went so high I could [ ] see the adverbial phrase parking lot. prepositional phrase

a Categories and descriptions from Huber et al. (2012). b Descriptions from Goldman-Eisler (1968), Hawkins (1971), and Winkworth et al. (1994). c This category includes silent intervals shorter than 150ms coinciding with stop gaps, glottal onsets, and articulatory hold gesture 21

Table 4.

Number of boundaries by type in the “Caterpillar Passage.”

Boundary Type Count Major 16 Minor 14 Optional 27 Syntactically Unrelated 137

Figure 2. Annotated waveform and spectrogram of an example of a silent interval associated with a major syntactic boundary (MB; sentence-ending punctuation). 22

Phonemic boundaries. For each silent interval that occurred at a location unrelated to syntax, the manner of the preceding and subsequent phoneme was categorized. The preceding and subsequent phonemic environments were categorized as either stop, fricative, affricate, nasal, liquid, glide, or vowel. For the subsequent phoneme designation, the specific stop consonant was recorded if the interval marked a stop gap. Due to the large number of manner categories and the relatively limited number of opportunities in the reading sample, the above phoneme manners were collapsed into three main classes: stops, fricatives, and sonorants (i.e., nasals, liquids, glides, and vowels), for the statistical analyses examining the effect of preceding and subsequent phonemic environment. Because there were so few opportunities for affricate consonants in the passage, silent intervals associated with affricates were also excluded from the analyses.

Reliability

Inter and intra-rater reliability were calculated for the syntactic boundary and phonemic environment silent interval categorization using percent correspondence between observations for 20% of the participants, a total of four participant reading samples (two participants with PD and two control speakers). For the calculation of inter-rater reliability, undergraduate research assistants received detailed instruction in the categorization system. After instruction and practice, they re-categorized samples that were previously categorized by the primary investigator. They were 90% reliable with the primary investigator. For the calculation of intra- rater reliability, the primary investigator re-categorized 20% of the participants four months after they were originally categorized. Any disagreements in categorization of silent intervals between raters were resolved with a consensus. Intra-rater reliability for the primary investigator was calculated to be 93%. 23

Statistics

Linear mixed model analyses (LMM) were used to analyze the duration and number of silent intervals by group and identified boundary or phonemic context. The duration data of between-word intervals by syntactic boundary type were negatively skewed, and were therefore

log-transformed for analysis. Linear mixed modeling was selected for the current study, as it has

several advantages over traditional statistical analyses, such as analysis of variance (ANOVA) or

repeated measures analysis of variance. Repeated measures analysis of variance is used when

comparing groups of participants who have completed repeated trials for measurement of the

dependent variable of interest (e.g. Quené & Van den Bergh, 2004). As Quené and Van den

Bergh (2004) illustrate, one advantage to using LMM is that it is robust to assumptions that are

often violated with traditional ANOVA, including sphericity or homogeneity of variance. The

LMM analysis is robust to these assumptions because the between- and within-subject variances

are modeled explicitly, not assumed to be homogeneous, and can be used to determine if these

variances affect the dependent variables of interest (Quené, 2008). Quené and Van den Bergh

(2004) also demonstrate how LMM allows for hierarchical sampling and a nested data structure.

Finally, LMM also allows for missing data to be present without necessitating the removal of all

data associated with the subject (Quené & Van den Bergh, 2004). The alpha level for statistical

significance was set at 0.05. 24

CHAPTER III: RESULTS

Overall Measures of Speech Rate and Percent Pause

The mean speech rate, articulation rate, and percent pause for the speakers in the PD and control groups are provided in Table 5. Articulation rate and percent pause were calculated based on three different minimum pause criteria used in the literature: 50 ms, 150 ms, and 250 ms.

Independent t-tests revealed that speech rate, percent pause, and articulation rate did not significantly differ between the control and PD groups, p>0.05 for all comparisons. When the minimum pause criterion was increased from 50ms to 250ms, the mean percent pause time decreased by 4.744% for controls and 5.135% for individuals with PD. For the same minimum pause criterion comparison, the articulation rate decreased by 0.283 syllables per second for controls and 0.339 syllables per second for individuals with PD on average. Additionally, percent pause of control speakers and speakers with PD differ by 3.752% with a minimum pause duration criteria of 50 ms and 3.361% when the minimum pause duration was 250 ms.

Table 5.

Comparisons of average speech rate (syllables per second), percent pause (%), and articulation rate (syllables per second) measures for the control and Parkinson Disease (PD) groups.

Control Group PD Group t-value p-value Speech Rate (syl / sec) 4.106 (0.464) 3.892 (0.502) -0.992 0.334 Percent Pause (%) Percent Pause >50 ms 19.425 (4.060) 23.177 (6.654) 1.522 0.177 Percent Pause >150 ms 16.031 (4.193) 19.142 (6.054) 1.336 0.198 Percent Pause >250 ms 14.681 (4.080) 18.042 (5.875) 1.486 0.155 Articulation Rate (syl/ sec) Articulation Rate >50 ms 5.092 (0.473) 5.128 (0.967) 0.106 0.917 Articulation Rate >150 ms 4.885 (0.438) 4.858 (0.857) -0.089 0.930 Articulation Rate >250 ms 4.809 (0.451) 4.789 (0.832) -0.064 0.949 Note: Three measures of percent pause and articulation rate were calculated using three different pause criteria, defining pause as a silent interval lasting at least 50 ms (>50 ms), 150 ms (>150 ms), and 250 ms (> 250ms); df=19. 25

The total number and duration of disfluencies that were inaudible fixed postures and therefore, corresponded to a silent interval for individuals in the PD group are shown in Table 6.

Perceptual evaluation of voice and speech samples revealed participants in the PD group exhibited two inaudible fixed posture on average, Range: 0-6 disfluencies, in the reading passage. Of the ten participants in this study, half exhibited no or one disfluency. The average duration of the disfluencies for the group was 366.70 ms and ranged from 56.55 to 1022.00 ms.

Table 6.

Number and duration of inaudible fixed posture disfluencies in the Parkinson Disease (PD) group.

Participant Number Average Duration (ms) Duration Range (ms) PD01 4 606.534 329.089 – 890.232 PD02 1 933.968 – PD03 3 127.652 83.949 – 174.228 PD04 2 358.079 350.325 – 365.382 PD05 1 89.389 – PD06 2 223.413 56.974 – 389.851 PD07 1 1022.000 – PD08 – – – PD09 – – – PD10 6 305.951 56.550 – 474.650

Effect of Syntactic Boundary Type To examine the effect of the surrounding linguistic context on pause duration, means and standard deviations for interval duration and number of between-word intervals were examined for each boundary type and for both intervals that contained and did not contain an identifiable inspiratory breath. These descriptive statistics are shown in Table 7. Because the proportion of silent interval types differed between intervals that contained and did not contain an inspiratory breath, the main effect of an inspiratory breath on pause duration was examined in the statistical model. 26

Table 7.

Mean and standard deviation (SD) for the duration (ms) and number of silent intervals by boundary type for the control and Parkinson Disease groups.

Control Group Parkinson Disease Group Mean (SD) N (SD) Mean (SD) N (SD) Breath Major 558.01 (86.38) 11.5 (2.0) 549.76 (57.75) 11.5 (1.9) Minor 440.65 (116.17) 2.2 (1.3) 452.23 (54.53) 3.3 (1.8) Optional 387.89 (61.77) 2.4 (3.1) 478.74 (103.29) 3.4 (1.4) Unrelated 433.22 (65.82) 1.0 (0.0) 537.18 (99.38) 2.3 (1.5) No Breath Major 251.70 (155.57) 3.2 (1.7) 287.42 (146.15) 3.0 (1.7) Minor 139.42 (48.84) 5.9 (2.0) 152.88 (61.88) 5.0 (2.3) Optional 92.63 (62.57) 4.0 (2.8) 114.69 (74.97) 2.3 (1.7) Unrelated 62.23 (18.74) 38.9 (7.4) 88.99 (29.63) 37.1 (9.5)

To examine differences between the groups for each boundary type, an LMM analysis was conducted for the silent interval duration. The dependent variable was duration and the model included the main effects of Boundary Type (levels: major, minor, optional, and unrelated), Group (levels: PD, Control), Inspiratory Breath (levels: breath interval, no breath interval), and the Boundary Type by Group interaction. As shown in Figure 3, the interval duration data were negatively skewed. Therefore, the duration variable included in the LMM was log-transformed. Figure 4 shows the distribution of interval durations for both groups by boundary type. Because the number of syntactic boundaries was dictated by the passage, the frequency count of silent interval type was not examined statistically. 27

Figure 3. Distribution of between-word silent intervals before (a) and after (b) log transformation for the control (CN; top panes) and Parkinson Disease (PD; bottom panes) groups. Note: bin width for (a) is 30 ms; bin width for (b) is 0.1 log(ms). 28

Figure 4. Distribution of silent intervals by syntactic boundary type for the control (CN; left panes) and Parkinson Disease (PD; right panes) groups. Note: Major indicates sentence-ending punctuation; Minor indicates sentence-continuing punctuation; Optional indicates other between- word silent intervals that coincide with a clause or phrase boundary; Unrelated indicates other between-word silent intervals that do not coincide with a clause or phrase boundary. 29

Fixed effects estimates for the LMM analysis of syntactic boundary are reported in Table

8. The LMM for duration showed no statistical differences between groups for the major

boundary, p>0.05. The duration of the minor, optional, and syntactically unrelated boundaries

was significantly shorter than silent intervals at major syntactic boundaries, which was mapped

to the intercept, p<0.001 for all comparisons. Additionally, boundaries which coincided with a

visually identifiable inspiratory breath were significantly longer than boundaries that did not

contain breaths, p<0.001. These trends were statistically similar for the PD group, as there were no significant Boundary X Group interactions for the minor or unrelated boundaries, p>0.05 for

both comparisons. However, the PD group exhibited significantly longer silent intervals at

syntactically unrelated boundaries than the control group, p=0.017. 30

Table 8.

Fixed effect estimates of log-transformed silent interval duration by group and boundary type with the control group, major boundary that is not associated with an inspiratory breath set as the intercept.

Estimate SE df t-value p-value (Intercept) 2.200 0.037 76.100 59.961 <0.001***

Minor Boundary -0.171 0.039 1323.400 -4.397 <0.001***

Optional Boundary -0.253 0.042 1328.700 -5.985 <0.001***

Unrelated Boundary -0.516 0.031 1323.200 -16.581 <0.001***

PD Group 0.025 0.045 43.900 0.557 0.581

PD Group: Minor Boundary 0.074 0.052 1321.400 1.420 0.156

PD Group: Optional Boundary 0.047 0.060 1325.200 0.783 0.434

PD Group: Unrelated Boundary 0.086 0.036 1321.500 2.395 0.017*

Inspiratory Breath 0.559 0.024 1329.700 23.801 <0.001***

Note: ***p<0.001, *p<0.05, Parkinson Disease (PD) Group 31

Comparison of Between-word and Within-word Intervals An LMM analysis was conducted to determine if the duration and number of within-word intervals were comparable to the duration and number of between-word intervals not associated with a major, minor, or optional syntactic boundary. The dependent variables were duration and

count and the independent variables were Interval Type (levels: between- vs. within-word),

Group, and the associated interaction. Fixed effect parameter estimates for the full LMM of the

duration of between- and within-word silent intervals by group are shown in Table 9.

The LMM analysis showed no statistical differences in duration for between- and within-

word silent intervals, regardless of group, p=0.51. The PD group exhibited significantly longer

between-word silent intervals than control speakers, p=0.039. This difference was not significant

for within-word intervals, p=0.55.

Table 9.

Fixed effect estimates for the duration of between- and within-word silent intervals with the control group, between-word silent interval duration set as the intercept.

Estimate SE df t-value p-value (Intercept) 48.710 2.293 23.200 21.241 <0.001***

Within-Word Intervals -1.221 1.835 1291.400 -0.665 0.506

PD Group 7.182 3.281 24.100 2.189 0.039*

PD Group: Within-Word Intervals -1.590 2.684 1292.000 -0.593 0.554 Note: ***p<0.001, *p<0.05, Parkinson Disease (PD) Group 32

Fixed effect parameter estimates for the LMM analysis for the number of between- and

within-word silent intervals by group are shown in Table 10. The LMM showed no statistical

differences in number of between- and within-word silent intervals, regardless of group, p>0.05.

Because within-word intervals were statistically similar to the between-word intervals not

associated with a major, minor, or optional boundary, they were pooled for subsequent analyses

which examined the effect of the surrounding phonemic environment on silent interval duration.

Table 10.

Fixed effect estimates for the number of between- and within-word silent intervals with the control group, between-word silent interval count set as the intercept.

Estimate SE df t-value p-value (Intercept) 36.500 2.576 21.898 14.172 <0.001***

Within-Word Intervals -3.300 1.619 18.000 -2.039 0.057

PD Group -3.700 3.642 21.898 -1.016 0.321

PD Group: Within-Word Intervals -0.900 2.289 18.000 -0.393 0.699 Note: ***p<0.001, Parkinson Disease (PD) Group

Effect of Preceding Phoneme Manner To determine the extent to which the phonemic context affected silent interval duration,

the preceding phoneme manner was examined descriptively. Categories for this analysis included

silent intervals that were preceded by a stop, fricative, or sonorant. Silent intervals that were

preceded by glide, liquid, and nasal consonants and vowels were combined to form the sonorant

category. These manners were combined because of the low number of observations for each

manner category in the samples. Table 11 includes the average number and duration of silent

intervals associated with each category of preceding manner by group. The number of preceding

phoneme manner types for each participant in the PD and control groups is reported in Appendix

C. 33

Table 11.

Average number and duration (ms) of intervals for each preceding phoneme manner for the control and Parkinson Disease (PD) groups.

Control Group Parkinson Disease Group Mean (SD) N (SD) Mean (SD) N (SD) Stops 57.480 (12.814) 13 (3.055) 64.112 (12.500) 12.1 (3.755)

Fricatives 42.159 (5.355) 14.9 (3.381) 49.923 (7.995) 12.9 (4.408)

Sonorants 47.413 (3.260) 41.7 (6.717) 52.165 (9.863) 36.4 (11.853)

In addition to examining the mean duration and number of silent intervals by preceding phoneme manner, LMM analyses were also conducted. The dependent variable was duration and the independent variables were Preceding Phoneme Manner (levels: voiceless stops, fricatives, and sonorants), Group, and the associated interaction. Fixed effects parameter estimates for the full LMM are shown in Table 12. The LMM showed significant statistical differences in duration for silent intervals preceded by fricatives and sonorants as compared to stops in the control group, p<0.001 for all comparisons. Compared to the control group, the PD group exhibited significantly longer silent intervals when the preceding phoneme was a stop consonant, p=0.043.

The findings are graphically represented in Figure 5. 34

Table 12.

Fixed effect estimates for the duration of short silent intervals by preceding phoneme manner, with intervals preceded by a stop for speakers in the control group set as the intercept.

Estimate SE df t-value p-value (Intercept) 56.635 2.814 54.400 20.123 <0.001***

Fricatives -14.415 2.849 1288.900 -5.060 <0.001***

Sonorants -8.993 2.383 1288.000 -3.775 <0.001***

PD Group 8.344 4.027 56.700 2.072 0.043*

PD Group: Fricatives -0.863 4.138 1288.700 -0.209 0.835

PD Group: Sonorants -3.145 3.445 1288.200 -0.913 0.362

Note: ***p<0.001, *p<0.05, Parkinson Disease (PD) Group 35

80 * 70

40 CN Duration (ms) 30 PD

0 Stops Fricatives Sonorants

Phoneme Manner

Figure 5. Fixed effect estimates and standard error for the duration of short silent intervals that were preceded by stops, fricatives, and sonorants for the control (CN; light gray) and Parkinson Disease groups (PD; dark gray). Note: * denotes p<0.05.

Effect of Subsequent Phoneme Manner

The effect of subsequent phoneme manner on silent interval duration was also examined.

The categories for defining manner were the same as in the analysis of preceding phoneme manner: voiceless stops, fricatives, and sonorants. Table 13 shows the mean number and duration for each group by subsequent phoneme manner. Examination of the number of observations for each subsequent phoneme manner revealed a low average number of observations of silent intervals that were followed by fricatives and sonorants. In the control group, only eight of the ten participants exhibited intervals associated with subsequent fricatives and only two had more than two observations. For sonorants, six of the ten had four or fewer observations. In the PD 36 group, only six of ten participants exhibited intervals with subsequent fricatives, and one had more than two observations. Relative to sonorants, nine of ten participants with PD had four or fewer intervals that were followed by sonorants. Therefore, due to the low frequency of occurrence, and sometimes missing observations, fricatives and sonorants were collapsed into a continuants category for further analysis. The number of observations of each subsequent phoneme manner type are reported in Appendix D for each participant.

LMM analyses were conducted to examine differences between groups in the duration and frequency count of voiceless stop gap and non-stop gap intervals. The dependent variables were duration and count and the independent variables were Subsequent Phoneme Manner

(levels: stop gaps and continuants), Group, and the associated interaction. Fixed effect parameter estimates for the full LMM of the duration of short silent intervals with and without stop gaps are shown in Table 14 and are graphically represented in Figure 6. The LMM showed no statistical differences in duration of intervals with and without stop gaps, regardless of group, p>0.05. The

PD group exhibited an overall longer duration of short silent intervals as compared to the control group, p=0.032.

Table 13.

Average number and duration (ms) of intervals for each subsequent phoneme manner for the control and Parkinson Disease (PD) groups.

Control Group Parkinson Disease Group Mean (SD) N (SD) Mean (SD) N (SD) Stops 48.264 (4.949) 60.1 (7.651) 53.916 (8.445) 52.1 (14.433)

Fricatives 62.154 (32.641) 2.625 (2.263) 62.464 (24.046) 2.833 (0.983)

Sonorants 51.819 (21.181) 5.8 (4.158) 61.297 (11.704) 6.444 (3.127) 37

Table 14.

Fixed effect estimates for the silent interval duration by subsequent phoneme manner, with intervals followed by a subsequent continuant produced by speakers in the control group set as the intercept.

Estimate SE df t-value p-value (Intercept) 45.582 2.949 63.300 15.458 <0.001***

Stop Gaps 3.045 2.476 1303.700 1.230 0.219

PD Group 9.088 4.143 61.400 2.193 0.032*

PD Group: Stop Gaps -3.148 3.480 1302.100 -0.905 0.366 Note: ***p<0.001, *p<0.05, Parkinson Disease (PD) Group

70 * 60

CN 30

Duration ms) (in PD

0 Continuants Stops Phoneme Manner

Figure 6. Fixed effect estimates and standard error for the duration of short silent intervals that were followed by continuants and stops for the control (CN; light gray) and Parkinson Disease groups (PD; dark gray). Note: * denotes p<0.05. 38

To examine potential differences in number of between intervals that were associated with stop gaps and continuants, the LMM analysis of frequency count was examined. Fixed effects parameter estimates for the full LMM of the number of short silent intervals with and without stop gaps are shown in Table 15 and graphically represented in Figure 7. The LMM revealed a significant difference in the number of silent intervals with and without stop gaps for the control group, p<0.001. While there was no significant difference in count of short silent intervals associated with continuants, p>0.05, they produced significantly fewer stop gaps, p=0.030 (Table 15).

Table 15.

Fixed effect estimates for the number of silent intervals by subsequent phoneme manner, with intervals followed by a subsequent continuant produced by speakers in the control group set as the intercept.

Estimate SE df t-value p-value (Intercept) 11.900 2.830 28.970 4.204 <0.001***

Stop Gaps 45.900 2.851 18.000 16.098 <0.001***

PD Group 0.600 4.003 28.970 0.150 0.882

PD Group: Stop Gaps -9.500 4.032 18.000 -2.356 0.030* Note: ***p<0.001, *p<0.05, Parkinson Disease (PD) Group 39

70 *

Number CN 30 PD

0 Continuants Stops Phoneme Manner Figure 7. Fixed effect estimates and standard error for the number of short silent intervals that were followed by continuants and stops for the control (CN; light gray) and the Parkinson Disease groups (PD; dark gray). Note: * denotes p<0.05.

The distribution of intervals associated with voiceless stop gaps is shown in Figure 8.

Intervals associated with voiceless stop gaps used in the above analyses are visually represented

in Figure 9 by place of articulation and group. The total number of stop gaps at each place of

articulation was directly influenced by the reading passage. The total number for each voiceless

stop consonant in the Caterpillar passage is represented in Table 16. As seen in Figure 9,

participants with PD produced fewer stop gaps across all places of articulation, further qualifying

the results of Table 15. Visual inspection of Figure 9 suggests that the statistical trend for fewer

stop gaps in the PD group would likely hold for each voiceless stop. 40

Table 16.

Number of voiceless stop gaps by place in the “Caterpillar Passage.”

Voiceless Stop Gap Count /p/ 17 /t/ 64 /k/ 32

Figure 8. Histogram of voiceless stop gap interval duration for the control (CN; blue) and Parkinson Disease (PD; orange) groups. 41

Figure 9. Histogram of voiceless stop gap interval duration by place of articulation for the control (CN; left panes) Parkinson Disease (PD; right panes) and groups. 42

CHAPTER IV: DISCUSSION

The purpose of the current study was to determine the extent to which the duration and number of silent intervals in the speech of individuals with PD differed from healthy controls at

different syntactic and phonemic boundaries. Relative to syntax, individuals with PD exhibited

silent intervals that were significantly longer than control speakers at between-word boundaries

that were unrelated to the syntax of the passage. The duration of silent intervals that coincided with major, minor, and optional syntactic pause boundaries did not statistically differ between

groups. Relative to phonemic context, between group differences were observed for the duration

and number of silent intervals that occurred at between-word boundaries unrelated to the syntax

of the passage and within words. Specifically, the duration of silent intervals that were preceded

by a stop consonant were significantly longer for speakers with PD than controls. Additionally,

silent intervals that were followed by a fricative or sonorant were significantly longer for

speakers with PD than controls. Speakers with PD also exhibited significantly fewer stop gaps

than controls, though the duration of stop gaps did not differ significantly between groups.

Overall, the findings from the current study suggest that speakers with PD exhibit longer silent

interval durations than control speakers that are associated with the phonemic context rather than

syntactic processes.

Silent Intervals Associated with Syntactic Boundaries

In the current study, longer, between-word silent intervals that contained an inspiratory

breath or coincided with a major syntactic boundary were on average 558 ms for controls and

550 ms for individuals with PD. This difference is not statistically significant. At major

boundaries, the majority of silent intervals coincided with inspiratory breaths. These findings

may be attributed to a physiological constraint for breathing, as the average duration for 43

inspiration during a reading passage for older adults has been reported at 530 ms for control

speakers, and 580 ms for individuals with PD (Huber & Darling, 2011). However, even without an inspiratory breath, silent intervals at major boundaries that were not associated with inspiration were longer than any other boundary type. Studies have indicated that adults produce

longer pauses at major prosodic boundaries than any other boundary (Price, Ostendorf, Shattuck-

Hufnagel, & Fong, 1991). While major prosodic boundaries are not synonymous with major

syntactic boundaries (e.g., Ferreira, 1993), they often occur together (e.g., Price et al., 1991).

Therefore, longer silent intervals that coincide with major syntactic boundaries would likely be

considered a true “pause” by a listener as they indicate a natural break in the utterance.

Between-word silent intervals at syntactically unrelated boundaries were significantly longer for speakers with PD than controls. This may be related to several factors, including

differences in articulatory timing, difficulty initiating the next subsequent speech movement, or

the presence of stuttering like disfluencies. Huber et al. (2012) reported that individuals with PD

had more inspiratory breaths at locations unrelated to syntactic boundaries than older adult

controls. Additionally, individuals with PD in this study exhibited disfluencies at syntactically

unrelated locations, which is consistent with other accounts that suggest that speakers with PD

exhibit stuttering-like disfluencies (Goberman et al., 2010). This may also contribute to the

reported differences, as control speakers did not have stuttering-like disfluencies during the

reading task. In the current sample, inaudible fixed postures were relatively infrequent but

ranged from 90 ms to 1020 ms on average.

Between- and Within-Word Intervals

When examining the duration of within-word and between-word intervals not associated

with a major, minor, or optional syntactic boundary, individuals with PD exhibited significantly 44

longer between-word intervals than the control speakers, but no difference in frequency of

occurrence of these intervals. This longer duration of short, between-word intervals may be

attributed to bradykinesia or akinesia, which may result in an overall slowness of movement and

difficulty initiating movement. Additionally, longer duration of between-word intervals may, in

part, explain a greater proportion of pause noted in other studies of parkinsonian speech

(Goberman et al., 2005). Furthermore, this finding accounts for the findings reported by

Whitfield et al. (2015), in which the individuals with PD had significantly longer, Mode 1 (i.e.,

short) silent intervals than control speakers.

Skodda and Schlegel (2008) reported that individuals with PD exhibited fewer pauses and

a lower proportion of pause within polysyllabic words than control speakers. While the current

study did not find a significant difference in the number or duration of between-word and within-

word intervals between groups, within-word intervals were measured in both monosyllabic and

polysyllabic words. All within-word intervals in the current study were associated with phoneme-to-phoneme transitions. Additionally, Skodda and Schlegel (2008) examined German

speakers with and without PD. The difference in measurements, and perhaps native language

phonology, may explain overall differences in the results between these two studies.

Recent work has suggested that individuals with PD experience stuttering-like

disfluencies that affect timing and disrupt the forward flow of speech (Goberman & Blomgren,

2003; Goberman et al., 2010). In this study, only inaudible fixed postures were measured, as they

are the only stuttering movement that would result in a silent interval. Fixed postures, likely

associated with akinesia, are the common type of stuttering moments observed in speakers with

PD (Goberman et al., 2010; Whitfield, Goberman, Simon, Blomgren, & DeLong, 2014).

Although percent syllables stuttered was not examined in the current study, the group of 45 individuals with PD were relatively fluent, with five of the ten participants with PD exhibiting less than two stuttering-like disfluencies during the reading passage.

Effect of Preceding Phoneme Manner on Silent Interval Duration

Silent intervals preceded by a stop consonant were significantly longer than those preceded by fricatives or sonorants for the control group. The longer duration observed for silent intervals that were preceded by a stop consonant may be due to a time constraint of the articulatory process required for a final stop. This pattern was accentuated for the PD group, as silent intervals which were preceded by a stop consonant were longer for speakers with PD than controls. This finding, again, may reflect symptoms associated with PD including hypokinesia, or slowness of movement, and akinesia, difficulty initiating movement. Additionally, this finding may account for the increased percent pause time observed for speakers with PD in studies for which a pause was defined as a silent interval lasting for more than 50 ms because the mean duration of these intervals was greater than 50 ms (e.g., Goberman et al., 2005).

Effect of Subsequent Manner on Silent Intervals: Stop Gaps

Relative to the effect of subsequent phoneme manner, the majority of silent intervals were associated with the stop gaps of voiceless stop consonants. This finding is likely influenced by the fact that a silent interval is a prominent feature of voiceless stop consonants. The duration of stop gaps did not significantly differ between individuals with PD and controls. This finding may suggest that the motor plan associated with a stop gap is still intact for individuals with PD.

Silent intervals that were not associated with a stop gap were significantly longer for speakers with PD than controls. These silent intervals likely correspond to the longer between-word interval durations described above. The frequency of occurrence of stop gaps was significantly less for speakers with PD than controls. This finding may reflect articulatory undershoot and 46

blurring observed in the speech of individuals with PD that has been reported by other authors

(Ackermann & Ziegler, 1991; Mcauliffe et al., 2006; Skodda et al., 2009). Additionally, these data further qualify and explain the results of Whitfield et al. (2015), who reported that individuals with PD exhibited significantly fewer Mode 1 (i.e., short) silent intervals compared to control speakers.

Methodological Notes

Percent pause and articulation rate measures are affected by the minimum pause duration criterion. This becomes important when interpreting findings from studies with different pause criteria. While the selection of pause criterion did not change the statistical significance or

relationship for this study, a higher minimum pause duration criteria affects the specificity of

these measures and, therefore, across study comparisons. For example, the current study found

that silent, between-word intervals on the order of 40 to 60 ms were significantly longer for

speakers with PD than controls. These short intervals, that likely reflect articulatory processes,

would not be included in a percent pause measurement that was derived using a minimum pause

duration criterion of 150 or 250 ms. Therefore, criteria used to define pause should represent the

specific process under investigation (e.g., phonemic, prosodic, linguistic). Additionally, the

criteria used to define a pause are important when comparing percent pause and articulation rate

measures across studies.

Limitations

The current results should be interpreted relative to a few inherent limitations of the

study. First, one reading passage was utilized in this analysis. The phonemic and linguistic

contexts were dictated by the passage and, therefore, may not be a true representation of the

contemporaneous speech and language production of individuals with PD. Many studies report 47 differences in pause time, speech rate, respiration, articulation, and disfluencies between reading and extemporaneous speech tasks (Dromey, 2003; Goberman et al., 2010; Huber et al., 2012).

Results of this study, therefore, represent a speech production in a controlled reading context and may not reflect the differences noted in contemporaneous speech. Additionally, the categorization process was performed manually and was time intensive. This process would be more difficult with spontaneous, connected speech because the phonemic and syntactic context would not be controlled. 48

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APPENDIX A. HUMAN SUBJECTS REVIEW BOARD APPROVAL LETTER 57

APPENDIX B: CATERPILLAR PASSAGE: BETWEEN-WORD SYNTACTIC

BOUNDARIES

Do · you · like · amusement · parks[?] Well|,|I · sure · do[.] To · amuse · myself|,| I · went ·

twice · last · spring[.] My · most \ MEMORABLE \ moment · was · riding \ on · the ·

Caterpillar|,| which · is · a · gigantic · rollercoaster \ high · above · the · ground[.] When · I · saw

· how · high · the · Caterpillar · rose \ into · the · bright · blue · sky \ I · knew · it · was · for ·

me[.] After · waiting · in · line \ for · thirty · minutes|,| I · made · it · to · the · front \ where · the

· man · measured · my · height \ to · see · if · I · was · tall · enough[.] I · gave · the · man · my ·

coins|,| asked · for · change|,| and · jumped · on · the · cart[.] Tick|,| tick|,| tick|,| the · Caterpillar · climbed \ slowly \ up · the · tracks[.] It · went \ SO \ high \ I · could · see · the · parking · lot[.]

Boy · was · I \ \ SCARED[!] I · thought · to · myself|,| “There’s · no · turning · back · now[.]”

People · were · so · scared \ they · screamed \ as · we · swiftly · zoomed · fast|,| fast|,| and · faster

\ along · the · tracks[.] As · quickly · as · it · started|,| the · Caterpillar · came · to · a · stop[.]

Unfortunately|,| it · was · time \ to · pack · the · car \ and · drive · home[.] That · night \ I ·

dreamt · of · the · wild · ride \ on · the · Caterpillar[.] Taking · a · trip · to · the · amusement ·

park \ and · riding · on · the · Caterpillar \ was · my \ MOST \ memorable · moment \ ever[.]

Key Boundary Type Symbol Major Syntactic Boundary [ ] Minor Syntactic Boundary | | Optional Pause \ Unrelated · 58

APPENDIX C: OCCURRENCE OF PRECEDING PHONEME MANNER CATEGORIES BY PARTICIPANT

Participant Stops Fricatives Sonorants CN Group OA01 10 12 31 OA02 16 11 39 OA03 18 20 49 OA04 17 16 51 OA05 13 21 44 OA06 9 16 37 OA07 11 14 40 OA08 11 14 50 OA09 12 13 41 OA10 13 12 35 PD Group PD01 12 13 35 PD02 4 6 19 PD03 11 12 37 PD04 17 20 44 PD05 16 12 48 PD06 10 14 28 PD07 10 6 22 PD08 15 17 49 PD09 14 16 53 PD10 12 13 29 59

APPENDIX D. OCCURRENCE OF SUBSEQUENT PHONEME MANNER CATEGORIES BY PARTICIPANT

Participant Stops Fricatives Sonorants Affricates CN Group OA01 47 3 2 1 OA02 57 2 7 - OA03 65 8 11 3 OA04 67 2 14 2 OA05 65 2 8 3 OA06 56 - 4 2 OA07 59 1 3 2 OA08 73 - 1 1 OA09 60 1 4 1 OA10 52 2 4 2 PD Group PD01 50 3 5 2 PD02 27 - - 2 PD03 55 - 5 - PD04 63 4 11 3 PD05 61 2 10 3 PD06 45 - 6 1 PD07 36 - 2 - PD08 67 2 10 2 PD09 73 2 5 3 PD10 44 4 4 2