Auditory P300 Responses Evoked by Perceptually Different Between-Category CV Stimuli
§ Ji Young Lee Department of Audiology and Speech Pathology, University of Tennessee Health Science Center, Tennessee, USA
Background & Objectives: Event-related potentials (ERPs) research has shown that the P300 reflects the categorical perception of speech sound. Using within-category or across-category stimuli, research has reported the controversial findings whether the P300 represents phonetic processing rather than acoustic processing, or acoustic processing as well. The present study explored whether the P300 response is sensitive to the perceptually different between-category consonant-vowel (CV) stimuli, and if so, whether the P300 response varies as a function of deviancy of between-category CV stimuli. Methods: The P300 was measured in an oddball paradigm from 10 normal hearing adults. Based on the results of identification test of a speech continuum, 1 within- category CV was selected as a standard stimulus and 2 between-category CVs were selected as deviant stimuli. The 2 deviant stimuli consisted of the weak deviant (WD) and strong § Correspondence to deviant stimuli (SD). A total of 600 stimuli were composed of 480 standard stimuli (80%), 60 Ji Young Lee, WD (10%), and 60 SD (10%). Results: (1) the P300 was elicited by both WD and SD, (2) the Department of Audiology and P300 amplitude was larger in SD than WD, (3) the P300 amplitude was larger over central and Speech Pathology, parietal regions than the frontal region, and (4) the P300 latency was not different for deviancy University of Tennessee Health condition and scalp distribution. Discussion & Conclusion: The results indicate that the P300 Science Center, 578 South Stadium Hall, can reflect the sub-phonetic or acoustic processing of speech sound. The scalp distribution of University of Tennessee, the P300 is more dominant in the centro-parietal regions. (Korean Journal of Communication Knoxville, Tennessee Disorders 2012;17:499-507) 37996-0740, USA email: [email protected] Key Words: event related potentials, P300, oddball paradigm, category perception, between- tel: +1 865 974 4494 category stimuli, VOT
Ⅰ. Introduction Event related potentials (ERPs) refer to the electrical brain activities which are temporally synchronized Speech perception is a human’s high-level cognitive to some specific tasks. As ERPs have proven to reflect processing. Much research has examined how human the high level processing such as cognition, attention, hear acoustic cues, recognize speech sound, and under- or memory, a lot of research has studied the speech stand the meaning of language. Of them, categorical and language processing using ERPs. For the past perception has been widely studied behaviorally and decades, ERPs have been widely used to investigate electrophysiologically. According to categorical per- the time course of the neural system related to acoustic- ception, we perceive gradually changing physical phonetic, phonological, semantic, and syntactic pro- information in terms of the psychological category cessing (Bonte et al., 2006). Particularly, it has been represented in our brain. Thus, the speech sounds in of interest to researchers in the area of neurology, the different phoneme category can be discriminated cognitive psychology, and neuroscience in that it better than the speech sounds within the same phoneme is a noninvasive procedure and can provide brain category when they have the same physical dif- response with high temporal resolution. ferences (Liberman et al., 1957; Studdert-Kennedy The P300 is one of the most studied ERP components et al., 1970). due to the robust and reliable peak (Patel & Azzam,
■ Received July 20, 2012 ■ Final revision receiv ed August 26, 2012 ■ Accepted August 30, 2012. ⓒ 2012 The Korean Academy of Speech-Language Pathology and Audiology http://www.kasa1986.or.kr
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2005). The P300 is most commonly elicited by the category (WC), and across-category (AC) conditions low probability stimulus in an oddball paradigm at the native and non-native (Hindi) phonetic bound- where a low probability stimulus (or deviant stimulus) ary. Hindi listeners perceive 1st-6th sound as /ba/, is presented randomly in a series of high probability 7th-10th as /da/, and 11-16th as retroflex /Da/ while stimulus (or standard stimulus). The less demanding English listeners perceive 1st-6th as /ba/ and 7th-16th st th th the task is, the greater the P300 amplitude is (Polich, as /da/. 1 , 5 and 9 sound was used for native th th th 2007). The P300 is an endogenous and nonsensory phonetic contrast, and 8 , 12 , and 16 sound was specific response (McPherson & Ballachanda, 2000). used for non-native phonetic contrast as stimuli. It has been known that the amplitude of P300 reflects The four sequential CV syllables (e.g. /ba/ 5- /ba/ 5 stimulus probability and task relevance, and its la- - /ba/ 5 - /ba/ 5 for CO; /ba/ 1- /ba/- 1 /ba/- 1 /ba/ 5 tency reflects stimulus evaluation time (Johnson & for WC; /ba/ 9 - /ba/ 9 - /ba/ 9 - /ba/ 5 for AC) were Donchin, 1980; Picton & Hillyard, 1988; Sutton & presented. The results showed both MMN and P300 Ruchkin, 1984). The longer latency has been elicited were more sensitive to phonetic contrasts rather than for the psychological disordered or brain damaged acoustic ones, using across-category and within- people compared to normal people (Onofrj et al., category stimuli. 1991; Sangal, Sangal & Belisle, 1999). The P300 has Dalebout & Stack (1999) explored the MMN and the most negativity over centro-parietal midline P300, using a /da/ to /ga/ continuum. There were three scalp sites (Duncan et al., 2009). stimulus conditions of the most difficult (7th-9th pair), The P300 is currently in greater interest for clinical difficult (subject’s individual 2-step pair with the application such as diagnosing the pathological status highest discrimination performance), and easy contrast st th and predicting/monitoring the progress. Numerous (1 -9 pair). The results showed that for most dif- clinical research has been done, including people ficult, difficult, and easy contrasts, the MMN was with Attention Deficit Hyperactivity Disorders (ADHD), elicited in 50%, 25%, and 50% of the subjects whereas Alzheimer’s disease, cochlear implant, and hearing the P300 was elicited in 0%, 33%, and 100% of the impairment (Kileny, 1991; Barrett, 1993; Jordon et subjects. They concluded that P300 is elicited by al., 1997; Hutchinson & McGill, 1997; Salamat & phonetic/phonemic differences while MMN is elicited McPherson, 1999; Jeon & Polich, 2003). by acoustic differences. To examine how perceptually deviant contrasts the Tampas, Harkrider & Hedrick (2005) investigated P300 is sensitive to, the effect of stimulus frequency, the MMN and P300, using speech contrasts (two intensity, and duration has been studied (O’Brien & within- category CV stimuli) and nonspeech contrasts
Stuart, 2001; Vesco et al., 1993). Though the P300 to (two glides of which frequency ramp matched the speech sound has not been deeply studied compared formant transitions of CV). The results showed that to tone sound, research has shown that the P300 the MMN was elicited by the nonspeech only while reflects the categorical perception of speech sound the P300 was elicited by both the speech and non- (Horev, Most & Pratt, 2007; Maiste et al., 1995). Using speech with larger amplitude and shorter latency in within- category or across-category stimuli, research nonspeech. They concluded the acoustic and phonetic has reported the controversial findings as to whether information are processed in parallel at the level of the P300 represents phonetic changes rather than MMN up to P300. acoustic changes (Dalebout & Stack, 1999; Dehaene- The objective of the present study was to explore Lambertz, 1997), or acoustic changes as well (Tampas, whether the P300 response is sensitive to between- Harkrider & Hedrick, 2005). category stimuli, and if so, whether the P300 response To investigate the acoustic versus phonetic sen- varies as a function of the deviancy of between-category sitivity of Mismatch Negativity (MMN) and P300, CV stimuli. To minimize the factors related with Dehaene- Lambertz (1997) constructed a /ba/-retroflex speech perception other than acoustic feature, non- /Da/ continuum and designed control (CO), within- sense CVs were used as stimuli. From a /bi/-/pi/
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continuum, one within-category CV was selected as using a high quality microphone (Spher-O-Dyne), a standard stimulus and two between-category CVs which was saved as a file sampled at 44.1 kHz (CSRE, were selected as deviant stimuli based on the results Version 4.5). This /bi/ sound was used as an endpoint of behavioral identification test. Two between-category stimulus (i.e. Stimulus 1) after getting rid of the minor deviant stimuli consisted of weak deviant (WD-the noise at the beginning burst to make VOT 0 msec. deviant stimulus is acoustically closer to the standard The total duration of Stimulus 1 was 347 msec. The stimuli) and strong deviant (SD-the deviant stimulus noise burst portion of synthetic /pi/ was used to ma- is acoustically farther from the standard stimuli). nipulate voice onset time systematically. By digitally There are three specific research questions in this increasing the noise burst by 6 ms from the Stimulus study. The first question was whether the P300 is 1 (i.e. prototypical /bi/), a nine-step series of a /bi/-/pi/ elicited by between-category stimuli. It was hypothe- continuum was constructed so that the Stimulus 9 sized that the P300 would be elicited to both WD (i.e. prototypical /pi/) had VOT of 64 msec (Adobe and SD. The second question was whether the P300 Audition, Version 1.5). is different for deviancy condition (WD, SD). In other From the results of identification test on a /bi/-/pi/ words, it was whether the P300 varies as a function continuum, one within-category CV was selected as of deviancy of between-category stimuli. It was hy- the standard stimulus and two between-category pothesized that the P300 amplitude would be larger CVs were selected as the deviant stimuli. Two deviant in SD than WD and the P300 latency might be longer stimuli consisted of weak deviant (WD-the deviant in WD than SD. The last question was whether the stimulus acoustically closer to the standard stimuli) P300 would yield a scalp distribution different or and strong deviant (SD-the deviant stimulus acoustically similar to that reported in previous studies. It was farther from the standard stimuli). Stimulus 2 was hypothesized that the P300 amplitude would be larger used as a standard stimulus, Stimulus 4 as WD, and over central and parietal regions versus the frontal Stimulus 5 as SD. region. To measure the P300, a total of 600 stimuli were presented in an active oddball paradigm with one standard and two deviant stimuli divided into two Ⅱ. Methods blocks. Each block included 300 stimuli which were composed of 240 standard stimuli (80%) and 30 weak 1. Participants deviant (10%) and 30 strong deviant stimuli (10%). The order of presentation of blocks was counterbal- Ten native English speakers (male 4, female 6) anced. The stimuli were presented in pseudorandom participated in the study. The participants were ranged sequences with at least eight standard stimuli pre- in age from 18 to 28 years old (Mean = 22.3). They were ceding the first deviant and no less than 3 standard right-handed with no history of neurological, psych- stimuli after one deviant. Each stimulus was presented ological/ psychiatric, speech, language, or hearing with a 1,100 msec ISI to allow the response time. The disorders. They showed the normal audiometric time to complete each block was 5 minutes 30 seconds. thresholds at or below 15dB HL for the frequencies between 250 and 8,000 Hz (re: ANSI, 2004). 3. Procedure
2. Stimuli Identification test To select the standard and deviant stimuli for an A nine-step Series /bi/-/pi/ continuum was made oddball paradigm, a two-forced choice identification by manipulating voice onset time (VOT) from a nat- test was administered prior to the experiment. Par- urally produced /bi/. A male native English speaker ticipants listened to the sounds at a comfortable level recorded his live voice /bi/ sound in a quiet room (approximately 75dB SPL) through headphones in a
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sound-treated booth. They were instructed to select baseline (-100～0 msec). The P300 amplitude was the letter ‘b’ or ‘p’ on the computer screen by using scored as the most positive peak between 300 and a mouse as they listened. Each sound was presented 450 msec after stimulus onset. The latency was scored ten times in random order, resulting in 90 sound as the time from the stimulus onset to the P300 peak. stimuli presented in total. This window interval was determined based on previous research and the visual inspection of the P300 individual waveform. Two two-way repeated measures Participants were given the response pad and ANOVAs were conducted on the P300 amplitude seated comfortably in a reclining chair in a sound- and latency with the stimulus condition (2 levels: treated booth. They were instructed to press the WD, SD) and scalp distribution (3 levels: Fz, Cz, Pz) response button as soon as they heard deviant stimuli. as the factors, respectively. When Mauchly’s test of Participants took part in the experiment only after sphericity was significant, Greenhouse-Geisser adjust- their performance reach 100% on the preliminary ed degrees of freedom, F- and p-values were reported. test. The stimuli were presented binaurally, using Bonferonni adjustments were made to account for Etymotic ER-3A insert earphones at a comfortable the use of multiple ANOVAs, thus an alpha level of level of loudness (i.e. 75 dB SPL). 0.025 (.05/2) was considered significant. For post All data was collected using a 64-channel NeuroScan hoc test, Bonferroni corrections were used. system. EEG responses were acquired from Fz, Cz, and Pz,(re: International 10-20 System) referenced to an electrode between Pz and Pcz and grounded Ⅲ. Results by the cap electrode at Fpz. Vertical and horizontal electrooculograms (EOGs) were recorded by elec- Identification test trodes placed above, below, and on the inner and From the results of identification test, Stimulus 2 outer canthi of the left eye. All electrodes were Ag/ was selected as a standard stimulus, Stimulus 4 as AgCl, and impedance was maintained at 5 K Ω. The WD, and Stimulus 5 as SD. The mean /bi/ response continuous EEG recordings were obtained using a was 100% in Stimulus 2, 68% in Stimulus 4, and bandpass of 0.01-30 Hz and digitally sampled at 12% in Stimulus 5. The identification performance
500 Hz for 100 ms before and 1,000 ms after the was different for stimulus condition (F(2, 18) = 121, 2 stimulus onset. For further analysis, EEG data asso- p < .001, ηp = .931) with large effect size (Cohen, ciated with an incorrect response and an EOG greater 1992). Stimulus 2 was significantly greater than Stimu- than 70 μV was excluded. An offline re-reference lus 4 and 5, and Stimulus 4 was significantly greater was administered. All participants had more than than 5.
4. Analyses
For identification test, the mean /bi/ response was calculated to select a standard and two deviant stimuli. Also, a one-way repeated measures analysis of vari- ances (ANOVA) was conducted on the percentage of /bi/ response with the stimulus condition (3 levels: standard, WD, SD) as the factor. For post hoc test, Bonferroni corrections were used. For P300, all post-stimulus data (0～1,000 msec
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2 P300 for scalp distribution (F(2, 18) = 41.856, p < .001, ηp = The robust P300 response was elicited by both .823) with medium and large effect size, respectively deviant stimuli (WD, SD) on the overall scalp dis- (Cohen, 1992). There was no significant interaction tribution with larger amplitude on the central and of deviancy condition and scalp distribution (F(2, 18) parietal regions. The grand average waveform of P300 = 1.350, p = .284). The P300 amplitude by deviancy is seen in Error bars indicate 1 standard error from the mean Contrast pair p-value Fz vs Cz .000** Cz vs Pz .249 ** Fz vs Pz .000 *p < .025, **p < .001 The P300 latency was also analyzed using a two- 503 Korean Journal of Communication Disorders 2012;17:499-507 Amplitude (µV) Latency (ms) WD SD WD SD Fz Cz Pz Fz Cz Pz Fz Cz Pz Fz Cz Pz S1 -0.96 4.96 14.91 4.77 9.52 19.70 334 338 352 338 326 328 S2 -3.72 6.71 11.82 -1.15 9.13 13.87 356 364 364 414 366 362 S3 3.57 10.16 10.90 2.55 7.03 10.42 326 328 326 312 318 344 S4 -1.93 6.71 6.68 4.76 9.84 7.99 374 360 398 404 384 370 S5 2.37 9.85 8.98 5.65 10.51 12.42 416 416 370 380 412 330 S6 -0.82 2.16 1.25 -3.31 1.77 2.64 440 440 348 412 412 410 S7 2.01 13.75 16.40 7.43 15.83 14.41 336 334 334 386 390 336 S8 0.27 13.09 15.03 3.67 14.43 15.52 354 352 320 348 342 342 S9 -1.97 3.53 5.44 -0.89 5.12 6.55 432 428 348 352 338 300 S10 -3.26 2.63 2.72 -1.19 6.26 5.62 326 342 346 354 342 330 Mean -0.45 7.36 9.41 2.23 8.94 10.91 369 370 350 370 363 345 SD 2.45 4.19 5.31 3.61 4.19 5.23 44.3 41.8 22.7 34.4 34.8 29.8 Std. & Hedrick (2005)’s study in that P300 was elicited N Minimum Maximum Mean Deviation to within-category CV stimuli. Actually, the P300 Type20_Fz 10 326 440 369.40 44.282 seems to be more dependent on the perceptual per- Type20_Cz 10 328 440 370.20 41.777 formance on the stimuli rather than acoustic versus Type20_Pz 10 320 398 350.60 22.746 phonetic contrasts. As the P300 is engaged with Type30_Fz 10 312 414 370.00 34.422 conscious cognitive process and shows good correlation Type30_Cz 10 318 412 363.00 34.772 with behavioral performance (Dalebout & Stack, 1999; Type30_Pz 10 300 410 345.20 29.802 White, Stuart & Najem, 2010), it seems to make more Valid N 10 sense to interpret the P300 response with the behav- (listwise) ioral performance on the stimuli used. Using tone stimuli, White, Stuart & Najem (2010) showed all participants had the P300 to the perceptible contrasts Ⅳ. Discussion with no response to the imperceptible contrasts. Likely, the P300 response is likely to be elicited even The P300 amplitude was significantly larger in by within-category stimuli when they exhibit per- SD than WD. The larger P300 was expected to be ceptual difference in behavioral response. elicited by SD because SD is perceptually more deviant The P300 amplitude was significantly larger over from the standard stimulus than WD. It has been the central and parietal regions than the frontal region. known that the amplitude of the P300 is very sensitive It is in line with previous literature’s findings that to stimulus probability and task (Folstein & Van the P300 occurs maximally over the centroparietal Petten, 2008) and the less demanding the task is, the areas (Folstein & Van Petten, 2008; Martin, Tremblay greater the amplitude is (Polich, 2007). Because the & Korczak, 2008; Picton, 1992). P300 amplitude was sensitive to the degree of deviancy The P300 latency was not different for deviancy of between-category stimuli, the findings also suggests condition and scalp distribution. Though some re- that the P300 can reflect the sub-phonetic or acoustic search reported the longer P300 latency for more processing. It is consistent with Tampas, Harkrider difficult tasks (Fitzgerald & Picton, 1983; Johnson 504 Lee / Auditory P300 Responses Evoked by Perceptually Different Between-Category CV Stimuli & Donchin, 1980), the current data did not show the Duncan, C. D., Barry, R. J., Connolly, J. F., Fischer, C., Michie, P300 latency effect on WD and SD. Because the psych- P. T., Näätänen, R., Polich, J., Reinvang, I., & Van Petten, C. (2009). Event-related potentials in clinical research: ological disordered or brain damaged people have Guidelines for eliciting, recording, and quantifying shown the longer latency than normal people (Onofrj, mismatch negativity, P300, and N400. Clinical Neuro- physiology, 120, 1883-1908. 1991; Sangal, Sangal & Belisle, 1999), it might be Fitzgerald, P. G., & Picton, T. W. (1983). Event-related potentials because WD is more difficult task but not as difficult recorded during the discrimination of improbable stimuli. as it takes more evaluation time than SD. The eval- Biological Psychology, 17, 241-276. uation time was not analyzed in the present study, Folstein, J. R., & Van Petten, C. (2008). Influence of cognitive thus more detailed behavioral data could clearly control and mismatch on the N2 component of the ERP: A review. Psychophysiology, 45, 152-170. examine whether the P300 latency is associated with Horev, N., Most, T., & Pratt, H. (2007). Categorical perception evaluation time. of speech (VOT) and analogous non-speech (FOT) In summary, the purpose of the present study was signals: Behavioral and electrophysiological correlates. Ear and Hearing, 28, 111-128. to examine the nature and characteristics of the P300 Hutchinson, K., & McGill, D. M. (1997). The efficacy of utilizing to between-category CV syllable. Results indicate that the P300 as a measure of auditory deprivation in the P300 can reflect the sub-phonetic or acoustic pro- monaurally aided profoundly hearing impaired children. Scandavian Audiology, 26, 177-185. cessing of speech sounds when they are perceptually different, and the scalp distribution of the P300 is Jeon, Y. W., & Polich, J. (2003). Meta-analysis of P300 and schizophrenia: Patients, paradigms, and practical im- more dominant in the central and parietal regions plications. Psychophysiology, 40, 684-701. versus frontal region. With the advantage of robust Johnson, R. Jr., & Donchin, E. (1980). P300 and stimulus categorization: Two plus one is not so different from and reliable response, the P300 could be used as a one plus one. Psychophysiology, 17, 167-178. useful tool to investigate the speech perception pro- Jordon, K., Schmidt, A., Plotz, K., von Specht, H., Begall, cess and develop the clinical application. Future K., Roth, N., & Scheich, H. (1997). Auditory event- research could be developed on the present study so related potentials in post-and prelingually deaf cochlar that the ERPs can provide more integrative information implant recipients. American Journal of Otology, 18, 116-117. by using between-category stimuli as well as within- Kileny, P. R. (1999). Use of electrophysiologic measure in the category or across-category stimuli. management of children with cochlear implants: Brain stem, middle latency, and cognitive (P300) responses. American Journal of Otology, 12 (Suppl.), 37-42. Liberman, A. M., Harris, K. S., Hoffman, H. S., & Griffith, B. C. REFERENCES (1957). The discrimination of speech sounds within and across phoneme boundaries. Journal of Experimental American National Standards Institute (2004). Specifications Psychology, 54, 358-368. for audiometers (ANSI S3.6). New York, NY: Author. Maiste, A. C., Wiens, A. S., Hunt, M. J., Scherg, M., & Picton, T. Barret, G. (1993). Clinical applications of event-related po- W. (1995). Event-related potentials and the categorical perception of speech sounds. Ear and Hearing, 16, 68-90. tentials. In A. M. Halliday (Ed.), Evoked Potentials in Clinical Testing (pp. 589-633). London: Dhurchill Martin, B. A., Tremblay, K., & Korczak, P. (2008). Speech evoked Livingstone. potentials: From the laboratory to the clinic. Ear and Bonte, M., Parviaine, T. Hytonen, K., & Salmelin, R. (2006). Hearing, 29, 285-313. Time course of top-down and bottom-up influences McPherson, D. L., & Ballachanda, B. (2000). Audiology Diag- on syllable processing in the auditory cortex. Cerebral nosis. In R. J. Roesser, M. Valente, & H. Hosford-Dunn Cortex, 16, 115-123. Holly (Eds.), Middle and long latency auditory evoked Cohen, J. (1992). A power primer. Psychological Bulletin, 112, potentials (pp. 471-501). New York, NY: Thieme. 155-159. O’Brien, P. J., & Stuart, A. (2001). The effect of auditory stimulus Dalebout, S. D., & Stack, J. W. (1999). Mismatch negativity to duration on the P300 response. Journal of Speech- acoustic differences not differentiated behaviorally. Language Pathology and Audiology, 25, 19-23. Journal of the American Academy of Audiology, 10 , 388-399. Onofrj, M., Curatola, L., Malatesta, G., Bazzano, S., Colamartino, Dehaene-Lambertz, G. (1997). Electrophysiological correlates P., & Fulgente, T. (1991). Reduction of P3 latency during of categorical phoneme perception in adults. Neuroreport, outcome from post-traumatic amnesia. Acta Neurologica 8, 919-924. Scandinavica, 83, 273-279. 505 Korean Journal of Communication Disorders 2012;17:499-507 Patel, S. H., & Azzam, P. N. (2005). Characterization of N200 and Studdert-Kennedy, M., Liberman, A. M., Harris, K. S., & Cooper, P300: Selected studies of the event-related potential. F. S. (1970). Motor theory of speech perception: A International Journal of Medical Sciences, 2, 147-154. relay to Lane’s critical view. Psychological Review, 77, Picton, T. W. (1992). The P300 wave of the human event-related 234-249. potential. Journal of Clinical Neurophysiology, 9, 456-479. Sutton, S., & Ruchkin, D. S. (1984). The late positive complex: Picton, T. W., & Hillyard, S. A. (1988). Endogenous event- Advances and new problems. Annals of the New York related potentials. In Picton, T. W. (Ed.), Handbook of Academy of Science, 425, 1-23. Electroencephalography and Clinical Neurophysiology, Tampas, J.W., Harkrider, A.W., & Hedrick, M.S. (2005). Revised Series, Vol 3: Human Event Related Potentials Neurophysiological indices of speech and nonspeech (pp. 361-426). New York, NY: Elsevier Science. stimulus processing. Journal of Speech, Language, and Polich, J. (2007). Updating P300: An integrative theory of Hearing Research, 48, 1147-1164. P300a and P300b. Clinical Neurophysiology, 118, Vesco, K. K., Bone, R. C., Ryan, J. C., & Polich, J. (1993). P300 2128-2148. in young and elderly subjects: Auditory frequency and Salamat, M. T., & McPherson, D. L. (1999). Interactions among intensity effects. Electroencephalography and Clinical variables in the P300 response to a continuous perform- Neurophysiology, 88, 302-308. ance task. Journal of the America Academy of Audiology, White, L., Stuart, A., & Najem, F. (2010). Mismatch negativity 10, 379-387. and P300 to behaviorally perceptible and imperceptible Sangal, R. B., Sangal, J. M., & Belisle, C. (1999). Longer auditory temporal contrasts. Perceptual and Motor Skills, 110, and visual P300 latencies in patients with narcolepsy. 1105-1118. Clinical Electroencephalography, 30, 28-32. 506 이지영 / 지각적 차이를 보이는 음소 범주 간 CV 자극등에 대한 P300연구 지각적 차이를 보이는 음소 범주 간 CV 자극들에 대한 P300 연구 이 지 영 § 테네시대학교 청각 ․ 언어병리학과 배경 및 목적: 말소리에 대한 Event related potentials (ERP) 연구들은 P300가 범주 지각을 반영하는 것으로 보고하였다. 같은 음소 범주에 속하는 혹은 다른 음소 범주에 속하는 자극들 을 이용하여 P300 반응이 음성적인 프로세스 외에 음향적인 프로세스와도 관련이 되어 있는 가가 연구되었으나 결과에는 논란이 있어 왔다. 본 연구의 목적은 음소 범주 사이에 있는 자음- 모음(CV) 자극에 의해 P300가 유발되는지, 유발된다면 표준자극으로부터 이탈되는 정도에 따 라 민감한 차이를 보이는지를 연구하는 것이다. 방법: 10명의 정상청력 성인을 대상으로 양자극 방안을 이용하여 P300를 측정하였다. 말소리 연속체의 판별 검사 결과에 따라 1개의 음소 범주 내 CV가 표준자극으로, 2개의 음소 범주 간 CVs가 이탈자극(약한 이탈자극과 강한 이탈자극) 으로 사용되었다. 총 600개의 자극은 480개의 목표자극 (80%), 60개의 약한 이탈자극(10%), 그리고 60개의 강한 이탈자극(10%)으로 구성되었다. 결과: P300가 약한 이탈자극과 강한 이 § 교신저자 탈자극에 의해 모두 유발되었으며, P300 진폭은 약한 이탈자극보다 강한 이탈자극에 대해 이지영 유의미하게 크게 나타났다. P300 진폭은 전두부보다 중앙․두정부에서 유의미하게 크게 나타 테네시대학교, 청각 ․언어병리학과 났다. P300 잠복기는 자극조건과 두피분포에 대해 유의미한 차이를 보이지 않았다 . 결론: P300 578 South Stadium Hall, 가 표준자극으로부터의 이탈 정도에 따라 다르게 유발됨으로써 P300가 음성학적인 단계뿐 University of Tennessee, Knoxville, 아니라 음향학적인 단계의 프로세스를 반영하는 것으로 나타났다. P300는 중앙․두정부에서 Tennessee 37996-0740, USA 보다 두드러지게 유발되었다. 언어청각장애연구, 2012;17:499-507. email: [email protected] tel: +1-865-974-4494 핵심어: 사건관련전위, P300, 양자극방안, 범주 지각, 범주 간 자극, VOT ■게재 신청일: 2012년 7월 20일 ■최종 수정일: 2012년 8월 26일 ■게재 확정일: 2012년 8월 30일 ⓒ 2012 한국언어청각임상학회 http://www.kasa1986.or.kr 507 The individual P300 amplitude and latency data are presented in
Post hoc tests for scalp distribution
P300 amplitude and latency data by subject