Brain Activation for Lexical Decision and Reading Aloud: Two Sides of the Same Coin?
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Brain Activation for Lexical Decision and Reading Aloud: Two Sides of the Same Coin? Manuel Carreiras1,2, Andrea Mechelli3, Adelina Este´vez1, and Cathy J. Price4 Downloaded from http://mitprc.silverchair.com/jocn/article-pdf/19/3/433/1756592/jocn.2007.19.3.433.pdf by guest on 18 May 2021 Abstract & This functional magnetic resonance imaging study com- bilateral insulae), but task differences were observed bilaterally pared the neuronal implementation of word and pseudoword in sensorimotor areas. Lexical decision increased activation in processing during two commonly used word recognition tasks: areas associated with decision making and finger tapping lexical decision and reading aloud. In the lexical decision task, (bilateral postcentral gyri, supplementary motor area, and right participants made a finger-press response to indicate whether cerebellum), whereas reading aloud increased activation in a visually presented letter string is a word or a pseudoword areas associated with articulation and hearing the sound of the (e.g., ‘‘paple’’). In the reading-aloud task, participants read spoken response (bilateral precentral gyri, superior temporal aloud visually presented words and pseudowords. The same gyri, and posterior cerebellum). The effect of lexicality (pseudo- sets of words and pseudowords were used for both tasks. This word vs. words) was also remarkably consistent across tasks. enabled us to look for the effects of task (lexical decision vs. Nevertheless, increased activation for pseudowords relative reading aloud), lexicality (words vs. nonwords), and the to words was greater in the left precentral cortex for reading interaction of lexicality with task. We found very similar patterns than lexical decision, and greater in the right inferior frontal of activation for lexical decision and reading aloud in areas cortex for lexical decision than reading. We attribute these associated with word recognition and lexical retrieval (e.g., left effects to differences in the demands on speech production and fusiform gyrus, posterior temporal cortex, pars opercularis, and decision-making processes, respectively. & INTRODUCTION table, dog) and half are ‘‘nonwords’’ (e.g., pable, Reading is a remarkable skill that only humans have dnom). Usually, the participant is asked to press one achieved. Understanding the cognitive steps involved button for words and another for nonwords. The main has required some ingenious techniques based on reac- dependent variable is response time (the time elapsed tion times. The most popular of these tasks are lexical between the presentation of the stimulus and the re- decision and reading aloud: The lexical decision task sponse), but accuracy is also of interest. The basic requires participants to determine whether a letter string assumption behind this technique is that to decide is a word or a nonword, whereas the reading-aloud task whether a given letter string is a word or not, partici- requires the participant to pronounce the letter string. pants need to check whether it corresponds to a lexical Lexical decision and reading aloud have been the major representation. Hence, the time required to make a driving force in gathering empirical evidence for devel- lexical decision to a word stimulus gives us an estimation oping computational models of lexical processing (see of how this string is represented in the lexical network Coltheart, Rastle, Perry, Langdon, & Ziegler, 2001; and/or the operations needed to access to the lexical Grainger & Jacobs, 1996; Plaut, McClelland, Seidenberg, representation. However, the total response time is also & Patterson, 1996; Coltheart, Curtis, Atkins, & Haller, affected by some early encoding processes and some 1993; Seidenberg & McClelland, 1989). late response processes responsible for the motor re- In the lexical decision task, participants are presented sponse (Ratcliff, Gomez, & McKoon, 2004). Further- with strings of letters and asked to decide as rapidly as more, given that the lexical decision task is a word/ possible whether the letter constitutes a word or not. In nonword discrimination task, it has been criticized on a typical experiment, half of the items are words (e.g., the basis that the decision processes may play an important role in the obtained response time, for in- 1Universidad de La Laguna, Tenerife, Spain, 2Institute of Cog- stance, the choice of the nonword foils modulates the nitive Neuroscience, London, 3King’s College, London, 4Insti- magnitude of many lexical effects (Carreiras, Perea, & tute of Neurology, London Grainger, 1997; Balota & Chumbley, 1984). D 2007 Massachusetts Institute of Technology Journal of Cognitive Neuroscience 19:3, pp. 433–444 Downloaded from http://www.mitpressjournals.org/doi/pdf/10.1162/jocn.2007.19.3.433 by guest on 26 September 2021 In the reading-aloud task, the participant has to decision (Yes, it’s a word vs. No, its not a word). Indeed, pronounce aloud as quickly as possible the sounds the longer response times to pseudowords than words associated with a presented stimulus. The main depen- during lexical decision has been attributed to the time dent variable is again response time (i.e., the amount taken to check the response (Perea, Rosa, & Go´mez, of time elapsing between presentation of the stimulus 2005; Ziegler, Jacobs, & Kuppel, 2001; Forster, 1976) or and the onset of the participant’s vocalization). How- to an extended temporal deadline for pseudowords if ever, the advantage of reading aloud over lexical deci- a word has not been recognized (Grainger & Jacobs, sion is that reading aloud does not require any overt 1996; Coltheart, Davelaar, Jonasson, & Besner, 1977). discrimination about the stimulus, even when the stim- During reading aloud by contrast, increased response Downloaded from http://mitprc.silverchair.com/jocn/article-pdf/19/3/433/1756592/jocn.2007.19.3.433.pdf by guest on 18 May 2021 uli include both words and pseudowords. It is well times for pseudowords relative to words have been known that words are named faster than nonwords, attributed to the absence of semantics or lexical ortho- which allows reading-aloud time to be used as an index graphic-to-phonologic mappings. of lexical access time (e.g., Fredericksen & Kroll, 1976; The task-dependent nature of lexicality effects may Forster & Chambers, 1973), although a number of other be even more striking in a language with a shallow or- factors can influence reading-aloud speed (Carreiras thography such as Spanish. Low-frequency words and et al., 1997; Paap, McDonald, Schvaneveldt, & Noel, pseudowords may be processed similarly as both may 1987). engage in mandatory phonologic sublexical processes Unfortunately, response times are always measured during reading aloud, and can be read without deep within the distorting lenses of the particular task used. lexical processing, whereas in the lexical decision task, To overcome this problem, most current studies use a more lexical processing is needed to decide whether multitask approach (e.g., a combination of lexical deci- a particular string of letters is a word or not. Such dif- sion and reading aloud) to study word recognition ferent task demands may reflect a differential pattern of processes because the comparison among different activation for pseudowords and words in the two tasks. tasks permits a more comprehensive analysis of the core To date, however, the task-dependent nature of lexi- processes underlying lexical access (Carreiras et al., cality effects on blood-oxygen-level-dependent (BOLD) 1997). The performance in these two tasks clearly re- signal may have been confounded by different proce- lates to core shared basic processes involved in visual dures (e.g., block designs vs. event-related designs), word recognition (see Carreiras et al., 1997; Grainger & different materials, and different languages. To our Jacobs, 1996, for the idea of functional overlap). How- knowledge, only one previous functional magnetic res- ever, each task also promotes the use of particular onance imaging (fMRI) study has directly compared input–output processes. For instance, the reading-aloud the neuronal implementation of reading aloud and lexi- task requires the activation of articulatory phonologic cal decision with the same group of participants (Katz codes, whereas such processes are not necessarily re- et al., 2005). However, this study did not manipulate quired in the lexical decision task. lexicality during the reading-aloud task, which presented Functional imaging studies have started to investigate only a limited number of words and no pseudowords. the biological basis of visual word recognition during Therefore, although a similarity in the activation pat- both reading aloud (e.g., Binder, Medler, Deasi, Conant, tern for lexical decision and reading aloud is noted, no & Liebenthal, 2005; Heim et al., 2005; Mechelli et al., formal task comparison is reported, nor was it possible 2005; Price et al., 2003; Turkeltaub, Eden, Jones, & to examine the effect of task on lexicality. In contrast, Zeffiro, 2002; Fiez, Balota, Raichle, & Petersen, 1999; the fMRI study we report below recorded hemody- Hagoort et al., 1999, among others) and lexical decision namic responses to words and pseudowords during (Katz et al., 2005; Ischebeck et al., 2004;1 Binder et al., reading aloud and lexical decision to ascertain the com- 2003; Fiebach, Friederici, Mu¨ller, & von Cramon, 2002; mon and unique activation patterns for each task, stim- Mummery, Shallice, & Price, 1999; Price et al., 1994), ulus