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Poster A58, Wednesday, November 8, 10:30 – 11:45 am, Harborview and Loch Raven Ballrooms

Sight or Sound? Individual Differences in the Neural and Cognitive Mechanisms of Single Word Reading

Simon Fischer-Baum1, Jeong Hwan Kook1, Yoseph Lee1, Aurora Ramos-Nuñez1, Marina Vannucci1;1Rice University

Most research on reading and its neural substrates has focused on a universal theory, identifying the common set of cognitive and neural processes shared across individuals. Within this framework, one area of debate has been the role of phonology in word reading – that is whether phonology is critical for mapping from written form to meaning. In the current study, we consider the possibility that there may be individual differences in the role that phonology plays in reading. Specifically, a group of thirty highly skilled adult readers participated in an experiment lasting two sessions, an fMRI study and a battery of behavioral reading tasks; a pseudohomophone lexical decision experiment that probes the role of phonology in reading (e.g. Rubenstein et al., 2001) and a set of standardized measures of reading skills (Nelson-Denny Reading Test, Brown et al., 1993; Test of Word Reading Efficiency, Torgesen et al., 2012). During the fMRI portion of the study, participants read aloud regular and irregular words and pronounceable pseudowords. We then applied a novel, data-driven approach to analyzing multi-subject, task-based fMRI data (Zhang et al., 2016) that clustered subjects into subgroups characterized by similar patterns of brain responses across the whole brain to written words. With this approach we identified two, roughly equally sized clusters of participants and a single outlier. We then compared these two groups on their performance on the behavioral reading tasks. Strikingly, the two groups differed in performance on the pseudohomophone lexical decision task. While there were no significant differences between individuals in Cluster 1 and 2 in the overall lexical decision time, the group by nonword-type interaction was significant (F(1,26) = 6.50, p = .017). Specifically, individuals in Cluster 2 showed a robust pseudohomophone effect (596 vs. 577, t(15) = 4.58, p = .0004), with slower reaction times for pseudowords that were pronounced like real words (e.g., BRANE) compared to matched pseudwords that were not pronounced like real words (e.g. BRAME). In contrast, Cluster 1 showed no pseudohomophone effect (625 vs 622, t(11) = .85, p =.42). The groups did not differ in their performance on any of the standardized measures of reading skill, from reading comprehension to vocabulary knowledge to decoding ability. The pseudohomophone effect has been used to argue that phonological information plays an important role in lexical access for visually presented words (e.g. Frost, 1998). Based on this logic, our results suggest hetereogeneity in the role of phonology during visual word recognition, with one group showing clear effects of phonology during reading and the other group not showing any effect. This heterogeneity can be interpreted in the context of dual-route theories of reading aloud, further assuming that some readers depend more on lexical/semantic processing while other readers depend more on sublexical/phonological processing, with no differences in overt reading skill between these different modes of reading. In general, cognitive neuroscience needs to consider not only what tends to be true of group-average data, but also the patterns of variability that are observed across the population.

Topic Area: Perception: Orthographic and Other Visual Processes

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