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Laurie Schwarz Glezer, Xiong Jiang, Maximilian Riesenhuber; fMRI-RA evidence for a neural representation in the “Visual Word Form Area” based on whole words. Journal of Vision 2007;7(9):516. doi: https://doi.org/10.1167/7.9.516.
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© ARVO (1962-2015); The Authors (2016-present)
Successful reading requires the brain to correctly recognize printed words. Recent research has identified an area in the left fusiform gyrus that responds preferentially to written words, termed the “visual word form area” (VWFA). Studies using fMRI rapid adaptation (fMRI-RA) techniques have provided information about the invariance properties of the representation in the VWFA. However, the neural code for individual written words in the occipitotemporal cortex is still not well understood. Here, we used an fMRI-RA paradigm to examine neuronal tuning specificity and the nature of the word representation in the VWFA. Subjects (n=7) performed a primed semantic decision task in the scanner. We examined three conditions: 1) a “same” condition, in which the same word was presented twice (as prime and target) in each RA trial, 2) a “1L” condition in which the prime and target words differed by one letter, and 3) a “different” condition, in which the target word shared no letters with the prime. All words were real high frequency nouns. Our assumption was that the two words in the “different” condition should activate disjoint neuronal populations, leading to maximum release from adaptation, whereas suppression should be strongest in the “same” condition with the two stimuli activating the same neurons. Our results indeed showed that there was significant adaptation in the VWFA for the “same” condition when compared with the “different” and “1L” conditions (p=0.004 and p=0.001, respectively). Interestingly, average BOLD contrast response levels did not differ significantly between the “1L” and “different” conditions (p=0.852), suggesting that even though the two words in the “1L” condition shared sub-lexical units (e.g., letters or bigrams), there was no adaptation when compared to the “different” condition. This suggests that in the VWFA words are processed as whole word units and not as sub-lexical units.
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