The goal of the study was to investigate the neural circuit recruited by adult readers during performance of a lexical decision task by assessing the relative timing of neurophysiological activity in the brain regions that comprise this circuit. The time course of regional activation associated with lexical decision was studied in 17 adult volunteers using magnetoencephalography. Following activity in mesial occipital cortices, activation progressed to lateral and ventral occipito-temporal regions (often encompassing the posterior portion of the middle temporal gyrus), followed by activity in the superior temporal gyri (STGp), motor/premotor cortices, and the inferior frontal gyrus. The latency of STGp activation relative to the latency of the motor response to the word stimuli did not support critical involvement of this area in lexical decision. Timing, word length, and word frequency effects found for activity in each area are discussed in relation to the purported roles of each region into the brain circuit for reading.
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