Neural substrates of orthographic lexical access as demonstrated by functional brain imaging

Objective: To delineate regions involved in visual word recognition. Backgr ound: The processes and regions involved in visual word recognition have be en somewhat controversial for over 100 years. Methods: This study used regi onal cerebral blood flow as assessed by functional magnetic resonance imagi ng to study normal subjects (N = 9) on an individual within-subject basis w hile they were actively engaged on-line in a visual lexical decision task. Standard analysis techniques were used for identifying regions of activatio n. Results: Across subjects, the task activated a number of regions, includ ing the occipital pole, lateral and basal occipitotemporal (including lingu al and fusiform) regions, superior and middle temporal gyri, and supramargi nal and angular gyri. Typically, these regions were activated bilaterally; when activation was unilateral, it was on the left. Some of the areas activ ated (e.g., inferior parietal regions) have not been previously reported to be involved in such types of processing by activation studies but have bee n implicated in lesion studies. Conclusions: These results broaden the area s known to be involved in visual word recognition. The bilateral activation associated with visual word recognition is in some respects analogous to t he "what" system in visual recognition described in subhuman primates. In a ddition, the study raises several methodologic issues. The within-subject a nalysis showed variability in the specific regions activated when subsequen tly comparing across individuals, raising implications for future functiona l imaging studies.