Walsh & Hoyt: Functional Imaging of Reading

Only a few functional neuroimaging studies of visual language processing have been published, with conflicting results. Interestingly, activation of the left angular gyrus has not been found, with the possible exception of one study that found spread from the left posterior temporal lobe into the inferior parietal lobe. Petersen et al. had subjects first passively view words, read words aloud, then describe uses for the objects represented by the words, a task that requires semantic processing. Striate and lateral temporal extrastriate areas were activated by viewing of a word, reading aloud recruited motor and articulation areas, and the semantic association task activated a left lateral inferofrontal area. A later study found activation of the lateral extrastriate areas not only with words and pseudo-words but also with complex letter-like forms (false fonts), suggesting that this was related to processing of complex visual features and not specific for words. Words and pseudo-words, but not the letter-like forms, activated a left medial extrastriate area, which was attributed to activation of visual word forms. Similar preference for alphabetic characters over checkboards has been found in the left medial occipitotemporal sulcus, a region named the ""visual word form area."" While Howard et al. confirmed striate and lateral extrastriate activation with false fonts, they found that reading words activated the left posterior middle temporal gyrus, which they suggested was the location of the visual lexicon.