PHONOLOGICAL AND ORTHOGRAPHIC COMPONENTS OF WORD RECOGNITION - A PET-RCBF STUDY

Pronunciation (of irregular/inconsistent words and of pseudowords) and lexical decision-making tasks were used with O-15 PET to examine the neural correlates of phonological and orthographic processing in 14 he althy right-handed men (aged 18-40 years). Relative to a visual-fixati on control task, all four experimental tasks elicited a left-lateraliz ed stream of activation involving the lingual and fusiform gyri, perir olandic cortex, thalamus and anterior cingulate. Both pronunciation ta sks activated the left superior temporal gyrus, with significantly gre ater activation seen there during phonological (pseudoword) than durin g orthographic (real word) pronunciation. The left inferior frontal co rtex was activated by both decision-making tasks; more intense and wid espread activation was seen there during phonological, than during ort hographic, decision making, with the activation during phonological de cision-making extending into the left insula. Correlations of referenc e voxels in the left superior temporal gyrus and left inferior frontal region with the rest of the brain were highly similar for the phonolo gical and orthographic versions of each task type. These results are c onsistent with connectionist models of reading, which hypothesize that both real words and pseudowords are processed within a common neural network.