Learning to Read an Alphabet of Human Faces Produces Left-lateralized Training Effects in the Fusiform Gyrus

Numerous functional neuroimaging studies have shown that most orthographic stimuli, such as printed English words, produce a left-lateralized response within the fusiform gyrus (FG) at a characteristic location termed the visual word form area (VWFA). We developed an experimental alphabet (FaceFont) comprising 35 face-phoneme pairs to disentangle phonological and perceptual influences on the lateralization of orthographic processing within the FG. Using functional imaging, we found that a region in the vicinity of the VWFA responded to FaceFont words more strongly in trained versus untrained participants, whereas no differences were observed in the right FG. The trained response magnitudes in the left FG region correlated with behavioral reading performance, providing strong evidence that the neural tissue recruited by training supported the newly acquired reading skill. These results indicate that the left lateralization of the orthographic processing is not restricted to stimuli with particular visual-perceptual features. Instead, lateralization may occur because the anatomical projections in the vicinity of the VWFA provide a unique interconnection between the visual system and left-lateralized language areas involved in the representation of speech.