The neural substrates of writing: A functional magnetic resonance imaging study

Background: Hypotheses regarding the neural substrates of writing have been derived from the study of individuals with acquired agraphia. Functional neuroimaging offers another methodology to test these hypotheses in neurologically intact individuals. Aims: This study was designed to identify possible neural substrates for the linguistic and motor components of writing in normal English-speaking individuals. Methods & procedures: Functional magnetic resonance imaging was used with 12 adults to examine activation associated with generative writing of words from semantic categories contrasted with writing letters of the alphabet and drawing circles. In addition, the generative writing condition was contrasted with a subvocal generative naming condition. Outcomes & results: Semantically guided retrieval of orthographic word forms for the generative writing condition revealed activation in the left inferior and dorsolateral prefrontal cortex, as well as the left posterior inferior temporal lobe (BA 37). However, no activation was detected in the left angular gyrus (BA 39). The motor components of writing were associated with activation in left fronto-parietal cortex including the region of the intraparietal sulcus, superior parietal lobule, dorsolateral and medial premotor cortex, and sensorimotor areas for the hand. Conclusions: These observations suggest an important role of the left posterior inferior temporal cortex in lexical-orthographic processing and fail to support the long-held notion that the dominant angular gyrus is the storage site for orthographic representations of familiar words. Our findings also demonstrate the involvement of left superior parietal and frontal premotor regions in translating orthographic information into appropriate hand movements.