A functional study of auditory verbal imagery

Background. We used functional MRI to examine the functional anatomy of inn er speech and different forms of auditory verbal imagery (imagining speech) in normal volunteers, We hypothesized that generating inner speech and aud itory verbal imagery would be associated with left inferior frontal activat ion, and that generating auditory verbal imagery would involve additional a ctivation in the lateral temporal cortices. Methods. Subjects were scanned, while performing inner speech and auditory verbal imagery tasks, using a 1.5 Tesla magnet. Results. The generation of inner speech was associated with activation in t he left inferior frontal/insula region, the left temporo-parietal cortex, r ight cerebellum and the supplementary motor area. Auditory verbal imagery i n general, as indexed by the three imagery tasks combined, was associated w ith activation in the areas engaged during the inner speech task, plus the left precentral and superior temporal gyri (STG), and the right homologues of all these areas. Conclusions. These results are consistent with the use of the "articulatory loop" during both inner speech and auditory verbal imagery, and the greate r engagement of verbal self-monitoring during auditory verbal imagery.