Functional neuroanatomy of verbal self-monitoring

The neural correlates of verbal self-monitoring were examined by measuring the response to alternations in auditory verbal feedback while subjects read aloud. Six normal subjects were studied with PET, using (H2O)-O-15 as a tracer of regional CBF. There was no difference between the temporal cortical response to reading aloud (and hearing one's own speech) and reading silently while hearing the words spoken by someone else. Distortion of subjects' speech (by pitch elevation) while they read aloud led to a bilateral activation of lateral temporal cortex, with a greater response on the right side than the left. A similar pattern of activation was evident when subjects read aloud, but the words they heard were spoken by someone else. These data suggest that (i) self- and externally generated speech are processed in similar regions of temporal cortex, and (ii) the monitoring of self-generated speech involves the temporal cortex bilaterally, in areas associated with the processing of speech which has been generated externally

Functional anatomy of inner speech and auditory verbal imagery

The neural correlates of inner speech and of auditory verbal imagery were examined in normal volunteers, using positron emission tomography (PET). Subjects were shown single words which they used to generate short, stereotyped sentences without speaking. In an inner speech task, sentences were silently articulated, while in an auditory verbal imagery condition, subjects imagined sentences being spoken to them in an another person's voice. Inner speech was associated with increased activity in the left inferior frontal gyrus. Auditory verbal imagery was associated with increases in the same region, and in the left premotor cortex, the supplementary motor area and the left temporal cortex. The data suggest that the silent articulation of sentences involves activity in an area concerned with speech generation, while imagining speech is associated with additional activity in regions associated with speech perception