Parametrically dissociating speech and nonspeech perception in the brain using fMRI

Candidate brain regions constituting a neural network for preattentive phon etic perception were identified with fMRI and multivariate multiple regress ion of imaging data. Stimuli contrasted along speech/nonspeech, acoustic, o r phonetic complexity (three levels each) and natural/synthetic dimensions. Seven distributed brain regions' activity correlated with speech and speec h complexity dimensions, including five left-sided foci [posterior superior temporal gyrus (STG). angular gyrus, ventral occipitotemporal cortex, infe rior/posterior supramarginal gyrus, and middle frontal gyrus (MFG)] and two right-sided foci (posterior STG and anterior insula). Only the left MFG di scriminated natural and synthetic speech. The data also supported a paralle l rather than serial model of auditory speech and nonspeech perception. (C) 2001 Academic Press.