Functional neuroanatomy of segmenting speech and nonspeech.

This fMRI study investigates the extent to which frontal brain activation observed during speech discrimination is due to processes specific to articulatory recoding of speech or is due to segmenting and comparing portions of any continuous acoustic stimuli. A set of ten participants performed same/different judgments on the first speech sound in pairs of consonant-vowel-consonant (CVC) syllables or the first tone in pairs of sequences of three tones. Comparison between speech and tone tasks demonstrated significant bilateral temporal activation, which was associated with differences in perceptual analysis of complex acoustic stimuli. Both speech and tone tasks also showed significant activation in the left inferior frontal gyrus (IFG) compared to baseline. These results suggest that portions of the left prefrontal cortex may be important for selecting and comparing auditory stimuli for decision, but may not be specifically related to speech.