Lateralization of phonetic and pitch discrimination in speech processing

TLDR

PET measured cerebral activation in ten volunteers. Noise bursts activated primary auditory cortex, while speech syllables engaged bilateral secondary auditory cortices; attribute judgments elicited lateralized networks, with phonetic discrimination recruiting left Broca’s area and pitch changes engaging right prefrontal cortex.

Abstract

Cerebral activation was measured with positron emission tomography in ten human volunteers. The primary auditory cortex showed increased activity in response to noise bursts, whereas acoustically matched speech syllables activated secondary auditory cortices bilaterally. Instructions to make judgments about different attributes of the same speech signal resulted in activation of specific lateralized neural systems. Discrimination of phonetic structure led to increased activity in part of Broca's area of the left hemisphere, suggesting a role for articulatory recoding in phonetic perception. Processing changes in pitch produced activation of the right prefrontal cortex, consistent with the importance of right-hemisphere mechanisms in pitch perception.