Some neural correlates of speech and nonspeech perception

Abstract

In a series of functional magnetic resonance imaging experiments aimed at examining the perceptual boundary between speech and nonspeech stimuli, brain activation signals were measured while subjects listened passively to a continuum of sounds ranging from noise to speech, detected speech signals in varying levels of noise, and perceived the same sinewave speech replicas as either nonspeech or speech while performing an auditory discrimination task. Activation at the anterolateral aspect of left Heschl’s gyrus increased with signal-to-noise ratio in the passive listening and noise masking experiments, and was higher when subjects heard sinewave speech as nonspeech than when they heard the same stimuli as speech while performing an auditory task that conflicted with the speech percept. Activation in this area was correlated with behavioral measures of phoneme perception and was unrelated to attentional demands. The data suggest a key role for this region in the representation of spectrotemporal information underlying phoneme recognition.