Neural mechanisms of selective listening to pitch and timbre in musical sounds

Abstract

Previous research showed that different dimensions of sound such as pitch and timbre elicit distinct patterns of neural activities. Here, we report event related potential (ERP) along with functional magnetic resonance imaging (fMRI) data during a selective listening task of musical sounds. The participants were 12 normal adults. The stimuli were 4 musical tones with timbre (piano vs. violin) and pitch (high vs. low) contrasts. The stimuli were normalized for duration and intensity. In the timbre condition, the listener needed to indicate the instrument category. In the pitch condition, the listener needed to indicate the pitch level. While both conditions reached the ceiling-level accuracy, the pitch condition required significantly longer reaction time. Significant fMRI activations were found in the superior temporal gyri with right dominance for both conditions. The right superior temporal gyrus and left inferior frontal regions were important for coding pitch whereas the anterior cingulate cortex was exclusively active in selectively attending to timbre. These data demonstrate how different cortical networks contribute to selective listening. The ERP data further showed larger N1 and N2 peaks for the timbre condition than the pitch condition, suggesting that attentional modulation operates at both early and later stages of processing for selective listening.