Cortical representations of pitch in monkeys and humans

Abstract

Pitch perception is crucial for vocal communication, music perception, and auditory object processing in a complex acoustic environment. How pitch is represented in the cerebral cortex has for a long time remained an unanswered question in auditory neuroscience. Several lines of evidence now point to a distinct non-primary region of auditory cortex in primates that contains a cortical representation of pitch.

Figure 1

Example of the spectrum and acoustic waveform for three different acoustic signals that have the same pitch (100 Hz). A. Harmonic complex tone: composed of the 1^st (fundamental), 2^nd, and 3^rd harmonic, each with randomized phase. B. Repeated broadband noise burst (100 Hz repetition rate). C. Missing fundamental harmonic complex tone: composed of the 2^nd, 3^rd, and 4^th harmonic, all in cosine phase.

Figure 2

Diagram of human and marmoset auditory cortex A. Side view of a human brain (top), horizontal cross section of temporal lobe (middle), and zoomed in view of Heschl’s gyrus (bottom). Primary auditory cortex is presumed to occupy the medial portion of Heschl’s gyrus (with variability between subjects). The location of neighboring areas (R, pitch center, lateral belt) is an approximation based on Schneider et al. [6], Formisano et al. [33], and Patterson et al. [3]. B. Side view of a marmoset monkey’s brain (top) and a zoomed in view of the temporal lobe (bottom), indicating core, belt, parabelt, and the pitch center. The borders between each auditory area are estimated based on data from Bendor and Wang [7], and Pistorio et al. [60]. Legend: HG-Heschl’s gyrus, STG-Superior temporal gyrus, ITG-Inferior temporal gyrus, aSTG-Anterior superior temporal gyrus, PT-Planum temporale, SI-Intermediate sulcus, HS-Heschl’s sulcus, CS-Circular sulcus, FTS-First transverse sulcus, LS-Lateral sulcus, STS-Superior temporal sulcus, AI-Primary auditory cortex, R-Area R (Rostral auditory cortex), RT-Area RT (Rostrotemporal auditory cortex)