Functional MRI Evidence of an Abnormal Neural Network for Pitch Processing in Congenital Amusia

Abstract

Congenital amusia (tone deafness) is a lifelong disorder that prevents typically developing individuals from acquiring basic musical skills. Electrophysiological evidence indicates that congenital amusia is related to a musical pitch deficit that does not seem to arise from a dysfunction of the auditory cortex but rather from an anomaly along a frontotemporal auditory pathway. In order to better localize the neural basis of this pitch disorder, here we conducted a functional magnetic resonance imaging (fMRI) study. Congenital amusic adults and "musically intact" controls were scanned while passively listening to pure-tone melodic-like sequences in which the pitch distance between consecutive tones was varied parametrically. In both amusics and controls, brain activity increased as a function of increasing pitch distance, even for fine pitch changes, in both the left and right auditory cortices. These results support prior electrophysiological work showing that the auditory cortex of amusic individuals responds normally to pitch. In contrast, the right inferior frontal gyrus showed an abnormal deactivation in the amusic group, as well as reduced connectivity with the auditory cortex as compared with controls. These fMRI data are highly consistent with previous gray and white matter anomalies found in amusics in the auditory and inferior frontal cortices, as well as reduced white matter connections between these 2 regions.