The amusic brain: in tune, out of key, and unaware

TLDR

Music engagement is universal, yet about 4 % of people suffer from congenital amusia, a hereditary pitch‑perception deficit associated with abnormal grey and white matter in the auditory and inferior frontal cortices. The study aimed to link these anatomical anomalies to behavioral deficits by measuring brain activity while participants monitored melodies for pitch anomalies. EEG recordings were taken as subjects listened to melodies and identified pitch deviations. Amusic brains can detect quarter‑tone differences, showing early right‑lateralized negative responses that indicate near‑normal neural processing of fine‑grained pitch, but they lack awareness and responsiveness to semitone changes, revealing a disconnect between neural pitch representation and musical pitch knowledge.

Abstract

Like language, music engagement is universal, complex and present early in life. However, ∼4% of the general population experiences a lifelong deficit in music perception that cannot be explained by hearing loss, brain damage, intellectual deficiencies or lack of exposure. This musical disorder, commonly known as tone-deafness and now termed congenital amusia, affects mostly the melodic pitch dimension. Congenital amusia is hereditary and is associated with abnormal grey and white matter in the auditory cortex and the inferior frontal cortex. In order to relate these anatomical anomalies to the behavioural expression of the disorder, we measured the electrical brain activity of amusic subjects and matched controls while they monitored melodies for the presence of pitch anomalies. Contrary to current reports, we show that the amusic brain can track quarter-tone pitch differences, exhibiting an early right-lateralized negative brain response. This suggests near-normal neural processing of musical pitch incongruities in congenital amusia. It is important because it reveals that the amusic brain is equipped with the essential neural circuitry to perceive fine-grained pitch differences. What distinguishes the amusic from the normal brain is the limited awareness of this ability and the lack of responsiveness to the semitone changes that violate musical keys. These findings suggest that, in the amusic brain, the neural pitch representation cannot make contact with musical pitch knowledge along the auditory-frontal neural pathway.