Neural Substrates of Amusia: Insights from a Narrative Review of Pure Acquired Amusia Cases.

BACKGROUND: Approximately 100 cases of amusia have been documented to date. However, the neural mechanisms underlying amusia remain insufficiently understood. AIMS: This narrative review aims to synthesize existing literature on amusia, with a particular focus on reported cases of "pure acquired amusia" which means the acquired selective impairment of music processing in the brain. METHODS: The clinical characteristics of documented cases with pure acquired amusia were comprehensively reviewed and summarized. Furthermore, common lesion sites were identified by analyzing the lesion data from cases, and the crucial regions for music processing was estimated. RESULTS: Eleven cases with pure acquired amusia were identified. Analyses of symptoms and lesion sites revealed following things: first, most of cases with pure acquired amusia was caused by right hemisphere lesion. Second, there are three brain regions which damaged in many cases, that is superior temporal gyrus, insula, isthmus, and temporal pole. Third, until now, pure cases with musical alexia and/or agraphia have not been reported. CONCLUSION: These findings suggest that there are some brain regions which play a crucial role in music processing: the right superior temporal gyrus, the isthmus, the insula, and the temporal pole.