Musical Processing in the Brain: A Neuropsychological Approach through Cases with Amusia

Over the last decade, a considerable number of studies have been made on the cognitive processing of music. In this review, I discuss the cognitive processing of music based on the findings of our amusic cases. A patient with pure amusia (case 1) due to infarction of the anterior portion of the bilateral temporal lobes revealed a disturbance in the discrimination of chords. The patient also showed an impairment in singing familiar songs, along with the replacement of phrases (paramelodia). My positron emission topography (PET) study, which investigated the brain regions participating in chord perception, showed bilateral activation of the anterior portion of the temporal lobes. From the results of this clinical case and PET study, I can reasonably conclude that these brain regions have a relationship with chord perception. The second patient (case 2) had a large infarction of the bilateral temporal lobes, and also exhibited word deafness, environmental sound agnosia and receptive and expressive amusia. Thoughthe patient produced normal scores in tasks of chord and pitch discrimination, the recognition of tonality was impaired. It was suggested that tonality might be one of the independent factors for receptive processing of music. From these findings, some characteristic symptoms of amusia are described and I present a diagram regarding musical processing in the brain.