A Case of Vocal Motor Amusia in a Non-musician Following Cerebral Infarction in the Right Hemisphere─Disorder of Pitch Expression during Singing─

Abstract

  We report a patient with vocal amusia who was not a musician. The patient was an 81-year-old right-handed woman whose singing ability decreased after infarctions in the right hemisphere. This change was not accompanied by dysarthria or dysprosody. On head MRI, cerebral infarctions were detected mainly in the cortex and subcortical region of the right precentral gyrus, and extended to the central region of the insula, cortex of the posterior end of the middle frontal gyrus, and a part of the medial cortex of the superior temporal gyrus. To define the characteristics of the disorder in this case and investigate the association with the developmental mechanism and lesions, receptiveness and expressiveness of music were compared between the patient and 8 control subjects. Music receptiveness had not declined in the patient, but abnormal pitch expression in music expressiveness and flattening to a lower pitch than the target sound were noted, in contrast to the control group. These changes suggest that disorder of pitch expression during singing was not caused by motor or music-receptive disorder, and that the main lesions in the motor-related area of the right frontal lobe and central area of the right insula were involved in pitch phonation control.