Brain injuries may affect motor or expressive functioning, including the ability to sing, whistle, or hum a tune (oral-expressive amusia), the ability to play an instrument (instrumental amusia or musical apraxia), and the ability to write music (musical agraphia). Additionally, brain damage to the receptive dimension affects the faculty to discriminate tunes (receptive or sensorial amusia), the ability to read music (musical alessia), and the ability to identify songs that were familiar prior to the brain damage (amnesic amusia).Research suggests that patients with amusia also have difficulty when it comes to spatial processing. Amusics performed more quickly than normal individuals on a combined task of both spatial and musical processing tasks, which is most likely due to their deficit. Normal individuals experience interference due to their intact processing of both musical and spatial tasks, while amusics do not. Pitch processing normally depends on the cognitive mechanisms that are usually used to process spatial representations.Those with congenital amusia show impaired performance on discrimination, identification and imitation of sentences with intonational differences in pitch direction in their final word. This suggests that amusia can in subtle ways impair language processing. Social and emotional
Amusic individuals have a remarkable sparing of emotional responses to music in the context of severe and lifelong deficits in processing music. Some individuals with amusia describe music as unpleasant. Others simply refer to it as noise and find it annoying.
While various causes of amusia exist, some general findings that provide insight to the brain mechanisms involved in music processing are discussed below. Pitch relations
Studies suggest that the analysis of pitch is primarily controlled by the right temporal region of the brain. The right secondary auditory cortex processes pitch change and manipulation of fine tunes; specifically, this region distinguishes the multiple pitches that characterize melodic tunes as contour (pitch direction) and interval (frequency ratio between successive notes) information. The right superior temporal gyrus recruits and evaluates contour information, while both right and left temporal regions recruit and evaluate interval information. In addition, the right anterolateral part of Heschls gyrus (primary auditory cortex) is also concerned with processing pitch information. Temporal relations
The brain analyzes the temporal (rhythmic) components of music in two ways: (1) it segments the ongoing sequences of music into temporal events based on duration, and (2) it groups those temporal events to understand the underlying beat to music. Studies on rhythmic discrimination reveal that the right temporal auditory cortex is responsible for temporal segmenting, and the left temporal auditory cortex is responsible for temporal grouping. Other studies suggest the participation of motor cortical areas in rhythm perception and production. Therefore, a lack of involvement and networking between bilateral temporal cortices and neural motor centers may contribute to both congenital and acquired amusia. Memory
Memory is required in order to process and integrate both melodic and rhythmic aspects of music.