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

Review Article

Austin J Clin Neurol 2014;1(2): 1009.

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

Masayuki Satoh*

Dementia Prevention and Therapeutics, Mie University, Japan

*Corresponding author: Masayuki Satoh, Dementia Prevention and Therapeutics, Graduate School of Medicine, Mie University, 2-174 Edobashi, Tsu, Mie 514- 8507, Japan

Received: March 18, 2014; Accepted: April 02, 2014; Published: April 17, 2014


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.

Keywords: Amusia; Neuropsychology; Paramelodia; Conduction amusia; Chord


It is often said that music has no borders. It is also a fact that there are differences in the style and content of music, depending on the culture and the era. However, among members of the same culture, music can evoke the same feeling immediately and easily. For example, adults who live in cultural areas related to western music need less than 0.25 seconds to identify whether the music is happy or sad [1]. This nature of music is assumed to be useful to the adaptation of living in human society. Music can act as a strategy for non-verbal communication, to associate citizens and to facilitate the unity of a group. In this process, two components of music (pitch and rhythm) are thought to play an important role. When some tones sound with a specific frequency ratio, these tones make a consonance. Moreover, the regularity of time makes the movements of most people synchronize, as in dancing [2]. Therefore, one way to know how music is recognized and represented in the brain may be to understand the relationship between human behavior and the brain. In this review, I describe two cases of amusia who showed the impairment of musical ability due to the brain damage, and propose some aspects about the perception and coding of music in the brain.


Definition of amusia

It is widely accepted that neuropsychology began from the first case report of aphasia by Broca. A few years later, it was reported that not only language but also music was impaired by brain damage [3].A musician with aphasia could not read a musical score [3] or hum a tune [3]. The concept of amusia appeared on the stage.

Amusia is defined as an acquired deficit of music processing [4]. In musicology, it is thought that melody, rhythm, and harmony are the three basic components of music. Melody is the tonal sequence made up of changes in pitch and rhythm, which are integrated into an entity. In other words, I can say that these three components are pitch, rhythm and harmony. As mentioned below, tonality is sometimes regarded as another component of music [5,6]. Because several cases with pure amusia, meaning the sole impairment of musical ability without affecting the other cognitive functions, have been reported, it was supposed that music has an independent processing in the brain, at least to some extent [7].

Diagnosis and categorization of amusia

Musical ability consists of the perception of the basic components (such as pitch and rhythm), the singing and playing of musical instruments, the reading and writing of musical scores and musical appreciation with emotional experiences [8,9]. When one or more of these abilities are impaired by brain damage, dysfunctionality, and influences of drugs, the patient is diagnosed with amusia.

The categorization of amusia corresponds to that of aphasia (Figure 1). Amusia is generally classified as one of two types, receptive or expressive [10,11]. Receptive amusia specifies an inability to remember (amnestic amusia), read (musical alexia) or understand music (narrow receptive amusia), while expressive amusia indicatesdifficulty in singing (oral–expressive amusia), writing music (musical agraphia), or in instrumental performance (instrumental amusia or musical apraxia) [12]. In reported cases of receptive amusia, the degree of the impairment of pitch and rhythm are different in their severity, suggesting that perception of these two music components occurs independently in the brain [13]. Studies of expressive amusia have shown that the degree of the impairment differs between singing and instrument playing [14], thus expressive amusia is often subdivided into vocal and instrumental motor amusia.