L’anhédonie musicale : des neurosciences à la psychiatrie

Abstract

Music has always been part of our culture. Listening to it can convey strong and many emotions in humans. By its capacity to move us, it occupies an important value in the lives of people. There are important differences in the ability to enjoy listening to music. Some people will find music more enjoyable than others. Part of the population is unable to experience pleasure, or has lost the ability to do so. This fact is called “musical anhedonia”. Mas-Herrero et al. have developed a psychometric instrument that studies this sensitivity to musical reward; this is the “Barcelona Music Reward Questionnaire”. Mas-Herrero et al. in 2014, measured the physiological responses of subjects insensitive to music. They found that these people had no changes in their heart rate, temperature or sweat levels when listening to a piece of music, as well as no subjective sensations such as a chill. They thus confirmed the existence of this musical anhedonia. It is to be distinguished from amusia, which concerns the capacities of sensory perception to music. Amusia, that is not associating with the presence of musical anhedonia, is a rare phenomenon, which appears to involve the lower right frontal gyrus and the upper and right middle temporal gyrus. It is most often the consequence of ischemic or hemorrhagic vascular injury and is more frequent and severe in the presence of an injury to the right hemisphere. Several studies highlight the existence of a musical anhedonia in healthy subjects, not depressed, in the absence of amusia, but also in the absence of a loss of pleasure to the presentation of other stimuli, such as money in particular. We speak of “specific” musical anhedonia to describe a loss of pleasure that only concerns musical stimuli. It is a rare phenomenon. There does not seem to be a relationship between a perception deficit and musical anhedonia. In 5% of people, musical anhedonia is congenital. It can also be acquired following focal brain lesions of various locations. In this case, people with it have lost their ability to enjoy listening to music, which they were likely to experience before. Musical reward appears to be processed by the connectivity that exists between the auditory cortical areas, responsible for analyzing musical content and located at the level of the superior temporal gyrus, and areas of the reward system, responsible for assigning a value, such as the nucleus accumbens (at the level of the ventral striatum), the caudate nucleus (at the level of the dorsal striatum) and the limbic system (amygdala and anterior insula). The enjoyment of listening to music varies from individual to individual on a spectrum from musical anhedonia to musicophilia. Thus, some people are more sensitive than others to the emotional stimuli generated by music. The “Barcelona Music Reward Questionnaire” by Mas-Herrero et al. allows individuals to be divided into three classes according to their emotional and sensory experience of music: “anhedonic”, “hedonic” and “highly hedonic” or musicophiles. The context in which a melody is heard for the first time would be crucial. Indeed, there would be an association between a positive or negative emotional experience with music. It also appears that the same neural circuits are activated when listening to sad or happy music, resulting in dopaminergic release. Musical pleasure seems to remain intact in a wide variety of neurological disorders involving impaired cognitive functions, such as Alzheimer's disease, frontotemporal dementia and even Parkinson's disease. Anhedonia is one of the psychopathological features present in many mental disorders such as major depression and schizophrenia. Although anhedonia is a major symptom of depression, the literature on the subject has not yet established the link between musical anhedonia and depression. When it comes to schizophrenia, anhedonia can be considered a negative symptom of the disease. To date, we have not found any studies linking depression and loss of pleasure specific to music.