Congenital amusia (commonly known as “tone deafness”) is a lifelong impairment of music perception that affects 4% of the population. To estimate whether congenital amusia can be genetically transmitted, its prevalence was quantified by direct auditory testing of 71 members of 9 large families of amusic probands, as well as of 75 members of 10 control families. The results confirm that congenital amusia is expressed by a deficit in processing musical pitch but not musical time and also show that the pitch disorder has a hereditary component. In amusic families, 39% of first-degree relatives have the same cognitive disorder, whereas only 3% have it in the control families. The identification of multiplex families with a high relative risk of experiencing a musical pitch deficit (λs=10.8; 95% confidence interval 8–13.5) enables the mapping of genetic loci for hereditary amusia.
Brain. 2009 May;132(Pt 5):1277-86. doi: 10.1093/brain/awp055. Epub 2009 Mar 31.
BRAMS Laboratory and Department of Psychology, University of Montreal, C.P. 6128, succ. Centre-ville, Montreal, Québec, Canada H3C 3J7. firstname.lastname@example.org
Like language, music engagement is universal, complex and present early in life. However, approximately 4% of the general population experiences a lifelong deficit in music perception that cannot be explained by hearing loss, brain damage, intellectual deficiencies or lack of exposure. This musical disorder, commonly known as tone-deafness and now termed congenital amusia, affects mostly the melodic pitch dimension. Congenital amusia is hereditary and is associated with abnormal grey and white matter in the auditory cortex and the inferior frontal cortex. In order to relate these anatomical anomalies to the behavioural expression of the disorder, we measured the electrical brain activity of amusic subjects and matched controls while they monitored melodies for the presence of pitch anomalies. Contrary to current reports, we show that the amusic brain can track quarter-tone pitch differences, exhibiting an early right-lateralized negative brain response. This suggests near-normal neural processing of musical pitch incongruities in congenital amusia. It is important because it reveals that the amusic brain is equipped with the essential neural circuitry to perceive fine-grained pitch differences. What distinguishes the amusic from the normal brain is the limited awareness of this ability and the lack of responsiveness to the semitone changes that violate musical keys. These findings suggest that, in the amusic brain, the neural pitch representation cannot make contact with musical pitch knowledge along the auditory-frontal neural pathway.
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Since the first listening test was launched at the end of January 2006 it has been taken 195968 times. The second test was added in 2007 and has been taken 89590 times.
This page contains a summary of the study's progress. The histograms and mean data for each task are still shown below.
Amusia: the story so far...
For most of us the appreciation of music is acquired effortlessly, much like language, in the early years of our lives. This appreciation forms an important social, cultural and emotional role, indeed one that is so central to everyday life that it is difficult for us to imagine being without.
However, people with a disorder recently termed 'congenital amusia' fail to recognize common tunes from their culture, do not hear when notes are 'out of tune' and sometimes report that music sounds like a 'din' or 'banging'. At a perceptual level, congenital amusia is most commonly associated with finding it difficult to notice changes in pitch.
People who experience these phenomena when listening to music are otherwise socially, emotionally and intellectually normal. Famous figures in history, Milton Friedman and Che Guevara, are thought to have been afflicted with the disorder, though such cases must remain anecdotal.
Although difficulties in other areas of sound perception are not immediately obvious, current studies are investigating whether the processing of contours in speech, and other higher-order patterns of sound, might be affected.
The First Case Study of Congenital Amusia
The first reported case of amusia was published more than a century ago but it is only within the last five years that case studies have been anything other than anecdotal. While many people claim to be 'tone-deaf, this is typically a label for people who cannot sing in tune, and it is estimated that only about 4% of the population have perceptual difficulties with listening to music.
The term 'congenital amusia' was introduced as an alternative to tone-deafness. It is now possible to systematically assess different aspects of people's musical listening ability using the Montreal Battery for the Evaluation of Amusia, designed by Isabelle Peretz and colleagues in Canada.
How Does Amusia Manifest?
While most normal listeners can judge the direction of a pitch change with intervals smaller than a semitone, people with amusia often require the change to be much greater. In severe cases, a person with amusia might require two notes to be very far apart in pitch, for instance, the distance between the first two notes of Somewhere over the Rainbow, before they can hear them as different.
Given that most pieces of Western music move in small steps - a semitone is a very commonly occurring interval - it is not surprising that for those with amusia, one song sounds much the same as another. However, this inability to hear small changes in pitch is clearly not the whole story, since those with amusia also perform poorly when required to tell the difference between two musical phrases, even when the constituent pitch changes of the phrases can all be heard. This shows that the relationship between the ability to hear a pitch change between two notes in isolation, and the ability to hear a single change in the context of a whole phrase of music is a complex one.
Amusia and language
Amusics have normal intellectual functioning and do not appear to have any difficulty in understanding speech, including the melody of speech. The intact ability to hear the music of speech may be related to the fact that, in languages such as English, pitch changes are often several semitones and commonly co- occur with changes in stress and timing, therefore problems in hearing subtle pitch changes will not be a limiting factor. In the future, it will be important to investigate whether amusics who speak a tonal language, such as Mandarin, are sensitive to pitch changes in a linguistic context, where subtle changes can profoundly alter semantic meaning.
Amusia and rhythm
While most amusics appear to have no problems with rhythm perception, this aspect of the disorder seems variable (Che Guevara was notoriously useless on the dance floor, as depicted in the film The Motorcycle Diaries). One study found that those with amusia could not spot a subtle change in pitch but were able to spot deviations in time. However, other researchers have found that problems with timing are seen when the pitch context is more complex and have suggested that difficulties with pitch may have knock-on consequences for the development of rhythmic skills.
Do those with Amusia have different Brains?
Amusics do not have a history of neurological damage and structural brain imaging using magnetic resonance imaging (MRI) does not reveal any obvious anatomical differences. However, the technique of voxel-based morphometry allows MRI data from two groups, for example amusics versus non- amusics, to be compared in terms of differences in volume of grey and white brain matter.
A recent study using this approach revealed subtle differences in white matter (the neural connections) between amusics and control participants in the right frontal cortex, suggesting that abnormalities occur in areas outside of the auditory cortices. We know from neuroimaging studies that this area is involved in musical perception, and seems to be particularly important for the sequential aspect of musical listening.
The condition of congenital amusia, commonly known as tone‐deafness, has been described for more than a century, but has received little empirical attention. In the present study, a research effort has been made to document in detail the behavioural manifestations of congenital amusia. A group of 11 adults, fitting stringent criteria of musical disabilities, were examined in a series of tests originally designed to assess the presence and specificity of musical disorders in brain‐damaged patients. The results show that congenital amusia is related to severe deficiencies in processing pitch variations. The deficit extends to impairments in music memory and recognition as well as in singing and the ability to tap in time to music. Interestingly, the disorder appears specific to the musical domain. Congenital amusical individuals process and recognize speech, including speech prosody, common environmental sounds and human voices, as well as control subjects. Thus, the present study convincingly demonstrates the existence of congenital amusia as a new class of learning disabilities that affect musical abilities.
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