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Congenital amusia: a group study of adults afflicted with a music-specific disorder Ayotte J, Peretz I, Hyde K Brain 2002 Feb, 125: 238-251 Congenital amusia: a disorder of fine-grained pitch discrimination Peretz I, Ayotte J, Zatorre RJ, Mehler J, Ahad P, Penhune VB, Jutras
B Neuron 2002 Jan, 33: 185-191 Comment: Not all who keep away from music are pitch-deaf. But those who are have good reasons to do so. Based on previous large-scale studies in Britain (1948, 1980) it could be estimated that about 4-5 % of the population are amusical. The definition of amusia, however, had always been lacking a satisfactory empirical basis. This situation may now change. Ayotte, Peretz, and others tested eleven adults (first study) and one in more detail (second study) on various musical and linguistic abilities. All persons were highly educated and had self-declared a handicap for music, which was then confirmed in a careful pre-test screening. The most remarkable result is that all musical disabilities may be caused by one single deficit: pitch-deafness. Because the handicap did not affect speech, timbre perception, or large tone intervals, we can assume that only the pitch detector, presumably in the auditory midbrain, was dysfunctional. Further studies are likely to reveal the genetic origin of pitch-deafness, which in turn can lead to a major step forward in clarifying the brain function of pitch detection. (Comment Martin Braun) From p. 250 of the first article: "On the basis of the present behavioural results and in line with
the literature, we propose that one likely origin for congenital amusia
is related to a deficiency in musical pitch recognition. Indeed, all amusical
participants score below the normal range in the discrimination of musical
stimuli that differ on the pitch dimension, while a majority of them succeed
in discriminating the same stimuli when these differ in temporal structure.
This difficulty in detecting pitch-related changes extends to dissonance,
for which amusical subjects show little sensitivity. The pitch-related
defect also extends to the detection of an anomalous pitch inserted in
an otherwise conventional melody. This task is particularly sensitive
to the presence of amusia since there was no overlap between the normal
variations and the scores of the amusical subjects. The test is diagnostic
in the sense that it provides a behavioural marker of congenital amusia.
Interestingly, the detection of an anomalous pitch in conventional melodies
is a test that is very similar to that originally used by Kalmus and Fry
to discover congenital amusical subjects in the general British population
(Kalmus and Fry, 1980). More importantly, the test has been shown to tap
an ability that is genetically determined in the general population (Drayna
et al., 2001). Therefore, it is tempting to propose that heritability
of pitch recognition abilities can also be demonstrated by its deficiency,
and that its manifestation is congenital amusia." |