The Cognitive Neuroscience of Music

while a majority of them succeed to discriminate the same stimuli when these differ in
temporal structure. None of the amusic subjects is experiencing an isolated deficit on the
rhythmic dimension. This difficulty in detecting pitch-related changes extends to disso-
nance for which amusics show little sensitivity.^21 The defect also extends to the detection of
an anomalous pitch inserted in an otherwise conventional melody.^21 We propose that one
likely origin for congenital amusia is related to a deficiency in musical pitch recognition.19,21
The deficit seems limited to music. Amusic subjects retain the ability to process non-
musical material as well as their matched controls. In one set of tests originally designed for
music agnosic patients,^7 amusic participants, and their matched controls are presented with
standard memory recognition tasks that only differ by the domain from which the test items
are taken. In the music memory test, subjects are presented with 20 instrumental tunes
(taken from familiar songs) to memorize. The melodies are then represented among 20
unstudied (but equally familiar) melodies that are randomly mixed. The subject is requested
to indicate which melodies were heard in the study phase. For comparison purposes, in the
lyrics and the environmental sound tests, subjects are given similar opportunities to learn
and recognize 20 spoken lyrics (taken from the same familiar songs) and 20 environmental
sounds (e.g. a barking dog), respectively. The three tests are performed in different sessions.

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Figure 13.1 Percentage of correct responses obtained by 21 congenital amusics relative to the normal distribu-
tion (constituted by 60 nonmusicians, age range: 14–74 years; education range: 7–20 years) in two series of tests
of the montreal battery of evaluation of amusia17–19assessing melodic change discrimination (abscissa) and
rhythmic change discrimination (ordinate axis). Chance level is at 50 per cent of correct responses.

100

90

80

70

60

Rhythm (% C.R.)

50

50 60 70 80 90 100

Melody (% C.R.)

Control subjects

Amusic subjects

Monica