Hamilton APinBlinds, Ebook, Neuronauka, Psychologia, Psychology of Music
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AUDITORYANDVESTIBULAR SYSTEMS
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Absolute pitch in blind musicians
Roy H. Hamilton,
1, 2
Alvaro Pascual-Leone
1
and Gottfried Schlaug
1,C A
1
Department of Neurology, Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Palmer1, Boston, MA 02215;
2
Harvard Medical School,
Boston, MA,USA
CA
Corresponding Author: gschlaug@bidmc.harvard.edu
Received 8 January 2004; accepted 9 January 2004
DOI:10.1097/01.wnr.0000118981.36602.90
Absolute pitch (AP) is possessed by only a small percentage of mu-
sicians (typically
o
20%). From a sample of 46 early blind subjects,
we identi¢ed 21 who had musical training, 12 of whom (57.1%) re-
ported having AP, re£ecting markedly increased prevalence com-
pared to sighted musicians, despite the fact that mean age of
commencement of musical training was signi¢cantly later among
blind than sighted AP musicians in our database. MR images
acquired in a subset of blind APmusicians revealedgreater variabil-
ity in planum temporale asymmetry compared with the increased
left-sided asymmetry previously described in sighted AP musicians.
This suggests that neural mechanisms underlying AP in blindmusi-
cians could di¡er from those in sighted musicians. NeuroReport
15 : 8 03 ^ 8 0 6 c 2004 Lippincott Williams &Wilkins.
Key words:Absolutepitch;Morphometry;Musicians;Blind;Planumtemporale
2 years while non-AP
musicians typically started 1–2 years later. Even among
early-trained musicians, however, AP occurs in a minority
of individuals, sometimes with a higher than expected
familiar incidence, suggesting that there are additional
factors (e.g. particular anatomical brain features and genetic
traits) that may contribute to the AP phenotype.
Although the neural underpinnings of AP remain unclear,
recent neuroimaging studies have elucidated functional and
anatomical brain correlates to AP [7–11]. A growing body of
data indicates that there are significant differences in brain
morphology between sighted musicians with AP and those
without AP in the planum temporale (PT), a region
traditionally associated with language and auditory proces-
sing. Sighted individuals with AP show an exaggeration of
the normal leftward asymmetry of the PT seen in both right-
handed non-AP musicians and non-musicians [8,11]. Recent
evidence suggests that the basis of this increased asymmetry
is a significant reduction in the size of the right PT with a
non-significant trend for a larger left PT [7]. Recent
functional imaging studies showed activation of the left
more than the right PT in musical tasks in AP musicians, not
seen in non-AP subjects [10,11]. Since the prevalence of AP
7
among Anglo-American musicians is relatively low, there
has been an interest in examining whether AP develops
more frequently among other groups. Several studies have
reported a 2- to 3-fold higher incidence of AP musicians in
Asian countries [2] and among Asian Americans [4]. Other
studies examining relationships between autistic children
and AP suggest that the prevalence of AP among people
with autism could be as high as 1 in 20 (5%) [12]. Patients
with Williams syndrome also seem to have a higher
incidence of AP than one would expect to find in the
normal population [13]. The observation that many blind
musicians achieve very high levels of musical proficiency
has lead to the popular impression that blindness may be
associated with special auditory perceptual skills. Indeed,
there is evidence that early blind subjects are able to localize
sound sources better than sighted subjects [14,15] and that
in doing so they engage parietal and occipital lobe
structures [16–18]. In the present study, we surveyed a
group of blind subjects to determine the incidence of AP
among those who had musical training. We also sought to
determine whether early age at onset of musical training or
interhemispheric asymmetry of the PT seen in sighted AP
musicians play a critical role in the development of AP
among the blind.
MATERIALS AND METHODS
Subjects: A total of 46 early blind individuals was
recruited on a voluntary basis from regional schools for
the blind for previous studies unrelated to musical aptitude,
musical exposure, or AP ability. This group was then
screened for musicianship, and twenty-one (nine males, 12
females; mean age 47.4 years) were either professional or
0959-4965 c Lippincott Williams &Wilkins Vol 15 No 5 9 April 2004
803
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INTRODUCTION
Absolute pitch (AP) is defined as the ability to identify a
particular pitch of the Western musical scale without any
external reference tone [1–3]. AP is present in a minority of
trained Western musicians [4]. The prevalence of AP in the
general population has been estimated as 1/1500–1/10 000
[3]. Several studies into the role of musical training have
demonstrated that AP is more likely to develop if the
commencement of training is early [4–7]. A number of
investigators reported that their groups of AP subjects had a
typical age of commencement of 5
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R. H. HAMILTON, A. PASCUAL-LEONE AND G. SCHLAUG
Ta b l e 1 . Right, left, and combined PTsurface areas and asymmetry coe⁄cients (mean
7
s.d.) in blind and sighted absolute pitchmusicians and sighted non-
musicians.
Right PT
Lef t PT
Total PT
d
PT
AP blind
909.02
7
223.67
1106.23
7
291.83
2015.25
7
332.28
0.18
7
0.39
Non-AP blind
852.53
7
134.66
1225.52
7
13 2 . 41
2 0 7 8 . 0 6
7
203.34
0.36
7
0.17
AP sighted
a
828.17
7
232.61
1401.55
7
444.71
2229.72
7
606.89
0.50
7
0.27
Non-AP sighted
a
1079.02
7
212 .18
1333. 8 2
7
285.84
2412.84
7
461.02
0.21
7
0.16
Non-musician sighted
a
10 43.0 0
283.07
1365.01
7
342.73
2408.01
7
388.01
0.28
0.33
a
Adapted from [7].
Fig. 1. Two blind subjects with AP. Subject (a) had a rightward PTasymmetry, subject (b) had an increased leftward PTasymmetry.The PT is marked in
white on two sagittal slices representing right and left hemisphere (see [8,20] for details on PT delineation).
amateur musicians. The remaining blind subjects did not
have any musical training. All 21 subjects were Caucasian,
blind due to peripheral causes, and had acquired blindness
before age 6. None had any residual vision (absolute
blindness). All of the subjects gave written informed consent
to the study, which was approved by the institutional
review board. Subjects were administered a questionnaire
that queried various aspects of their musical experience and
the presence or absence of AP. Although several groups
have reported a high agreement between self-report of AP
and performance on AP tests [1,4,7,19], we confirmed the
presence of AP using two established tests in a subset of 7
subjects who reported AP and agreed to be tested. Other
subjects who reported AP were unavailable for formal
testing. The first test consisted of 13 sine wave tones taken
from the chromatic scale (F#3 to F#4), repeated randomly
four times for a total of 52 tones. The second AP test
consisted of 12 sine wave tones taken from 4 1/2 octaves (F2
to G5), separated by musical fourths (F2, Bb2, Eb3, etc.),
presented four times in random order for a total of 48 tones.
In each task, subjects listened to the complete set of tones
twice and were permitted to make corrections as they saw
fit. Responses that were within one semitone difference
from the presented tone were regarded as correct [2,19], and
90% accuracy on both tests was set as a cutoff for the
determination of AP ability (see [7] for more details on these
tests). All seven of the blind musicians tested who had
claimed to have absolute pitch were confirmed by these
criteria, thus confirming the validity of our AP question-
naire.
reported AP subjects who were imaged included all seven
subjects who had undergone pitch testing (see above) and
one who had not due to scheduling conflicts. Images were
acquired using a T1-weighted magnetization prepared,
rapid acquisition gradient-echo (MPRAGE) pulse sequence
on a 1.5 T Siemens Vision MR system with echo-planar
imaging capability (Siemens Medical Systems, Erlangen,
Germany). The image dataset had a voxel resolution of
1.0mm
3
.
The anatomical boundaries of the PT were defined
according to previously published criteria [7,11,20]. The PT
contours on sagittal slices were represented as splines in
order to approximate the curvature found in the gyral
pattern of the brain [20]. A triangular mesh was generated
between contours on consecutive slices, and the surface area
was then calculated as a sum of the area of all the triangles
defining the surface of interest. Left-right asymmetry of the
PT surface area was expressed as the asymmetry coefficient
dPT (R
L/(R + L)
0.5) with R and L representing the
surface areas of the right and left PT. Negative values
indicate leftward asymmetry; positive values indicate right-
ward asymmetry (Table 1; Fig. 1).
RESULTS
In our sample of 21 blind musicians 12 (57.1%) reported
having AP. The accuracy of subject self-reporting of AP was
confirmed in a subset of seven of these 12 subjects using
established tests. In comparison to a group of sighted
musicians previously tested in an identical fashion [7], the
prevalence of AP seen in blind musicians was significantly
elevated (w
2
¼
21.60, a
o
0.001). Interestingly, the age of
commencement of musical training among the blind AP
musicians (average 8.0 years; range 3–14 years) was
significantly (t
¼
3.93, p
o
0.001) later (three subjects at age
8, two at 9, one at 10, one at 14) than that which had been
MR data acquisition and morphometric analysis: We were
able to obtain high resolution anatomical scans on a total of
13 subjects. A subset of eight blind subjects with self-
reported AP and five blind subjects without AP underwent
high-resolution magnetic resonance imaging. The eight self-
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7
7
ABSOLUTE PITCH IN BLIND MUSICIANS
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0.39; range
0.98 to
0.25) previously observed in sighted AP musicians (mean
dPT
¼
0.50; range
1.04 to 0.06). In contrast, blind AP
musicians showed a much greater degree of variability in
dPT (Fig. 1) than had been previously demonstrated in
sighted AP musicians, non-AP musicians, and non-musi-
cians [7]. Furthermore, blind AP musicians demonstrated
greater variability of PT asymmetry than blind non-AP
musicians in our subject population (mean dPT
¼
0.36
7
s.d.) dPT
¼
0.18
7
blind. Some subjects were extremely lateralized to the left,
others to the right, and some did not differ from sighted
non-musician control groups. Certain methodological lim-
itations to the current study should be addressed. One
important caveat is that, due to the limited size of our
subject pool of early peripherally blind musicians, subjects
were unselected for handedness. Although blind subjects’
degree of PT asymmetry did not correlate with handedness
in this small subject population, a larger sample of patients
should be tested in order to determine whether handedness
has the same correlation with PT asymmetry indices in blind
subjects as it does in sighted subjects. In addition, hand
preference and hand dominance may be differently dis-
tributed in blind subjects compared to sighted subjects [22].
In this context it is important to note that hand dominance
in early blind subjects is a notably unreliable measure that
may depend on the tasks explored [23]. A second
methodological limitation is that pitch testing was not
pursued among blind musicians who denied having AP or
among blind non-musicians. The correlation between self-
reporting of AP and the presence of AP has in prior
literature been shown to be very high [3,4,7,8], and there is
little reason to suspect that experienced musicians, blind or
sighted, would be unaware of their own AP ability. If,
however, this were not the case for blind musicians
who denied having AP, the actual prevalence of AP
among the blind may have actually been underestimated.
It is also plausible that blind persons irrespective of
musicianship generally have better pitch processing abil-
ities, and that the increased prevalence of AP observed in
our study reflects an overall increase in AP among
blind individuals compared with the sighted. Because AP
in non-musicians is extremely rare, a very large survey of
blind non-musicians would have to be undertaken to
answer this question definitively. Such a finding would
further support our hypothesis that fundamental epidemio-
logic and anatomic differences exist between blind and
sighted subjects with regard to AP ability. Taken together,
the findings of increased prevalence of AP among blind
musicians, their later age at commencement of musical
training, and the lack of a consistently leftward PT
asymmetry suggests that AP, at least in some blind
musicians, could manifest itself through a different mechan-
ism than in the sighted. A growing body of evidence
indicates that early blind subjects are able to recruit
the visually deafferented occipital cortex for non-visual
tasks, including auditory information processing [16–18].
This cross-modal plasticity may provide an additional
substrate for the development of AP in the blind compared
with the sighted, which could account for the higher
than expected prevalence and prolonged critical period of
AP development in the blind. The ability to perceive
auditory stimuli as belonging to categories is one of the
features that differentiates AP musicians from individuals
without AP [24]. Recent evidence demonstrates that visual
association areas are intimately involved in the processing
of categorical visual information [25]. In the absence of
sight, these visual association areas may facilitate categor-
ization of auditory information. Such cross-modal cortical
plasticity may at least partially account for our finding that
blind subjects with AP are not as dependent upon the same
morphologic changes in the auditory cortex that correlate
with AP ability among the sighted.
7
0.17; range
0.58 to
0.11) (Table 1).
18%. For reasons that are yet to be fully
explained, the prevalence of AP among Asians is higher [4].
Our finding of a 57.1% prevalence of AP among a group of
blind Caucasian musicians is therefore remarkable. Further-
more, these results add to a growing body of data regarding
the interactions between environmental and presumed
genetic factors in the development of AP. Studies demon-
strating increased prevalence of AP within families [4], and
observations from twins studies [21] suggest a heritable
component to pitch discrimination ability. Since all of the
blind musicians in our study were rendered blind by
peripheral causes that occurred after birth, the high
prevalence of AP in these subjects indicates that an
environmental stimulus such as the loss of sight can
somehow facilitate the development of AP, leading to a
higher number of AP in this group then would be expected
based on the incidence in sighted groups. In previous
studies among sighted subjects, AP was found to most likely
manifest itself during a critical period of development early
in life, during which time exposure to music was a
prerequisite [4–7]. In blind subjects however, it seems
that an early age of commencement of musical training
does not play as critical a role. Even in our small sample
of blind subjects, several individuals with AP had not
initiated musical training until their late childhood or
adolescence, which is unusually late compared to sighted
individuals with AP. This suggests that in blind subjects,
even late onset of musical training serves to induce
the neural changes that may underlie the development of
AP. It is tempting to hypothesize that the plastic changes
induced in the brain by blindness [16–18] contribute to
this fact. Finally, among sighted subjects with AP, PT
asymmetry has been shown to be a critical factor in the
development of AP [7,8,11]. Our preliminary morphometric
data suggests that the increased leftward asymmetry of the
PT that has been robustly demonstrated in sighted AP
musicians is not a necessary feature of AP among the
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observed among sighted AP musicians (average 5.2 years;
range 3–7 years) taken from our database of AP musicians.
Blind AP musicians (unselected for handedness) did not
demonstrate the same increased planum temporale asym-
metry (mean (
DISCUSSION
This study builds upon a body of prior evidence in which
key characteristics of AP in sighted patients have been
convincingly demonstrated. The results of this study
suggest that there are at least three major differences in
the phenomenology of AP between sighted and blind
musicians: (1) increased prevalence of AP among blind
musicians, (2) later onset of musical training among blind
AP musicians, and (3) increased variability of PT asymmetry
among blind AP musicians.
The highest reported prevalence of AP among Caucasian
musicians is
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R. H. HAMILTON, A. PASCUAL-LEONE AND G. SCHLAUG
CONCLUSIONS
While this study is limited in its scope, and does not
establish a specific mechanism for the acquisition of AP in
blind musicians, our results argue that AP among the blind
is not due to an enhancement of the same determinants that
are critical among the sighted: early musical training and
increased PT asymmetry. The notion that cross-modal
plasticity involving the occipital cortex may provide an
additional neural substrate for the development of AP in the
blind is an intriguing hypothesis that merits further
investigation. It would be informative for future studies to
replicate the current findings in larger populations of blind
musicians as well as to further investigate the anatomic and
functional underpinnings of AP in blind and sighted
musicians.
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Acknowledgements: We would like to thank Demma Rodriguez for her involvement in subject testing and Marc Ruel for critically
reading a previous version of this manuscript.This study was supported by a grant from the International Foundation for Music
Research (IFMR) and in part by grants from the National Science Foundation (BCS- 0132508), National Eye Institute (EY12091),
National Institute of Mental Health (MH57980, MH60734), and the General Clinical Research Center at Beth Israel Deaconess
Medical Center (National Center for Research Resources MO1RR01032). G.S. is also supported in part by a Doris Duke Charitable
Foundation Clinical Scientist Development Award.
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