Book Review: Brain Specialization for Music

Abstract

Music, like language, is a universal and specific trait to humans. Similarly, music appreciation, like language comprehension, appears to be the product of a dedicated brain organization. Support for the existence of music-specific neural networks is found in various pathological conditions that isolate musical abilities from the rest of the cognitive system. Cerebrovascular accidents, traumatic brain damage, and congenital brain anomalies can lead to selective disorders of music processing. Conversely, autism and epilepsy can reveal the autonomous functioning and the selectivity, respectively, of the neural networks that subserve music. However, brain specialization for music should not be equated with the presence of a singular “musical center” in the brain. Rather, multiple interconnected neural networks are engaged, of which some may capture the essence of brain specialization for music. The encoding of pitch along musical scales is likely such an essential component. The implications of the existence of such special-purpose cortical processes are that the human brain might be hardwired for music.

Full text

372 THE NEUROSCIENTIST Brain Specialization for Music
Copyright © 2002 Sage Publications
ISSN 1073-8584
To begin, I will introduce the topic of brain specializa-
tion for music by way of two examples coming from
clinical neurology. The first case is a professional com-
poser, Vissarion Shebalin, who sustained a second vas-
cular hemorrhage in the left hemisphere of the brain at
the age of 57. This stroke left him speechless and deaf to
the spoken world. Although Shebalin could no longer
communicate verbally, he continued to compose until his
death 4 years later. Shebalin was particularly prolific
musically despite his vast left hemispheric lesion; he
wrote 14 chorales, 2 sonatas, 2 quatuors, 11 songs, and
1 symphony. According to Shostakovitch, one of his
peers, Shebalin’s music was undistinguishable from
what he had composed before his illness (Luria and oth-
ers 1965). The case of Shebalin, a musician with essen-
tially no language consequent to brain damage, is known
as the condition of aphasia without amusia. It is spec-
tacular but not exceptional. Similar cases have been
reported in the literature (e.g., Assal 1973; Basso and
Capitani 1985; Signoret and others 1987).
The second case, Isabelle R., represents the reverse
condition. Isabelle R. is an ordinary woman, devoid of
any apparently special talents, be it musical or linguistic.
She was a restaurant manager when, at the age of 28, she
underwent successive brain surgeries for the repair of
ruptured aneurysms in the left and right middle cerebral
arteries. She survived, but with two vast brain lesions
invading the auditory cortex bilaterally and extending to
the frontal areas on the right side (for more details, see
Griffiths and others 2000). In this context, it is surpris-
ing to note that Isabelle R. is fully functional in lan-
guage, memory, and intelligence. She even writes poems
(for an example, see Peretz and others 1997). Her per-
sisting and major problem concerns music. Isabelle R.
can no longer recognize the music that was familiar to
her prior to her brain accident; she cannot relearn the
musical corpus due to the fact that melodies no longer
leave a trace in her memory; finally, she can no longer
carry a tune. Isabelle R. regularly practiced these skills
before her brain injury, and music was an important part
of her life. She was raised in a musically inclined fami-
ly; her only brother is a professional musician. Isabelle
R. is a case of amusia without aphasia. This condition
has been known for more than a century (Marin and
Perry 1999), although more detailed cases have been
documented recently (Peretz and others 1994; Griffiths
and others 1997; Piccirilli and others 2000).
The major conclusion to be drawn from these two
neurological cases is that brain specialization for music
does seem to exist. Cases such as Shebalin show how
these specialized neural circuitries can be selectively
spared. Conversely, cases such as Isabelle R. demon-
strate that these music-specific circuitries can be selec-
tively damaged. This double dissociation points to the
existence of neural networks that are dedicated to the
processing of music. This point requires both clarifica-
tion and elaboration. First, there is a need to specify the
circumstances under which such a specialization can be
observed. Second, the nature and function of the special-
ized mechanisms that are subserved by these music-spe-
cific neural modules must be specified. Finally, the rea-
sons why the human brain might be equipped with musi-
Brain Specialization for Music
ISABELLE PERETZ
Department of Psychology
University of Montreal
Research Center of the University Institute of Geriatrics of Montreal
Music, like language, is a universal and specific trait to humans. Similarly, music appreciation, like language
comprehension, appears to be the product of a dedicated brain organization. Support for the existence of
music-specific neural networks is found in various pathological conditions that isolate musical abilities from
the rest of the cognitive system. Cerebrovascular accidents, traumatic brain damage, and congenital brain
anomalies can lead to selective disorders of music processing. Conversely, autism and epilepsy can reveal
the autonomous functioning and the selectivity, respectively, of the neural networks that subserve music.
However, brain specialization for music should not be equated with the presence of a singular “musical cen-
ter” in the brain. Rather, multiple interconnected neural networks are engaged, of which some may capture
the essence of brain specialization for music. The encoding of pitch along musical scales is likely such an
essential component. The implications of the existence of such special-purpose cortical processes are that
the human brain might be hardwired for music. NEUROSCIENTIST 8(4):372–380, 2002
KEY WORDS Music, Amusia, Brain, Pitch
The research from my laboratory is supported by grants from the
Canadian Natural Science and Engineering Research Council and the
Canadian Institutes of Health Research. I thank Krista Hyde, Paule
Samson, and Francine Giroux for editing assistance.
Address correspondence to: Isabelle Peretz, Département de Psych-
ologie, Université de Montréal, C.P. 6128, succ. Centre-ville, Montréal
(Qué), H3C 3J7 Canada (e-mail: Isabelle.Peretz@umontreal.ca).
■ REVIEW

Volume 8, Number 4, 2002 THE NEUROSCIENTIST 373
cal modules must be examined. The present review will
treat each of these questions in turn.
Isolation of the Music-Specific Networks
The classical method for examining brain specialization
is via lesions in humans, as illustrated above and as reex-
amined below. Yet, this is not the only method.
Identification of musical modules can take place in a
variety of pathological contexts, such as autism,
Williams syndrome, epilepsy, and Alzheimer disease.
Moreover, it can be observed in individuals who suffer
from a learning disability for music. Finally, the exis-
tence of music-specific brain circuitries may also be
revealed by brain imaging and electrophysiological tech-
niques in neurologically intact individuals.
Autism
Brain anomalies can produce cognitive deficiencies that
are so pervasive that the individual needs constant assis-
tance, even in adulthood. These anomalies can be con-
genital, as in autism and in Williams syndrome, or
acquired late in life with the progression of the dement-
ing process in Alzheimer’s disease. Yet, despite the pres-
ence of mental retardation, individuals often enjoy a
fully functional system for music and can even achieve a
high level of music proficiency (see Don and others
1999 for Williams syndrome; Miller 1989 for the music-
savant syndrome in autism).
We have been able to observe this fascinating condi-
tion in an autistic young adult, Pauline (i.e., QC in
Mottron and others 2000). Pauline lives with her parents
and is unable to earn her living. She is considered to be
deficient intellectually (her IQ is 70) and was diagnosed
as autistic at the age of 2. Language was delayed, with
the first words articulated at 30 months and the first two-
word sentences at 48 months. In contrast, Pauline has
always shown a keen interest for music and has dis-
played remarkable musical skills. She started to play
piano informally at the age of 2 and received formal
piano lessons at the age of 5. Since then, Pauline has
continued to play music, although at a moderate pace.
Her level of achievement corresponds to that of an ama-
teur pianist with an equivalent number of years of train-
ing. However, Pauline has an exceptional memory for
music; she is able to reproduce a conventional piece of
music composed for experimental purposes after hearing
it only once. Her reproduction is informative because
she does not reproduce the piece as a recording machine;
rather, she harmonizes and improvises in a skillful man-
ner. She also possesses absolute pitch, being able to accu-
rately sing a named pitch. None of these skills are in
themselves the signature of talent or prodigy. Yet, these two
skills reveal a fully functional musical system in an oth-
erwise low-functioning individual.
Pauline is a typical case of the “music-savant syn-
drome.” Similar cases have been reported in the litera-
ture (e.g., Sloboda and others 1985; Hermelin and others
1987). In general, autistic subjects are more apt in the
area of music than in language (Heaton and others
1998). Autistic individuals provide strong case demon-
strations of brain specialization for music because their
musical abilities emerge as an isolated area of normal
functioning. Their musical proficiency suggests that
music must be subserved by music-specific mecha-
nisms, which are left intact by the autistic brain patholo-
gy. Unfortunately, the neural correlates of the preserved
musical skills have not yet been studied. In fact, the
study of the atypical cerebral functioning in autism is
just beginning (e.g., Ring and others 1999).
Epilepsy
Investigations with epileptic patients provide another
valuable source of evidence that suggests the existence
of neural networks that are dedicated to music. In a few
individuals, music will be the exclusive trigger of the
pathological firing of neurons that underlies seizures.
This unusual but well-documented form of epilepsy is
called musicogenic epilepsy and shows that the epilepto-
genic tissue lies in a neural region that is tied to music
processing.
Epileptic attacks may be induced by simply listening
to music. The musical trigger can be highly selective, as
described by Critchley (1977). In one of his patients,
only “classical” music provoked a seizure, although the
patient confessed that she had no particular preference
for this kind of music. During such musicogenic epilep-
tic seizures, abnormalities in electrical activity (recorded
from the scalp) are generally observed at the temporal
lobes, with a slight bias toward the right one (for a recent
review, see Wieser and others 1997). Thus, some pro-
cessing component that is exclusively related to music
must be located in those regions.
Musicogenic epilepsy can be simulated by direct elec-
tric stimulation of the brain (e.g., De Graaf and others
2000). It has been well known since the classical studies
of Penfield and Perot (1963) that electric stimulation of
particular areas of the auditory associative cortex of
awake patients may produce highly vivid musical hallu-
cinations. For example, Penfield and Perot (case 5, p
620) report stimulating a particular region of the first
right temporal circumvolution of an awake epileptic
patient before surgery. After stimulation, the patient
reported that she heard music. The experimenters then
repeated the stimulation, without telling the patient, who
immediately reported, “I hear the music again. It is like
the radio.” The stimulation was again repeated and the
patient shouted, “I hear it!” The electrode was kept in
place, and the patient was asked to describe what she
heard. The patient hummed the tune quite distinctly. The
song came out so clearly that one of the nurses recog-
nized the song “Rolling Along Together.” The patient
agreed that this sounded like the words in the song.
These provoked hallucinations suggest that the stimu-
lation be applied to circuits that contain memories of
musical experiences. These musical experiences are
slightly more often evoked by stimulation of the right
than the left temporal regions (Penfield and Perot 1963).

374 THE NEUROSCIENTIST Brain Specialization for Music
The fact that musical memories can be selectively elicit-
ed is once again indicative of a brain specialization for
music.
Acquired Amusia
The patient-based approach converges on an important
point: neuronal networks that are situated in or close to
the superior temporal gyrus participate in music percep-
tion and memory in a decisive and exclusive manner.
This is best documented in cases of acquired amusia as
a consequence of brain damage.
Following bilateral lesions of the auditory cortex,
patients can show highly specific disorders of music per-
ception and recognition (e.g., Peretz 1996; Peretz and
others 1997). This music-specific impairment is readily
discernable in experiments testing memory recognition.
In the music memory test, subjects are presented with 20
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), respec-
tively. The three tests are performed in different sessions.
As can be seen in Figure 1, the two patients—Isabelle
R. (IR, described previously) and CN (another similar
case; Peretz, 1996), who suffers from musical disorders
as a consequence of bilateral lesions to the auditory cor-
tex—perform at chance in the melody recognition test,
but they perform in the normal range with spoken lyrics
and environmental sounds. Importantly, the patients fail
to recognize the tunes of songs from which they are able
to recognize the lyrics. The disorder is clearly music spe-
cific. Thus, the critical mechanisms that are necessary
for music perception and memory are not only special-
ized for the musical domain but also appear to be sub-
served by neural networks that are anatomically distinct.
Congenital Amusia
As a result of early abnormalities in music-specific net-
works, normal acquisition of musical competence would
be expected to be affected in a highly selective manner.
That is, certain individuals might be born with a musical
deficiency. This possibility has been envisaged for more
than a century (see Grant-Allen 1878 for the first report;
Geschwind 1984). Such individuals are musically inept,
despite a normal exposure to music, normal intelligence,
and social adaptation. They are sometimes referred to as
tone-deaf. However, this term is too restrictive. We pre-
fer the term congenital amusia because it reflects better
the likelihood that there are multiple forms of musical
learning disabilities, as there are various patterns of
acquired amusia resulting from brain accident.
In an effort to learn more about congenital amusia, we
actively searched for adults with a lifelong history of
musical learning disabilities. To date, we have identified
11 such cases (Ayotte and others 2002). All participants
declared themselves as musically impaired since birth,
and their self-report was confirmed by formal testing.
We selected participants who exhibited clear-cut per-
formance deficits in laboratory tests, who had no psy-
chiatric or neurological history, and who possessed a
high level of education. To ensure adequate exposure
and motivation, only volunteers who had attempted to
learn music during childhood were considered.
To confirm the presence of a musical defect and to
determine whether the deficit is specific to music, sub-
jects were evaluated over numerous tests that were ini-
tially designed for the assessment of brain-damaged
patients with probable acquired amusia (e.g., Peretz
1990; Liégeois-Chauvel and others 1998; Ayotte and
others 2000). The most sensitive test that was able to dis-
tinguish amusic from normal performance required the
detection of an anomalous pitch in an otherwise conven-
tional melody. Subjects were presented with two sets of
melodies. The first set comprised familiar melodies, and
the second set had unfamiliar melodies. In each set, half
of the melodies were modified by shifting the pitch of
one note by one semitone so that the note fell out of key
while preserving the original contour. The position of the
modified note varied across melodies, avoiding the first
and last note positions. The melodies were 6 to 15 notes
long and were presented only once. After each presenta-
tion, subjects were asked to judge whether the melody
contained a “wrong note.”
As can be seen in Figure 2, the two groups can be dif-
ferentiated; there is no overlap between the amusic
scores and the scores of normal controls who were
matched in sex, age, and education. The results obtained
with this anomalous pitch detection test are important
for several reasons. From a practical perspective, this
test clearly distinguishes amusic subjects from normal
individuals and hence may serve as a diagnostic tool.
From a theoretical point of view, the results are impor-
Fig. 1. Percentage of correct responses obtained by 2 amusic
patients with brain damage (CN and IR) and 29 unselected con-
trol adults with no musical experience in the memory recogni-
tion of studied melodies, lyrics, and environmental sounds.
Error bars represent standard deviation from the mean obtained
by controls. Chance performance is 50%.

Volume 8, Number 4, 2002 THE NEUROSCIENTIST 375
tant because they converge with prior findings in identi-
fying a deficiency in musical pitch perception (Kalmus
and Fry 1980). Such a pitch defect is the most likely ori-
gin of congenital amusia.
The notion that congenital amusia results from a basic
auditory problem related to fine-grained pitch discrimi-
nation has theoretical appeal. Fine-grained discrimina-
tion of pitch is probably more relevant to music than to
any other domain, including speech intonation. Speech
intonation contours, for example, use variations in pitch
that are larger than half an octave to convey relevant
information (e.g., Patel and others 1998). In contrast,
melodies mostly use small pitch intervals (of the order of
a one-twelfth or one-sixteenth of an octave). Therefore,
a degraded pitch perception system may compromise
music perception but leave speech prosody unaffected
(Ayotte and others 2002; Peretz and others 2002). This
suggests that the pitch perception deficit experienced by
congenital amusic subjects is not specific to the musical
domain but is domain relevant.
It is worth emphasizing that the defect appears indeed
limited to the musical domain. For example, our group
of congenital amusics behaves exactly as brain-damaged
patients who suffer from acquired amusia in the memo-
ry recognition of melodies, lyrics, and common environ-
mental sounds (see Fig. 1). Thus, congenital amusics
appear to be born without the essential neural elements
that allow development of a normally functioning system
for music. Yet, these individuals have achieved a high
degree of proficiency in most, if not all, other domains.
Therefore, congenital amusia is another pathological
condition that reveals brain specialization for music.
Because congenital amusia is the mirror image of the
music-savant syndrome described earlier in autism, it
provides strong evidence for the presence of early pres-
sures to develop neural networks that are dedicated to
music. These predispositions may not fine-tune the neu-
ral circuitries of the congenitally amusic’s brain proper-
ly, whereas the same predispositions may adequately
guide the neural wiring of the autistic brain.
Normal Adults
Up to this point, we have seen how various brain anom-
alies can reveal the existence of music-specific net-
works. Imaging and electrophysiological explorations of
the brain of normal subjects might also be expected to
provide relevant information, especially regarding the
localization of these networks. However, this is a com-
plex task. Musical abilities are numerous and dissociable
(for an example, see Peretz 2001a), and domain special-
ization must be examined at the level of each relevant
processing component. Hence, the search for conver-
gence between pathological and normal brain conditions
will require sustained research efforts.
The recent study of song component processing pro-
vides a good illustration of both the advances and diffi-
culties that characterize the current search of music-spe-
cific networks in the normal brain. In accordance with
the patient-based approach, the processing of melody
and lyrics of a same song has been shown to be separa-
ble in the brain of normal individuals. Event-related
brain potentials have been recorded while musicians lis-
tened to excerpts from an opera sung without accompa-
niment. Excerpts were ended by semantically congruous
or incongruous words sung either in or out of key. The
situation is illustrated in Figure 3. The evoked responses
associated with the semantically incongruous sung word
showed a negative waveform component that peaked 400
ms (N400) after word onset. In contrast, the brain poten-
tials evoked by a congruous word that is sung out of key
showed a late positive deflection (P600). When the sung
word is both semantically and melodically unexpected,
the obtained waveform shows an additive effect of the
N400 and the P600. This electrophysiological pattern
suggests that the monitoring of speech and music in
songs is performed by independent neural processors
(Besson and others 1998).
Converging evidence was later obtained with the same
opera excerpts in a functional brain imaging study that
used the positron emission tomography technique
(Warrier and others 1998). Monitoring for semantic
incongruity produced activation localized to the left
inferior frontal cortex (Brodmann’s areas 44 and 45).
This region was not involved in the monitoring of the
same song excerpts for the presence of melodic incon-
gruities. However, more recent data obtained with mag-
netoencephalography suggest that the detection of a har-
monic incongruity in music might also involve Broca’s
areas (e.g., Brodmann’s area 44) (Maess and others
2000). Therefore, the implication of the left inferior
frontal cortex might not be specific to language but
could reflect a general intervention in detecting rule vio-
lations. This latter result highlights the difficulty in try-
ing to identify brain areas that work solely during musi-
Fig. 2. Distribution of individual correct scores obtained by con-
genital amusic subjects relative to the distribution of the indi-
vidual scores obtained by 20 nonmusicians who were matched
in education, age, and sex to the amusic individuals. The
scores were obtained in a pitch anomaly detection task involv-
ing 36 familiar melodies (abscissa) and 30 unfamiliar melodies
(ordinate axis). Half of the melodies contained a pitch that was
out of key. Note that most amusic subjects perform at chance
(around 15 correct responses) in the unfamiliar melody set and
that there is not overlap in the amusic and control distribution.

376 THE NEUROSCIENTIST Brain Specialization for Music
cal tasks. However, the evidence is scarce because the
issue has not been sufficiently addressed.
The Origins of Brain Specialization for Music
Taken together, neuropsychological explorations, partic-
ularly the patient-based approach, point to the existence
of brain specialization for music. One important impli-
cation of this observation is that music does not seem to
be a by-product of a more important brain function, such
as language. However, brain specialization for music
does not entail that a “musical center” must exist in the
brain. Rather, brain specialization for music may lie in
several largely distributed neural circuitries that are
essential to the normal functioning of musical activities.
One essential mechanism was delineated previously
in the study of congenital amusia. This mechanism is
related to the computation of musical pitch. However, it
seems unlikely that a function as complex as music
appreciation and expression could be reduced to a single
mechanism. During music acquisition, it is possible that
a faulty perception of pitch might bring the development
of the entire musical system to a halt. However, in a fully
and normally developed musical system, many other
essential processing components intervene. Clearly,
what is needed at the present stage is a grid that allows
specification of the processing mechanisms that are
essential and specific to music. Once these essential
ingredients have been identified, their respective local-
ization can, in principle, be tracked down in the brain of
musicians and nonmusicians of different musical cul-
tures. The research agenda involved will only be briefly
sketched in the next section.
Music Essential Mechanisms
Likely candidates for brain specialization are those
mechanisms that are acquired by all individuals, musi-
cians and nonmusicians alike. This common core of
musical abilities is supposed to allow each member of
the same culture to appreciate the music of their com-
munity, to sing and to dance together. These shared
musical abilities can probably be reduced to a few essen-
tial processing components that capture the essence of
brain specialization for music. From this perspective,
there is no need for all musical abilities to have initial
Fig. 3. Example of opera excerpt that was sung a capella by a professional singer with four different endings. The final word was either
original, in being semantically and melodically congruous, and served as the baseline condition; semantically incongruous and sung
in key; semantically congruous but sung out of key; or both semantically and melodically incongruous. Neurologically intact musicians
monitored the presence of these incongruities in 200 opera excerpts, and event-related potentials that were time-locked to the final
word onset were recorded, amplified, and averaged for the four conditions separately and then averaged for the 16 musicians. The
resulting averaged waveform is illustrated on the right side of the figure for the midline parietal electrodes, with negative being up. The
vertical bars represent the onset of the final word.

Volume 8, Number 4, 2002 THE NEUROSCIENTIST 377
specialization. Brain specialization for a few mecha-
nisms that are essential to the normal development of
musical skills should suffice.
I am proposing that the two anchorage points of brain
specialization for music are the encoding of pitch along
musical scales and the ascribing of a regular beat to
incoming events. The notion that a special network exists
for tonal encoding of pitch is presently compelling, as
summarized below. Moreover, the notion that regularity
might be fundamental to music appreciation is slowly
emerging (e.g., Drake 1998), although its specificity to
music is rarely addressed.
Encoding pitch along musical scales is construed as a
building block of the musical knowledge that is embed-
ded in one of the music-specific networks of the brain. It
involves knowledge and procedures that reflect the high-
ly organized use of pitch in the music of the environ-
ment. Generally, music makes use of a limited set of dis-
crete pitches. In a given piece, only a small subset
(around seven pitches) is used and is referred to as scale
tones. These are not equivalent and are organized around
a central tone, called the tonic. Usually, a piece starts and
ends on the tonic. For example, “The Star-Spangled
Banner” starts with a tonic chord (C-E-G) followed by
C, the tonic; then E, the third; then G, the fifth degree;
and then back to the tonic C, but played an octave above.
These three notes reflect a hierarchy of importance or
stability in the key of C major, with the fifth scale tone
(G) and the third scale tone (E) being more closely relat-
ed to the tonic (C) than the other scale tones (i.e., D, F,
A, B). The nonscale tones that do not belong to the key
(e.g., C# in the key of C major) are the least related; the
latter often sound like “foreign” tones. Listeners are
highly sensitive to this hierarchy of pitches, as illustrat-
ed in Figure 4. This sensitivity reflects the tonal
knowledge that is proposed to be essential to music
development and to be subserved by specialized neural
networks.
The encoding of pitch variations in music is crucially
dependent on tonal functions but also involves other
melodic features. However, these other melodic features
are not unique to music. For example, pitch contours and
intervals are also used in speech prosody, as mentioned
earlier. In contrast, tonal encoding of pitch can be con-
sidered as the “germ around which a musical faculty
could have evolved” (Jackendoff 1987, p 257). In music,
pitch variations generate a determinate scale, whereas in
human speech the intonation contours do not usually
elicit such effects (Balzano 1982). Moreover, perception
of tonal pitch may require universal processing mecha-
nisms. These mechanisms are probably related to the
exploitation of scale peculiarities. Indeed, most musical
scales make use of unequal-spaced pitches and are
organized around 5 to 7 focal pitches (Dowling 1982).
There is substantial empirical evidence that listeners
use tonal regularities in an implicit manner (for a recent
review and a computer simulation, see Tillman and oth-
ers 2000). Moreover, as we have argued elsewhere in
detail (Peretz and Morais 1989), translation of pitch into
tonal scales fits with the definition of a modular system
in Fodor’s (1983) sense. Most notably, the tonal system
seems to mediate perception of musical pitch in an auto-
matic way and without conscious awareness (Shepard
and Jordan 1984) and to operate very early in ontoge-
netic development (e.g., Trehub and others 1999).
Finally, tonal knowledge can be selectively impaired by
brain damage (Peretz 1993).
In effect, selective disturbance in tonal interpretation
of pitch, as opposed to difficulties from other sources
(such as an impairment in short-term memory, contour,
or interval processing), can be observed after brain dam-
age (e.g., Peretz 1993). This impairment affects percep-
tion of pitch structure so that pitch is no longer encoded
in terms of its tonal function but is perceived into a con-
tinuum of pitch height (i.e., intervals) and pitch direction
(i.e., contour).
One of the tasks that we used to document this selec-
tive impairment is a classical paradigm in the psycho-
logical literature. It is called the probe-tone task (for a
detailed analysis of the task, see Krumhansl 1990). In
this paradigm, listeners hear a context sequence fol-
lowed by a tone that can take any value in the octave (see
the musical score at the top of Fig. 4). Their task is to
assess the extent to which the final tone constitutes an
acceptable conclusion to the melody. Judgments given
by children and by adults with no musical training gen-
erally correspond to tonal constraints—subjects system-
atically prefer scale tones, most notably those making up
the major triad (e.g., C, E, G in C major). In contrast, the
judgments of the brain-damaged patient under study
(GL) were determined by pitch direction and pitch prox-
imity, not the tonal status of the pitches. In GL’s brain,
the lesions had selectively interfered with the normal
operation of the tonal module.
As mentioned above, this tonal module is expected to
be one origin of brain specialization for music. However,
and despite several attempts, brain localization of this
network is undetermined (for a recent review, see Peretz
2001a).
1
It is hoped that the increase in temporal and
spatial resolution of the new brain imaging techniques
will soon provide some insight on this issue.
In summary, there are good reasons to view musical
pitch perception as an essential mechanism underlying
brain specialization for music. Likewise, perceiving reg-
ularity in music might be another candidate for music
specificity. Both abilities are fundamental to musical
activities. Pitches that stand in a tonal relation allow har-
monious voice blending and regularity favor motor syn-
chronicity. These two musical features are highly effec-
tive at promoting simultaneous singing and dancing
(Brown 2000). This type of synchronization may well be
specific to music. In language communication, for
1. It is worth adding that this search of a neural substrate for a
music-specific circuitry should not be limited to the Western culture.
Modularity for tonal encoding of pitch is not meant to apply only to the
Western tonal system. This specificity refers to some sort of abstract
principles that are instantiated in the tonal system but that essentially
cut across styles and time. It is an analogous claim, in essence, to the
less controversial notion that there are modules devoted to the under-
standing of speech in general, not just of French in particular.

378 THE NEUROSCIENTIST Brain Specialization for Music
instance, intelligibility requires individuality (i.e., avoid-
ance of simultaneity).
A Note on Brain Localization
Localization of the music-specific neural networks
remains elusive (see also Tramo 2001). The only con-
sensus that has been reached today regarding the local-
ization of music-processing components concerns pitch
contour. Both lesion studies and neuroimaging explo-
rations converge in locating the pitch contour extraction
mechanism in the superior temporal gyrus and frontal
regions on the right side of the brain (e.g., Zatorre and
others 1994; for a recent review, see Peretz 2001a).
However, this mechanism may not be dealing with music
exclusively. The same mechanism may be involved in the
monitoring of speech intonation (e.g., Patel and others
1998). Nevertheless, this consensus concerning the pro-
cessing of pitch contours may explain why the right
hemisphere of the brain has been traditionally viewed as
the “musical hemisphere.”
However, there is increasing evidence that musical
functions recruit neural mechanisms in both cerebral
hemispheres and also engage multiple brain regions in
each hemisphere. Moreover, Patel and Balaban (2000)
have recently suggested that music processing may be
distinguished by its characteristic dynamic activity and
the pattern of brain interactions it engenders rather than
by the particular brain regions that respond to it. Thus,
brain specialization for music may not only be reflected
in the location of the music-specific neural networks, as
traditionally construed, but also may lie in the dynamic
characteristics of their functioning and interactions.
Thus, brain localization of musical functions is a com-
Fig. 4. The probe-tone task used with the brain-damaged patient (GL) is represented with the stimulus in the upper musical staff and
GL’s judgments of appropriateness of final tone below. The stimulus consists of a context (C, E, C, G, which correspond to the major
triad tones in the key of C major) followed by a probe tone that could take any musical pitch value between A# and A. The results
obtained under the same conditions by 6-year-old children tested by Cuddy and Badertscher (1987) are included for comparison.
Children’s judgments preserve tonal constraints—they systematically prefer scale tones (black and blue notes on the musical staff)
and, most notably, those making up the major triad (black notes on the same staff). GL, however, proceeded otherwise. As he himself
explained, his judgments were based on his impression that singers normally conclude on a note that is close but lower in pitch. In
other words, he relied on interval size and contour. This is effectively what emerges from an analysis of his responses. Apart from the
most distant tones (A# and B, which in fact had an ambiguous pitch), GL felt that the last tone was appropriate when it descended
(i.e., all tones preceding G), more particularly so when it was close in pitch, and rejected those that ascended (i.e., G#, A). His judg-
ments were thus made without regard to the tonal status of the pitches.

Volume 8, Number 4, 2002 THE NEUROSCIENTIST 379
plex issue. Advances in this direction depend not only on
the dynamic resolution of neuroimaging techniques but
also on the relevance of the fractionation that is operat-
ed in musical processing skills.
A Note on Emotions
Discrimination and memorization are not the central rea-
son why people listen to music. Humans are musically
inclined because music has emotional appeal. The ques-
tion, then, is how the evidence reviewed previously on
brain specialization relates to emotional responses to
music. Surprisingly, we cannot provide a clear answer at
this stage because of the scarcity of relevant studies.
Humans have been mostly studied as information-pro-
cessing machines without emotional biases. Part of this
situation may be attributed to the widely held belief that
emotional responses to music are highly personal and
variable, hence precluding scientific examination. This
belief appears to be false. A recent study (Peretz and oth-
ers 1998) shows that emotional appreciation of music is
highly consistent across individuals, has immediacy, and
is available to the layman without conscious reflection
and with little effort. Therefore, emotional appreciation
of music fits well with the product of a specialized cor-
tical arrangement.
It remains to be determined to what extent musical
emotions are distinct from other kinds of emotions, such
as those evoked by vocal sounds, and to what extent
musical emotions rely on the operation of specialized
mechanisms such as those involved in the tonal encod-
ing of pitch. Provisional answers are reported in Peretz
(2001b) and Peretz and others (2001). We propose that
the emotional pathway is isolable from the nonemotion-
al analysis of music. However, we do not conceive the
emotional pathway as entirely parallel to the rest of the
musical system. Rather, we propose that the perceptual
analysis that takes place prior to emotional evaluation
requires cortical mediation and cuts across judgments
and tasks. The study of emotional appreciation of music
is a fairly novel research avenue in both cognitive psy-
chology and cognitive neuroscience. Hence, progress in
this direction should not take long.
Why Is There Brain Specialization for Music?
Showing brain specialization for music suggests but
does not imply that the brain is prewired for music.
Music may simply recruit any free neural space in the
infant’s brain and modify that space to adjust it to its pro-
cessing needs. These needs may be computationally
complex to satisfy and hence require free and plastic
neural tissue. This adaptation of the brain to musical
pressures might simply be an adjustment to a “pure
pleasure technology” (Pinker 1997, p 528) and not a
response to a biological force.
However, I am more inclined to endorse the view that
brain specialization for music has evolved as a response
to the needs of a faculty that has biological functions. In
my view, music pertains more to biology than to culture
because music cannot be reduced to an ephemeral (cul-
tural) product. Music was not invented by a group of
individuals. Rather, music exists in all forms of soci-
eties. Moreover, music seems to have emerged sponta-
neously and very early in human evolution (Wallin and
others 2000). Thus, not only is music ubiquitous to
human societies, but it is also old in evolutionary terms.
The key question, obviously, is why music would have
biological foundations. What adaptive function was
served by music in ancestral activities to provide its
practitioners with a survival advantage in the course of
natural selection? There are two main explanations. The
initial account was provided by Darwin himself (1871),
who proposed that music serves to attract sexual part-
ners. This view has been recently revived by G. Miller
(2000), who reminds us that music making is still a
young male trait. However, the dominant view of the
adaptive value of music lies at the group level rather than
at the individual level because music promotes group
cohesion. Music is present in all kinds of gatherings—in
dancing, religious rituals, ceremonies—thereby
strengthening interpersonal bonds and identification
with one’s group. The initial step for this bonding effect
of music could be the mother-infant interactive pattern
created through singing and mothereese (which refers to
the musical way adults talk to infants), thereby favoring
emotional communion. These different adaptive roles
attributed to music do not need to be mutually exclusive.
As pointed out by Kogan (1994), individuals taking the
lead in ceremonies by virtue of their musical and dance
prowess can achieve leadership status in the group, a fac-
tor that contributes to reproductive success. All these
forces may explain why the human brain has evolved so
as to accommodate neural networks to deal exclusively
with music.
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