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Absolute Pitch and Planum Temporale Julian Paul Keenan*, Ven Thangaraj*, Andrea R. Halpern‡, Gottfried Schlaug* NeuroImage Vol. 14, No. 6, December 1, 2001, pp. 1402-1408 *Department of Neurology, Beth Israel Deaconess Medical Center, 330 Brookline
Avenue, Boston, Massachusetts, 02215 Abstract: An increased leftward asymmetry of the planum temporale (PT) in absolute-pitch
(AP) musicians has been previously reported, with speculation that early
exposure to music influences the degree of PT asymmetry. To test this
hypothesis and to determine whether a larger left PT or a smaller right
PT actually accounts for the increased overall PT asymmetry in AP musicians,
anatomical magnetic resonance images were taken from a right-handed group
of 27 AP musicians, 27 nonmusicians, and 22 non-AP musicians. A significantly
greater leftward PT asymmetry and a significantly smaller right absolute
PT size for the AP musicians compared to the two control groups was found,
while the left PT was only marginally larger in the AP group. The absolute
size of the right PT and not the left PT was a better predictor of music
group membership, possibly indicating "pruning" of the right
PT rather than expansion of the left underlying the increased PT asymmetry
in AP musicians. Although early exposure to music may be a prerequisite
for acquiring AP, the increased PT asymmetry in AP musicians may be
determined in utero, implicating possible genetic influences on PT asymmetry.
This may explain why the increased PT asymmetry of AP musicians was not
seen in the group of early beginning non-AP musicians. Comment: This is the first report of anatomical evidence that subjects with absolute
pitch (APers) may have something less than non-APers. The planum temporale
(PT) is a small part of the neocortex that contributes to language processing
and to general auditory processing. The right PT has now been found to
be significantly smaller in APers than in control groups. Interestingly,
an anatomical deficit in APers could indeed be expected, based on the
assumption hat the propensity to develop AP during childhood may be a
by-effect of a harmless developmental disorder. Due to such a (slight)
disorder, some children may have difficulties in doing the normal step
from implicit AP at birth to implicit relative pitch (RP) when learning
their first language. Implicit RP helps understanding the speech intonation
of speakers other than the mother. So, while still struggling with acquiring
implicit RP, these children may - if there is a musical environment -
extend their implicit AP to explicit AP. From a neuroanatomical point
of view, AP clearly is an easier task than RP. This is simply due to the
tonotopic neural wiring throughout the auditory brain. For AP one only
needs a certain memory connection. For RP, however, one needs a computation
that compares pitch intervals across different spectral ranges, and thus
across different neural map sections. Many have wondered why not all have
explicit AP. The likely answer is that RP is of more use than AP in speech.
A deficit in the right PT may impede the development of implicit RP, and
then, by triggering a compensatory measure, lead to the development of
explicit AP. |