plicated sight-reading task apparently acts as a kind of Broca’s area for
the hand.As such,it would be interesting to learn if this region is speci-
fically involved in production of American sign language that,like lan-
guage,is left-hemisphere dominant and dissociated from nonlinguistic
gesture (Hickok,Bellugi,and Klima 1996).
To summarize,the experiments of Sergent et al.(1992) are extremely
important for three reasons.First,they document the existence of a dis-
tributed neural network that incorporates specialized nodal regions for
processing sensory and motor aspects of music,as is the case for lan-
guage.Second,in some cases,cortical areas that underlie musical activi-
ties have been shown to be next to,and partly overlap with,those
engaged in similar language tasks.Finally,portions of certain areas are
differentially activated in the left hemisphere during specific musical
activities;for example,area 22 from listening to simple scales,part of area
19 with simple reading of a musical score,motor and premotor (area 6)
cortices (plus right cerebellum) during simple playing of the keyboard
with the right hand,and the top part of area 44 during the multifaceted
sight-reading task.Thus,musicians,at least,rely a good deal on their left
hemisphere when processing music.
These findings were confirmed and extended by other researchers.
Chen et al.(1996) used fMRI to study four healthy subjects as they imag-
ined a familiar piece of classical music.Again,area 42 became activated
bilaterally and area 22 was more responsive on the right.Deeper brain
structures that contribute to the auditory ascending pathway were also
activated (medial geniculate nuclei,inferior colliculus,lateral lemniscus),
causing the authors to conclude that imagining music and actually
hearing it activate the same neurological substrates.They also noted that
another deep structure,the putamen,which is activated on the left,may
be involved with timing of the imagined music.(Of interest,the left
putamen also lit up when bilingual volunteers spoke words in their
second language,French,but not when they uttered words in their native
English [Barinaga 1995].) Chen et al.also found that two limbic struc-
tures that participate in processing emotions including visceral reactions,
the hypothalamus and amygdala,were activated differently in the right
hemisphere.This study is important because it is one of the few that
imaged deep brain structures during musical cognition.
If there is a surprise in the above recent findings,it is the extent to
which musical activities engage the left hemisphere in a manner that par-
allels the processing of language.What,then,is the right hemisphere
doing? For one thing,as noted,the right temporal association cortex
(area 22) is recruited on first hearing a piece of music (Sergent et al.1992;
Zatorre,Evans,and Meyer 1994).In particular,the right hemisphere
attends to melodic aspects of music.(Melody and rhythm appear to be203 Hominid Brain Evolution and the Origins of Music