Before concluding, I would like to say a few words about the more theoretical attractions
and implications of the massive redeployment hypothesis. First of all, the hypothesis
offers the potential for explaining both localization of function (cognitive functions only
use limited and specific parts of the brain), and diversity of purpose (a typical brain area
is activated by highly diverse cognitive tasks). This may help dissolve the debate
between localization and holism (Uttal, 2001), which in its typical form offers a false
choice between equipotentiality (a given brain area can do many different things when it
is activated) and strict localization (each brain area does one and only one thing).
According to the massive redeployment hypothesis, the fact that a brain area is dedicated
to some highly specific low-level task is perfectly compatible with its being used to
support many different cognitive functions (Anderson, 2006; in press). In fact, if brain
areas were multi- or equi-potential, and so could easily be recruited to compute
substantially different functions, then it is hard to understand why older brain areas are
more often recruited than younger ones, and why newer cognitive functions recruit more
widely scattered brain areas. It would seem that such a pattern of redeployment would
only arise if the low-level (computational) functions of brain areas were relatively fixed,
such that developing a new cognitive function requires either developing new capacities
de novo, or finding areas already performing some required role. If brain areas could
instead be easily encouraged to compute many different functions, then considerations of
information-processing efficiency would favor recruitment of nearer areas over areas
already computing some desired function, but further away.
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