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Abstract:
The lateral prefrontal cortex has long been implicated as a
possible substrate of working memory. Recent research has
reinforced this idea and provided evidence that various subcortical
structures may also help mediate working memory function (e.g.,
head of the caudate nucleus, globus pallidus, medial dorsal nucleus
of the thalamus). We describe a computational model in which
working memory is mediated by parallel, prefrontal
cortical-thalamic loops. Activation reverberates in these loops
because prefrontal cortical excitation of the head of the caudate
nucleus leads to disinhibition of the thalamus (i.e., by inhibiting
the globus pallidus, which tonically inhibits the thalamus).
Switching from one loop to another is mediated by dopamine release
from the substantia nigra and the ventral tegmental area.
Simulations are reported in which the model is used to account for
the results of single-cell recording studies and human behavioral
data in spatial delayed matching-to-sample tasks.
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