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Abstract:
We present computer simulations of deficits in working memory
function due to attentional switching of thalamocortical circuits
modulating prefrontal cortex. This model is consistent with the
anatomy and physiology of prefrontal cortex and associated
subcortical structures (Gelfand et al., Proc. Cog. Sci.
Conf.,253-258,1997). Short term persistent response of prefrontal
cortex neurons has been postulated as a mechanism for short-term
memory (STM) (Fuster, The Prefrontal Cortex, 1989; Goldman-Rakic,
in Motor and Cognitive Functions of the Prefrontal Cortex, 1994).
Prefrontal cortex has highly specific reciprocal projections with
the thalamus, resulting in local thalamocortical loops. When
activated, these loops can sustain activity in prefrontal cortex
neurons (Alexander et al., in The Prefrontal Cortex: Its Structure,
Function and Pathology,119-146,1990). These loops are activated
through selective disinhibition by the basal ganglia (Chevalier
& Deniau, TINS, 13, 277-280,1990). This modulation mechanism
serves as a control structure for task dependent attention in
working memory. We have simulated deficits in this inhibition
during task switching and have observed effects which are similar
to perseveration and interference phenomena characteristic of
schizophrenia and aging.
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