Differential Activation of the Caudate Nucleus in Primates Performing Spatial and Nonspatial Working Memory Tasks

Abstract

The caudate nucleus is part of an anatomical network subserving functions associated with the dorsolateral prefrontal cortex (DLPFC). The aim of the present study was to investigate whether the metabolic activity in the striatum reflects specific changes in working memory tasks, which are known to be dependent on the DLPFC, and whether these changes reflect the topographic ordering of prefrontal connections within the striatum. Local cerebral glucose utilization (LCGU) rates were assessed in the striatum by the 14 C-2-deoxyglucose method in monkeys that performed a spatial (delayed spatial alternation), a nonspatial (delayed object alternation) visual working memory task, or tasks that did not involve working memory, i.e., a visual pattern discrimination or sensorimotor paradigm.The results show a topographic segregation of activation related to spatial and nonspatial working memory, respectively. The delayed spatial alternation task increases LCGU rates bilaterally by 33-43% in the head of the caudate nucleus, where efferents from the dorsolateral prefrontal cortex project most densely. The delayed object alternation task enhances LCGU rates bilaterally by 32-37% in the body of the caudate nucleus, which is innervated by the temporal cortex. The visual pattern discrimination task similarly activated the body of the caudate, but in a smaller region and only in the right hemisphere.These findings provide the first evidence for metabolic activation of the caudate nuclei in working memory, supporting the role of this nucleus as a node in a neural network mediating DLPFC-dependent working memory processes. The double dissociation of activation observed suggests an anatomical and functional segregation of cortico-striatal circuits subserving spatial and nonspatial cognitive operations.

Identifying regional activity associated with temporally separated components of working memory using event-related functional MRI

“…During the delay periods of delayed-response tasks, striatal neurons exhibit sustained activity that closely resembles that of the DLPFC (Apicella et al, 1992). Such findings have led to the hypothesis that this circuitry plays a role in maintaining tonic activity of the DLPFC during maintenance periods in which information critical to a correct response is held "on line" (Goldman-Rakic, 1995;Levy et al, 1997). Positive feedback in these reverberating loops has been hypothesized to provide a mechanism for sustaining WM (Beiser and Houk, 1998).…”

Basal Ganglia Shape Abnormalities in the Unaffected Siblings of Schizophrenia Patients

“…The basal ganglia play important roles in the regulation of both motor and non-motor functions (9)(10)(11), and motor abnormalities can occur in neuroleptic-naïve schizophrenia patients (12). Basal ganglia dysfunction, assessed with functional MRI, has been reported in schizophrenia and their unaffected siblings (13)(14)(15).…”

Putamen Mitochondrial Energy Metabolism Is Highly Correlated to Emotional and Intellectual Impairment in Schizophrenics

“…In this regard, it was suggested that the effects of neuroleptics in the caudate may be subordinate to those upon the putamen in terms of elevating functional activity (Prince et al 1998a). This is of importance based upon recent evidence that the caudate is involved in working memory (Levy et al 1997). Thus, an alternative explanation in this matter is that a lack of correlation in the caudate in schizophrenics may itself be "pathological" and suggestive of damaged circuitry.…”