Dissociation of human caudate nucleus activity in spatial and nonspatial working memory: an event-related fMRI study.
We employed a novel event-related fMRI design and analysis technique to explore caudate nucleus contributions to spatial and nonspatial working memory. The spatial condition of a delayed-response task revealed greater mnemonic activation in four of six subjects when the delay period preceded immediately a probe stimulus requiring an overt motor response, as contrasted with a probe requiring no response. This effect was not seen in frontal or parietal cortical areas, and was seen in the caudate nucleus in a formally identical object condition in just one of six subjects. We hypothesized that this pattern of activity represented spatially dependent motor preparation. A second experiment confirmed this hypothesis: delay-period activity of the caudate nucleus showed greater time dependence in a task that featured spatial and motoric memory demands than in a comparable nonspatial task that featured the same response contingencies. These results suggest an important subcortical locus of the dissociation between spatial and nonspatial working memory, and a role for the human caudate nucleus in the integration of spatially coded mnemonic information with motor preparation to guide behavior.
Department of Neurology, University of Pennsylvania Medical Center, 3 West Gates, Area 9 3400 Spruce St., Philadelphia, PA 19104, USA. postle@mail.med.upenn.edu
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D000328:Adult; D002421:Caudate Nucleus / Q000502:physiology*; D005071:Evoked Potentials / Q000502:physiology; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology; D013037:Spatial Behavior / Q000502:physiology*