Abstract
AbstractThe role of prefrontal cortex in working memory (WM) is well established. However, questions remain regarding the topography and “domain-specific differentiation” of different types of information processing in the cortex. While it has been theorized that dorsolateral (DPFC) and ventrolateral (VPFC) prefrontal cortex preferentially process spatial and object WM, respectively, both electrophysiological evidence in the monkey and neuroimaging in the human have largely failed to demonstrate such regional differentiation. In this study we use near-infrared spectroscopy (NIRS) to detect functional changes, across relatively large cortical cell populations, simultaneously from prefrontal and posterior parietal cortices. Imaging data were recorded from a Rhesus macaque performing two types of WM tasks: a spatial task in which the animal had to retain the spatial position of a visual stimulus, and a non-spatial task where he had to retain its color (red or green) during a 20s delay. During performance of the spatial WM task, cerebral activation trends were found in which DPFC exhibited stronger activation than did the VPFC, and posterior parietal cortex maintained higher delay activation than did frontal regions. These differences were less pronounced during performance of the non-spatial task. Additionally, incorrect trials generally elicited lower activations during the delay period than did trials ending with a correct response. Furthermore, NIRS data collected during the performance of a haptic WM task also appear to exhibit inter-regional differences in delay activation. The data thus suggest the presence of preferential cognitive processing between and within posterior and frontal cortical regions.
Highlights
The cerebral cortex represents information in widely distributed, highly overlapping neural networks
Because of methodological differences between different investigations questions remain pertaining to the hypothesis of “domain-specific differentiation” in the LPFC, where dorsolateral prefrontal cortex (DLPFC) and ventrolateral prefrontal cortex (VLPFC) are proposed to selectively process spatial and nonspatial visual information, respectively
The present study aims to test that hypothesis by simultaneously examining BOLD activations in posterior parietal cortex (PPC) and LPFC
Summary
The cerebral cortex represents information in widely distributed, highly overlapping neural networks. In the case of visual working memory (WM), the degree of functional specialization for processing spatial information in the lateral prefrontal cortex (LPFC) remains unclear. Because of methodological differences between different investigations (the animal studies that suggest such local specialization have been electrophysiological while the conflicting human studies have used imaging) questions remain pertaining to the hypothesis of “domain-specific differentiation” in the LPFC, where dorsolateral prefrontal cortex (DLPFC) and ventrolateral prefrontal cortex (VLPFC) are proposed to selectively process spatial and nonspatial visual information, respectively. The present study aims to test that hypothesis by simultaneously examining BOLD activations in posterior parietal cortex (PPC) and LPFC. The following hypotheses are tested: 1) During the performance of a spatial visual WM task, DLPFC exhibits a higher degree of covariance with PPC than does VLPFC
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