Prefrontal cortex and basal ganglia contributions to visual working memory

Abstract

Visual working memory (VWM) is a remarkable skill dependent on the brain's ability to construct and hold an internal representation of the world for later comparison with an external stimulus. The prefrontal cortex (PFC) and basal ganglia (BG) interact within a cortical and subcortical network supporting VWM. We used scalp electroencephalography in groups of patients with unilateral PFC or BG lesions to provide evidence that these regions play complementary but dissociable roles in VWM. PFC patients show behavioral and electrophysiological deficits manifested by attenuation of extrastriate attention and VWM-related neural activity only for stimuli presented to the contralesional visual field. In contrast, patients with BG lesions show behavioral and electrophysiological VWM deficits independent of the hemifield of stimulus presentation but have intact extrastriate attention activity. The results support a model wherein the PFC is critical for top-down intrahemispheric modulation of attention and VWM with the BG involved in global support of VWM processes.attention | electroencephalography | lesion | stroke E ven a seemingly simple action such as determining which of two bananas is riper requires us to compare real world visual information, such as the color of the banana you are currently looking at in the store, with your memory of the yellowness of the other banana you just put down. This relies in part on visual working memory (VWM), a remarkable ability wherein we construct and hold an internal model of a real-world visual stimulus that we then later compare against another stimulus. In essence, we construct and hold a model of the visual world and compare that model against subsequent inputs from the external world. VWM relies upon an intact and functioning prefrontal cortex (PFC), and damage to this region, such as from stroke, causes VWM impairments (1-3). However, cognitive processes do not localize to specific brain regions per se and a behavior as complex as VWM recruits a distributed network of cortical and subcortical structures (4-8), including the basal ganglia (BG) (9, 10) and visual extrastriate regions (11)(12)(13).Most computational models of VWM rely upon intercommunication between the PFC and the striatum such that memories are maintained via recurrent activation in fronto-striatal loops (14-16). In vivo, working memory maintenance is associated with sustained delay-period activity in the PFC (5, 17) and BG (18), although the BG are thought to play a role in gating information into the PFC to allow it to update representations where necessary (19). Although neurons in both visual extrastriate and the PFC maintain VWM representations during delay periods, PFC neurons encode more information about the stimuli and are more resistant to distractors than visual extrastriate neurons (20). Animal research shows that the BG rapidly learn task-relevant rules and may send relevant, preprocessed information to the PFC for subsequent selection and further processing (21). Anatomically, the BG are situate...

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