Cognition in schizophrenia: core psychological and neural mechanisms

Abstract

The challenge in understanding cognitive impairment in schizophrenia is that people with this illness have deficits in an array of domains. Here, we briefly review evidence regarding the pattern of deficits within three domains: context processing, working memory and episodic memory. We suggest that there may be a common mechanism driving deficits in these domains - an impairment in the ability to actively represent goal information in working memory to guide behavior, a function we refer to as proactive control. We suggest that such deficits in proactive control reflect impairments in dorsolateral prefrontal cortex, its interactions with other brain regions, such as parietal cortex, thalamus and striatum, and the influence of neurotransmitter systems, such as dopamine, GABA and glutamate.

Figure 1. Brain Regions Showing Altered Activity During Executive Function in Schizophrenia

Brain regions with significant activation across executive function task types. In the bottom row, clusters in which controls showed more activation than schizophrenic patients are in red and clusters in which schizophrenic patients showed more activation than controls are in blue. Reproduced, with permission, from [18].

Figure 2. Regions Showing Altered Activity During Working Memory in Schizophrenia

Regions in red showed reduced activity in individuals with schizophrenia compared to controls in a comparison of working memory performance to a control task in [46]. Regions in blue and green on the left hemisphere showed greater activity for verbal and than non-verbal working memory in both healthy controls and individuals with schizophrenia. Regions in blue and green on the right hemisphere are homologous regions to those on the left hemisphere.

Figure 3. Potential Common Mechanisms of Cognitive Dysfunction in Schizophrenia

Figure illustrating two potential pathways linking deficits in goal maintenance/proactive control, DLPFC function, and other cognitive impairments in schizophrenia. The figure on the left illustrates a pathway in which the influence of DLPFC dysfunction on deficits in cognitive domains such as executive control, working memory and episodic memory in schizophrenia is mediated by an impairment in proactive control, which leads to impairments in these other domains. The figure on the right illustrates a pathway by which DLPFC function directly influences cognitive function in many domains in schizophrenia (including proactive control), but in which deficits in other cognitive domains are not mediated through proactive control impairments.