Functional brain imaging of episodic memory in schizophrenia and first episode of psychosis

Memory is one of the cognitive functions that is most affected in schizophrenia and memory dysfunctions have a major impact on the functioning and quality of life of these patients. Functional brain imaging can help us identify the brain structures that are affected during the performance of a memory task. Identifying these regions can help us identify the specific cognitive processes that are affected in schizophrenia. To this end, I performed a meta-analysis of published functional brain imaging studies of episodic memory in schizophrenia. This meta-analysis showed that the prefrontal cortex and the medial temporal lobes are the brain regions that are most consistently reported as being affected in schizophrenia during the performance of a memory task. Most studies however used a low-level baseline condition that did not target a specific cognitive process. In addition, they included patients with a long-term history of schizophrenia, leaving open the possibility that factors linked to illness chronicity could have influenced the pattern of results. Based on the insights gleaned from the meta-analysis, I performed a functional magnetic resonance imaging study of episodic memory encoding in patients with a first episode of a schizophrenia spectrum psychosis (FEP) and healthy subjects. Three processes known to be involved in memory encoding were targeted, namely associative processing, semantic associative novelty and encoding success. In healthy subjects, both associative processing and semantic associative novelty were associated with increased activation in the medial temporal lobes, with no interaction between these two variables. In people with FEP, encoding success and associative processing revealed intact patterns of prefrontal and medial temporal lobe activation. In contrast, semantic associative novelty was associated with a marked reduction in medial temporal activation. The identification of selectively intact and deficient processes involved in memory encoding has potential clinical relevance for the development of more focused cognitive remediation strategies