Enhanced semantic priming in schizophrenia: A computer model based on excessive pruning of local connections in association cortex

Abstract

Background: Many studies have found that people with schizophrenia exhibit abnormally high levels of semantic priming. Post-mortem and neuroimaging studies of schizophrenia suggest a reduction of neuritic processes (dendrites and synapses). Aims: To demonstrate that reductions in neuritic processes can produce excessive priming in patients with schizophrenia. Method: Associative memory was simulated using a computer-based neural network system consisting of two interactive neural groups, one coding for individual memories and the other for the category to which each memory belonged. Results: Variation of a single parameter determining the density of local connections within the two neuronal groups gave a close approximation to levels of memory access and semantic priming previously reported in normal subjects and in patients with schizophrenia. Conclusions: This study suggests that schizophrenia arises from excessive pruning of local connections in association cortex. Its findings shed light on the mechanisms underlying cognitive priming more generally, and how it might emerge developmentally.