Intellectual functioning and memory deficits in schizophrenia

There is converging evidence about the existence of different subgroups of patients with schizophrenia in relation to intellectual ability (intelligence quotient [IQ]). Studying cognitive deficits in such patients in relation to IQ, and more specifically to memory, could help determine the patterns of preserved and impaired functioning in cognitive abilities in association with patterns of preserved and compromised intellect. This information could serve to delimit the possibilities of treatment and rehabilitation in those patients.

A total of 44 patients with schizophrenia completed a cognitive battery that included executive functioning, attention, speed of information processing, working memory, explicit memory, implicit memory, and everyday memory. Their IQ was also measured to identify 2 subgroups with an IQ of 85 as the cutoff point. Then, differences between the groups in the neurocognitive measures were studied.

Performance in executive functioning, attention, working memory, and everyday memory, but not that in speed of information processing, explicit memory, and implicit memory, was associated with intellectual functioning. Patients performed at the same level in perceptual implicit memory but at a lower level in conceptual implicit memory as did healthy control subjects.

Cognitive deficits in schizophrenia are associated with intellectual functioning. Implicit memory should not be considered as a unique entity. It is suggested that conceptual implicit memory deficit may be a core feature of schizophrenia.