Cognitive changes in schizophrenia-a critical look

Examination of neuropsychological functioning in schizophrenia indicates that against a background of diffuse impairment, some neurocognitive domains are differentially impaired. These include attention, memory and, to a lesser extent, abstraction and mental flexibility ('executive functions'). The deficits are present at the onset of illness and persist despite clinical improvement. The severity of initial deficits is weakly related to initial severity of symptoms, but a follow-up longitudinal evaluation suggests that the less patients improve in negative symptoms, the less they improve in neuropsychological performance. By contrast, improvement in some positive symptoms is associated with less improvement in some neuropsychological functions. The cognitive deficits are related to data from structural and functional imaging. Lower temporal lobe volume is associated with poorer cognitive abilities, and abnormally high left temporal lobe metabolism is also associated with poorer memory. The interplay between cognitive functioning, measures of brain structure and function, and clinical data is complex and seems to merit intensive and focused investigation. Such work can help elucidate pathophysiologic processes related to the phenomenology of schizophrenia.