Profiles of neuropsychologic function in schizophrenia.

In this article, the author reviews basic neuropsychologic issues in the study of schizophrenia. The first issue is whether cognitive dysfunction reflects a degenerative process or is a core feature of the disorder. Evidence demonstrating that cognitive difficulties are present at illness onset and are not caused by medication, illness progression, or other nonspecific factors is reviewed. The second question is less easily answered and deals with whether cognitive difficulties represent generalized dysfunction or differential deficits in specific neurocognitive domains. One difficulty in answering this question is the heterogeneous nature of the disorder. Clinical and cognitive subtyping approaches to reducing heterogeneity are discussed, with the conclusion that cognitive approaches hold the most promise for understanding subtype differences in neurobiologic substrates. Finally, the relation of cognitive ability to functional outcome is described, and it is explained why there is a resurgent interest in remediation efforts. The article closes with suggestions for future directions.