Pathways to similar executive impairment: Comparison of schizophrenia patients and healthy aging individuals

Executive impairment is prominent in schizophrenia, in conditions such as Parkinson's disease and dementia and in healthy aging. Identifying processes that critically constrain executive function can advance investigation of their biological basis and treatment planning. Recent findings that elderly healthy individuals showed similar impairment on conditional exclusion task as schizophrenia patients raised the question whether similar processes are impaired. To test this we compared 56 schizophrenia patients, 57 elderly and 77 young healthy individuals on three executive tests: conditional exclusion, abstraction and inhibition and tests of working memory and psychomotor speed. Schizophrenia patients performed worse than elderly healthy on abstraction, inhibition and verbal working memory. They were similarly impaired on Penn Conditional Exclusion Test (PCET) outcome measures but differed in performance characteristics. Schizophrenia patients needed relatively more trials to learn the first PCET category than the second or the third. This correlated with other cognitive impairments, particularly in working memory. Elderly healthy individuals found it most difficult to learn the last category. The two groups showed different error patterns. We propose that schizophrenia patients have particular difficulty in early (probabilistic) learning (“what to do”) while aging individuals have selective impairment in executive integration. These constitute distinct targets for customized treatment in the two conditions.