Measuring the executive functions in schizophrenia: the voluntary allocation of effort.

INTRODUCTION: Executive functioning reflects not only what a patient does, but also how he does it or whether he does it at all [Lezak MD. The problem of assessing executive functions. Int. J. Psychol. 17 (1982) 281]. Standard test procedures strongly prompt subjects to certain behavior, so that initiative and the amount of voluntary effort one is willing to invest are therefore not being adequately assessed. METHODS: We developed the Cognitive Effort Test (CET); a test for executive functioning specifically aimed at measuring subject's free initiatives, and the amount of effort they invest voluntarily. It is a complex planning task, and performance is being judged by three subscales: Initiative, Planning, and Workload. 36 schizophrenia patients and 30 healthy controls were tested with the CET, and a battery of other cognitive tests (executive functioning, memory, attention and psychomotor speed) was added to investigate construct and divergent validity. Negative symptoms were also recorded (predictive validity). RESULTS: Patients scored below controls on Planning and Workload, but not on Initiative. The CET was significantly related to other tests for cognition but not to negative symptoms. CET Planning and Workload predicted group membership (patients-controls) better than the other tests for executive functioning combined. CONCLUSION: The CET appears to be a clinically useful test that measures an aspect of schizophrenia that is not being assessed by existing tests, presumably the voluntarily allocation of effort.

What is measured by verbal fluency tests in schizophrenia?

INTRODUCTION: Schizophrenia patients perform below the norm on verbal fluency tests. The causes for this are unknown, but defective memory, executive functioning and psychomotor speed may play a role. METHOD: We examined 50 patients with schizophrenia and related disorders, and 25 healthy controls with a cognitive test battery containing tests for verbal memory, executive functioning and psychomotor speed, and a categorical fluency test. RESULTS: Patients obtained significantly lower test results than the controls on most cognitive measures including the verbal fluency test. During the fluency test, they formed as many clusters, and switched as often between clusters as the controls did, but they generated fewer words per cluster. Interestingly, in the control group, fluency performance was predicted by memory and executive functioning, but not by psychomotor speed. In patients, verbal fluency was predicted by psychomotor speed, but not by memory or executive functioning. DISCUSSION: We conclude that psychomotor speed could be a crucial factor in cognition, and its influence on cognitive test performance should be considered in schizophrenia research. Furthermore, these data illustrate the importance of qualitative analysis of cognitive impairments in schizophrenia patients, as traditional cognitive tests often only provide quantitative information.

Deviant strategy on The Modified Six Elements Test in patients with schizophrenia.

Impaired executive functioning is found in a considerable proportion of schizophrenia patients. Neuropsychological tests are originally designed to measure the behavior of neurological patients and may therefore miss psychiatry-related cognitive deficits. Qualitative information on tests for executive functioning is important in psychiatric populations. The Modified Six Elements Test (MSET) is a planning test that consists of 6 tasks, for which subjects have limited time and have to obey to switching rules. This study concerns a qualitatively different approach schizophrenia patients use on the MSET, and its relationship with cognitive measures. MSET scores and strategies of schizophrenia patients were compared to those of healthy controls, closed-head-injury patients, and peripheral injury patients. Also, schizophrenia patients and healthy controls were compared on verbal memory and vigilance. Schizophrenia patients finish fewer assignments on the MSET, receive a lower profile score compared to healthy controls, and use a different strategy on the test compared to the other groups. They also perform below healthy controls on the tests for verbal memory and vigilance. Use of the different strategy in schizophrenia patients was related to impaired cognitive functioning. An interesting strategy used by schizophrenia patients on the MSET appears to be indicative of impaired cognitive functioning. This strategy may be a compensatory strategy to spare cognitive resources. It could also be the result of a concrete interpretation of the test instructions.

Attention and driving in traumatic brain injury: a question of coping with time-pressure.

BACKGROUND: Diffuse and focal traumatic brain injury (TBI) can result in perceptual, cognitive, and motor dysfunction possibly leading to activity limitations in driving. Characteristic dysfunctions for severe diffuse TBI are confronted with function requirements derived from the hierarchical task analysis of driving skill. OBJECTIVE: Specifically, we focus on slow information processing, divided attention, and the development of procedural knowledge. Also the effects of a combination of diffuse and focal dysfunctions, specifically homonymous hemianopia and the dysexecutive syndrome, are discussed. Finally, we turn to problems and challenges with regard to assessment and rehabilitation methods in the areas of driving and fitness to drive.

Cognitive deficits and social functioning in schizophrenia: a clinical perspective.

Impaired social functioning is one of the diagnostic features of schizophrenia. Cognitive functioning is also often impaired in several domains. Meta-analysis has shown a predictive value of cognition for a variety of domains related to social functioning (Green, Kern, Braff, & Mintz, 2000). The significance of these findings for clinical practice has remained largely uninvestigated, however, and is therefore taken up here. We investigated verbal memory, attention and executive functioning in 52 schizophrenia patients. Social functioning was assessed for different types of social roles. The percentages of cognitive and social impairments in our group were assessed according to clinical principles, normally used to judge an individual patient. A possible predictive relationship between cognition and social functioning was studied on the basis of these clinical criteria. A large proportion of patients showed impairments in both cognitive functioning and social functioning. However, the clinical method resulted in a successful prediction of social functioning in only 21-69% of the cases. Social functioning and cognitive functioning were impaired in a large proportion of patients, but were largely independent from each other. Since relationships between cognition and social functioning are weak, assessment procedures are inconsistent and possibly not optimally adjusted to the psychiatric population, the clinical relevance of cognitive testing in order to predict social functioning is as yet questionable.