Interactive effects of maintenance decay and interference on working memory updating in schizophrenia.

BACKGROUND: Deficits in working memory have been identified as a core cognitive impairment in schizophrenia. Prior work has identified a unique pattern of rapidly decreasing accuracy following intact encoding and updating of a single visuospatial target in patients with schizophrenia. Understanding whether these deficits are related to disruption of working memory stores following retrieval or part of a broader maintenance dysfunction may help elucidate the specific subprocesses underlying working memory deficits in schizophrenia. METHODS: Participants were 71 patients with a schizophrenia spectrum disorder and 43 healthy controls who completed a working memory paradigm that parametrically varied maintenance demands from 1000 to 8000 ms. RESULTS: Patients with a schizophrenia spectrum disorder were comparable to healthy controls at delays of 1000 ms. However, when delays were extended to 2000 and 4000 ms, the patient group showed significantly decreased accuracy. Additionally, the patient group showed a greater decline in accuracy following a second delay. CONCLUSIONS: These findings suggest that early encoding of one item is intact in patients with a schizophrenia spectrum disorder, but information rapidly decays from working memory stores with extended delays. Accuracy further decreased when information was retrieved from working memory, suggesting that working memory stores may also be susceptible to disruption from internal stimuli. Thus, working memory stores in patients with a schizophrenia spectrum disorder may be vulnerable to both rapid decay and interference.

Comprehensive neuropsychological findings in a case of Marchiafava-Bignami disease.

OBJECTIVE: Marchiafava-Bignami disease (MBD) is a rare complication associated with chronic heavy alcohol use, with case reports documenting a range of cognitive outcomes. Given the variability in MBD presentation and outcomes, milder cases may remain undiagnosed and few studies or case reports have presented a comprehensive neuropsychological profile of these patients. The objective of this case study was to describe the neuropsychological presentation and findings of a case of likely MBD. METHOD: The patient was a 46-year-old, African American female with a complex history of malnutrition and alcohol abuse presenting for outpatient neuropsychological evaluation. She was administered a comprehensive battery of neuropsychological tests as part of routine clinical care. RESULTS: Neuropsychological data demonstrated severe deficits in executive functions, complex visuoconstruction, and motor dexterity, as well as an amnestic verbal and visual memory pattern. CONCLUSIONS: Overall, data and the patient's initial presentation of acute behavioral change were consistent with some reports of cognitive and behavioral sequela of MBD. Additionally, the patient's history of chronic poor nutritional intake with exacerbation from chronic heavy alcohol use, and imaging findings of severe cerebral/corpus callosum white matter loss and bilateral frontoparietal atrophy, were highly suggestive of MBD.

Distinguishing patterns of impairment on inhibitory control and general cognitive ability among bipolar with and without psychosis, schizophrenia, and schizoaffective disorder.

BACKGROUND: Deficits in inhibitory control on a Stop Signal Task (SST) were previously observed to be of similar magnitude across schizophrenia, schizoaffective, and bipolar disorder with psychosis, despite variation in general cognitive ability. Understanding different patterns of performance on the SST may elucidate different pathways to the impaired inhibitory control each group displayed. Comparing nonpsychotic bipolar disorder to the psychosis groups on SST may also expand our understanding of the shared neurobiology of this illness spectrum. METHODS: We tested schizophrenia (n = 220), schizoaffective (n = 216), bipolar disorder with (n = 192) and without psychosis (n = 67), and 280 healthy comparison participants with a SST and the Brief Assessment of Cognition in Schizophrenia (BACS), a measure of general cognitive ability. RESULTS: All patient groups had a similar degree of impaired inhibitory control over prepotent responses. However, bipolar groups differed from schizophrenia and schizoaffective groups in showing speeded responses and inhibition errors that were not accounted for by general cognitive ability. Schizophrenia and schizoaffective groups had a broader set of deficits on inhibition and greater general cognitive deficit, which fully accounted for the inhibition deficits. No differences were found between the clinically well-matched bipolar with and without psychosis groups, including for inhibitory control or general cognitive ability. CONCLUSIONS: We conclude that 1) while impaired inhibitory control on a SST is of similar magnitude across the schizo-bipolar spectrum, including nonpsychotic bipolar, different mechanisms may underlie the impairments, and 2) history of psychosis in bipolar disorder does not differentially impact inhibitory behavioral control or general cognitive abilities.