Abnormal response to negative feedback in depression

Background. Recent studies have suggested that subjects with depression suffer a diagnosis-specific motivational deficit, characterized by an abnormal response to negative feedback that endures beyond clinical recovery. Furthermore, it has been suggested that negative feedback may motivate non-depressed controls, but not depressed patients, to improve their performance in neuropsychological tests. Methods. We describe two studies. The first compared performance on the simultaneous and delayed match to sample (SDMS) task from the CANTAB neuropsychological test battery, in 20 patients with severe depression with 20 with acute schizophrenia, 40 with chronic schizophrenia and 40 healthy controls. The second examined the performance of depressed patients with diurnal variation in symptoms and cognitive function. Results. All patients groups showed impairments on the simultaneous and delayed match to sample task compared to controls. Depressed patients did not show an abnormal response to negative feedback. Controls did not show a motivational effect of negative feedback. Depressed patients with diurnal variation showed no variation in their response to perceived failure. There was no evidence of abnormal response to negative feedback in any patient group using the ‘runs test’ or of a motivational effect in controls. Conditional probability analysis was not independent of the total number of errors made in the SDMS task. Conclusions. Further studies are suggested to examine whether an abnormal response to negative feedback characterizes particular subgroups of patients suffering from depression

An analysis of memory dysfunction in major depression

15 patients suffering from DSM-III-R major depression were compared with 15 age-, sex-and intelligence-matched controls on a battery of memory tests, aimed at fractionating memory dysfunction in depression. Patients were unimpaired relative to controls on measures of short-term memory, recognition, semantic memory and implicit memory. There was no evidence of a hedonic bias in recall of positive vs. negatively valenced stimuli, nor was there any correlation between depression severity and level of memory impairment. Psychotic patients did not demonstrate greater memory impairment relative to nonpsychotic depressed patients. As a group, however, depressed patients demonstrated deficits in psychomotor speed and in free recall of material (both immediate and delayed). The selective recall deficit suggests that material has been encoded but that patients are particularly impaired with regard to search and retrieval processes

A double-blind, placebo-controlled study of tacrine in patients with Alzheimer's disease using SPET

Background: the effect of single-dose and long-term cholinergic enhancement with tacrine on regional cerebral perfusion was examined in patients with Alzheimer's disease using single-photon emission tomography (SPET). Method: 23 patients with probable Alzheimer's disease (DSM-III-R and NINCDS-ADRDA criteria) were scanned before and after a single oral dose of tacrine at the start of the study and again after 12 weeks of randomized, double-blind treatment with tacrine or placebo, using high resolution 99mTc-Exametazime SPET. Patients also underwent neuropsychological testing with the CAMCOG, the Mini-Mental State Examination and the Rivermead Behavioural Memory Test before and after 12 weeks of treatment. Results: occipital count ratios in all regions of interest declined by 3% over 12 weeks, indicating a progression of the disease. Acute tacrine challenge resulted in a 16% increase in the superior frontal and a 11% decrease in the anterior temporal cortex. The acute effects of tacrine were modified by 12 weeks of treatment, particularly in the medial frontal (cingulate) cortex where active treatment was associated with a reduced acute tacrine response. There were no changes in cognitive function associated with active treatment. Conclusion: the study demonstrates the sensitivity of cerebral perfusion measures to changes during acute and medium-term tacrine treatment