ABSTRACT
BACKGROUND: Numerous studies have suggested, via the interpretation of negative priming effects, that subjects with schizophrenia are less able than controls to inhibit irrelevant distracting information. Further issues concerning impairment in inhibitory processes are investigated here. First, recent research has revealed that negative priming (NP) effects can be caused by different processes, distractor inhibition or perceptual review. Therefore, conclusions concerning reduced inhibition in patients with schizophrenia are not possible from previous NP research. Secondly, previous NP studies have required subjects to identify some feature of the target. This is the first study to examine NP that uses a spatial task in patients with schizophrenia. METHOD: Twenty-eight subjects with schizophrenia and 28 age and sex matched non-psychiatric control subjects completed a computerized NP task that eliminated the possible contribution of perceptual review. RESULTS: Subjects with schizophrenia had reduced levels of NP compared to control subjects on this spatial NP task (t = 2.46, P < 0.02). Current age, positive, negative or total PANNS scores did not correlate with negative priming scores, but post hoc analyses revealed that clozapine-treated patients had significantly greater levels of negative priming than patients receiving typical antipsychotic medications. CONCLUSIONS: The present experiment eliminated the contribution of perceptual review to negative priming and demonstrated that when a pure measure of inhibition is taken on a localization task, patients with schizophrenia were less able to inhibit irrelevant distracting stimuli. The fact that NP was reduced in a spatial task suggested a more diffuse reduction in inhibition than previous studies that examined only identification-based responses.
Subject(s)
Attention , Inhibition, Psychological , Psychomotor Performance , Schizophrenia/diagnosis , Schizophrenic Psychology , Adult , Antipsychotic Agents/adverse effects , Attention/drug effects , Case-Control Studies , Female , Humans , Male , Psychiatric Status Rating Scales , Psychomotor Performance/drug effects , Reaction Time , Schizophrenia/drug therapy , Severity of Illness IndexABSTRACT
BACKGROUND: Neuropsychological studies have suggested that memory systems reliant on medial temporal lobe structures are impaired in patients with depression. There is less data regarding whether this impairment is specific to recollection memory systems, and whether clinical features predict impairment. This study sought to address these issues. METHOD: A computerized process-dissociation memory task was utilized to dissociate recollection and habit memory in 40 patients with past or current major depression and 40 age, sex and IQ matched non-psychiatric control subjects. The Cognitive Failures Questionnaire was used to assess patients' perceptions of day-to-day memory failures. RESULTS: Patients had impaired recollection memory (t = 4.7, P < 0.001), but no impairment in habit memory when compared to controls. Recollection memory performance was not predicted by indices of current mood state, but was predicted by self-assessments of impairment (beta = -0.33; P = 0.008) and past number of depressions (beta = -0.41; P = 0.001). There was no evidence that standard therapy with antidepressant medication either improved or worsened memory performance. CONCLUSIONS: The results confirm that patients with multiple past depressions have reduced function on recollection memory tasks, but not on habit memory performance. The memory deficits were independent of current mood state but related to past course of illness and significant enough that patients detected impairment in day-to-day memory function.
Subject(s)
Affect , Depressive Disorder, Major/psychology , Mental Recall , Neuropsychological Tests , Adult , Affect/physiology , Antidepressive Agents/therapeutic use , Depressive Disorder, Major/diagnosis , Depressive Disorder, Major/drug therapy , Depressive Disorder, Major/physiopathology , Female , Humans , Male , Mental Recall/physiology , Middle Aged , Paired-Associate Learning/physiology , Recurrence , Retention, Psychology/physiology , Temporal Lobe/physiopathologyABSTRACT
BACKGROUND: Several studies have suggested that visual backward masking (VBM) impairment is present in patients with bipolar disorder, but the clinical features, such as current symptoms, treatment status and past burden of illness that may contribute to the impairment have not been well described. This study examined well-characterized euthymic patients on two VBM tasks to ascertain the extent of VBM impairment in this group and the clinical correlates of this impairment. METHOD: Twenty-eight euthymic patients with a DSM-IV diagnosis of bipolar disorder were matched by age, sex and IQ with 28 non-psychiatric control subjects. Both groups completed two VBM tasks; one required subjects to locate the target stimulus, one required identification of the target stimulus. Reaction times and error rates across a range of target-mask inter-stimulus intervals were assessed. RESULTS: Patients were significantly slower and had more errors on both VBM tasks. There was a significant relation between reaction times on the identification task and past burden of illness, particularly past number of depressions. There was no discernible impact of treatment status on reaction time or performance, including no difference in lithium-treated versus not treated subjects. CONCLUSIONS: These results are consistent with previous reports of neuropsychological deficits in euthymic bipolar disorder patients. The potential benefit to employing tasks such as VBM is that it may provide a method for relating clinical variables such as illness burden with known neural pathways in order to elucidate better the pathophysiology leading to impaired cognitive performance in patients with bipolar disorder.
