Stroop stimuli were used to measure the negative priming effect in eight positive and 10 negative schizophrenics, 21 depressive and 35 healthy control subjects in order to test hypotheses of insufficient versus persistent cognitive inhibition in schizophrenia. Data show that schizophrenics do not increase their response times to suppressor Stroop items compared to identical but neutral Stroop stimuli because the insufficiency of their inhibitory processes weakens the distractor-suppression effect. However, pre-exposure of the lexical distractor can compensate for insufficient inhibitory mechanisms in positive but not negative schizophrenics, suggesting more severe deterioration in the latter. Depressed subjects showed a slower development of cognitive inhibition. The results suggest important differences in the temporal evolution of inhibitory processes, and are discussed in terms of Hemsley's (1977) and Frith's (1979) theories.
Cognitive impairments in depression have recently been proposed as secondary to more basic attentional disturbances. Studies have shown that performance on the Stroop Color-Word Test is impaired in depressives, but it is not clear whether this impairment reflects a primary distractor inhibition disturbance or a more global cognitive dysfunction, such as a reduction of processing resources. In the present study, unmedicated clinical depressives were evaluated using a computerized Stroop Color-Word Test and the Visuo-Spatial Interference Test, a selective attention task that makes fewer demands on resources. Compared with normal subjects, depressives presented increased choice reaction times (CRT) and interference in both tests. Correlations were found between CRT and interferences only in depressives, favoring the processing resource hypothesis. Further exploratory analysis comparing the more rapid depressives and the slower normal subjects on CRT revealed that although these subgroups had comparable CRT, rapid depressives still exhibited increased interference on the Visuo-Spatial Interference Test. Thus, in non- or mildly retarded patients, a specific distractor inhibition deficit was observed in absence of resource deficit.
Disruptive vocalizations (DVs) constitute a serious problem in geriatric nursing homes. The current literature suggests that DV can be interpreted as a way for demented persons with language limitations to communicate with others. In an attempt to test this hypothesis, 59 participants were recruited from six nursing homes to form two groups: one group of individuals with preserved language skills (PLS) and another group with altered language skills (ALS). They were compared on the frequency and types of DV. The results indicate that individuals with ALS manifest DV at a greater frequency than those with PLS. These persons also present a greater number of distinct DV forms. The results are interpreted in terms of language deterioration associated with dementia.
The present results suggest cognitive deficits (mostly of executive functions) and vascular and neurodegenerative vulnerability in LOPS. Further studies with larger samples are needed to confirm the present findings.
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