Reaction-times and bioelectrical brain signals of drug-naive schizophrenic first-onset patients in identification and classification tasks
ABSTRACT The question of the present study is whether disturbances of response-selection in schizophrenic patients are discernible only if overt motor-actions are required, or also if covert cognitive actions are necessary.
Visual identification (digits) and classification (dot-enumeration) tasks were presented to 18 drug-naive, first-onset schizophrenic patients and healthy controls. It is assumed that enumeration of more than three dots requires additional cognitive processes as buffering and re-focusing of attention. Reaction-times and 21-channel-EEG were measured. For eye-movement artefact-elimination a new non-parametric regression approach was applied.
Reaction-times revealed that in the patient group response selection is lengthened in both tasks. Perception of dot numbers is not affected. Bioelectrical data depicted a left-lateralization of posterior P100 and N 100 in the patient group as well as an enhanced fronto-central P200.
Whereas in reaction-times of patients only a disturbance of response selection is discernible, bioelectrical measurements also point to an altered organization of perceptive processes.
Conference Paper: Two VLSI structures for implementing the gray level co-occurrence method[Show abstract] [Hide abstract]
ABSTRACT: The gray-level co-occurrence (GLC) method is a powerful technique that computes several GLC matrices on subregions of an image to measure its textural qualities. The method is not suitable for real-time image analysis and pattern recognition because of its high compute time. The authors propose a systolic array and a parallel architecture for evaluating the algorithm in an optimum time. Novel features of the structures include the minimization of intermediate I/O operations and the use of current existing hardware devices. The architectures are time optimal and are suitable for algorithm partitioningSystem Theory, 1990., Twenty-Second Southeastern Symposium on; 04/1990
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ABSTRACT: Schizophrenia patients (SZ) show early visual processing deficits in many, but not all, tasks. These deficits may be associated with dysregulation of intrinsic oscillatory activity that compromises signal-to-noise in the SZ brain. This question was studied using visual steady-state stimulation and post-steady-state presentation of transient visual stimuli. SZ had higher intrinsic oscillatory activity at the steady-state stimulation frequency (12.5 Hz) and at the 6.25 Hz subharmonic, showed a significant decrease in visual steady-state magnitude over 2s of stimulation, and were unable to promptly terminate the steady-state response following stimulation offset. If adjustment for levels of intrinsic brain activity were made, however, it would have appeared that SZ had activity of similar magnitude as healthy subjects following steady-state stimulus termination, indicating that such adjustments could substantially alter theoretical interpretations. Visual evoked potential abnormalities (N1/P2 amplitudes) present among SZ at the initiation of steady-state stimulation were less apparent in the 750 ms immediately following steady-state stimulation offset. Higher intrinsic oscillatory brain activity may be a fundamental characteristic of SZ that merits further evaluation for understanding this disorder's neuropathological correlates and associated symptomatology.Schizophrenia Research 08/2011; 133(1-3):106-11. DOI:10.1016/j.schres.2011.07.016 · 4.43 Impact Factor
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ABSTRACT: Response selection dysfunction contributes to processing speed impairment in schizophrenia. However, it is unclear if response selection impairment transcends sensory and motor modalities or is modality specific. To address this question, healthy subjects and individuals with schizophrenia completed reaction time (RT) experiments with different combinations of sensory cues (i.e. visual, auditory) and motor response (i.e. manual, vocal). We found that response selection impairment in schizophrenia was present regardless of the sensory and motor modality of the tasks and correlated with performance on neuropsychological tests of processing speed. These results implicate dysfunction of amodal response selection brain regions in schizophrenia. Interventions that reduce the length of response selection stage processing may improve processing speed in schizophrenia.Schizophrenia Research 12/2013; 152(2-3). DOI:10.1016/j.schres.2013.11.038 · 4.43 Impact Factor