In order to elucidate possible factors that effect P3s to task-irrelevant visual stimuli (non-target P3s), we made a normative visual event-related potential study with button-press tasks in four different conditions in which two factors (the number of colors of non-target stimuli, and the shape of the stimuli) were manipulated without any change in task nor target/non-target ratio.The peak distributions of non-target P3s (centrally peaking) were significantly different from those of task-relevant P3s (parietally peaking) in all conditions. The amplitude of non-target P3 decreased as the variety of colors of the non-target stimuli increased. The amplitude of nontarget P3 to colored solid circles was larger than that of non-target P3 to colored Stroop stimuli. Between each condition, task-relevant P3 and reaction time showed no significant difference. Both the variety of non-target stimuli and the shape of the stimuli were shown to have effects on the amplitudes of non-target P3s without any alteration in task-relevant P3s. It is suggested that the amplitude behaviors of non-target P3s partly reflect the amount of cognitive resource allocated for each different kind of task-irrelevant visual stimuli.
Abstract. To elucidate possible factors affecting the incidence of high-frequency positive occipital sharp transients of sleep (H-POSTS) and to investigate whether H-POSTS are associated with any specific pathophysiological conditions, we visually inspected on consecutive routine diurnal EEGs (2705 records) using our criteria for identification of H-POSTS. H-POSTS were observed in 164 records (subject age: 7.9 to 83.2 years). The incidence of H-POSTS was lower in subjects with highly abnormal EEG findings. Female subjects had a significantly higher incidence of H-POSTS than males that could not be explained by other factors. Patients with either fainting or headache had a sig nificantly higher incidence of H-POSTS and lower grade of EEG abnormality. The precise mechanism of the gender difference in the incidence of H-POSTS could not be determined. The occurrence of H-POSTS seemed to be associated with healthy sleep macrostructure, rather than with any specific pathophysiological phenomena. (Keio J Med 52 (1): 25-29, March 2003)
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