Rapid eye movements (REMs) in REM sleep and voluntary saccades in wakefulness were compared in terms of the brain potentials preceding eye movements and the speed of eye movements. Sixteen undergraduate and graduated students who reported having dreams frequently participated in the experiment. REMs in REM sleep were recorded during natural nocturnal sleep and saccades in wakefulness were recorded during a self-paced visual search task. Brain potentials were averaged time-locked to the onset of eye movements. A negative potential shift (presaccadic negativity) occurred at central sites of the scalp before the onset of saccades, whereas no potential shift was found before the onset of REMs. Moreover, the velocity of REMs was slower than that of saccades. These findings suggest that REMs in REM sleep are initiated without voluntary preparation and controlled by a different neural mechanism from that in wakefulness. (Japanese Journal of Physiological Psychology and Psychophysiology, 20 (3) : 207-214, 2002.)

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Visual evoked potentials (VEPs) were recorded in normal human subjects using visual line stimuli with different orientation/color conjunction properties. A target specified as a orientation/color combination was flanked with distractor stimuli with irrelevant orientation and color. Subjects were asked to press one of the two buttons to indicate whether a stimulus at the target position was a target stimulus or not. The target position was either above (or below) 9 or 6 degree from the fixation point in the upper (or lower) visual field. The results showed that the accuracy of reporting was reduced when the target was in the upper visual field (UVF) compared to that of when the target was in the lower visual field (LVF). We found a significant VEP waveform change to target position, possibly due to the attention effect of 200ms after stimulus onset. When target position was at LVF6 and 9 deg, the N2pc amplitude form the right occipital-parietal region (P4) was maximized for the target presentation than the non-target. While no clear N2pc increase was observed for target presentation in the UVF6 and 9 deg. We concluded that the less performance to detect the target at UVF9 deg compared to that at LVF9 deg (as high as UVF/LVF6 deg) was due to lack of attention effect measured by N2pc amplitude. Thus, we suggest an asymmetry of feature-based attention processing between the upper and lower visual fields in the occipitoparietal lobe. (Japanese Journal of Physiological Psychology and Psychophysiology, 20 (3) : 215-224, 2002.)

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The purpose of this study was to examine the function of the hippocampus on time perception. The relationship between time perception and rhythmic neural activity in the hippocampal CA1 was investigated by analyzing hippocampal theta during performance of temporal discrimination and control tasks in rats (n= 8). A resetting of the hippocampal theta that time-locked at the stimulus onset was observed in the temporal discrimination task, but not in the control task. However, the resetting of the hippocampal theta was not observed at the stimulus offset in both tasks. The power of the hippocampal theta increased during the presentation of stimulus in the temporal discrimination task. These results suggested that the hippocampus played a role concerning time perception in the process related to working memory, but was not involved in the representation of temporal information. (Japanese Journal of Physiological Psychology and Psychophysiology, 20 (3) : 225-232, 2002.)

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This study investigated the effect of encouraged active coping through changed task difficulty on baroreceptor reflex sensitivity (BRS), an index of vagal activity, by use of mirror drawing (MD) which is considered to be a typical attentional task.
This study consisted of two experiments. In both of these, heart rate (HR), systolic blood pressure (SBP), and diastolic blood pressure (DBP) were measured, and BRS was computed using the sequence scanning method. In the first experiment, 24 subjects carried out simple computerized MD. As a result, increases in HR, SBP, DBP, and BRS were observed. In the second experiment, 14 subjects performed two MD conditions. In the restricted condition, a maximum time for going round the star and a limit to the degree of deviation outside its border were established whereas in the non-restricted condition, these parameters were not applied. Increase in HR, SBP, and DBP was more remarkable in the former than in the latter condition. BRS increased in the latter, but decreased in the former.
From the first experiment, it was revealed that simple MD fundamentally increases vagal activity. This may be attributable to the attentional nature of MD. In the second experiment, it was found that the encouragement of active coping suppressed vagal activity, even in the attentional task. These results suggested that the amount of mental effort required by the task has a large influence on the suppression of vagal activity. (Japanese Journal of Physiological Psychology and Psychophysiology, 20 (3) : 233-239, 2002.)

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In the present research, we investigated how stressor evoked by cold water affected somatosensory perception. The SEPs (somatosensory evoked potentials) were recorded under three conditions. The first was a coldwater condition (C condition) in that immersion in cold water was regarded as the stressor. The second was a hotwater condition (H condition) in that participants immerse hot water. The third was no-stressor condition (N condition) in that no stressor was given. The SEPs were recorded by electrical stimulation to upper parts of inside arms of subjects. As a result, in the N condition, the amplitudes of both N26-P38 and N50-P62 were larger than those in both C and H conditions. Following these results, amplitudes of the SEPs decreased by immersion in cold or hot water. In conclusion, some kinds of stressor on a part of the skin affect the other somatosensory perception. (Japanese Journal of Physiological Psychology and Psychophysiology, 20 (3) : 241-247, 2002.)

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