The effects of the presence of a supportive other on hemodynamics were assessed in 28 male undergraduate students. Participants were assigned to a support group or to a non-support group and they executed a mental arithmetic task. In the support group, a close friend accompanied participants to the laboratory and they executed the task in the proximity of the friend. To minimize evaluative aspects, friends executed their own task (cross word puzzle) while listening to music with headphones. Heart rate, blood pressure, impedance cardiography and emotional responses were recorded. Participants in the support group relative to the non-support group showed reduced reactivity only in diastolic blood pressure. Distinct differences in hemodynamics were not found between the two groups. There were no group differences in negative affects, but obvious differences were found in positive affects. Interpersonal support may reduce cardiovascular response through cognitive processes. The role of positive affects was particularly emphasized as a stress buffer process. (Japanese Journal of Physiological Psychology and Psychophysiology, 23 (3) : 197-205, 2005.)

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To determine whether self-control of breathing can alter cardiovascular and psychological reactivity to a laboratory stressor, 29 male and female subjects were assigned at random to either experimental (n=13) or control (n=16) groups. All of the subjects completed two sessions of three trials each following a laboratory stress protocol involving mental arithmetic and cold pressor tests. The experimental subjects did not regulate their breathing during the first trial of each session, and tried to regulate their minute ventilation (MV) at their resting level during the following two trials using breath-by-breath MV feedback. The experimental subjects were able to prevent increases in their MV in response to the stressor, and had a significantly slower respiration rate, larger tidal volume, and higher end-tidal PCO₂ than the control subjects. The experimental subjects also had smaller increases in their heart rate than the control subjects (p <0.08). There was no statistical difference in either blood pressure or psychological mood between the two groups. These results suggest that self-control of breathing can be effective in altering cardiac parasympathetic inhibition during stress. ( Japanese Journal of Physiological Psychology and Psychophysiology, 23 (3) : 207-215, 2005.)

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This study investigated the effect of sweat secretion on negative and positive skin potential responses. In Experiment 1, the relationship between the rate of negative skin potential amplitude in the skin potential response (negative component rate) and the latency from the onset of the skin potential response to the sweating response (SPR-sweating latency) were determined. Six students participated in Experiment 1. Student's t-test indicated that the lower was the negative component rate, the shorter was the SPR-sweating latency. This result suggests that the less negative component shortens the SPR-sweating latency. In Experiment 2, the influence of the amount of sweat in the ducts on the positive component was investigated to clarify whether the presence of sweat in the ducts was important for the efficient secretion of sweat. Eight students participated in Experiment 2. It was found that when the ducts were saturated with sweat, the positive monophasic wave increased. Based on these results, we have developed an efficient-sweating model. ( Japanese Journal of Physiological Psychology and Psychophysiology, 23 (3) : 217-226, 2005.)

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The effects of time pressure (TP) on stimulus evaluation and reaction preparation processes were investigated using P300 and the lateralized readiness potential (LRP). Event-related potentials (ERPs) of participants performing visual and auditory discrimination tasks were recorded. TP was manipulated by using moderate or severe response time limits. TP effects on the P300 and LRP latency were compared between two levels of discriminability, which was manipulated by stimulus intensity. Results indicated that P300 latency was reduced by severe TP only when discrimination was difficult. LRP latency was affected by TP regardless of stimulus intensity. These results suggest that the durations of both stimulus evaluation process and reaction preparation process were reduced by TP. ( Japanese Journal of Physiological Psychology and Psychophysiology, 23 (3) : 227-236, 2005.)

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