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Biomedical subjects

D M Landers

Publications and source records attributed to D M Landers.

At least 37 records · Page 2Linked to original sources
PubMed1987

Cardiac-related cortical activity during variations in mean heart rate.

Koriath and Lindholm (Int. J. Psychophysiol., 1986; 4: 183-195) reported cardiac-related cortical inhibition and speculated that cardiovascular events could modulate electrocortical activity by setting constraints on cortical excitability during diastole based on levels of blood pressure during systole. One dimension of this proposal could be supported if the extent of cardiac-related cortical activity (CRCA) varies with changes in heart rate and blood pressure. The current study investigated this dimension of cardio-cortical relationship by having each subject perform a fixed-foreperiod reaction time task while pedalling a bicycle ergometer under three conditions of workload: No Pedal (0 kpm/min), Lo Pedal (150 kpm/min), and Hi Pedal (450 kpm/min). Mean HR increased significantly from No Pedal to Lo Pedal to Hi Pedal. Results confirmed the presence of CRCA during variations in mean HR and indicated that the extent of CRCA increases with increases in mean HR. This investigation reinforces the importance of the extrahomeostatic effects of cardiovascular afferent fibers and supports the importance of psychophysiological measures which integrate the activity of cardiovascular, autonomic, and central nervous systems.

Adolescent↗
PubMed1987

A meta-analytic review of aerobic fitness and reactivity to psychosocial stressors.

The effects of aerobic fitness on resistance to psychosocial stressors are reviewed. To unravel the inconsistent results in studies examining the relationship between aerobic fitness and psychosocial stress response, a meta-analysis was conducted. The results of 34 studies having 92 effect size estimates from 1,449 subjects were statistically combined to compare psychosocial stressor tasks and arousal measures. The average effect size estimate of 0.48 was significantly different from zero (P less than 0.01), indicating that aerobically fit subjects had a reduced psychosocial stress response compared to either control group or baseline values. The test for the homogeneity assumption showed that it could not be rejected, and thus none of the proposed moderating variables altered the aerobic fitness-psychosocial reactivity relationship. Various underlying mechanisms which may contribute to this response are discussed, and future research directions are presented.

Aerobiosis↗
PubMed1981

Temporary keratoprosthesis for use during pars plana vitrectomy.

We have developed a series of temporary keratoprostheses that permit closed pars plana vitrectomy in eyes with abnormal corneas. These devices are placed into a trephined opening in the cornea, and provide a clear, stable view of the intraocular contents. Immediately after vitrectomy, the keratoprosthesis is replaced with a corneal graft. We have used this technique successfully in four eyes with opaque or severely traumatized corneas.

Adult↗
PubMed1980

Iris pigmentation and fractionated reaction and reflex time.

Recent investigations indicate that an iris pigmentation-motor behavior exists, but may be limited to the reaction time component of a motor task. The absence of differences in peripheral nervous conduction (Wolf and Landers, 1978) suggests that a central nervous system mechanism may be operating, possibly dependent on the characteristics of neuromelanin or catecholamine turnover. Experiment 1 tested this notion by fractionating simple reaction time into the premotor and motor components by electromyography. ANOVA revealed that dark-eyed subjects had faster total reaction times and premotor times, but only the premotor time component approached significance (p < 0.07). Experiment 2 fractionated patellar reflex time of light-eyed and dark-eyed subjects into reflex lagency and motor components. There were no eye color differences for any of the reflex time measures. The results of Experiments 1 and 2 support a central nervous system explanation for the iris pigmentation-reaction time phenomenon.

Brain↗
PubMed1978

Social facilitation during the initial stage of motor learning: a re-examination of Martens' audience study.

This study partially replicated Martens' (1969a) social-facilitation study of motor behavior. His very robust performance findings provided impressive confirmation for Zajonc's hypothesis, and his arousal findings have since been used as evidence for a nonlearned-drive basis for social facilitation. The present study also extended Martens' investigation by examining the separate and combined effects of an audience and videotape camera. The effects due to the presence of the audience and camera were not additive; instead, the audience detrimentally affected subjects' performance consistency and the camera resulted in more trials with errors greater than 30 msec after the performance criteria had been attained. Martens' most robust findings for constant error were not replicated, nor were some of his physiological arousal findings. His pattern of constant error results over all trials is atypical of known learning strategies that subjects use to reduce error over successive trials. Overall, audience effects accounted for only a very small portion of the variance.

Journal Article↗