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Biomedical subjects

J R Jennings

Publications and source records attributed to J R Jennings.

At least 73 records · Page 4Linked to original sources
PubMed1991

Behavioral modulation patterns fit an animal model of vagus-cardiac pacemaker interactions.

The present study used a computer model of the dynamic interaction between the vagus nerve and the sinoatrial pacemaker membrane potential in the heart of the rabbit to reconstruct heart rate changes under vagal excitation conditions. We asked whether a hypothetical pattern of vagal acetylcholine (ACh) release, which was based on human heart rate results in a reaction time task, could be fit to this model. The reconstructed heart rate results showed changes that were highly consistent with experimental human heart rate changes. The model reliably reproduced effects of parameters such as intrinsic heart rate level, ACh stimulus intensity, and ACh stimulus duration. In addition, the effects of anticipatory vagal ACh release, stimulus-induced ACh, and subsequent blocking of ACh, which usually interact in human cardiac cycle time functions, could be untangled in the reconstructed heart rate results. We concluded that the mathematical model may be useful for formulating hypotheses and constructing experimental task designs for studies of human heart rate.

Acetylcholine↗
PubMed1991

Graphical and statistical techniques for cardiac cycle time (phase) dependent changes in interbeat interval.

Cardiac cycle time effects refer to the relative lengthening or shortening of a single cardiac cycle as a function of when in the cycle brief sensorimotor events occur. These effects may provide short-latency measures of cardiac sensitivity to psychological events. Conventional representations have, however, failed to clearly separate changes in interbeat interval due to cycle time--i.e., phase dependent changes--from other types of change. This paper advocates a particular technique of plotting to solve these representation problems. Heartbeat timing is represented in real time and in the context of beats both preceding and following the event of interest. The plot, a phase-sensitive plot, conceptualizes phase-sensitive (cardiac cycle time) effects as a change in linear or higher order trend. Thus, an adaptation of trend analysis is proposed as an efficient statistical analysis that follows directly from the proposed representational technique.

Data Display↗
PubMed1991

Weak sensory stimuli induce a phase sensitive bradycardia.

We attempted to demonstrate that significant perceptual stimuli would induce different degrees of heart rate deceleration depending on when (phase) in the cardiac cycle they occurred. Relative to previous work, we concurrently examined a number of factors that might alter the amplitude of such a cardiac cycle time effect. Stimulus intensity and presence or absence of a speeded response were manipulated. Liminal stimuli and a perceptual rather than motor set were expected to maximize any cardiac cycle time effect. Respiratory phase, length of average interbeat interval, and number of trials were also investigated. Twenty-four college aged, male volunteers were randomly separated into equal groups receiving instructions either to judge which of two weak visual stimuli occurred or to execute a speeded, discriminative response to the stimuli. Discriminative stimuli were presented at either 0, 150, 250, 350, or 500 ms after the R-wave of the electrocardiogram. Stimuli were presented with an intensity that had yielded either 63% or 90% correct detections in a prior psychophysical assessment. A phase dependent deceleration occurred after both intensities of stimuli. Poststimulus deceleration was greater for stimuli in early to mid cycle as suggested by earlier work. As expected, this result was clear when the stimuli were presented during the expiratory phase of respiration. Neither perceptual/motor set nor stimulus intensity altered the phase sensitive deceleration. Thus, phase sensitive deceleration was confirmed using demanding sensory stimuli and an improved representational technique.

Adolescent↗
PubMed1991

Response inhibition initiates cardiac deceleration: evidence from a sensory-motor compatibility paradigm.

Two experiments tested the hypothesis that response selection processes alter the timing of the shift between anticipatory cardiac deceleration and acceleratory recovery. Experiment 1 compared changes in cardiac interbeat interval induced by the manipulation of sensory-motor compatibility in a four choice reaction time task. A direct spatial mapping between a linear array of light-emitting diodes (LEDs) was compared to randomly assigned, indirect (non-compatible) mappings. Experiment 2 repeated these two tasks and added a two choice condition with direct spatial mapping, a task frequently employed to examine heart rate deceleration. Fifteen college aged males participated in Experiment 1; 18 college aged males participated in Experiment 2. In both experiments anticipatory cardiac deceleration either reached a plateau or shifted to acceleration by the interbeat interval in which the stimulus occurred. In contrast to previous reports, a secondary deceleration, rather than cardiac acceleration, often followed the stimulus. The secondary deceleration was greater with non-compatible mapping, slow response speeds, and short intertrial intervals. The findings suggested that the motoric inhibition required during response selection induces a phasic cardiac deceleration.

Adolescent↗
PubMed1991

Daytime sleepiness in the healthy "old old": a comparison with young adults.

OBJECTIVE: To determine if excessive daytime sleepiness is an inevitable consequence of aging. METHODS: Daytime sleepiness was measured using Multiple Sleep Latency Tests (MSLT's) before and after a night of total sleep deprivation in a sample of 22 healthy men and women in their eighties and 29 men and women in their twenties. RESULTS: Young adults were somewhat sleepier than elders, as measured by rapidity of sleep onset during daytime nap recordings using the MSLT, and showed a higher incidence of REM sleep during naps. However, recovery from the effects of acute sleep loss was slower in the elderly, judging from the presence of more daytime sleepiness 2 days after a night of total sleep deprivation. Such persistent sleepiness was absent in the young adult control group. CONCLUSIONS: Healthy persons in late old age may have a level of daytime sleepiness no greater than, and perhaps even less than, that seen in healthy young adults.

Adult↗
PubMed1990

Effects of smoking context on habituation to a repeated cognitive task.

This study assessed the role of smoking-related cues on habituation of electrodermal responding and facial neuromuscular responses in male smokers. In three of the four groups, subjects smoked for the first five trials followed by the laboratory arithmetic task. On the sixth trial one group of subjects continued to smoke nicotine cigarettes, while the context was changed for subjects in the other groups by 1) omitting the pharmacological cues (smoking a non-nicotine cigarette) or 2) omitting both the pharmacological and behavioral cues (not smoking). Subjects in a non-smoking control group did not smoke before any of the six trials. During trials 1-5, smoking significantly increased the rate of habituation of electrodermal activity. On trial 6, electrodermal activity significantly increased for subjects who had a change in smoking context, whether it involved removal of pharmacological or smoking plus pharmacological cues. No differences in electrodermal activity were observed between subjects in these groups compared to non-smoking control subjects. Smoking increased zygomatic activity (predominant during smiling) during trials 1-5, consistent with an interpretation of the positively reinforcing nature of smoking. Corrugator activity (predominant during frowning or concentration) increased for subjects who had both the pharmacological and behavioral smoking cues omitted on trial 6.

Adolescent↗
PubMed1990

Aging increases the energetic demands of episodic memory: a cardiovascular analysis.

We hypothesized that older volunteers allocate more attentional resources to memory maintenance than do younger volunteers. Allocation of a resource supporting memory maintenance was inferred from performance and cardiovascular measures. Eighteen 18- to 26-year-old men and eighteen 60- to 79-year-old men performed a serial memory task both as a single task and as a dual task that added simple reaction time stimuli. Items presented early or later in the serial list created relatively low or high memory load. The results suggested that older men allocated greater attention to memory maintenance, particularly during high-memory-load items. They showed a slowing of dual-task reaction time and increased heart rate during high- vs. low-memory-load items. Cardiac and vascular reactions further suggested that memory maintenance is supported by phasic autonomic adjustments and that with age, more of this support is required for adequate maintenance of episodic memory.

Adolescent↗
PubMed1990

On the shift from anticipatory heart rate deceleration to acceleratory recovery: revisiting the role of response factors.

The influence of inducing motor responses of low and high force at different times in the cardiac cycle was examined. A handgrip response was used which allowed the separation of response initiation from response completion. Based on earlier work, we expected initiation, rather than completion, to initiate poststimulus cardiac acceleration. We also thought that preparation for a high force response might alter preparatory changes of interbeat interval differently from preparation for a low force response. Fifteen college-aged male subjects performed a warned reaction time task in which a visual stimulus signalled a handgrip requiring either a high or a low force to close. NoGo trials in which an inhibit signal was presented occurred on 12% of the trials. Stimuli occurred either on the R-wave of the electrocardiogram or 300 ms later. Reaction speed was varied in different trial blocks by rewarding response times of 200 ms (+/- 50 ms), 300 ms, or 400 ms. Results based on the timing of response initiation were essentially identical to those based on the timing of response completion. High force relative to low force was associated with both earlier response initiation and earlier cardiac acceleration. Force did not alter preparatory cardiac deceleration. Force and response speed did, however, alter the level of heart rate after response occurrence. Thus, response initiation (or an earlier response process) appears to induce a cardiac acceleration whose level is influenced by the speed and force of the motor response.

Adult↗
PubMed1990

Sleep stage physiology, mood, and vigilance responses to total sleep deprivation in healthy 80-year-olds and 20-year-olds.

Little is known about sleep and the effects of total sleep loss in the 'old old' (i.e., 80-year-olds). We investigated sleep, mood, and performance responses to acute sleep deprivation in healthy 80-year-olds (n = 10) and 20-year-olds (n = 14). The protocol consisted of three nights of baseline sleep, one night of total sleep deprivation, and two nights of recovery sleep. Mood and vigilance were tested using visual analog scales and a Mackworth clock procedure in the morning and evening of each study day. Daytime sleepiness was measured by five naps on the days following the third and sixth nights. Old subjects had lower sleep efficiency and less delta sleep than young subjects. However, sleep continuity and delta sleep were enhanced in both groups on the first recovery night, indicating that sleep changes in old subjects are at least partially reversible by this procedure. Surprisingly, young subjects had shorter daytime sleep latencies than the old, suggesting a greater unmet sleep need in the former group. Mood and performance were disturbed by sleep loss in both groups, but to a greater extent among the young. This suggests that acute total sleep loss is a more disruptive procedure for the young than for the old.

Adult↗
PubMed1989

Does the heart know what the eye sees? A cardiac/pupillometric analysis of motor preparation and response execution.

Autonomic response measures are well suited for the study of preparation because they allow the analysis of covert aspects of performance. This is illustrated by an experiment in which task-evoked cardiac and pupillary responses were compared during a disjunctive (Go/No Go) reaction task. The motoric demands of the task were varied by manipulating foreperiod length (4 and 8 s) and probability of response (25%, 50%, and 75%). Reaction time increased with foreperiod length and decreased with probability of response. The depth of anticipatory heart rate deceleration was affected only by foreperiod length. Analysis of the beats during, and directly preceding and following the imperative stimulus revealed that interbeat intervals increased with probability of responding and foreperiod duration. The effect of stimulus timing relative to the R-wave of the ECG was also analyzed. Early occurring stimuli prolonged the cycle of their occurrence more than late occurring stimuli. The cycle time effect was somewhat more pronounced for No Go stimuli than for Go stimuli. The subsequent cycle was shorter for early occurring stimuli compared to late stimuli. This effect was stronger for Go compared to No Go trials. Both Go and No Go reactions elicited significant pupil dilations. The No Go dilation peaked earlier than the Go dilation and its amplitude was smaller. Probability of responding affected the latency of the No Go dilation but not that of the Go dilation. The current results justify an interpretation of preparation in terms of a timing mechanism (indexed by heart rate deceleration during the foreperiod) and a mechanism allocating processing resources to stimulus encoding (indexed by cardiac slowing just prior to stimulus occurrence) and response preparation (indexed by continued cardiac deceleration and pupillary dilation).

Adult↗
PubMed1989

Nocturnal penile tumescence in healthy 20- to 59-year-olds: a revisit.

This report presents data on normative nocturnal penile tumescence (NPT), based on a study of 48 healthy men aged 20-59 years, without complaints of erectile dysfunction. In general, the current measures show good concordance with those reported by Karacan and colleagues in 1976. The effect of "pathology-free" aging (from age 20 to 59) on electrographic measures of NPT is relatively modest, accounting for 8.4-14.4% of the variance. Furthermore, no age effect on visual estimates of erectile fullness or on buckling force estimates of penile rigidity were present. Maximum buckling force and maximum erectile fullness showed stability across the four decades of the Pittsburgh sample.

Adult↗
PubMed1988

Nocturnal penile tumescence is diminished in depressed men.

Although depressed individuals commonly report decreased libido, it was not known if such changes are accompanied by neurophysiological alterations. Preliminary studies suggest that some depressed men may manifest diminished nocturnal penile tumescence (NPT), an objective measure of erectile capacity. We report NPT findings in 34 male outpatients with major depression (SADS/RDC) and an age-matched group of 28 healthy controls. A 3-night electroencephalographic (EEG) sleep/NPT protocol was utilized, with penile rigidity (buckling force) determined on night 3. Analysis of night 2 data by MAN-COVA revealed significant effects for age, the covariate (F = 2.86, p = 0.002), and diagnosis (F = 2.32, p = 0.02). Depressed men had significantly diminished NPT time (F = 16.8, p less than 0.001), even when adjusted for sleep time (F = 13.4, p less than 0.001) or rapid eye movement (REM) time (F = 7.2, p less than 0.01). NPT time was reduced by greater than or equal to 1 SD below the control mean in 40% of depressives and was comparable to the level seen in 14 nondepressed patients with a clinical diagnosis of organic impotence. An intermediate proportion of depressed patients (38%) had maximum buckling forces less than or equal to 500 g, indicating diminished penile rigidity, when compared to controls (16%) and men with presumed organic impairment (93%) (p less than 0.001). Diminished NPT time and low buckling force were associated with a history of erectile dysfunction within the index depressive episode (p less than 0.001). These findings suggest that depression in men is associated with a potentially reversible decrease in erectile capacity, which may be associated with significant sexual dysfunction.

Adult↗
PubMed1988

Diagnostic performance of nocturnal penile tumescence studies in healthy, dysfunctional (impotent), and depressed men.

Nocturnal penile tumescence (NPT) studies were evaluated in 17 men with a clinical diagnosis of organic erectile dysfunction in comparison to age-matched healthy controls (n = 17) and depressed men (n = 17). The dysfunctional group had significantly fewer NPT episodes and reduced maximal penile tip changes when compared to healthy controls and depressed patients. Further, the dysfunctional group had significantly diminished erectile fullness and reduced penile rigidity. Diagnostic performance of polygraphic (night 1) and visual inspection (nights 2 or 3) components of the NPT protocol were examined in these criterion groups. A diagnostic classification based on polygraphic measures successfully discriminated 73.5% of dysfunctional and healthy control subjects, but classified 47% of depressives in the dysfunctional range. Use of visual inspection indices correctly identified 88% of the dysfunctional sample and 94% of normal controls, and reduced the "false-positive" rate in depression to only 18%. Results support the diagnostic utility of NPT studies, particularly when enhanced by visual inspection procedures. Nevertheless, the presence of major depression may confound interpretation of such studies.

Circadian Rhythm↗
PubMed1988

Assessment of sexual function in depressed, impotent, and healthy men: factor analysis of a Brief Sexual Function Questionnaire for men.

We report a study of sexual function in outpatient men with major depressive disorder (n = 42), compared with healthy control men (n = 37) and a clinic sample complaining of erectile dysfunction (n = 13). A principal-components factor analysis of the Brief Sexual Function Questionnaire confirmed differences in the clinical dimensions of sexual activity/performance, interest, satisfaction, and physiological competence. The four factors accounted for 72% of the variance in the analysis. Acceptable test-retest reliability, construct validity, and concurrent validity (with the Derogatis Sexual Function Inventory and a self-report behavioral log) were demonstrated. Parallel observations with findings from previous nocturnal penile tumescence studies in these same men are discussed.

Adult↗