Cardiac Arousal Research Articles

Effects of arousal and natural baroreceptor activation on the human muscle stretch reflex

The nociceptive flexion reflex is inhibited during systole; this inhibition may be due to increased baroreceptor stimulation. It is yet to be determined whether other spinal reflexes are similarly modulated across the cardiac cycle. There is also evidence that stretch and tendon reflexes are facilitated by increased arousal. This study investigated the effects of phase of the cardiac cycle and arousal on the muscle stretch reflex components M1, M2, and M3. Stretch reflexes were elicited in leg muscles at six intervals across the cardiac cycle during rest, number repetition, and mental arithmetic. Mental arithmetic provoked increased cardiovascular arousal and facilitated both M1 and M2 compared to rest and number repetition. The stretch reflex did not vary with the phase of the cardiac cycle. While the stretch reflex is susceptible to arousal, natural baroreceptor-mediated modulation across the cardiac cycle may be specific to nociception.

Heart rate activation during spontaneous arousals from sleep: effect of sleep deprivation

Objective: Arousal (AR) from sleep is associated with an autonomic reflex activation raising blood pressure and heart rate (HR). Recent studies indicate that sleep deprivation may affect the autonomic system, contributing to high vascular risk. Since in sleep disorders a sleep fragmentation and a partial sleep deprivation occurs, it could be suggested that the cardiovascular effects observed at AR from sleep might be physiologically affected when associated with sleep deprivation. The aim of the study was to examine the effect of sleep deprivation on cardiac arousal response in healthy subjects. Methods: Seven healthy male subjects participated in a 64 h sleep deprivation protocol. Arousals were classified into four groups, i.e. >3<6 s, >6<10 s, >10<15 s and >15 s, according to their duration. Pre-AR HR values were measured during 10 beats preceding the AR onset, and the event-related HR fluctuations were calculated during the 20 beats following AR onset. As an index of cardiac activation, the ratio of highest HR in the post-AR period over the lowest recorded before AR (HR ratio) was calculated. Results: For AR lasting less than 10 s, the occurrence of AR induces typical HR oscillations in a bimodal pattern, tachycardia followed by bradycardia. For AR lasting more than 10 s, i.e. awakenings, the pattern was unimodal with a more marked and sustained HR rise. The HR response was consistently similar across nights, during NREM and REM sleep, without difference between conditions. Conclusions: Overall, total sleep deprivation appeared to have no substantial effect on cardiac response to spontaneous arousals and awakenings from sleep in healthy subjects. Further studies are needed to clarify the role of chronic sleep deprivation on cardiovascular risk in patients with sleep disorders. Significance: In healthy subjects acute prolonged sleep deprivation does not affect the cardiac response to arousal.

Involvement of the cerebellum in classical fear conditioning in goldfish

To investigate the emotional role of the cerebellum of fish, we conducted experiments examining effects of cerebellar manipulations on fear-related classical heart rate conditioning in goldfish. We performed total ablation of the corpus cerebelli to examine the effect of irreversible effects. We also performed localized cooling of the corpus cerebelli, in place of the ablation, for reversible inactivation of the cerebellar function. Both the cardiac arousal response to the first presentation of the conditioned stimulus and the cardiac reflex to the aversive unconditioned stimulus were not impaired by the ablation or cooling of the corpus cerebelli. On the other hand, inactivation of cerebellar function severely impaired the acquisition of a conditioned cardiac response in the fear-related conditioning. In addition, localized cooling of the corpus cerebelli reversibly suppressed the expression of established conditioned response. We suggest that the cerebellum of fish is not only being a motor coordination center but also is involved in emotional learning.

Age related differences in electroencephalographic and cardiac arousal at the termination of sleep apnea/hypopnea.

The purpose of the present study was to determine whether electroencephalographic (EEG) and cardiac arousal, i.e. heart rate elevation at the termination of apnea/hypopnea are related to aging. The subjects were 13 middle-aged (40-60 years of age, 47.8+/-5.35 years) and 10 elderly (>60 years of age, 69.8+/-5.31 years) male patients with obstructive sleep apnea syndrome. We evaluated the number of apneas per an hour of sleep (apnea index: AI), the number of hypopneas per an hour of sleep (hypopnea index: HI), the summation of HI and AI (apnea/hypopnea index: AHI), sleep stage, the amount of time during which nocturnal oxygen saturation was decreased below 90% (oxygen desaturation time: ODT), and EEG and cardiac arousal at the termination of apnea/hypopnea using polysomnography with pulse oximetry. There was no significant difference in AHI, duration of apnea/hypopnea, and sleep stage distribution between the two groups. However, the ratio of apnea/hypopnea with EEG and cardiac arousal was significantly higher in middle-aged than in elderly patients. The ratio of HI to AHI was significantly lower in middle-aged than in elderly patients. In middle-aged patients, EEG and cardiac arousal were significantly correlated with AI, AHI, and ODT, whereas, in elderly patients, these parameters were not similarly correlated. Our findings suggest that the differences in EEG and cardiac arousal, and the pattern of sleep-disordered breathing (SDB) between middle-aged and elderly patients with SDB might be a physiological phenomenon of aging.

Cardiac reactivity to traffic noise during sleep in man

A relation between stimulus characteristics of traffic noise and cardiac response mechanisms during sleep was studied in 12 subjects, living along a highway with a high traffic density. Two experimental conditions were created inside the bedroom with (1) a normal sound level and (2) a reduced sound level. The indoor sound levels were reduced by means of acoustical double glazing of the windows facing the motorway with high traffic density. Ten nights were recorded per subject in each condition. Evoked Cardiac Responses (ECR) were observed due to peaks in the indoor recorded sound level signal in both conditions. The lowering of the sound level by sound insulation did not reduce the magnitude or the absolute level of the cardiac responses to the peaks in the traffic noise. This may be related to the fact that the sound insulation decreased the mean sound level, but not the number of sound peaks, thus indicating that the double glazing sound insulation was not optimal. Cardiac acceleration due to traffic noise stimuli did not decrease with time over the ten nights with high sound level. A relation was found between the magnitude of the ECR and the slope and the duration of the peaks in the sound level signal of the traffic noise as recorded in the bedroom. Our results provide evidence that “cardiac arousal” in response to traffic noise persists even during sleep. The cardiac reactivity was sensitive to changes in stimulus characteristics. Thus traffic noise can disturb sleep even without waking the subjects.

Affect intensity and cardiac arousal.

Relationships between affect intensity and basal, evoked, and perceived cardiac arousal were investigated in 3 experiments. Affect intensity was assessed using Larsen and Diener's (1987) Affect Intensity Measure (AIM). Cardiac arousal was evoked with exercise in the 1st study and with mental arithmetic in the 2nd and 3rd. Perceived cardiac arousal was measured under optimal conditions using a standard heartbeat discrimination procedure. Women as a group scored higher on the AIM. Affect intensity was unrelated to basal or evoked cardiac arousal and was negatively related to perceived cardiac arousal in all 3 studies. Data suggest that affect intensity, although unrelated to actual physiological arousal, is negatively related to the accuracy with which individuals perceive their own arousal. Results are discussed within the context of an expanded arousal-regulation model (Blascovich, 1990).

Affect intensity and cardiac arousal.

Affect intensity and cardiac arousal.

Glutamate, not gaba, causes prolonged elevation of cardiac arousal responses in goldfish

1. Goldfish ( Carassius auratus) were fitted with electrodes for recording electrocardiograms (ECGs) and catheters for intracranial perfusion of glutamate, GABA or teleost saline. 2. Glutamate elevated cardiac responses to the onset of illumination in a dose-related manner. 3. Habituation was considerably prolonged with the glutamate but not the GABA treatment. 4. The slight elevation of responses due to GABA was not maintained and may have been due to its use as a metabolic substrate. 5. It is suggested that glutamate may have a role in elevating responsiveness during aroused behaviour.

Epileptogenesis is associated with heightened arousal responses in fish

Intramuscular injection of sodium penicillin in roach ( Rutilus rutilus) caused delayed habituation of arousal responses to repeated presentation of the onset of illumination or of a ‘tap’ stimulus. Topical application of aluminium hydroxide to the telencephalon of roach had a similar effect but was shown, also, to induce electroencephalographic seizures, in which the EEG amplitude was elevated from 4–20 times its normal level. Both treatments caused intermittent, abnormal ‘weaving’ behaviour and sporadic, violent, uncoordinated motor activity. In goldfish, Carassius auratus, topical application of aluminium hydroxide also caused delayed habituation of quantitatively measured, cardiac arousal responses to a moving shadow stimulus, compared to controls. This delayed habituation was, however, largely a result of the elevated magnitude of these arousal responses. The results are discussed in relation to brain mechanisms normally operative during arousal which may be hyperactive in epilepsy.

Anticipatory changes in state, dual-process theory, and preliminary OR processes

Recent studies of phasic response fractionation in the OR context have led to a theoretical development of the multiregister model of Barry (1979), which emphasizes the role of preliminary processes in OR elicitation. In this new model (e.g., Barry, 1981b), the novelty and magnitude of the stimulus are coded in separate registers which are similar in their operating characteristics to the hypothetical processes H and S of dual-process theory +(Groves & Thompson, 1970), and which interact to produce the OR. The present study examined the parallel between S and the stimulus magnitude register by manipulating anticipatory cardiac arousal between stimuli. A warned target stimulus was predicted to provide a context of enhanced cardiac arousal in comparison with a warned nontarget. The predicted S effect was obtained in the peripheral pulse amplitude response (PPAR), an index of the magnitude register. This and other results of response fractionation support the new model of preliminary OR processes. The results also bear upon recent findings of inconsistent habituation with PPAR measures.

Deficits in habituation of cardiac arousal responses incurred by telencephalic ablation in goldfish, Carassius auratus, and their relation to other telencephalic functions.

The effects of telencephalic ablation on the habituation of cardiac arousal responses in goldfish was studied. The ablation was performed either by ligating the telencephalon of habituated fish between stimulus presentations or by aspiration prior to habituation. The former technique caused dishabituation; the latter, a slower rate of habituation than that of sham-operated controls. The habituation deficit incurred by surgical ablation was found to decline with time, being small after 2 wk. The results are discussed in relation to other telencephalic involvements in behavior and to the plasticity of other parts of the brain which enables them to assume telencephalic functions.

Choice between melodies differing in complexity under divided-attention conditions.

The processing-capacity and arousal-level effect on choice between computer-generated "melodies" differing in complexity were compared in a divided-attention situation. Subjects were exposed to either aversive (97 dB, 350-Hz square wave) or mold (56 dB) auditory stimulation prior to blocks of trials involving choice between simple (4.00 bits/tone) and complex (9.17 bits/tone) melodies. Concurrently with the processing of the chosen melody on each trial, subjects either had no task at all or worked on one of four tasks that systematically differed in (a) the processing effort demanded, and (b) the likelihood of an arousal-level increase due to conceptual conflict and/or physical exertion. Measures were obtained of changes in choice and cardiac arousal due both to auditory stimulation and tasks. Results showed that the processing-capacity factors influenced choice quite independently of the arousal-level fluctuations due to tasks, and suggested that an arousal-level increase (due to stimulation), even when relevant for choice, may be mediated by a reduction in processing capacity.

Signal Detection and the “Cardiac Arousal Cycle”

ABSTRACTThe hypothesis was tested that different phases of the cardiac cycle would be associated with differences in either sensory capacity or response bias, as estimated by signal detection analyses. Each of 10 subjects was given 800 signal (SN) and 800 non‐signal (N) trials randomly distributed throughout the cardiac cycle. The signal was a 35 msec duration, 1000 Hz tone, which was preceded by a 1 sec warning light. Electrocardiograph (EKG) cycles were subsequently divided into four phases, and the phase during which the SN or N trial fell was determined. Signal detection analyses performed on auditory sensitivity (d.) and estimate of response bias (Criterion Location) showed no measurable effect of EKG phase on either parameter. Results are discussed in terms of recent neurophysiological findings of cardiac rhythmic input to the nucleus tractus solitarius (which can inhibit cortical arousal), but little cardiac rhythm in the observed output. These considerations imply that “cardiac cycle arousal effects” are likely to be minute or nonexistent.

Patterns of cardiac arousal during complex mental activity.

Patterns of cardiac arousal during complex mental activity.