The relationship between physiological arousal and cortical and autonomic responses to postural instability

Postural instability evokes cortical and autonomic reactions in addition to the primary compensatory response, and it is hypothesized that these responses may be related to underlying affective influences such as tonic physiological arousal. The purpose of this study was to determine whether perturbation-evoked cortical potentials (N1 and P2) and electrodermal responses (EDRs) were related to each other or to tonic electrodermal level (EDL). Ten healthy individuals received sixty perturbations while standing at ground level (LOW) and at the edge of an elevated platform (HIGH), where an unsuccessful reaction could lead to a fall from a height of 160 cm. Postural responses, tonic EDLs and N1 potentials were all significantly larger (p ≤ 0.01) at the HIGH height relative to LOW. EDR amplitudes did not show a main effect of condition, but habituated less at the HIGH height (interaction p = 0.04). P2 potentials were not different between conditions (p > 0.05). There was no statistically significant relationship between the magnitude of change in N1 amplitude between conditions and the change in EDR amplitude between conditions (R = 0.25, p = 0.5), between magnitude of N1 change and magnitude of EDL change (R = −0.23, p = 0.25), or between magnitude of EDR change and EDL change (R = −0.51, p = 0.16). Altered cortical and autonomic responses at the HIGH height were independent of elevated physiological arousal. These findings have implications for understanding the role of cortical and autonomic responses in compensatory balance control, and alleviate concerns about the potential influence of underlying arousal on electrodermal reactivity.     

Information processing strategies in good and poor readers

Visually presented information can be processed either by sequential analysis of individual bits or in parallel by grasping the total information as a complete pattern. Reading provides an example of a stimulus to which either process can be applied. Learning to read, however, appears to require a sequential process for efficient learning. Using a microcomputer, a program was generated to present arrays and sequences of Hebrew letters and Arabic numberals to 160 second‐and third‐grade Israeli school children. Using the computer output as a stimulus, we examined the children's facility in, and preference for, either holistic or sequential processing. The children's reading skills were assessed by their teachers and were used in analyses to examine the relationships among perceptual strategy, preferred strategy, and reading achievement. The results showed that, although the performance of good readers was better than that of poor readers on both strategies, the preference of individual pupils for the sequential strategy was positively correlated with reading achievement. Almost all good readers showed a preference for a sequential strategy, whereas a substantial proportion of the poor readers showed a preference for a holistic/parallel strategy. This computer‐generated testing technique provides a possible method for early identification of children at risk for reading failure.     

The relationship between a night's sleep and subsequent daytime functioning in older poor and good sleepers

Those suffering insomnia symptoms generally report daytime impairments. However, research has not assessed whether this relationship holds on a nightly basis, despite the strongly held belief that a night of poor sleep impairs mood and functioning the following day. The objective of this study was to test this relationship in a group of older poor sleepers with insomnia symptoms compared with good sleepers. This study utilized a within‐subjects design to investigate day‐to‐day subjective daytime functioning and its relation to the previous night's sleep. Seventeen older individuals (mean age: 67.5 years) were identified with a retrospective questionnaire and 2 weeks of sleep–wake diary to have poor sleep consistent with insomnia. Seventeen good sleepers (mean age: 67.8 years) were selected using the same measures. Participants reported their beliefs about sleep and daytime functioning on the Dysfunctional Beliefs and Attitudes about Sleep Scale (DBAS‐16). One week later they commenced a 14‐day period of sleep–wake diaries and concurrent responses to a modified Daytime Insomnia Symptom Scale (DISS). Results showed significant night‐to‐day covariation between sleep efficiency and daytime functioning for individuals with poor sleep (r = 0.34), but not for good sleepers (r = 0.08). Those poor sleepers who held this covariation belief most strongly were those who subsequently showed this night‐to‐day relationship the most strongly (r = 0.56). This was not true for good sleepers. For those suffering insomnia, these findings demonstrate their belief that a poor sleep is followed by an impaired daytime, consistent with their experience.     

Differences in cardio-respiratory responses to exhaustive exercise between athletes and non-athletes

Summary To study the factors limiting the O₂ supply in heavy exercise, O₂ uptake at exhaustion was determined by progressive loading method with a bicycle ergometer in 33 well-trained male runners and 34 male sedentary adults. Pulmonary ventilation, oxygen removal, respiratory rate, tidal volume, pulmonary diffusing capacity, alveolar-capillary oxygen difference, cardiac output, arterial-venous oxygen difference, stroke volume and heart rate were measured. It was found that pulmonary diffusing capacity, cardiac output and stroke volume were correlated with the difference in O₂ uptake at exhaustion between athletes and non-athletes.     

Nocturnal cardiac autonomic profile in young primary insomniacs and good sleepers

We investigated cardiac vagal and sympathetic activity in 13 young primary insomniacs (PI; 24.4 ± 1.6 years) and 14 good sleepers (GS; 23.3 ± 2.5 years) during nocturnal sleep. Pre-ejection period (PEP; inversely related to beta-adrenergic sympathetic activity), interval between consecutive R-waves (RR), and vagal-related indices of time- and frequency-domain heart rate variability were computed during pre-sleep wakefulness and undisturbed arousal-free sleep stages (N2, SWS, REM) as well as across the whole night irrespective of the presence of disruptive sleep events (e.g. sleep arousals/awakenings) and/or sleep stage transitions. Groups exhibited a similar vagal activity throughout each undisturbed sleep stage as well as considering the whole night, with a higher modulation during sleep compared to prior wakefulness. However, PEP was constantly shorter (higher sympathetic activity) during pre-sleep wakefulness and each sleep stage in PI compared to GS. Moreover, pre-sleep RR intervals were positively associated with sleep efficiency and negatively associated with wake after sleep onset in PI. Altogether our findings indicated a dysfunctional sympathetic activity but a normal parasympathetic modulation before and during sleep in young adults with insomnia.     

Ovalbumin-sensitized mice are good models for airway hyperresponsiveness but not acute physiological responses to allergen inhalation

Background Asthma is a chronic inflammatory disease that is characterized clinically by airway hyperresponsiveness (AHR) to bronchoconstricting agents. The physiological response of the asthmatic lung to inhaled allergen is often characterized by two distinct phases: an early‐phase response (EPR) within the first hour following exposure that subsides and a late‐phase response (LPR) that is more prolonged and may occur several hours later. Mouse models of asthma have become increasingly popular and should be designed to exhibit an EPR, LPR and AHR. Objective To determine whether a common model of asthma is capable of demonstrating an EPR, LPR and AHR. Methods BALB/c mice were sensitized to ovalbumin (OVA) and challenged with one or three OVA aerosols. Changes in lung mechanics in response to allergen inhalation were assessed using a modification of the low‐frequency forced oscillation technique (LFOT). In order to assess AHR, changes in lung mechanics in response to aerosolized methacholine were assessed using LFOT. Inflammatory cell infiltration into the lung was measured via bronchoalveolar lavage (BAL). ELISAs were used to measure inflammatory cytokines in the BAL and levels of IgE in the serum. Results An EPR was only detectable after three OVA aerosols in approximately half of the mice studied. There was no evidence of an LPR despite a clear increase in cellular infiltration 6 h post‐allergen challenge. AHR was present after a single OVA aerosol but not after three OVA aerosols. Conclusions The lack of an LPR, limited EPR and the absence of a link between the LPR and AHR highlight the limitations of this mouse model as a complete model of the lung dysfunction associated with asthma.     

Pituitary and autonomic responses to cold exposures in man

This review presents hormonal responses to various cold exposures and their calorigenic effects in man and some animals. Previous studies in rats have shown that cold exposures activate the hypothalamic-pituitary-thyroid axis. Increased thyroid hormone concentrations lead to heat production via general stimulation of metabolism (obligatory thermogenesis) and possibly via activation of thyroid hormone receptors and uncoupling protein 1 (UCP 1) and deiodinase enzyme genes in the brown adipose tissue (BAT). In human subjects long-term cold exposures do not seem to activate the pituitary-thyroid axis, but rather accelerate the elimination of triiodothyronine (T3), leading to low serum concentrations of free T3 hormone. In corollary to this a hypothyreotic condition with increased serum thyroid-stimulating hormone and impaired mood and cognitive performance can be observed after long-term cold exposures such as wintering. During cold exposures the sympathetic nerve system is activated and noradrenaline is released to blood circulation and to BAT, where it leads to production of cAMP, lipolysis and free fatty acids. Free fatty acids open the mitochondrial proton channel protein in BAT. Protons enter the mitochondria and inhibit ATP synthesis (uncoupling). By this way energy is transformed into heat (facultatory or adaptive thermogenesis). In adult human subjects the amount of BAT is small and adaptive thermogenesis (non-shivering thermogenesis) has a smaller role. UCP 1 with other uncoupling proteins may have other functions in the control of body weight, sugar balance and formation of reactive oxygen species.     

The association between parenting behavior and somatization in adolescents explained by physiological responses in adolescents

Introduction

This study adds to the knowledge on somatization in adolescents by exploring its relation with parenting behavior and the mediating/moderating role of physiological responses in adolescents to parenting behavior.

Method

Eighteen adolescents with high and 18 adolescents with low somatization scores and their mothers completed a discussion task, from which observed parenting behavior scores were derived. Skin conductance in adolescents was measured before and during the discussion.

Results

For adolescents with high levels of physiological responses, unadaptive parenting was related to a higher chance of high somatization scores. For low physiologically responsive adolescents, the relation between parenting behavior and somatization was not significant.

Conclusion

Parenting behavior is not univocally related to somatization in adolescents, but the association depends on physiological responses in adolescents.     

Early caregiving and physiological stress responses

Inadequate early caregiving has been associated with risks of stress-related psychological and physical illness over the life span. Dysregulated physiological stress responses may represent a mechanism linking early caregiving to health outcomes. This paper reviews evidence linking early caregiving to physiological responses that can increase vulnerability to stress-related illness. A number of high-risk family characteristics, including high conflict, divorce, abuse, and parental psychopathology, are considered in the development of stress vulnerability. Three theoretical pathways linking caregiving to physiological stress responses are outlined: genetic, psychosocial, and cognitive-affective. Exciting preliminary evidence suggests that early caregiving can impact long-term physiological stress responses. Directions for future research in this area are suggested.     

Subjective and autonomic responses to smoking-related visual cues

Nicotine, like several other abused drugs, is known to act on the reward system in the brain. Smoking-associated cues produce smoking urges and cravings accompanied by autonomic dysfunction to these cues in smokers. The present study was aimed at investigating whether cues related to smoking elicit the autonomic response in smokers. The subjective and physiological reactivity of 7 smokers and 12 nonsmokers in a supine position to smoking-related visual cues was assessed under indirect dim light using a self-assessment manikin and a specially designed pupillometer. The experimental procedure consisted of the elicitation and measurement of pupil size (PS) while the subjects viewed a smoking image and images from three valence-defined categories (i.e., pleasant, unpleasant, and neutral), based on normative affective ratings selected from the International Affective Picture System. Both groups produced significantly larger PS increases in response to pleasant or unpleasant images compared to neutral images. Smokers, viewing smoking-related visual cues but no other affective images, produced significantly larger PS's compared to nonsmokers. Moreover, smokers rated the smoking image with more pleasure and arousal than nonsmokers. These findings suggest that cues related to smoking induce not only a subjective emotional alteration, but also sympathetic activation, measured by the time-series PS data in smokers.     

A two-dimensional approach to assessing affective states in good and poor sleepers

This study examined a two-dimensional approach to assessing affective states among good and poor sleepers using the self-assessment manikin (SAM), a brief non-verbal self-report measure of affective states with separate ratings of valence and arousal. A sample of 286 undergraduate students completed the Pittsburgh Sleep Quality Index (PSQI) and the SAM. Participants were classified post hoc as either good (PSQI ≤ 5) or poor sleepers (PSQI > 5) using the PSQI and used the SAM to rate their current affective states (day) and their affective state at bedtime (night) the previous night. Compared to good sleepers, poor sleepers reported more negative affect and arousal at night and more negative affect during the day. Among poor sleepers, lower sleep quality and shorter sleep duration on the components of the PSQI were associated with more negative daytime valence. Among good sleepers, higher scores on the sleep medication and daytime dysfunction components of the PSQI were associated with more negative daytime valence. These findings indicate that the SAM appears to detect differences between good and poor sleepers on both valence and arousal of current daytime and retrospective night-time emotional states. This approach could be useful for the assessment of affective states related to sleep disturbance.     

Racial identity and autonomic responses to racial discrimination

Several studies identify racial identity—the significance and meaning that individuals attribute to race—as a mitigating factor in the association between racial discrimination and adjustment. In this study, we employed a visual imagery paradigm to examine whether racial identity would moderate autonomic responses to blatant and subtle racial discrimination analogues with Black and White perpetrators. We recruited 105 African American young adults from a public, southeastern university in the United States. The personal significance of race as well as personal feelings about African Americans and feelings about how others view African Americans moderated autonomic responses to the vignettes. We use polyvagal theory and a stress, appraisal, and coping framework to interpret our results with an eye toward elucidating the ways in which racial identity may inform individual differences in physiological responses to racial discrimination.     

Differences in regional sweating responses during exercise between athletes trained on land and in water

We investigated whether there are any differences in regional sweating responses during exercise between athletes trained on land and in water. We measured the local sweating rates on the left forearm (m_swf) and the left scapula (m_sws), body temperatures (mean skin temperature, and rectal temperature T _re) in eight athletes trained on land (five soccer players, one distance runner and two baseball players, L group) and seven athletes trained in water (seven swimmers, W group) during cycle ergometer exercise at 50% maximal oxygen uptake for 40 min. The heart rate and oxygen uptake in the two groups during exercise showed nearly the same pattern of change. The T _re at the end of the exercise were 38.13 (SEM 0.19)°C in the L group and 38.26 (SEM 0.34)°C in the W group. Although the m_swf in the two groups were similar, m_sws were significantly higher in L than in W at 30, 35 and 40 min of exercise. The m_sws at any given mean body temperature tended to be greater in L than in W. These results showed that a difference in regional sweating rate during exercise between the athletes trained on land and in water was present on the scapula.     

Metabolic and cardiovascular responses to epinephrine in diabetic autonomic neuropathy

Norepinephrine-induced vasoconstriction, which is mediated by alpha-adrenergic receptors, is accentuated in patients with autonomic neuropathy. In contrast, responses mediated by beta-adrenergic receptors, including vasodilatation and metabolic changes, have not been evaluated in these patients. To study these responses, we administered epinephrine in a graded intravenous infusion (0.5 to 5 micrograms per minute) to seven diabetic patients without neuropathy, seven diabetic patients with autonomic neuropathy, and seven normal subjects. Mean arterial pressure decreased significantly in the patients with autonomic neuropathy (P less than 0.01) but was unchanged in the other groups. Since cardiac output increased to a similar extent in the three groups, the decrease in blood pressure was due to a significantly larger decrease (P less than 0.01) in total peripheral vascular resistance in the patients with autonomic neuropathy. The heart rate increased significantly more during the infusions in the patients with neuropathy than in those without neuropathy. Epinephrine produced a greater increase in blood glucose, the glucose-appearance rate, lactate, glycerol, and free fatty acids in the patients with autonomic neuropathy than in the other groups (P less than 0.05). These findings indicate that several beta-receptor-mediated responses to epinephrine are enhanced in patients with diabetic autonomic neuropathy. The underlying mechanism remains to be elucidated.     

Shock-prod burying test in rats: autonomic and behavioral responses

Heart rate (HR), core temperature (CT) and gross locomotor activity (GLA) were recorded in rats by a computerized telemetry system before, during and after 15-min exposure to a constantly electrified (2mA) or nonelectrified (0mA) prod which was presented through a hole in the home cage with woodshavings on the floor [shock-prod burying (SPB) test]. Measurement of both autonomic and behavioral response continued up to 60 min after introduction of the prod in the home cage. Twenty-four h after the SPB test, rats were tested for retention. During the SPB test, significant increases in HR, respective to baseline values, were observed in both the 2mA and 0mA group, but the tachycardiac response in the former group significantly outweighed that in the latter group. In shocked rats, HR remained elevated during the entire 45-min posttest period, whereas HR declined immediately after removal of the prod in nonshocked animals. An onset in rise in CT was observed in the 2mA, but not in the 0mA group, during prod exposure time, which eventually resulted in an additional-more than two-fold--increase after termination of the test and outlasted total recording time. Marked behavioral activation was observed in the 2mA group, whereas the 0mA responded to a lesser extent. Approach and exploration of the prod was reduced when the prod was electrified. The total time spent by rats burying the prod was significantly longer in the shocked than in the nonshocked group. When exposed to the nonelectrified prod after 24 h, total burying time was reduced in the 2mA group but still significantly longer than in the 0mA group.(ABSTRACT TRUNCATED AT 250 WORDS)