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Biomedical subjects

M R Gunnar

Publications and source records attributed to M R Gunnar.

At least 37 records · Page 2Linked to original sources
PubMed1996

Dampening of adrenocortical responses during infancy: normative changes and individual differences.

Changes in cortisol and behavioral responses were examined longitudinally in 83 infants (39 girls, 44 boys) tested at their well-baby exams with inoculations at 2, 4, 6, and 15 months (72 infants completed all testing). Another sample of 2-, 4-, and 6-month-olds (n = 18 per age) received mock exams without inoculations to determine early developmental changes to the exam procedures. Behavioral distress was coded every 30 sec during the exam, a 5-min inoculation period, and a 20-min recovery period. Salivary cortisol was obtained upon arrival at the clinic and 25 min after the beginning of the inoculation period. To the exam-inoculation procedures, cortisol responses were high at 2 months, decreased significantly between 2 and 4 months, remained comparable between 4 and 6 months, and then declined again between 6 and 15 months. Between 6 and 15 months there was also a decrease in pretest cortisol. By 15 months, significant increases in cortisol from pre- to posttest were no longer observed for most infants. To the exam-only procedures, cortisol responses decreased between 2 and 4 months, and by 4 months most infants failed to show pre- to posttest increases in cortisol. Behavioral distress decreased between 2 and 6 months, but increased again at 15 months. While crying and cortisol were modestly correlated during the 2- to 6-month exam-inoculation procedures, at 15 months no significant correlations were obtained. Behavioral and hormonal reactions thus followed different ontogenetic paths and may provide different information about infant functioning. There was some evidence that the emergence of the circadian rhythm in cortisol might be related to the early decrease in cortisol response.

Adrenal Cortex↗
PubMed1995

Salivary cortisol in nursery-reared rhesus monkeys: reactivity to peer interactions and altered circadian activity.

Five nursery-reared rhesus (Macaca mulatta) infants were studied on 8 consecutive days over a period of 2 weeks when they ranged from 4 to 5.5 months. Saliva cortisol samples were obtained by giving each animal, while in its individual home cage, a 6-in. cotton dental roll pretreated with sugared fruit-drink crystals and dried. Subjects were allowed to mouth the cotton roll for 10 min during each collection period. Saliva was then expressed from the cotton and analyzed by radioimmune assay. Samples were collected at 0830, 1100, 1400, and 1630 hr on each of the 8 days. On four of the days, 2-hr peer socialization sessions were imposed between 1200 and 1400 hr. Significant time-of-day effects were obtained. Values tended to be low at 0830 hr, rising significantly to peak levels at 1100 hr, and then declining over the 1400-hr and 1630-hr sampling periods. All 4 subjects with sufficient samples had higher average cortisol concentrations when the 1400-hr sampling followed peer-socialization sessions, compared to no-socialization days. This difference was only marginally significant by paired t test, however. These results (a) support the feasibility of using noninvasive salivary sampling procedures with infant monkeys, and (b) indicate that salivary cortisol measures are sensitive to daily rhythms. Unexpectedly, the results also raise the possibility that nursery-reared infant rhesus macaques may be phase-delayed in their HPA rhythm, with the morning peak occurring several hours after rather than in the hour before lights-on and the morning feeding.

Aging↗
PubMed1995

Neonatal stress reactivity: predictions to later emotional temperament.

To investigate the relations among popular measures of neonatal stress and their link to subsequent temperament, 50 full-term newborns from a normal care nursery were examined responding to a heelstick blood draw. Baseline and heelstick measures of behavioral state, heart period, vagal tone, and salivary cortisol were obtained. Recovery measures of behavioral and cardiac activity were also analyzed. Mothers completed Rothbart's Infant Behavior Questionnaire when their infants reached 6 months of age. Baseline vagal tone predicted cortisol in response to the heelstick, suggesting that baseline vagal tone reflects the infants' ability to react to stressors. Greater reactivity to the heelstick (more crying, shorter heart periods, lower vagal tone, and higher cortisol) was associated with lower scores on "Distress-to-Limitations" temperament at 6 months. This finding was consistent with the expectation that the capacity to react strongly to an aversive stimulus would reflect better neurobehavioral organization in the newborn. Recovery measures of cardiac activity approximated and were correlated with baseline measures indicating the strong self-righting properties of the healthy newborn. Finally, vagal tone and salivary cortisol measures were not significantly related, suggesting the importance of assessing both systems in studies of the ontogeny of stress-temperament relations.

Arousal↗
PubMed1995

Adrenocortical and behavioral predictors of immune responses to starting school.

Associations between major psychologic stressors and immune function have been documented in previous research, but few studies have investigated immune changes attending minor, normative stressors. This study examined adrenocortical and behavioral predictors of immune responses to starting kindergarten in 39 five-year-old children, who completed laboratory visits for venipunctures 1 wk before (time 1) and 1 wk after (time 2) school entry. At time 1, children were also immunized with pneumococcal vaccine. Immune responses were measured as change scores for T (CD4+ and CD8+) cells, B (CD19+) cells, lymphoproliferative responses to pokeweed mitogen (PWM), and type-specific pneumococcal antibody responses (ABR). Adrenocortical response was assessed as the change in salivary cortisol level, and behavioral difficulty with school adjustment was scored using parental ratings of behavior problems, stress due to changes in routines, and degree of adaptive challenge. Salivary cortisol rose after kindergarten entry (means = 0.39 +/- 0.28 to 0.49 +/- 0.36 micrograms/dL, p = 0.03) and was unrelated to behavioral difficulties. CD4+ cells increased in number, whereas PWM declined, and CD19+ cells showed a borderline increase. Change in salivary cortisol was positively associated with change in CD19+ (delta CD19+) and inversely related to ABR. Scores for behavioral difficulty were inversely associated with delta CD4+ and delta CD19+. These data suggest that: 1) school entry is a stressor capable of evoking elevations in cortisol and behavior problems, accompanied by shifts in functional and enumerative measures of immune status; and 2) children with greater adrenocortical reactivity have increases in B cell numbers and less effective B cell-mediated antibody production, whereas children with more behavioral difficulties show declines in all T and B cell subsets.

Adrenal Cortex↗
PubMed1994

Adrenocortical activity and emotion regulation.

Activity of the HPA system does appear to be related to emotion regulation processes in children. The conditions known to modulate HPA activity in animals, adults, and children correspond well to the behavioral strategies often discussed in the domain of emotion regulation. Individual differences in emotion processes related to negative emotion temperaments appear to be associated with individual differences in HPA reactivity among normally developing children, with both fearful, inhibited temperaments and distressed, angry temperaments being associated with greater HPA reactivity. Among children exhibiting behavior problems in the clinical range, however, it may be the "internalizing" patterns that are associated with greater HPA reactivity. The body of research concerning the psychobiology of the HPA system strongly suggests that associations between emotion regulation styles and HPA activity are not merely correlations, that they do indeed reflect potential causal connections. HPA activation and regulation has been shown in animals both to influence and to be influenced by emotions and their corresponding behavioral and psychological processes. Despite a reasonable body of research that now exists on children, many questions regarding the relations between HPA activity and emotion processes remain to be examined. In addressing these questions, it may be useful to consider several periods of the HPA response. Most of the work on children involves the interrelations between emotion and adrenocortical systems during the first 10-15 min of the stress response. This would include the initial activation of the system and the subsequent emotion and physiological processes involved in continuing or terminating the response. Little attention has been paid to more slowly developing effects of HPA activity on the central nervous system in children, particularly with regard to its influence on children's memories for stressful events and the emotion regulation strategies that they employed during the event. Studies of change or continuity of these interconnections over several exposures to a stressor, as well as between earlier and later points in the activation and regulation process, will be especially important to our understanding of the regulation of affective behavior.

Adrenocorticotropic Hormone↗
PubMed1994

Event-related potentials in year-old infants: relations with emotionality and cortisol.

Event-related potentials (ERPs) were recorded from year-old infants presented with sets of familiar faces presented frequently and infrequently, and a set of novel faces presented infrequently. The normative response of infants in this sample was a late positive slow wave to the Infrequent Familiar faces, and a return to baseline to the Frequent Familiar and Infrequent Novel faces (although there was a tendency for some infants to show a positive slow wave to the latter events). A factor score based on data from frontal and central leads that reflected this normative pattern was significantly associated with infant emotional behavior and cortisol. Infants scoring higher on the normative ERP factor were more distressed during separation, were reported by their parents to smile and laugh more, and had lower cortisol concentrations during ERP testing. These data were interpreted as reflecting the coordination of adaptive responding among different physiological and behavioral systems.

Electroencephalography↗
PubMed1992

The stressfulness of separation among nine-month-old infants: effects of social context variables and infant temperament.

This manuscript reports on the results of 2 experiments dealing with behavioral and adrenocortical responses to separation among 9-month-old human infants. In both experiments the social context of separation was manipulated. The results of Experiment 1 yielded evidence of a statistically significant adrenocortical response to 30 min of separation under conditions in which the substitute caregiver responded sensitivity to infant distress, but was busy and relatively noninteractive when babies were not distressed during the separation period. Altering the behavior of the substitute caregiver such that she was warm, responsive, and interactive throughout the separation produced a significant reduction in adrenocortical activity and in negative affect. In fact, these measures were not significantly different than those obtained when the mother and infant remained together in the playroom (No Separation). In Experiment 2, the effects of group versus singleton care were examined using the less stressful mode of substitute caregiving as described above. No significant condition differences in behavioral distress or cortisol were found. Furthermore, neither condition elicited a significant increase in cortisol over basal levels. Finally, these data provide evidence that maternal reports of infant Distress to Limits temperament, using Rothbart's Infant Behavior Questionnaire, predict adrenocortical responses to separation, while reports of Fear of Novelty do not.

Adrenal Cortex↗
PubMed1991

Cortisol and behavioral responses to repeated stressors in the human newborn.

This manuscript reports on the effects of stressors repeated at a 24-hr interval on three samples of human newborns. In Study 1, newborns meeting criteria for obstetric and perinatal optimality experienced either 2 mock Discharge Exams, viewed as a type of handling stressor, or 2 Heelstick Blood Draws, viewed as a type of nocioceptive stressor. As in a previous study, newborns meeting optimality criteria showed habituation of the adrenocortical response to the repeated Discharge Exam. The adrenocortical response to the repeated Heelstick tended to increase or sensitize. In Studies 2 and 3, samples of newborns with more nonoptimal obstetric complication scale scores were examined. These newborns failed to show habituation of the adrenocortical response to the Discharge Exam, but responded like "Optimal" newborns to the repeated Heelstick. The applicability to these data of the Groves and Thompson (1970) Dual-Process Model of Habituation is discussed. The results also provided evidence of stability in behavioral distress independent of stability in adrenocortical activity. The implications of these data for studies using cortisol as an index of the physiological basis of early temperament are considered.

Adrenal Cortex↗
PubMed1991

The effects of morning naps, car trips, and maternal separation on adrenocortical activity in human infants.

3 studies of adrenocortical activity in healthy 9-month-old infants were conducted to examine unanticipated results obtained in previous research. In the first study, morning naps were examined and found to be associated with significant decreases in salivary cortisol. These decreases were followed by a significant return to prenap cortisol concentrations. In the second study, riding for 40 min in the car was also shown to significantly lower salivary cortisol concentrations. This effect was obtained both for infants who did and who did not sleep during the car trip. In the third study, the effect of 30 min of maternal separation in the laboratory on salivary cortisol was compared to the effect of 30 min of play with mother present. Separation resulted in significantly higher salivary cortisol concentrations as compared to play with mother present. In general, correlations between cortisol and behavior were found to be nonsignificant under conditions that did not produce stress elevations in cortisol, while less positive, more distressed behaviour was significantly correlated with cortisol under separation or stress conditions.

Adrenal Cortex↗
PubMed1989

Studies of the human infant's adrenocortical response to potentially stressful events.

Research on the regulation of the adrenocortical response in normal, healthy human infants is still quite new. The refinement of radioimmune assays to allow the measurement of cortisol in small samples of saliva, however, promises to stimulate a marked increase in work in this area over the next few years. To summarize the work to date, we can be fairly certain of the following points: (1) The adrenocortical system is responsive to stimulation at birth, and elevations can be produced by a variety of normal events, including such seemingly minor stimuli as undressing, weighing, and measuring the newborn. (2) Increases in cortisol are not always associated with behavioral distress in the infant, and at times quiescence may be the behavior associated with large elevations in cortisol. (3) At least under certain conditions, the parameters of which are as yet undetermined, the adrenocortical system of the infant appears to rapidly habituate or attenuate its response with repeated exposures to the same event. As in any new area of work, the questions left unanswered are numerous. Minimally, we can ask the following: (1) Are there stable individual differences in adrenocortical reactivity? If there are, then when do they develop, what determines these differences, and are they related to the infant's behavior or temperament? (2) Are stressors such as separation from attachment figures capable of producing large increases in cortisol (that is, a clear stress response)? If they can, then under what conditions and at what ages? (3) Finally, what are the psychological triggers of the adrenocortical stress response in human infants? While the data seem to lean toward novelty and uncertainty, the possibility that negative emotional states play a role has not been clearly ruled out. These questions and others are likely to be the focus of much of the work in this area in the near future.

Adrenal Cortex↗
PubMed1989

Lack of stability in neonatal adrenocortical reactivity because of rapid habituation of the adrenocortical response.

The purpose of the study was to examine the stability of the adrenocortical response to stimulation in the human neonate. Forty-nine healthy newborns were examined twice responding to discharge examinations performed on two consecutive days. The dependent measures were salivary and plasma cortisol and behavioral state. Little evidence of stability was obtained. Instead, the results showed significant elevations in cortisol only in response to the first discharge examination. No significant elevation in cortisol was noted to the second discharge examination although the newborns continued to exhibit behavioral distress. Time since delivery was not a significant factor in producing these results. The findings are discussed with regard to neonatal coping processes and the importance of novelty in regulating increases in adrenocortical activity.

Adrenal Cortex↗
PubMed1988

Local anesthesia for neonatal circumcision. Effects on distress and cortisol response.

A controlled, double-blind investigation was conducted to determine whether the dorsal penile nerve block using lidocaine hydrochloride without epinephrine would effectively reduce behavioral distress and adrenocortical responses to routine neonatal circumcision. The subjects were healthy male newborns whose parents had requested circumcision. Equal numbers (n = 20) were randomly assigned to circumcision with lidocaine, saline, or no injection. Dorsal penile nerve block was found to be a safe and easy technique that was effective in reducing behavioral distress and modifying the adrenocortical stress response. The injection itself did not increase stress reactions and did not offset the beneficial effects of anesthesia. If circumcisions are to be performed, they should be done as humanely as possible.

Circumcision, Male↗
PubMed1988

Adrenocortical activity and behavioral distress in human newborns.

The association between behavioral distress and adrenocortical activity was examined in two experiments with human newborns. In Experiment 1, behavioral and adrenocortical responses to 4 events (circumcision, blood sampling, weighing and measuring, and discharge examination) were compared using a between-subject design. All 4 events elicited fussing and crying and elevations in plasma cortisol; however, differences in behavioral distress among conditions did not reliably predict differences in plasma cortisol. In Experiment 2, nonnutritive sucking was used to effectively reduce behavioral distress, but was not associated with a reduction in the adrenocortical response to stimulation. Finally, using data from both experiments, correlations were computed between behavioral distress and cortisol. Both positive and negative associations were found as a function of the type of stressor and the biomedical status of the newborn.

Adrenal Cortex↗
PubMed1988

A descriptive analysis of infant social referencing.

The study was designed to provide a descriptive analysis of the frequency and patterning of social referencing in a seminaturalistic setting. 32 infants, half of them 12 and half 18 months old, were observed exploring a caged rabbit with their mothers present. Referencing was operationalized as looks directed toward the mother following a look to the rabbit, accompanied by quizzical facial or vocal expressions. As a function of initial reaction to the rabbit, the infants were classified as wary or bold. Wary infants were more likely to reference their mothers when the rabbit was first presented; however, as the exploration period progressed, bold and wary infants referenced equally often. Referencing occurred less often than affective sharing; it increased in frequency when the mother was instructed to actively offer information and the infant no longer needed to solicit information by looking at her. Mothers directed both affective and instrumental information to their infants, providing affective information through facial expressions and tone of voice, and emphasizing instrumental information in the semantic content of their vocalizations.

Adult↗
PubMed1987

Psychobiological studies of stress and coping: an introduction.

Developmental psychobiology is the study of how the interplay between behavioral and physiological processes supports and directs development. This symposium section is devoted to work in this interdisciplinary domain focused on examining stress and how young organisms cope with and are affected by stressful experiences. In this introduction to the symposium section, the problems of interpreting and integrating information on stress reactivity derived from a combination of behavioral and physiological measures are discussed.

Adaptation, Psychological↗
PubMed1987

Adrenocortical activity and the Brazelton Neonatal Assessment Scale: moderating effects of the newborn's biomedical status.

The Brazelton Neonatal Behavioral Assessment Scale with Kansas Supplement (NBAS-K) was administered midway between feedings to 60 newborns who were between 32 and 122 hours old. 35 of the newborns were classified as extremely healthy and normal (Subgroup I), whereas 25 (Subgroup II) were characterized by slight perinatal problems including gestational age 36-37 weeks or 42+ weeks, and fetal distress during labor. All of the newborns were healthy enough to be cared for in a healthy newborn, Level I nursery. Immediately following administration of the NBAS-K, a blood sample was obtained for plasma cortisol determination. Correlations between behavioral responding on the NBAS-K and levels of plasma cortisol revealed few significant relations for the sample as a whole. When the 2 subgroups were examined separately, a number of significant relations emerged. Newborns in Subgroup I who were more competent in their motor control and state regulation capacities as assessed by Lester's Cluster Scores for the NBAS-K exhibited higher levels of plasma cortisol. In contrast, newborns in Subgroup II who exhibited a greater adrenocortical response to the examination showed more behaviors indicative of high behavioral arousal and distress. This pattern of relations for Subgroup II appeared to be mediated by the number of hours that had elapsed since delivery. As postpartum time increased, the strength of the association between adrenocortical activity and behavioral arousal/distress decreased for Subgroup II. A systems theory approach is used to interpret the difference in patterns of correlations found for the 2 subgroups.

Arousal↗