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Biomedical subjects

M R Gunnar

Publications and source records attributed to M R Gunnar.

48 records · Page 3Linked to original sources
PubMed1985

Adrenocortical and behavioral responses to limb restraint in human neonates.

Two experiments were conducted on human neonates examining their behavior and adrenocortical activity in response to physical restraint. In both experiments, newborns (9 per condition in Experiment I; 10 per condition in Experiment II) were tested in one of three conditions: Restraint, which involved strapping newborns to a circumstraint board for 20 min; Strapping Control, which involved strapping newborns to the board and then immediately taking them off the board and returning them to their cribs; and Control, which did not involve any restraining manipulation. In Experiment I, blood samples for plasma cortisol determination were obtained via heel-stick immediately prior to the assigned manipulations and 30 min later. In Experiment II, only the postmanipulation blood sample was taken. Two behavioral states, Active Awake and Crying, were examined as indices of behavioral distress. In Experiment I, the effects of the blood sampling procedure on behavioral distress and plasma cortisol were significant; however, no significant effects of restraint were observed. In Experiment II, restraint was associated with small but significant increases in behavioral distress and in plasma cortisol levels.

Circumcision, Male↗
PubMed1985

Coping with aversive stimulation in the neonatal period: quiet sleep and plasma cortisol levels during recovery from circumcision.

Measures of behavioral state and plasma cortisol were obtained on 80 healthy, full-term, 2-3-day-old, male newborns who were scheduled to be circumcised. To establish baseline or precircumcision levels, the newborns were observed, and behavioral state was recorded for the half hour prior to circumcision. Blood was sampled via heelstick for plasma cortisol determination at the end of this observation period. The newborns were then circumcised and assigned randomly to one of 4 postcircumcision, blood-sampling time-point groups. The time points were 30, 90, 120, and 240 min following the beginning of circumcision. Behavioral state was observed during circumcision and for the half hour prior to taking the second blood sample. The results showed a return to baseline cortisol levels sometime prior to 240 min, with data from an additional group of 10 newborns indicating that the return occurred by 150 min. Behavioral distress during circumcision was associated with elevations in plasma cortisol at 30 and 90 min. Quiet sleep was correlated negatively with plasma cortisol prior to circumcision, and significant increases in quiet sleep followed circumcision, with the greatest increase corresponding to the period of most rapid reductions in cortisol.

Adaptation, Psychological↗
PubMed1984

Peer presence and the exploratory behavior of eighteen- and thirty-month-old children.

20 18- and 20 30-month-old children were observed in a situation requiring separation from the mother in order to play with attractive toys. An agemate was present for half the children but not the others. Peer presence facilitated leaving the mother and entering the playroom at both ages. Among 18-month-olds, the presence of the peer also shortened play bouts, increased unoccupied/self-solace behavior, and increased contact maintenance with the mother. Among 30-month-olds, however, the peer's presence did not have these effects. these children engaged in increased coordinate social interaction with the other child. Developmental changes occurring in the second and third year thus include the increased salience of agemates in supporting separation from the mother and exploration of the environment in the context of sustained social interaction.

Child Development↗
PubMed1982

Sex differences in biobehavioral responses to conflict in a taste aversion paradigm.

A conditioned aversion to a novel milk solution was produced, and animals were then reexposed to milk while nondeprived (low conflict) or following a 72-hr food and water deprivation regimen (high conflict). No sex differences occurred if animals were nondeprived throughout testing. However, if deprived during the interval between conditioning and reexposure, sex differences in both behavior and adrenocortical responses occurred: (1) Presession corticoid levels of females were higher than those of males. (2) On the first reexposure day, females showed a suppression of plasma corticosterone below presession levels, while males maintained elevated or increased corticosterone levels. (3) On the second reexposure day, when no longer deprived, males showed a marked suppression of intake compared to females, and females subsequently recovered to pretoxicosis intake levels faster than males. (4) Gonadectomy eliminated these sex differences. While ovariectomized females continued to resemble intact females in both behavioral and hormonal responses, castrated males exhibited a corticoid suppression on the first reexposure day, and subsequently recovered to pretoxicosis intake levels at the same rate as females.

Animals↗
PubMed1980

Sex differences in social responsiveness between six months and twelve months.

14 male and 14 female infants were observed interacting with their mothers for 4 min in a free-play situation at 6, 9, and 12 months, using a cross-sectional design. Both mother and infant initiations of interaction and responses to the other's initiations were recorded using an observational technique similar to that used by Clarke-Stewart. There were no age or sex differences in either maternal responsiveness or the number of attempts the mothers made to initiate interaction with the infants. Although no sex difference in responsiveness was observed when the mother used toys to elicit the infant's attention, girls were significantly more responsive when the mother merely spoke to them (vocal initiations). The frequency of social initiations made by the infants increased significantly from 6 to 9 months, but at all 3 ages girls initiated more interactions than did boys. These sex differences in sociability did not reflect differences in the amount of time spent manipulating toys, nor did they reflect sex differences in the frequency of vocalizations, although between 6 and 9 months there was a significant increase for both sexes in the percentage of vocalizations which were used to initiate interactions.

Female↗
PubMedDate not supplied

Quality of early care and buffering of neuroendocrine stress reactions: potential effects on the developing human brain.

Brain development is affected by stress early in development. Activity of the hypothalamic-pituitary-adrenocortical (HPA) axis plays a role in mediating the effects of adversity on the developing brain. The impact of glucocorticoids on brain development has been studied in animal models. The literature linking activity of the HPA axis to memory, attention, and emotion in human children is briefly reviewed. Evidence for decreased reactivity of the HPA system developing over the first year of life is presented. Finally, the role of sensitive and responsive caregiving in buffering reactivity of the HPA system to potentially stressful events is described. It is argued that these data provide yet more support for the importance of fostering safe, secure care for children early in their development.

Animals↗
PubMedDate not supplied

Behavioral and physiological responsivity, sleep, and patterns of daily cortisol production in infants with and without colic.

To describe the behavioral and physiological responses associated with colic, the responses of 20 two-month-old infants with and 20 without colic were studied during a physical examination. Parents kept a diary of infant behaviors (including crying and fussing) for 3 days following the visit. Using Wessel, Cobb, Jackson, Harris, & Detwiler criteria, colic was defined as fussing/crying for 3 hr or more on each of the 3 days. Behavioral data coded by "blind" observers showed that during the physical exam, colic infants cried twice as much, cried more intensely, and were more inconsolable than were control infants. Despite these behavioral differences, heart rate, vagal tone, and cortisol measures indicated no appreciable difference in physiological responsivity for the two groups. At home, parents collected saliva cortisol samples at wakeup, midmorning, midafternoon, and evening for 2 days. In a finding similar to that shown by the laboratory data, the colic and control infants did not have different levels of daily average cortisol. These laboratory and home data provide no evidence of greater responsivity in the physiological substrate of difficult temperament for colic infants and are consistent with evidence of similarity in temperament once colic is resolved. At home, compared with control infants, colic infants did display a blunted rhythm in cortisol production. By diary, they also slept about 2 hr less per day than did control infants. Nighttime sleep was still significantly different when fussing/crying was statistically controlled. These data suggest that colic might be associated with a disruption or delay in the establishment of the circadian rhythm in activity of the hypothalamic-pituitary-adrenocortical axis and associated sleep-wake activity.

Analysis of Variance↗