Stimulation In Infancy Research Articles

Stimulation in infancy facilitates interhemispheric communication in the rabbit

Experimental rabbits were stimulated in infancy by being handled, while controls were undisturbed. After reaching adulthood, the animals were tested for activity in an open field with: (i) the right eye occluded; (ii) the left eye occluded; and (iii) neither eye occluded. For rabbits not stimulated in infancy, the correlation between activity scores for the left eye and right eye occlusion conditions was not significant ( r = 0.115). In contrast, the correlation was highly significant for handled animals ( r = 0.829). The results of the nonhandled group are consistent with other research which has failed to find interocular transfer of visual information, while the significant interhemispheric correlations within the handled group are consistent with prior findings obtained with rats. The results suggest that stimulation in infancy may act to facilitate the functional competence of the corpus callosum.

General systems theory, brain organization, and early experiences.

Three hypothetical brain processes--interhemispheric coupling, hemispheric activation, and interhemispheric inhibition--are derived from an equation characterizing general systems theory. To investigate these processes, experimental rats were reared under differing early experience conditions. When adult, they had their right or left neocortex lesioned, had a sham operation, or were left undisturbed. Interhemispheric coupling was measured by means of a correlation coefficient between the right and left hemispheres. The presence of a significant positive correlation is taken as evidence of a negative feedback loop between the hemispheres. In one experimental population, in which rats did not receive any extra stimulation in infancy, the correlation was not significantly different from zero, thus implying that the two hemispheres were operating independently. In another population, in which rats had received handling stimulation in infancy, the correlation coefficient was significant (0.543), indicating that the hemispheres were coupled in a systems arrangement. The processes of hemispheric activation and interhemispheric inhibition were assessed by comparing the mean performance of the two unilateral lesion groups and the group with intact brain. The two rat populations had different forms of brain organizations as measured by these processes. These analyses show that the behavior of the isolated hemisphere cannot be directly extrapolated to the behavior of the connected hemisphere. If there is hemispheric coupling via a negative feedback loop or if there is interhemispheric inhibition, then the disconnected hemisphere may show behaviors that are not evident in the normal connected condition.

Psychology and Preschool Education

The term preschool education has come to be used for almost all out-of-home provision for children under statutory school age. Psychologists among others are coming to realise the difficulties arising from the separation of care and education in this period of the child’s development, and are concerned with conditions of intellectual stimulation in infancy as much as emotional and social security for the toddler. It is likely that future development and research in the area of linguistic and cognitive development will lie in the direction of studying behaviour in contextual situation. It now appears that the identification of situations of “high” and “low” context is a first priority in order that we can enable the child to use his latent competencies in these areas. In addition a positive and enquiring attitude to groups of very young children has suggested that we re-examine the static concept of attachment and stranger-anxiety. All psychologists have a special interest in early child development, if only by reason of the importance of these early years for adult behaviour. Advances in this area are therefore of special interest, but the value system subserving preschool education should also be a matter for constant review by all professional psychologists.

Stimulation in infancy: Unique effects of handling

During the first 5 days of life newborn rats were handled, shocked, or exposed to heat stress for 3 min. Controls were not disturbed during this interval. All animals were weaned at 21 days. At 35 days, the four groups were split into thirds and were stressed by exposure to an-open field, electric shock, or heat for 3 min. They were then returned to their home cages and killed 12, 27, or 57 min later and their blood analyzed for plasma corticosterone. The group handled in infancy had a significantly smaller corticosterone response than controls and those who received shock in infancy, regardless of the nature of the stress experienced at 35 days. The data are compatible with the hypothesis that handling has certain unique features not shared by other forms of infant stimulation.

Effects of early experience and dexamethasone on adrenocortical reactivity.

This investigation tested the hypothesis that changes in circulating adrenocortical hormones mediate the long term effects of shocking infant rats. Dexamethasone administered through the mothers' milk was used to block adrenocortical responses to peripheral shock stimulation by the young. Control experiments indicated that the dexamethasone was present in the pups as early as 2 days after the mothers began drinking water containing dexamethasone. Shock reduced adrenocortical reactivity under conditions where the mother and the young were capable of an adrenocortical response to the shock, where either the mother or the young could have a response, and where neither the mother nor the young could have an adrenocortical response to this early stimulation. These data do not support the hypothesis that a pituitary-adrenocortical response of either the mother or the young mediates the effects of stimulation in infancy on subsequent adrenocortical reactivity.

Sex differences in body weight and eating: Organization and activation by gonadal hormones in the rat

Female rats injected on the fifth day of life with testosterone propionate (TP) or estradiol benzoate (EB) weigh more in adulthood than control animals injected with oil. If rats are ovariectomized prior to steroid treatment on Day 5, body weight differences in adulthood are reduced and their initial appearance during development is delayed. Neonatal TP or EB treatment increases responsiveness to the weight-promoting effects of androgens in adulthood and decreases adult responsiveness to the weight depressing actions of ovarian hormones. We propose that hormonal stimulation in infancy affects body weight by altering hormonal sensitivity of neural weight regulating mechanisms. Non-neural mechanisms and behavioral effects which might contribute to changes in body weight are also considered. The adult sex difference in body weight is multiply determined by postnatal organizational and activational effects of gonadal hormones as well as by non-hormonal genetic factors and/or prenatal testicular secretions. The sex difference in eating is less subject to early organizing actions of hormones and is primarily attributable to the different hormones secreted by male and female gonads beginning sometime after the end of the neonatal organizational period.

Early androgen treatment and male and female sexual behavior in mice

To investigate the role of neonatal androgen stimulation in the development of the potential for masculine and feminine sexual behavior in the mouse, different groups of mice were hormonally manipulated early in life. One group of female mice was administered testosterone propionate (TP) within 24 hr of birth; a second group of females was given a control injection of oil on the day of birth; a third group of females received an injection of TP on the 10th day after birth. A group of males received a control injection of oil on the day of birth. All mice were gonadectomized at about 30 days of age. At 60 days of age, mice were injected with estrogen and progesterone and tested for sexual receptivity; several weeks later all mice were injected with TP and tested for male sexual behavior. Female behavior: Females given oil at birth and females given TP on the 10th day after birth showed high levels of sexual receptivity as adults following estrogen-progesterone treatment. Females given TP on the day of birth, and male mice, rarely exhibited lordosis following estrogen-progesterone treatment. Male behavior: Most mice, regardless of genetic sex or neonatal treatment, mounted in adulthood following administration of exogenous androgen. There was little difference in mounting frequency between groups, suggesting that exogenous or endogenous androgen stimulation of the neonatal mouse does not facilitate adult mounting behavior. These data for the mouse are in essential agreement with existing data for the rat, and indicate that sexual behavioral differentiation induced by androgen stimulation in infancy is best characterized as an inhibition of the potential to display feminine sexual behavior in adulthood.

Localization of 14C-4-corticosterone in the 2-day-old rat and a consideration of the mechanism involved in early handling.

IT has been known for several years that stimulation in infancy has important effects on a variety of behavioural and physiological processes in adulthood1,2. The most common procedure for stimulating infant animals is a technique called “handling”, although other forms of stimulation including electric shock, heat, cold and shaking have also been used3. When rats are handled in infancy it has been well known that, as adults, they will (a) be less emotionally reactive than non-stimulated controls, and (b) have an adrenocortical response pattern very different from that of controls4–6.

Physiological and behavioral effects of infantile stimulation

Abstract Male Purdue-Wistar rats were handled for 20 days in infancy or were not disturbed (total N = 312). In adulthood these animals were subdivided and tested in the open field for 1, 2, 3, or 4 days. Activity and defecation in the field were recorded. Following the termination of testing the animals were killed immediately, 5 min afterwards, or 15 min afterwards; and the free plasma corticosterone was assayed. Animals handled in infancy were more active in the open field on the last three test days, defecated less in the field on all four test days, and had a lesser corticosterone response on all four test days. These data allow one to draw the general conclusion that stimulation in infancy results in an animal which is less responsive to novel stimuli (i.e., is less emotional) as measured both at the behavioral and physiological level. In addition, the corticosterone response was found to increase as a function of time between removing from the open field and killing; and to decrease as a function of number of days of open field testing.

Conditioned emotionality in the rat as a function of stress in infancy

1. 1. Animals were shocked, handled, or not handled but exposed to the shock and handling compartment from birth until weaning. At 50 days of age, half of each infantile group were trained on a shock avoidance task and the other half were trained on an instrumental reward task. The groups were further subdivided in terms of whether the learning apparatus was identical to (Runway-S) or different from (Runway-D) the infant treatment setting. On both the stressful and nonstressful learning tasks, Ss shocked in infancy performed faster than controls in Runway-S but performed similarly in Runway-D. These results were dependent on the sex of the animal and the type of task, but the fact that differences were found only in Runway-S provided some evidence that repeated shock stimulation in infancy resulted in direct conditioning of emotional responses to situational cues. 2. 2. Emotionality, measured in terms of open field and consummatory behaviour, subsequent to the learning tasks, was found to be a curvilinear, rather than a monotonic function of the amount of infant stress. 3. 3. A discrepancy between learning data and emotionality data was noted and questions raised regarding the validity of unidimensional theories of early experience phenomena.

Modification of Sexual Development Through Stimulation in Infancy

Newborn rat pups were either handled for 3 min/day for the first 24 days of life or else they were not disturbed during this interval. After weaning at 25 days, females were raised either in groups or individually. Rupturing of the vaginal membrane and onset of estrus occurred significantly earlier for females which were handled in infancy and group-reared after weaning. Males were sacrificed at 35, 41 or 47 days; the testes, prostates and seminal vesicles were excised and weighed. The seminal vesicles and prostates of handled rats were found to be significantly heavier than those of unhandled controls. No differences were found for testes weight.

The interrelationships of shock and critical periods in infancy as they affect adult learning and activity

The purpose of this study was to investigate the inter-relationships among intensity of infantile stimulation, developmental period during which stimulation was administered, and adult shock levels as these variables affected several performance measures. The Ss were 290 highly inbred C57BL/10Sc mice. The Ss received infantile stimulation on days 2 and 3, 8 and 9, or 15 and 16. At these ages independent groups of Ss were administered 10 1-second shocks of 0·1, 0·3, or 0·5 ma. Other Ss were placed on the grid but did not receive shock at these ages. Still other Ss served as non-stimulated controls; they were never disturbed from birth until weaning. After weaning the Ss were reared undisturbed until the start of testing at 60 days. Starting at this age the Ss received, in sequence, habituation to an avoidance learning apparatus where an activity measure was obtained, three days of open field testing, seven days of avoidance learning testing, and one day of extinction testing. All three independent variables—age of stimulation in infancy, intensity of stimulation, and level of adult shock—singly or in varying combinations significantly affected each of the dependent variables.

Stimulation in Infancy

Stimulation in Infancy

THE RESPONSE TO PLANTAR STIMULATION IN INFANCY

In every piece of experimental work two steps seem to be necessary. The first is the development of an appropriate method for studying the problem; the second is the actual study. The variability of technic reported in the literature often makes it difficult to determine for any given problem the method which takes into full consideration the present accumulation of facts and theories. This seems to be particularly true for the study of reflexes. The flood of papers describing single reflex responses has reached a point at which it is difficult to keep track of fundamental principles. In this paper, I attempt to attack the study of plantar stimulation in infancy in the two ways described. The first part deals with the analysis of the observations contained in the English, French and German literature for the purpose of setting up a method of studying the response to plantar stimulation. The