摘要:

AbstractLatent inhibition (LI) is a behavioral paradigm in which repeated exposure to stimuli not followed by meaningful consequences renders these stimuli ineffective for subsequent learning. The development of LI is considered to reflect learning not to attend to, ignore, or tune out irrelevant stimuli. The present study investigated the differences in the development of LI between handled and nonhandled males and females. Infantile handled (Days 1–22) and nonhandled, male and female Wistar rats were tested in maturity in the LI paradigm. The LI procedure consisted of two stages: pre‐exposure, where animals received 60 presentations of the to‐be‐conditioned stimulus (tone) and test, where the animals acquired a two‐way active avoidance response with the tone serving as the warning signal. Handled animals reached higher percentage of avoidance responses as compared with nonhandled animals. Latent inhibition was obtained in both the handled and the nonhandled females, but only the handled males showed the LI effect. Nonhandled males failed to develop LI. The results indicate that (a) the effects of handling are evident in learning tasks that do not involve motivational‐emotional variables, i.e., learning to ignore irrelevant stimuli; (b) handling differentially affects males and females, with a much greater impact on males and (c) the nonhandling procedure has significant deleterious consequences on adu

ISSN:0012-1630    

DOI:10.1002/dev.420180402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

摘要:

AbstractFactors affecting the development of filial preferences in chicks were investigated. Four groups of chicks were hatched and maintained in darkness. When the chicks were 20‐hr old, three of these groups were exposed to an overhead light (“primed”) for .5 h. When 24‐hr old, all groups were placed in running wheels for 2 hr. While in the wheels one group was exposed to a visually complex pattern, one group to diffuse overhead light, and the remaining two groups (one primed and one not primed) were in darkness. All chicks were then returned to a dark incubator until their preference for a red box or a stuffed jungle fowl was measured in a simultaneous choice test either 2 hr (Test I) or 24 hr (Test II) later. At Test I the chicks which had been exposed to the complex visual pattern showed a significant preference for the fowl. Chicks in the other groups showed no preference. At Test II all groups showed a significant preference for the fowl. The results of a second experiment suggested that the later emerging preference was related to the chicks experience in the running wheel. It was concluded that the preference for the fowl will develop in entirely dark‐reared chicks that are allowed a period of time in a running wheel, but that this preference will appear earlier in chicks which have had experience of a complex visua

ISSN:0012-1630    

DOI:10.1002/dev.420180403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

摘要:

AbstractIndividual 18‐, 24‐, or 30‐day‐old male and female Wistar prepubertal rats (juveniles) were continuously exposed to 3–8‐day old pups in order to determine developmental differences in the expression of maternal and other behaviors during the process of sensitization. The results that emerged from this study are as follows: (a) Maternal behaviors are neither consistent nor integrated in their expression prepubertally; (b) exposure to pups facilitates the emergence of some maternal behaviors in juveniles more easily than others, e.g., retrieving and anogenital licking more than ventral crouching or nestbuilding; (c) there are age‐related differences in the expression of different maternal behaviors, e.g., 24‐day‐olds retrieve more than at other ages; (d) in our strain, few, if any, gender differences are apparent in the expression of maternal behaviors prepubertally; (e) juvenile play behaviors (charge, pounce) are related to retrieving behavior in the context of exposure to pups. Overall, the results suggest that maternal behaviors are distinct developmentally and probably involve different mechanisms in pr

ISSN:0012-1630    

DOI:10.1002/dev.420180404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

摘要:

AbstractPredominant mood states were assessed for 104 children via 24‐hr mother diaries during the first 2 years of life. Consistent sex differences were found across ages and across cohorts: boys were more often reported to be in a happy/excited mood, girls in a quiet/calm mood. The sexes did not differ in the frequency of negative moods (including crying), however. Scores for happy/excited and quiet/calm mood states were quite stable across the ages sampled: 6, 9, 12, 18, and 26 months. These stabilities were generally greater for boys. Negative moods showed only borderline stability. Relationships between the mood scores and five sex‐steroid hormones (progesterone, androstenedione, testosterone, estrone, and estradiol), assayed from umbilical cord blood at the time of the children's birth, were assessed. For boys small, but significant, positive relationships were found between happy/excited moods and androstenedione, estrone, and progesterone. Correlations of opposite sign were found between these hormones and boys' scores for quiet/calm mood. For girls, the correlations were low and insignificant, but generally of opposite sign from those found for boys, and a number of hormones showed significant sex‐b‐hormone interactions in their relation to children's mood scores. The implication of these findings for the understanding of sex differences is discussed. Also discussed are the problems of interpretation posed by the intercorrelations among hormones when hormone scores are used for prediction of aspects of later deve

ISSN:0012-1630    

DOI:10.1002/dev.420180405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

摘要:

AbstractNorway rats were reared either in a standard laboratory cage or in a nest constructed by the dam from newspaper strips. Growth, thermoregulatory ability, and adrenal, gonad, adipose tissue, and brian weights were measured at weaning on Day 21 postpartum. While there was no difference in growth, nest‐reared animals had lower body temperatures, but could thermoregulate as well as cage‐reared animals. Nest‐reared animals also had relatively smaller adrenals and less brown adipose tissue. Gonad and brain weights were similar. An interesting finding was that males and females were differentially affected by the nest‐rearing. Differences between cage‐ and nest‐reared animals were more evident in females, and thermoregulatory ability was more closely associated with the quality of the nest during the first 10 days than body weight in females. For males, body weight was more important. These latter data are discussed in relation to differential interaction between the dam and male and

ISSN:0012-1630    

DOI:10.1002/dev.420180406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

摘要:

AbstractWe have previously demonstrated increased myelination in adult rats that were adrenalectomized (ADX) neonatally. However, Preston and McMorris (1984) recently reported reduced myelination at Day 21 or 22 in day 14 ADX animals. The present experiment attempted to replicate Preston and McMorris' study to determine whether early adrenalectomy might be producing a transient hypomyelination prior to the hypermyelination observed at later time points. We were unable to duplicate the exact protocol of Preston and McMorris (which involved weaning at Day 18 with administration of saline and glucose drinking solutions) because of 100% mortality of our ADX rats by Day 20. However, using our standard mineralocorticoid replacement therapy which allowed the animals to remain with their mothers, all of the ADX rats survived, and we were able to assess myelination in these animals by means of standard biochemical methods. All measures showed absolutely no reduction in myelination in ADX rats compared with sham‐operated controls. The discrepancy between the present results and those of Preston and McMorris are attributed, at least in part, to the early weaning procedure used by these investigator

ISSN:0012-1630    

DOI:10.1002/dev.420180407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

摘要:

AbstractYoung rats, 11, 16, and 20 days of age, received bilateral injections of three antinicotinic agents into the posteroventral hippocampo‐subiculo‐entorhinal area, and were trained to learn a cool‐draft‐stimulus, passiveavoidance task shortly after (17 min). Gallamine triethiodide had no action at low doses and provoked convulsions at higher concentrations. Pempidine tartrate produced ageq and dose‐dependent impairments of the passive avoidance, and was much more effective in younger groups (11 and 16 days) than at 20 days. α‐bungarotoxin also induced dose‐dependent deficits. These results, together with the mecamylamine‐induced deficits already reported, suggest that nicotinic cholinergic synapses located in the posteroventral part of the hippocampal complex play a role in passive‐avoidance learning in the young rat as soon as this type of conditioning is possible, but become relatively less important at older ages, when muscarinic mechanisms al

ISSN:0012-1630    

DOI:10.1002/dev.420180408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY

ISSN:0012-1630    

DOI:10.1002/dev.420180401

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1985

数据来源: WILEY