摘要:

AbstractThe ontogeny of behavioral and heart‐rate orienting responses to a novel olfactory stimulus was examined in three experiments. The results of Experiment 1 demonstrated that behavioral responses to the olfactory stimulus were observed as early as early as Day 1, although heart‐rate deceleration in response to the stimulus was not observed until Day 9. In Experiment 2, bradycardia was observed in 6‐day‐old pups if stimulus‐elicited motor activity was reduced with haloperidol. Thus, the developmental asynchrony in the expression of behavioral and heart‐rate orienting responses was due, at least in part, to cardiosomatic coupling in the very young animal. The results of Experiment 3 demonstrated that although cardiosomatic coupling interferes with the expression of the heart‐rate orienting response very early in development, it has increasingly less impact over the course of the prew

ISSN:0012-1630    

DOI:10.1002/dev.420240102

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

年代:1991

数据来源: WILEY

摘要:

AbstractWe examined in rat pups the relation between the decline of suckling and the emergence of independent ingestion, and the role of milk delivery conditional on nipple attachment in the maintenance of suckling. Fifteen‐day‐old litters were reared for either 5 or 10 days, and 20‐day‐old litters for 5 days by either a thelectomized (no nipples), ligated (nipples but no milk), or intact (nipples and milk) dam. Pups' food and water intakes were monitored daily, and their suckling, feeding, and drinking behaviors were videorecorded for 24 hr in the presence of their foster dam (Day 19 or 24) and for 24 hr in the presence of an intact, lactating dam (Day 20 or 25). There were no differences between treatment conditions with respect to either the onset or rate of increase of independent feeding or drinking. Pups reared by a thelectomized dam for 10 days displayed a pronounced, lasting depression of suckling. Twenty‐five‐day‐old pups reared by a ligated dam displayed suckling levels comparable to those of control pups; in the presence of the ligated dam, however, their tendency to attach to a nipple was notably reduced. The implications of the findings for our understanding of the weaning process

ISSN:0012-1630    

DOI:10.1002/dev.420240103

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

年代:1991

数据来源: WILEY

摘要:

AbstractStudies of adults have shown that the contextual dependence of memory retrieval can be alleviated by training in multiple contexts. In the present studies with 3‐month‐old infants, retention was disrupted when infants were trained in one context and tested in another, but not when they were trained in multiple contexts prior to testing in a novel context. The retention advantage of multiple learning contexts was observed after 3 days in a simple forgetting paradigm (Exp. 1) and after 14 days in a reactivation paradigm (Exp. 2). These findings demonstrate that although the setting in which an event occurs is an important determinant of memory retrieval at 3 months, its protective function can be overridden by common experiences in varied setti

ISSN:0012-1630    

DOI:10.1002/dev.420240104

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

年代:1991

数据来源: WILEY

摘要:

AbstractSeveral investigators have reported that human newborn auditory brainstem evoked response (ABR) thresholds to clicks are about 10‐20 dB higher than human adult thresholds to the same stimuli (Galambos amp; Hecox, 1978; Shulman‐Galambos amp; Galambos, 1979; Lasky, Rupert, amp; Waller, 1987). The present study replicated these results, but, in addition, addressed developmental differences in ABR thresholds due to forward masking and changes in stimulus repetition rate. Eight human newborns and seven human adults served as subjects. Newborn ABR thresholds to a 100 μs click which followed a 82 db (A) SPL 50 ms broadband forward masker by 10 ms were significantly more elevated relative to their unmasked ABR thresholds than were those of the adults. Relatively loud sounds seem to have a greater effect on the newborn's ability to process subsequently presented soft sounds than they do on adult processing. In contrast, changes in repetition rate of 100μs clicks from 10/s to 50/s had no greater effect on newborn than adult ABR thresholds. At near threshold stimulus levels, rate effects on the ABR are not apparent in newborns nor a

ISSN:0012-1630    

DOI:10.1002/dev.420240105

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

年代:1991

数据来源: WILEY

摘要:

AbstractWeanling or adult rats that have sustained near‐total depletions of striatal dopamine (DA) on postnatal Day 3 do not exhibit the severe ingestive deficits seen in comparably depleted adults. The present experiments demonstrated that these animals are capable of ingesting independently, via an intraoral cannula, as early as three days after the depletion. Both activational and ingestive responses to maternal deprivation and intracellular dehydration were virtually identical to the responses of control pups. However, these responses may not be entirely dopaminergically mediated at Day 6 since administration of haloperidol failed to attenuate these behaviors in normal pups. When tested on Day 12, DA‐depleted pups continued to exhibit normal ingestive and activational behaviors, despite the fact that haloperidol now suppressed these behaviors in both groups of 12‐day‐old pups. These findings demonstrate that there is a developmental progression of dopaminergic involvement in the control of independent ingestion and the associated activational responses, yet a near‐total depletion of striatal DA is not sufficient to impair the expression of these

ISSN:0012-1630    

DOI:10.1002/dev.420240106

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

年代:1991

数据来源: WILEY

ISSN:0012-1630    

DOI:10.1002/dev.420240107

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

年代:1991

数据来源: WILEY

ISSN:0012-1630    

DOI:10.1002/dev.420240101

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

年代:1991

数据来源: WILEY