摘要:

AbstractThe responses of unweaned juveniles, 18 to 27 days of age, in brief tests with pups younger than 10 days were observed during initial exposure and at 4–6‐day intervals. They showed no aversive responses and actively sought contact with the pups until 24 days when contact‐seeking declined sharply. Young exposed to pups before 24 days continued to seek contact with them after 24 days showing an effect of the prior experience. Juveniles given a choice between young pups and a warm bowl chose the pups; given a choice between young pups and age mates, they chose the young pups until day 23, but chose the age mates after then. When housed continuously with young pups at 22 days of age, 5 of 9 retrieved and grouped pups with a latency of 1 day. Our results indicate that timidity or fear of novelty develops in rats in this situation about Day 24 and thereafter is a factor inhibiting the expression of positive social behavior toward

ISSN:0012-1630    

DOI:10.1002/dev.420120502

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

年代:1979

数据来源: WILEY

摘要:

AbstractMale and female rats that were nonhandled or that were handled from weaning, and that had intact or impaired olfaction (intranasal zinc sulfate), were sensitized through continuous pup exposure commencing at 30, 45, 60, or 90 days of age. Nonhandled males and females were alike in latencies to become maternal at Day 30 but thereafter latencies of females became shorter and latencies of males lengthened; by 90 days males had markedly longer latencies than females and only 1/3 became maternal. Handling facilitated sensitization at 30 days among males and females but only among males at 45 and 60 days. Intranasal zinc sulfate reduced latencies of both males and females at all ages tested, but appeared most effective after 45 days of age. Gender differences in latencies persisted in adult animals even after combined treatments. Results indicate that both timidity and olfaction inhibit the onset of maternal responses to pups in virgin males and females, but they differ in relative importance by age and gender.

ISSN:0012-1630    

DOI:10.1002/dev.420120503

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe activity of isolated rats from 6 to 25 days of age was analyzed at 10‐min intervals. Ultradian peak activity rhythms, with a rough 1‐2‐hr periodicity, developed between 9 and 12 days of age, and reached an extreme at 15 days. Ultradian periods of attenuated activity were however detectable even in 6‐day‐olds. Isolated rats at 15 days of age displayed greatly accentuated profiles characterized not only by heightened activity levels, but by an extreme cyclicity. These subjects spent most of their time oscillating between periods of marked activity and marked inactivity. Both the average and total duration of these extreme periods were greater in 15‐day‐olds than any of the other ages. Free‐running nocturnal activity rhythms were also observed to develop in isolated rats tested in continuous darkness

ISSN:0012-1630    

DOI:10.1002/dev.420120504

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

年代:1979

数据来源: WILEY

摘要:

AbstractObservations of 2 groups of dams and their litters were made every 3 hr around the clock on Days 1‐20 postpartum. The dams were fed either an 8% or a 25% casein diet for 5 weeks before mating and during gestation and lactation. Dams on the low protein diet spent more time in the nest actively nursing their young than did high protein dams, and they exhibited no deficits in other maternal behaviors. Five of 11 kinds of behavior developed more slowly in the undernourished pups than in the well‐nourished ones, but the developmental delays were no longer than a few days. Circadian fluctuations were apparent in all of the pups' activities during the 3rd postnatal week as well as in grooming and horizontal movement, 2 behaviors that were present earlier, by 6–10 days o

ISSN:0012-1630    

DOI:10.1002/dev.420120505

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

年代:1979

数据来源: WILEY

摘要:

AbstractNewly hatched domestic chicks were given extended free access to 7 rates of intermittent white light between .5 and 24 flashes per sec. Inspection of the data showed approaches and departures directed toward the light that increased in number and formed an orderly pattern as the rates neared 4 per sec and as the chicks exposed to this rate became older. Also, no differences were found in the amount of time chicks remained next to the various rates during each approach but only in the amount of time they remained away during each departure. The bearing of these results on the proposal that flicker phototaxis might stem from the neural excitation produced through photic driving was discussed along with relating further evidence to recent work in imprinting.

ISSN:0012-1630    

DOI:10.1002/dev.420120506

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

年代:1979

数据来源: WILEY

摘要:

AbstractTwo methods were investigated as attempts to undernourish rat pups without the disturbances in maternal behavior that accompany the procedures used to date for this purpose. In the 1st method, a litter of 12 pups was raised by both a lactating mother and a “sensitized” female. The sensitized female was provided under the assumption that she could correct for the deficit in maternal care when 1 mother raises a large litter. The results showed that the pups raised by the 2 females were constantly removed by the females from each other's nests; the females engaged in constant fighting and showed altered maternal behavior. As a consequence the pups lost more weight than control underfed young. The 2nd method consisted of removing 6‐8 nipples from virgin females which were mated 10 days later. After delivery these females raised litters of 6 pups. Their maternal behavior was equal to that of unoperated controls, and at weaning the pups had 20–50% less body weight. This method could be useful to study undernutrition effects on behavior, without confounding experimental va

ISSN:0012-1630    

DOI:10.1002/dev.420120507

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

年代:1979

数据来源: WILEY

摘要:

AbstractIn 2 experiments the performances of light‐reared (LR) and dark‐reared (DR) 90‐day‐old rats were compared on a variety of transfer tests following acquisition of 3 pattern discriminations. Significant differences due to rearing condition were found in performance on a discrimination involving horizontal separations between pairs of vertical contours. No such differences due to rearing were observed during either acquisition or transfer testing of a discrimination involving pairs of mirror image oblique contours. Significant differences due to rearing were observed in acquisition of a discrimination between a checkerboard pattern and a similar pattern containing an irregularity and in performance on a subsequent series of transfer tests. The results suggest that the spatial integration necessary to discriminate basic as well as complex relational properties between linear elements involves mechanisms which require experience for their development and main

ISSN:0012-1630    

DOI:10.1002/dev.420120508

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

年代:1979

数据来源: WILEY

摘要:

AbstractRat pups with histories of intergenerational malnutrition were rehabilitated by cross‐fostering at birth to well‐nourished females. These pups weighed slightly less than well‐nourished controls but significantly more than pups reared by malnourished females. Rehabilitated and control pups were both more active than malnourished pups reared by malnourished females. However, the percentage of nest returns by pups displaced to other parts of the cage was low among rehabilitated pups as compared with controls, but did not differ from that of pups with histories of intergenerational malnutrition reared by malnourished females. These data suggest that, although activity is a product of postnatal condition, home‐orienting behavior is affected by a history of intergenerational malnutrition regardless of rehabil

ISSN:0012-1630    

DOI:10.1002/dev.420120509

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

年代:1979

数据来源: WILEY

摘要:

AbstractFemale rats were exposed daily to 750 mg/kg of lead acetate via a restricted watering schedule for 70–80 days prior to mating and then throughout pregnancy and nursing. At weaning, litters from half of the lead dams were placed directly on treatment for the duration of the experiment. These manipulations yielded 3 groups: Group Pb/Pb, offspring exposed during pre‐ and postweaning periods; Group Pb/C, offspring exposed only during preweaning periods: and Group C/C, control offspring. Beginning at 42–49 days of age, postnatal, offspring were shaped to bar press under a fixed‐interval, 1‐min schedule (FI1) and then given 20 sessions, each 45 min in length. Analyses revealed that Group Pb/Pb received fewer reinforcements across sessions than the other 2 groups, which did not differ. However, when the Pb/Pb offspring did receive reinforcement, they exhibited the scalloped pattern of responding characteristic of fixed‐interva

ISSN:0012-1630    

DOI:10.1002/dev.420120510

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

年代:1979

数据来源: WILEY

摘要:

AbstractA comparison was made of MR, MNR, and RCA strains that had been injected with either 62.5 mg/kg of taurine or comparable volumes of physiological saline between postnatal Days 8 and 20 and later tested at 100 days of age in an open field and 1‐way shock avoidance situations. Taurine‐injected rats displayed significant elevation in defecation score in the open field. In addition a significant Treatment × Strain interaction was due to the larger defecation numbers displayed by the taurine‐injected MR rats relative to the saline‐injected

ISSN:0012-1630    

DOI:10.1002/dev.420120511

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

年代:1979

数据来源: WILEY