Effect of early auditory stimulation on the choice of acoustical environment by adult Swiss albino mice (Mus musculus).

In 2 experiments, 265 Swiss albino Rb-3 9-wk-old untreated mice, when placed in a novel environment composed of a central cage surrounded by 4 dark boxes in which different sounds were emitted, explored the boxes for 1 or 2 hrs. In most cases, Ss settled into 1 of the 4 boxes and built their nest. Most of the controls chose the silent compartment, whatever the sound delivered in the other boxes. An acoustic choice test was then carried out. Four groups of mice were exposed to a particular sound for 10 days: Group 1: Gestation Day 10 to birth; Group 2: birth to Day 10; Group 3: Day 10 to Day 20; Group 4: Day 20 to Day 30. Ss were then tested for box preference on Day 63 in the 4-box choice, one of which contained the sound of the earlier exposure. Ss stimulated before the 10th day after birth behaved in the same way as controls, whereas Ss stimulated between the 10th and the 20th days after birth exhibited a strong preference for the box delivering the sound of the previous treatment. This choice was significant, whatever the harmonic (Exp I) or impulsive (Exp II) nature of the sound. Ss stimulated between the 20th and the 30th days showed a preference for the silent box, but among the others, 75% chose the sound received during infancy. The behavior of Ss stimulated when adult was the same as that of the controls. (38 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sexual differentiation of play behavior in the ferret.

Three experiments examined the endocrine mechanisms responsible for sex differences in prepubertal play behavior of ferrets. In Exp I, 6 gonadally intact adolescent males exhibited higher levels of "stand-over" behavior than 6 females did in tests between 63 and 123 days of age with gonadally intact female partners of the same age. In Exp II, with 69 Ss, those Ss exposed to androgen or to ovarian steroids over Days 5–20 of postnatal life subsequently exhibited significantly higher levels of stand-over behavior in tests with females than did control females gonadectomized on Day 5 and not given steroids. None of the Ss in Exp II exhibited levels of stand-over behavior comparable to those of the gonadally intact males in Exp I. In Exp III, with 36 Ss, males gonadectomized and implanted subcutaneously with testosterone capsules on Day 70 and tested with females at 84–96 days of age exhibited levels of stand-over behavior comparable to those observed in Exp I in gonadally intact males of the same age (Weeks 12–24). Males gonadectomized on Day 70 and given no hormone at testing exhibited significantly lower levels of this behavior. Significantly lower levels were also exhibited by males gonadectomized on Day 35 and females gonadectomized on Day 70, regardless of whether they were tested with testosterone present after Day 70. Sex differences in the expression of prepubertal play behavior of ferrets apparently result from differential exposure of males and females to androgen over an extended postnatal period. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of learning and memory of -maze training in neonatal mice.

Presented 25 trials in a shock-escape maze to 90 Swiss-Webster mice at 9, 11, or 13 days of age. One-half of the Ss at each age were trained to the goal opposite their 1st-trial choice, while the other 1/2 served as yoked controls. 24 hr. later, the trained groups received 25 additional trials to the previous goal. The yoked groups and groups without prior exposure were trained to the goal opposite their 1st-trial choice. 9-day-old Ss trained to a specific goal showed some improvement in performance during original training, while the 11- and 13-day-old groups demonstrated substantial improvement. On retention tests, 9-day-old Ss trained to the same goal on both days did not differ from either control group, but 11- and 13-day-old trained Ss were reliably better than either control group. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Postnatal development of absolute auditory thresholds in kittens.

Measured postnatal development of absolute auditory thresholds in kittens from birth up to 1 mo of age. UCRs to pure tones were observed for Ss up to Day 12, and CRs were used from Day 10 onward. At 1 day after birth, the first noticeable responses were obtained in 4 of 11 Ss at frequencies of .5–2 kHz. At 2 days of age, 12 of 16 responded. Thresholds remained high (above 100 db) up to the 6th day, but the range of behaviorally effective frequencies extended from .2 to 6 kHz. All CR thresholds at Day 10 and most at Day 12 were significantly lower than those measured by UCRs. From 10 days onward, all threshold curves showed a characteristic sensitivity optimum at 4 kHz. For frequencies below 1 kHz, maximum sensitivity was reached at Day 15; for frequencies up to 20 kHz, at Day 20; and for even higher frequencies, at Day 30. At 1 mo of age, the frequency range was adultlike. Results closely follow structural maturation of the acoustic pathway and demonstrate limitations of the ability for acoustical communication during the 1st wk of life. (38 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of early food deprivation on mouse behavior.

Assessed the effects of early food deprivation upon open-field defecation and activity, running-wheel activity, and food-competition behavior using 76 A/J and 73 DBA/2J mice. Experimental Ss were food deprived from Day 18-27 of life for 10 hr/day. Food-deprived Ss defecated more in the open field and were less active in the running wheels. In these measures, strain and sex interacted with treatment. DBA mice which received the deprivation treatment were less competitive than the comparison Ss, but the treatment did not affect competition in the A/J Ss. It is suggested that the severity of the treatment and age when it was administered interfered with normal development of behavior. (21 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Precocious mating in male rats following treatment with androgen or estrogen.

Conducted 5 experiments with 179 male Royal Victoria Hospital hooded rats. Daily subcutaneous injections of 1,000 MUg/100gm testosterone propionate of 5 MUg/100gm estradiol benzoate (EB) after postnatal Day 10 accelerated initial intromission and ejaculation in intact Ss. Precocious Ss continued to copulate after treatments were stopped. Age at the 1st display of intromission was unrelated to age at the 1st injection of EB. However, initiation of EB treatments before Day 11 was associated with rapid loss of intromission following cessation of treatment in adulthood. EB activated the 1st mating of prepuberally castrated and sham-operated Ss with nearly equal facility. Also, prepuberal castrates primed with EB subsequently intromitted after receiving fewer androgen replacement injections than control Ss. (24 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of problem-solving abilities in the neonatal Peking duck.

294 Peking ducklings, aged 1–24 days posthatch, were tested in 3 experiments involving 3 different problem-solving situations: a delayed response task, spatial habit reversal learning, and a detour problem. In the delayed response task, the length of the delay did not improve significantly with increasing age, averaging 1.6 sec on Day 1 and 2.8 sec on Day 14. In the habit reversal learning, Ss were tested longitudinally beginning on Days 1, 2, 3, and 4. In each group, errors decreased rapidly and progressively with successive reversals, with this steady improvement resembling that found in adult birds and mammals. In the detour problem, groups of Ss were tested longitudinally, beginning on Days 1–6. In groups started at each age, learning was rapid, with criterion usually met within the 1st 1 or 2 days of testing. Even when testing began on Day 1, the Ss typically solved the problem on the 1st or 2nd day of testing, requiring a mean of 10.78 trials to criterion. Results suggest that the neonatal Peking duckling is well equipped to deal with its environment and is capable of a high level of adaptive modification in response to externally imposed stimulus contingencies. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Retention and durability of persistence acquired by young and infant rats.

Conducted 2 experiments in a runway apparatus with 72 young Holtzman rats. A classic partial reinforcement acquisition effect was obtained in Ss trained from 30 to 45 days of age but not in those trained from 18 to 25 days of age. In an immediate extinction test for half of the Ss, a partial reinforcement extinction effect (PREE) was found in both age groups, but there were differences in the extinction patterns. Following a 45-day retention interval and a continuous reinforcement reacquisition treatment for all groups, the PREE emerged clearly in adult Ss which had not undergone previous extinction. In those Ss which had previously been extinguished the PREE emerged again but was somewhat reduced. Results from the younger Ss suggest that relatively permanent persistence in approach to food can be formed in the days that normally immediately precede and follow weaning in laboratory rats. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Nutritive and nonnutritive determinants of milk intake of suckling rats.

Determined the factors that enhanced milk intake during deprivation in albino rats 15, 20, and 25 days of age. Ss were subjected, for 8 hrs, to 1 of 6 regimens. Results show that intake at Day 15 was reduced by the opportunity to suckle, independent of receiving a milk load. This same trend was apparent, although not as strong, among Day 20 Ss. By Day 25, nonnutritive suckling during the privation period no longer attenuated milk intake, although preloads did, whether or not they were paired with nonnutritive suckling. Thus, suckling in Ss became increasingly freed from oral demands and more responsive to the nutritive consequences. (13 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Biochemistry and genetics of thiodicarb resistance in the house fly (Diptera: Muscidae)

We have recently reported that environmental toxicants, such as DDT, PCBs, pyrethroids, and nicotine can induce permanent functional and neurochemical changes in adult mice when given to neonatal mice during the peak of rapid brain growth. In the present investigation the neurotoxic effects following neonatal exposure to paraquat (N,N'-dimethyl-4,4'-bipyridylium), a broad-spectrum herbicide with structural similarity to the 1-methyl-4-phenylpyridium ion (MPP+), the active metabolite of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) which can induce Parkinson's syndrome, and MPTP were studied. Five groups of mice were given paraquat or MPTP orally: group 1, vehicle; groups 2 and 3, MPTP 0.3 and 20 mg/kg; groups 4 and 5, paraquat 0.07 and 0.36 mg/kg when 10 and 11 days old. Neonatal spontaneous motor activity was tested on Day 18 in mice given paraquat 0.36 mg/kg body wt. Adult spontaneous motor activity testing was performed at ages 60 and 120 days. On Day 125 the mice were decapitated and the contents of dopamine (DA), serotonin (5-HT), and metabolites in striatum were analyzed. The results may be summarized as follows: (1) No signs of acute toxicity or differences in weight gain were observed in any of the groups. Nor was any respiratory distress or motor performance dysfunction evident on Day 18 in mice given paraquat 0.36 mg/kg body wt. (2) The behavioral tests at 60 days of age showed a marked hypoactive condition in the mice given paraquat (at both doses) and MPTP (at both doses). (3) At the age of 120 days the hypoactive behavior persisted and appeared even more pronounced. (4) The high doses of MPTP and paraquat--and to a less extent the low doses--reduced the striatal content of DA and metabolites without affecting 5-HT. The altered behavior, together with the dose-dependent reduction of DA and metabolites in neostriata in this study, further demonstrates the susceptibility to low-dose exposure to environmental pollutants during the neonatal period.     

Response strength as a function of stimulus novelty: Concept formation in the pigeon.

Cites a previous study which showed that a distinctive CS presented on the 1st trial of acquisition generated more responses after extinction than another CS presented regularly during acquisition. In the present study 140 pigeons were presented with a different distinctive CS on each 1st trial of 5 acquisition sessions. Ss were then broken down into 7 groups which were tested, following extinction, for residual response strength of (a) Day 1 novel CS, (b) Day 2 novel CS, (c) Day 3 novel CS, (d) Day 4 novel CS, (e) Day 5 novel CS, (f) the regular CS, and (g) a novel CS never presented before. Contrary to the previous study where a novel CS inhibited responding, Group 7 exhibited the most responding in this study. Results support a concept formation interpretation of the previous study and are difficult to explain from a "stimulus trace" or "identical elements" position. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Predation: Separation of aggressive and hunger motivation by conditioned aversion.

Reports results of 2 experiments with a total of 50 male Long-Evans rats. In Exp I, Ss were given LiCl 15 min after ingesting mice or saccharin for either 1 day or 4 days. Intake of both substances dropped in the 1-trial groups but not in the 4-trial groups. In Exp II, Ss that received LiCl after killing mice they were not permitted to eat showed no changes in mouse killing. Ss permitted to feed on mice they had killed continued to kill but ate less after a single LiCl trial. Feeding and killing appear to be separable by this technique. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prepartum changes in maternal responsiveness and nest defense in Rattus norvegicus..

Examined 297 female rats for changes in maternal responsiveness during late pregnancy by exposing Ss to foster pups in tests lasting 15–30 min under conditions favoring the rapid initiation of maternal behavior. Ss were divided into 17 groups according to state of pregnancy (nonpregnant, Day 17, Day 20, Day 21, or Day 22); type of nest; and parity. Nulliparous Ss were compared with primiparous and with experienced breeders. Nest defense was observed by introducing unfamiliar males (2-min tests) on Day 22. Results are presented for 3 periods: Days 17–20, when maternal responsiveness was lower than in the nonpregnant condition; Day 21, when maternal responsiveness returned to or rose above nonpregnant levels; and on Day 22 (the 3.5 hrs prior to delivery), during which 90% of Ss almost immediately retrieved, gathered, and tended foster pups and during which 92% attacked the unfamiliar intruders. (Attacks were rare earlier.) Maternally experienced Ss were more responsive to pups than nulliparous Ss when nonpregnant and throughout late pregnancy, but both groups were equally likely to show prepartum aggression. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Changes in cognitive task performance across the menstrual cycle.

Examined the effect on cognitive tests of menstrual-cycle-related changes in estrogen in 87 undergraduates. The estrogen peak was expected to facilitate performance of 4 "automatized" tasks and to impair performance of "perceptual-restructuring" tasks, compared with performance in the postovulatory phase when progesterone is thought to counteract the action of estrogen. Daily basal body temperature (BBT) records suggested that 21 Ss did not ovulate in the cycle(s) studied. No main effect of Day 10 of the cycle vs Day 20 occurred for any task in the 66 Ss who did appear to ovulate. However, the magnitude of predicted shifts in performance was significantly correlated with proximity of the "Day 10" testing day to the lowest BBT, the presumed preovulatory estrogen peak; and to the "Day 20" proximity to the highest BBT, the presumed progesterone peak. Ss tested 3 or fewer days before the thermal nadir and on or after the thermal peak had the predicted significant changes on 3 of the 4 tasks. Results support the hypotheses and indicate that precise timing is essential to demonstrate the phenomena. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of instructions and feedback on blood alcohol level discrimination training in nonalcoholic drinkers.

Investigated whether nonalcoholic drinkers can be trained to discriminate their blood alcohol levels (BAL) on the basis of internal cues. 72 male undergraduates classified as heavy drinkers came to the laboratory for 3 consecutive sessions, each consisting of 5 BAL estimation trials. The 2 manipulated independent variables factorially combined were beverage sequence and administration of BAL feedback. All Ss were told that they would receive mixed drinks containing vodka and tonic on each day, and all Ss received alcohol on Day 1. On Day 2, half of the Ss received alcohol and half received tonic alone; similarly, half of the Ss in each of these groups received either alcohol or tonic on Day 3. No S received BAL feedback on Day 1, and one-third of Ss did not receive feedback on Days 2 and 3. The remaining Ss received feedback on Day 2; half of the latter Ss also received feedback on Day 3, and half did not. Ss did not learn to discriminate their BAL on the basis of internal cues. Results are discussed in reference to the utility of BAL discrimination training in alcoholism prevention programs. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Open-field behavior of the rat as a function of age: Cross-sectional and longitudinal investigations.

Exposed 52 female Sprague-Dawley albino rats to an open field for 5 min. daily between the ages of 31-110 days. Ss 40 days old or younger showed day-to-day increments in activity during repeated apparatus exposures, while no group 70 days old or older showed this activity change. In Exp. II groups of 9 Ss, 31 and 110 days old, respectively, were given 60 open-field trials. The juveniles increased their activity and maintained this elevated behavior; adults never did exhibit any significant increase in activity. Results indicate a critical period among rats such that high rates of ambulation are typical of only those animals that are placed in the apparatus prior to Day 70. (22 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Experiential determinants of postpartum aggression in mice.

Explored the experiential determinants and the social controls of postpartum aggression in inbred ICR mice. In Exp I, 7 lactating females were tested repeatedly from Day 2 to Day 22 postpartum against male mice; attacks by the females continued through Day 18. Two other groups of 7 females tested only once showed diminished attacks against males by Day 14 postpartum. In Exp II, 8 females were paired with a male for 1 wk prior to parturition; they showed reliably fewer attacks on Day 2 postpartum than a group of 9 females that were isolated prior to parturition. All of these results were obtained in a standard 3-min test. A 24-hr test on Day 4 of Exp II revealed that in both groups female attacks dropped to near zero after 30 min. After female attacks declined, males initiated social behavior which occasioned vocalizations by the females. Further, males attacked in 65% of the tests and destroyed the litters of the females in 53% of the tests. The behavior of the male exerted important influences on the structure of extended female–male interactions. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Early postnatal handling alters glucocorticoid receptor concentrations in selected brain regions.

Long-Evans hooded rat pups were either handled or undisturbed between birth and weaning on Day 21. Following weaning, half of the Ss in each group were housed socially, and half were housed in isolation. At 120–250 days of age, [–3H]dexamethasone binding was examined. Binding was significantly higher in the hippocampus of handled than nonhandled groups. In the frontal cortex, binding was higher in the handled/socially reared Ss than in isolated Ss. There were no significant handling or housing effects found in the amygdala, hypothalamus, septum, or pituitary. Thus, early postnatal handling appears to influence the development of the glucocorticoid receptor system in the hippocampus and frontal cortex. Results are discussed as providing a possible mechanism for some of the previously reported effects of early handling on the development of the pituitary-adrenal response to stress. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Emerging cholinergic mechanisms and ontogeny of response inhibition in the mouse.

A total of 1,604 Swiss-Webster mice 7, 11, 15, 19, and 85–215 (adult) days of age, served as Ss in 5 experiments assessing effects of anticholinergics on the development of behavioral inhibition. The centrally active anticholinergic scopolamine produced a dose-dependent elevation in locomotor activity in 19-day-old and adult Ss. Acquisition and retention of a step-off passive avoidance response (PAR) was initially studied in nondrugged Ss. Ss as young as 7 days of age learned and retained the PAR for 1 hr. 24-hr savings, however, were not observed until 19 days of age. Simple PAR performance deficits following scopolamine injection were first seen at 15 days of age. Ss in those age groups exhibiting 24-hr retention (19-day-olds and adults) were used to assess carry-over effects of scopolamine on retest. Only in the case of juveniles did scopolamine, injected prior to training, disrupt 24-hr retest performance. Since methylscopolamine, a peripherally active anticholinergic, had no effect on activity and PAR performance, it is assumed that scopolamine's effects were of central origin. Results suggest that behavioral suppression comes under cholinergic control during the 2nd and 3rd postnatal weeks but that cholinergic mechanisms may not mediate response inhibition uniformly throughout development. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)