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Biomedical subjects

A Amsel

Publications and source records attributed to A Amsel.

At least 37 records · Page 2Linked to original sources
PubMed1992

Blood ethanol concentration from early postnatal exposure: effects on memory-based learning and hippocampal neuroanatomy in infant and adult rats.

Early postnatal exposure to ethanol (EtOH) that results in daily high-peak blood ethanol concentration (BEC) retarded the acquisition of single-patterned alteration (PA), a kind of memory-based discrimination learning, and was related to reduced brain weight, hippocampal cell number, and CA1 area in infant rats. These behavioral and neuroanatomical effects survived into young adulthood. On the PA discrimination, in both pups and young adults, postnatal exposure to high-peak EtOH condition, in relation to low-peak and control conditions, impaired the acquisition of PA at 60-s but not at 30-s intertrial intervals. These results provide further evidence of hippocampal involvement in intermediate-term memory and indicate that early postnatal EtOH is a behavioral and neuroanatomical teratogen, particularly when the BEC is relatively high.

Alcohol Drinking↗
PubMed1992

Memory-based learning in preweanling and adult rats after infantile x-irradiation-induced hippocampal granule cell hypoplasia.

Infantile exposure to x-irradiation induced severe hippocampal granule cell hypoplasia in preweanling and young adult rats. Hippocampally damaged pups, tested at 16 days of age, showed deficits in a memory-based discrimination based on single alternations of reward and nonreward when training was conducted at a 60-s intertrial interval (ITI) but not when conducted at a 30-s ITI. This deficit was still present at the 60-s ITI in animals x-irradiated in infancy and tested at 60-65 days of age. These data provide further support for the role of the hippocampus in intermediate-term memory and demonstrate, in a developmental context, the importance of an intact hippocampus in learning that depends on nonspatial memory.

Aging↗
PubMed1992

Frustration theory--many years later.

The role of frustration in learning theory, in the invigoration of behavior and in the development of learned persistence and discrimination learning, is conceptualized. This and other phenomena are facets of the larger explanatory domain of what has come to be known as frustration theory, a theory that has guided the author's own research--from behavioral to developmental to psychobiological --until the present time and has had some influence on the research of other investigators. This is a commentary on the 1st of several published theoretical papers on frustration theory.

Animals↗
PubMed1991

Effects of prenatal ethanol exposure on learned persistence and hippocampal neuroanatomy in infant, weanling and adult rats.

The present experiment examined whether deficits in learned persistence, previously seen in 15-day-old infant rats prenatally exposed to ethanol, would be present in weanling and adult animals. Three prenatal treatments, EtOH, PAIR-FED, and LAB CHOW, were combined factorially with partial (PRF) or continuous (CRF) reinforcement training followed by extinction, at 21 days or 6 months of age. The results at 21 days were virtually the same as our earlier findings for 15-day-olds: we did not find the higher level of persistence in PRF-trained EtOH pups relative to CRF-trained EtOH pups, which characterizes the partial reinforcement extinction effect (PREE). The EtOH-PRF and EtOH-CRF animals extinguished at about the same rate, both faster than PRF controls. However, when tested as adults, the EtOH-exposed animals showed a normal PREE, with no deficits relative to controls. An analysis of CA1 pyramidal cells in midtemporal hippocampus demonstrated no significant differences in cell density or in CA1 area among the 3 prenatal diet conditions; however, there was a significant reduction in cell density with age for all groups. These results suggest that a developmental delay, unrelated to these neuroanatomical measures, is responsible for the lack of persistence in young rats exposed prenatally to ethanol.

Aging↗
PubMed1990

Fetal ethanol exposure diminishes hippocampal beta-adrenergic receptor density while sparing muscarinic receptors during development.

Because of ostensible effects of fetal exposure to ethanol on cardiac and memory functions, beta-adrenergic and muscarinic receptor binding were surveyed in hippocampus and heart in 8- and 17-day-old rat pups. Pregnant, multiparous rats were intubated with either 6 g/kg ethanol or isocaloric dextrose twice daily from gestational days 10-16. At birth, offspring were fostered to untreated mothers. Pups exposed to ethanol had diminished birth weights, although there was no difference in the amount of weight gain by ethanol and control dams during gestation, nor in litter size. Ethanol pups remained smaller than control pups, but this difference was significant only until 8 days of age. At 17 days of age, ethanol pups had fewer hippocampal beta-adrenergic receptors than age-matched controls; muscarinic receptors and CA1 cell densities were not disparate. Parallel studies suggested that approximately 50% of the hippocampal beta-adrenergic receptors in 8-day-olds were of the beta 1 and beta 2 subtypes, while by 17 days of age approximately 70% of the receptors were beta 1. There was an ontogenetic increment in both beta-adrenergic and muscarinic binding from 8 to 17 days of age in hippocampus. No differences between age or drug groups were found in the binding measures in heart tissue. The present findings indicate that fetal ethanol treatment affects developmental measures and beta-adrenergic receptors in the hippocampus in a quasi-selective manner, but not hippocampal CA1-cell density.

Animals↗
PubMed1990

Behavioral and neuroanatomical effects of prenatal, postnatal, or combined exposure to ethanol in weanling rats.

Separate and combined effects of prenatal and postnatal exposure to ethanol on activity, emotionality, learning, and hippocampal neuroanatomy were examined in infant rats. Neonatal rats from mothers that were fed either a liquid ethanol (E) or control (C) diet on Gestational Days (G) 1-21 were artificially reared during Postnatal Days (P) 4-12 on either 3% ethanol (E) or isocaloric maltose/dextrin (C) in a milk formula. Pups in these treatment groups (EE, EC, CE, and CC) were tested for activity and emotionally in an open field on P19, for acquisition and extinction of an appetitive, straight runaway task on P20-P21, and for the effects of ethanol treatments on alterations in hippocampal neuroanatomy on P21. Differences in activity and emotionally were slight. Ethanol affected both the partial reinforcement acquisition effect and the partial reinforcement extinction effect. Hippocampal cell density (compared with Group CC) showed a 12% reduction in CA1 pyramidal cells and an 11% reduction in mature granule cells in Groups EC and EE; the CA4 area (compared with Group CC) was significantly larger after postnatal exposure (Groups CE and EE). Significant positive correlations were found between rate of extinction after partial reinforcement (PRF) training and CA1 pyramidal cell density in Groups CC and CE. A significant negative correlation was found between extinction rate after PRF training and CA4 area in Group EE.

Animals↗
PubMed1989

Patterned (single) alternation in infant rats after combined or separate lesions of hippocampus and amygdala.

The role of the developing hippocampus and the amygdala on patterned (single) alternation (PA) in the infant rat was investigated in 4 experiments. In Experiments 1 and 2, pups were given 2 bilateral electrolytic hippocampal lesions or sham surgeries at 10 or 11 days of age and were trained 6 days later in a straight runway. In Experiment 1, there were 120 trials in 1 day, with an 8-, a 15-, or a 30-s intertrial interval (ITI). PA learning occurred in lesion and sham pups at the 8- and 15-s ITIs, but it was reduced in both groups at the 30-s ITI. In Experiment 2, training was extended to 240 trials over 2 days, with a 30- or 60-s ITI. Sham and lesion pups showed PA at the 30-s ITI, but the emergence of PA was delayed in the lesion pups at the 60-s ITI. In Experiment 3, amygdaloid lesions had no effect on PA learning at the 8-s ITI. However, when pups with hippocampal and amygdaloid lesions were trained at the 8-s ITI, the emergence of PA was delayed, and its size was reduced (Experiment 4). The results of these experiments argue for a role of the hippocampus in PA learning at long ITIs and suggest that, even in 16-day-old pups exposed to an 8-s ITI, the combined hippocampal and amygdaloid lesion produces a deficit greater than either the hippocampal or the amygdaloid lesion. The results are discussed in relation to current theories that distinguish between 2 levels of memory function.

Amygdala↗
PubMed1988

Sparing of patterned alternation but not partial reinforcement extinction effect after prenatal chronic exposure to ethanol in infant rats.

The effects of in utero administration of ethanol on single patterned alternation (PA) and the partial reinforcement extinction effect (PREE) were studied in 15-day-old rat pups. This fetal-alcohol treatment had no effect on PA but eliminated the PREE by reducing persistence in extinction after partial reinforcement (PRF) training to its level after continuous reinforcement (CRF) training, which was not affected by the treatment. The results are discussed in terms of prenatal damage to the hippocampus and in relation to an earlier experiment (Lobaugh, Bootin, & Amsel, 1985), which found no effect of infant hippocampal lesions on PA but an elimination of the PREE, which, unlike the fetal-alcohol case, resulted from PRF-like persistence in extinction following CRF training.

Animals↗
PubMed1988

Effects on the partial reinforcement extinction effect and on physical and reflex development of short-term in utero exposure to ethanol at different periods of gestation.

Ethanol was intubated into pregnant rats at Gestational Days 7-9 (G7-9) or 14-16 (G14-16). At both gestational ages, ethanol intubation affected reflex development but not physical development of resulting offspring. At G14-16, but not at G7-9, ethanol intubation resulted in the elimination of the partial reinforcement extinction effect when pups were tested at 15 days of age. These latter results confirm and extend previous ones in which ethanol was administered in a liquid diet throughout gestation.

Animals↗
PubMed1987

The kinematics of locomotion toward a goal.

A mathematical model is developed that treats rats in runways as uniformly accelerated bodies. The purpose of the model is to permit conversion of the continuously varying measures of runway speeds at different points in the alley into three invariant parameters of performance: start latency, acceleration, and brakepoint. This simple model fits most of the data examined, and changes in the parameters throw new light on phenomena such as the partial reinforcement acquisition effect. In particular, it is shown that partially reinforced rats accelerate faster but cease accelerating earlier in the runway than do continuously reinforced rats. This explains the qualitative differences often found between start and goal speed measures. The analysis takes as its unit patterns of terminal behavior rather than the rate of the responses that constitutes them, and thus may permit coherent treatment of instrumental and operant behavior.

Humans↗
PubMed1986

Effects of photic stimulation on heart rate of infant rats.

We present the results of three experiments which characterize the heart rate (HR) response of infant rats at a number of different ages to the onset, or the offset, of a bright light. Experiment 1 demonstrated that at ages 5, 8, 11, 14, 17 and 21 days, a sudden increase in ambient illumination caused a HR deceleration, whereas a sudden decrease in ambient illumination caused a HR acceleration. At each age, the HR acceleration did not habituate over 60 stimulus presentations, whereas at all ages beginning at 8 days, the HR deceleration did habituate. By varying the intensity of either the visual or thermal component of the stimulus at ages 8 and 17 days, Experiment 2 revealed that the directional effects were a result of the visual and not the thermal component of the stimulus, thereby ruling out any account of the findings in terms of local adaptational reflexes. Finally, Experiment 3 varied the rate of stimulation, tested for spontaneous recovery, and demonstrated that the decrement in response magnitude observed across trials conformed to several of the accepted parametric characteristics of habituation, and could not be accounted for by changes in baseline HR across trials. These results are discussed in terms of traditional interpretations of HR changes as orienting and defensive reactions.

Age Factors↗
PubMed1985

Heart-rate responses of infant rats and guinea pigs to stimulus onset and offset: tests of the generality of a bidirectional effect.

To test the generality, across modality and across species, of a bidirectional effect of photic stimulation in infant rats found in previous experiments, two experiments examined the effects on heart rate (HR) of onset and offset of auditory stimulation in rats and of photic stimulation in guinea pigs. Experiment 1 demonstrated a unidirectional, decelerative response in rats 17 and 21 days of age to the onset and offset of a 1-kHz tone, at both low (80 dB) and high (100 dB) intensity levels and at 14 days to the onset of the high-intensity tone. Experiment 2 demonstrated that infant guinea pigs, which unlike infant rats are precocial and not nocturnal, responded to the offset but not to the onset of light, and that this response was decelerative. These results indicated a lack of generality of the bidirectional HR effect, and were discussed in terms of the orienting/defensive reflex distinction.

Acoustic Stimulation↗
PubMed1985

Sparing of patterned alternation but not partial reinforcement effect after infant and adult hippocampal lesions in the rat.

The effect of hippocampal lesions was assessed in patterned (single) alternation (PA) and the partial reinforcement extinction effect (PREE), the two reward-schedule effects that appear earliest in ontogeny. Three groups of rat pups, with appropriate controls, were tested for each effect: lesion as infant/test as infant, lesion as infant/test as adult, and lesion as adult/test as adult. Hippocampal lesions had no effect on PA in any of the three conditions except for a suggestion that the effect was mildly attenuated in the animals given lesions as infants and tested as adults: The pups were able to discriminate rewarded from nonrewarded trials and to inhibit responding on nonrewarded trials. On the other hand, the PREE was eliminated under all conditions of testing, in each case because of an increase in persistence following continuously reinforced acquisition. The results are discussed in terms of the functional maturation of the hippocampus and a possible dissociation of mechanisms that mediate response suppression in PA and in the PREE in infant rats.

Age Factors↗
PubMed1984

Age of first appearance of simultaneous and successive negative contrast in infant rats.

Simultaneous (SimNC) and successive negative contrast (SNC), two paradoxical effects that are related to shifts in reward magnitude, were studied in rats from 11 to 17 days of age. Experiments 1 and 2 looked at the emergence of SimNC at 11, 14, and 17 days. At all of these ages, rats were able to discriminate between the large (milk suckling) and small (dry suckling) reward odor cues as measured by attachment latencies, but only the 14- and 17-day-olds showed SimNC. At none of the three ages was a discrimination formed to the differential odor cues in the alley in terms of runway speeds. Experiment 3 was designed as a further test of the absence of SimNC at 11 days. In this experiment, the pups were placed directly on the dam's ventrum to facilitate attachment. As in the earlier experiment, the 11-day-old pups discriminated between the odors signaling the two reward conditions but did not show the SimNC effect. In Experiment 4, SNC was measured in pups 14 and 17 days of age. SNC was shown at 17 days but not at 14 days in the attachment latency measure and at neither age in the run measure. These four experiments extend our earlier findings that the paradoxical effects that emerge out of intermittent schedules of reward magnitude occur earlier than those associated with single abrupt shifts in reward magnitude.

Aging↗
PubMed1983

Ontogeny of heart rate response to milk infusion in infant rats as a function of level of deprivation.

The heart rate (HR) responses of infant rats aged 8, 11, 14, and 17 days were recorded during the intraoral infusion of milk. Subjects were deprived for various periods of time prior to the start of testing. The results revealed a transition from HR deceleration to HR acceleration between 8 and 14 days of age, with the magnitude of the response varying directly with the degree of deprivation. A follow-up experiment was run in order to demonstrate that the observed HR changes were not a result of the termination of infusion. Implications for a transition from infant to adult feeding systems as well as the development of a somatic-cardiac linkage are discussed.

Aging↗
PubMed1981

Adjustment of weanling and adolescent rats to a reward condition requiring slow responding.

The effects of a schedule of discontinuously negatively correlated reinforcement (DNC), in which only approach responses that take 5 sec or longer are reinforced, were studied in weanling rats that began training at 18 days of age and adolescents that began training at 60 days. Yoked partially reinforced subjects (PRF) received rewards on the same trials as corresponding DNC subjects of the same age, whereas continuously reinforced subjects (CRF) were rewarded on all trials. At the end of DNC training (210 trials), the older but not the younger DNC subjects were running slower than their yoked-PRF controls. The results are consistent with development of inhibition and suppression related to the developing brain, particularly the hippocampus.

Adaptation, Psychological↗