Water-maze learning in the mouse correlates with variation in hippocampal morphology.
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The effects of six independent variables on rhesus mother-infant relations are examined by comparing sub-groups of mother-infant pairs differing in only one of the variables. Variables compared and discussed include mother's parity, previous experience and social status, sex of the infant and the presence of peers. All variables except maternal parity appeared to affect the relationship, but none produced effects that were wholly consistent over all comparisons. Further tentative analyses were made of some age effects and interactions between variables which may have accounted for the inconsistencies.
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The feeding behaviour and diet of the black-and-white ruffed lemur (Varecia variegata variegata) was investigated in the Betampona Reserve, eastern Madagascar. The highly frugivorous diet of this subspecies was confirmed - feeding on fruits accounting for 92.0% of feeding records. Most feeding at Betampona was observed at 10-25 m above the forest floor amongst flexible, small (0.5-5.0 cm diameter) and oblique/horizontal (0-45 degrees ) supports. The Varecia spent on average 21.7% (+/- 1.5) of their daily activity budget feeding and employ a variety of postures that enable them to harvest fruits in the rain forest canopy. The suspensory postures were the most important in allowing Varecia to compete with other smaller-bodied frugivores.
Golden hamsters were exposed to conditions of 2.5 times normal gravity (hypergravity, HG) for 4 months. During this period, tests were carried out to study equilibrium maintenance, swimming behaviour and open-field behaviour of these HG hamsters and of control hamsters living in a normal-gravity environment. The tests proved to be useful devices for detecting differences in perceptive-motor behaviour between HG hamsters and control hamsters. The HG hamsters had more difficulties in balancing on tubes and orientation during swimming. In the open-field study, the HG hamsters showed less locomotor activity than control hamsters. However, no differences were observed between the groups in washing, rearing and number of times having defaecation. These findings indicate that the daily transition from 2.5 to 1 g was not experienced as stressful by the hamsters, although performance on several perceptive-motor tasks was decreased, especially during the first weeks.
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Subjects separated by a Plexiglas partition were trained to follow a cooperative escape procedure which produced behavior like the escape responding of individual subjects. Removal of the partition produced fighting and less efficient escape. Efficient escape behavior was restored and fighting disappeared when the partition was replaced. Neither increased space nor a moving toy affected escape behavior. The results indicate that switching animals from an isolated to a social situation produced a change in the effect of shock upon escape which was related to shock-induced fighting.
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The influence of matrilineal kinship on four socially affiliative behavior patterns--grooming, contact, proximity, and play--was studied in a little-known primate species, the Celebes black ape (Macaca nigra). Twenty group-living black apes, comprising four genealogical groups, were observed for more than 100 hr; data were collected by the instantaneous scan technique. Animals spent more time than was expected by chance grooming, in contact with, and in proximity to their matrilineal relatives, but they did not play with relatives more than was expected. The proximal mechanisms responsible for these results are unknown, and increased familiarity among matrilineal relatives may have influenced the interaction patterns in the group. The results obtained in this study are similar to those of many others that demonstrate differential behavior toward kin, and they are consistent with the theory that animals may increase their inclusive fitness by interacting preferentially with relatives.
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A preference test paradigm was used to assess the value of two enrichment techniques for rhesus macaques (Macaca mulatta): 1) a Kong toy stuffed with food treats and 2) a fleece board covered with particulate food. The duration of time spent in the enriched cage side was compared with that spent in the unenriched cage side. Additionally, the number of cage side changes made during an observation interval and the duration and frequency of occurrence of select behaviors were recorded. Half the subjects altered their cage side preference during the experimental condition, and a fifth animal reversed side preference in the postexperimental phase. Subjects spent a mean time of 14% of a session engaged with the foraging devices. The occurrence of several behaviors, including self-directed and locomotor activities, varied significantly with the experimental condition. These results were compared with data from a previous preference study of nonnutritive enrichments, and a hypothesis regarding the relative value of different types of enrichment was developed.
Ampakines are a family of drugs that selectively increase AMPA receptor-gated currents and improve performance on several behavioral tasks. This report describes evidence that ampakines cause a cumulative enhancement of performance in a spatial short-term memory task (Deadwyler et al., 1996). Two groups of rats were trained on a spatial variant of the delayed-nonmatch-to-sample (DNMS) paradigm. One group (n = 12) received the ampakine CX516 (Cortex Pharmaceuticals) alternated with vehicle for 17 consecutive days and then only vehicle for an additional 7 d. The second group (n = 6) received only vehicle injections over the same number of days. CX516 improved performance within sessions, particularly on trials with delays of 6-35 sec. In 9 of 12 rats, the positive effect of the drug was also present on nondrug days between CX516 administration and after cessation of CX516 injections. The animals that received only vehicle injections showed no improvement in DNMS performance over the entire 32 d of testing. Three of the 12 animals given CX516 did not exhibit "carryover" effects of the drug to the intervening (vehicle only) test sessions, but nonetheless exhibited superior performance during the first half of the session on days in which the ampakine was administered. Evaluation of errors suggests that the ampakine eliminated the necessity for a shift in response strategy that produced proactive interference on the following trial. Hippocampal involvement in these ampakine effects is discussed as a prelude to the second article in the series (Hampson et al., 1998).