Journal of comparative and physiological psychology最新文献

A laboratory model of garter snake aggregation behavior is described. Snakes tested in groups of eight established preferred shelter locations and reliably returned to these locations as a group or as individuals when the test aquaria were left undisturbed between trials. When the aquaria were cleaned and the contents were replaced on each trial, preferred shelter locations were not established over trials; however, the snakes were found under shelters in large aggregates more frequently than would be expected by chance. It appears that the snakes deposit cues in the apparatus that are subsequently used to return to preferred locations. Manipulations of various objects in the test arena strongly indicated that the relevant cues are deposited on the paper underlying the preferred shelter.

Two experiments were conducted to determine (a) whether male garter snakes (Thamnophis sirtalis) require a functional vomeronasal or olfactory system to return to previously preferred shelter locations and (b) the sensory modalities used by snakes to aggregate in the absence of previously deposited chemical cues. In Experiment 1, snakes with vomeronasal nerve lesions did not return to previously preferred shelter locations when tested individually. However, when tested with a group that included "control" animals, they returned to previously preferred shelters. The shelter-selection behavior of snakes with olfactory nerve lesions improved postoperatively, whereas the behavior of animals with sham lesions was unchanged. In Experiment 2, snakes were tested for aggregation in aquaria in which the substrate and other contents were cleaned between trials. After blindfolding or after olfactory nerve cuts, snakes aggregated at normal levels. When the snakes' vomeronasal ducts were sutured closed, aggregation scores were significantly depressed, although two of the three groups with vomeronasal duct sutures did aggregate just above chance levels. These studies indicate that use of chemical signals by garter snakes in shelter selection and aggregation is mediated by the vomeronasal system and that neither the olfactory nor the visual system is critical for these behaviors.

Although it is frequently stated that the frontal lobes play a significant role in memory function, research proof has been ambiguous at best. This problem was addressed by administering a variety of memory tests to 16 schizophrenic patients who had undergone prefrontal leucotomy approximately 25 years earlier. The 16 were divided into three groups on the basis of recovery after surgery. Two comparison groups were established to control for psychiatric symptomatology, years of institutionalization, age, and years of education. The results demonstrate that large bilateral orbitofrontal lesions may not result in amnesia; in fact, the nonoperated schizophrenic control group performed the most poorly. Proactive interference was demonstrated, however, resulting in significant impairment for all patients with prefrontal lobe damage despite normal scores on commonly used memory tests. Ability to maintain consistent and directed attention and to overcome interference is proposed as a role of the frontal lobes in memory function.

Cats were trained to press a lever for food reinforcement in response to stimulation of the ventral lateral (VL) nucleus of the thalamus and the deep cerebellar nuclei. By scaling stimulus intensities relative to the appearance of a minimal amplitude evoked response in pericruciate cortex, it was possible to measure behavioral detection thresholds and correlate behavior with electrocortical activity. With stimulus rates of 25 Hz or greater, VL was the least effective stimulus site for producing detection. At stimulus rates less than 25 Hz, stimulation of the lateral or interpositus nuclei was even less effective in eliciting behavior, but at rates of 25 Hz or more, detection thresholds decreased below those for VL stimulation; cerebellar stimulation produced detection as readily as had stimulation of the ventrobasal complex in other experiments. These findings suggest that the cerebellum may modulate sensory experiences and that some portions of cerebral cortex, the pericruciate and suprasylvian regions, do not appear to be directly involved in mediating sensory detection. It is postulated that the neural detection circuits are more likely to be found in subcortical than in cerebrocortical structures.

The importance of retroactive interference (RI) in memory for spatial locations was studied by using a 12-arm radial maze and a standard RI paradigm. Animals in the RI condition first learned to choose 4 of the 12 arms, followed by training to a second set of 4 arms. In the control condition for interference, rats learned the first set of arms but were not trained to approach the second set. Thereafter, animals in each interference condition were assigned to groups (hippocampal, cortical control, unoperated control), the operations were carried out, and then all animals were tested for retention of the set of arms learned first. Contrary to predictions of the cognitive map theory, O'Keefe & Nadel, 1978), RI was found in control animals. The severe memory deficit found in hippocampals was not influenced by the interference variable. In addition to impaired performance early in relearning, rats with hippocampal lesions continued to make many errors throughout the 10 wk of testing, including choices to unbaited arms and repeated entries into baited arms. However, hippocampals eventually learned not to reenter unbaited arms. These data indicate a deficit in the selection and utilization of sets of responses and are interpreted as implicating the hippocampus in retrieval processes.

The time course of memory decay for infant rats may shed light on the processes responsible for infantile amnesia. A taste aversion conditioning procedure appropriate for both neonatal and adult rats was employed in four experiments to investigate the ontogeny of extended retention. In Experiment 1, rats trained at 1, 10, 20, or 60 days of age were tested for retention of the taste aversion 25 days later. At testing, only those rats conditioned when 20 or 60 days old demonstrated significant taste aversions. Experiments 2 and 3 established that rats 14-15 days old and older were able to retain significant taste aversions following a 25-day retention interval. Younger rats did, however, acquire and retain the aversion for several days and showed a gradual retention loss over progressively longer retention intervals (Experiment 4). These findings suggest that preweanling rats demonstrate initial consolidation, storage, and retrieval of conditioned taste aversions. It is only after this initial period that retention deficits become evident.

Regional brain uptake of 2-deoxy-D-[14C]glucose (2-DG) was measured in mice following training in a discriminated Y-maze avoidance task. In comparison with yoked-control animals that could not escape the footshock, the animals that were trained had decreased uptake of 2-DG in the hippocampus and increased uptake in the striatum. There was no difference in 2-DG uptake between experimental and control animals in the cortex overlying the striatum. Additional control studies showed that 2-DG uptake into the brain was not influenced by ether anesthetization or the route of 2-DG administration (iv or ip). The results of this study indicate that the metabolic activity of regional brain areas following training may reflect the involvement of these structures in learning and memory processes.

Studies by Nelson (1971), Hirsch and McCauley (1977), and McGuire and Hirsch (1977) with the blow fly, Phormia regina, have reported evidence for conditioning. With respect to relative responsiveness to water or saline in the first position of the serial compound stimulus arrangement used, however, the evidence was inconsistent. These experiments show the effect on such responsiveness of the (a) method of mounting and (b) deprivation and satiation procedures. It is also possible that P. regina actively control internal ion concentration by saline intake.