Journal of comparative and physiological psychology最新文献

Injection of pentobarbital after a rat has consumed saccharin solution usually produces a mild aversion to the saccharin. However, the pentobarbital-produced aversion is eliminated or attenuated by prior pairings of pentobarbital injections with lithium injections. This is called the Avfail (aversion failure) effect. The present experiments dealt with the effect of the temporal relation of the pentobarbital injection to the lithium injection. After forward pairings (pentobarbital before lithium) with delays between the two injections varying among groups from 2.5 min to 320 min, Avfail was invariably obtained. There was little effect of the length of the forward delay, although the Avfail effect appeared to be slightly stronger at 30-40 min or so. When the two drugs were injected simultaneously or in a backward sequence, there was a weakening of the flavor aversion produced by pentobarbital, but this is attributable to habituation to the drugs, not to Avfail.

Potentiation of odor by taste in rats was tested in a variety of situations. In three experiments, almond odor and saccharin taste were presented either as a single conditioned stimulus (CS) or as a compound CS and followed by either toxic lithium chloride or footshock. Extinction tests with the almond and saccharin components were then given. In single CS-toxin experiments, taste was more effective than odor, and after compound conditioning, the taste component potentiated the odor component. Conversely, in single CS-shock experiments, odor was more effective than taste, and after compound conditioning, no potentiation was observed. Rather, interference effects were observed. In Experiments 1 and 2, the addition of taste disrupted odor CS-shock conditioning, and in Experiment 3, odor interfered with taste CS-shock conditioning. Visceral feedback is apparently a necessary unconditioned stimulus for the potentiation of odor by taste. These data support the neural convergence and gating hypothesis of flavor aversion conditioning.

Following lesions in the lateral hypothalamic area, animals failed to drink water for several postoperative days. This dysfunction was attenuated or prevented completely in rats that were subjected preoperatively to a restricted daily watering regimen. Postoperative drinking was vigorous and was not feeding associated. Reactivity to sensory stimuli was enhanced both pre- and postoperatively, particularly to stimuli associated with water. Larger lesions produced longer periods of adipsia which were resistant to the preoperative regimen. Restricted watering may exert its protective action by means of several central and peripheral mechanisms, but a behavioral/physiological conditioning hypothesis is emphasized.

Neocortical mechanisms do not directly contribute to the execution of taste discrimination, sodium appetite, or the acquisition of a taste aversion in the rat. Examination of previous studies led to the question of whether some permanent ingestive control deficit would be revealed if elements of these experimental paradigms were combined. A latent learning paradigm for the taste of salt was applied to decorticate rats. The ability of decorticate rats to associate how they obtained the taste of NaCl when sodium replete was assessed by examining bar presses during extinction when sodium depleted. Intact rats exposed to 4-6 hr of NaCl taste training retained the association after decortication; decorticate rats exposed to the same training acquired the association. What was most striking was that decorticate rats exposed to as little as 2 min of NaCl taste training demonstrated the ability to associate bar pressing with NaCl by their resistance to extinction. The association was specific to NaCl training; training with distilled water or KCl did not yield resistance to extinction during sodium depletion. Subcortical structures are therefore adequate for latent learning involving NaCl taste. Conversely, data of other investigators have revealed that the neocortex is required for the retention of taste aversion learning for the same taste.

Two experiments evaluated the contribution of the gustatory neocortex (GN) to the potentiation of odor by taste during illness-induced aversions in rats. In Experiment 1, rats lacking GN and control rats were given an odor, a taste, or an odor-taste compound cue followed by intragastric gavage of lithium chloride. Prior to conditioning, neophobia for flavored solutions was absent in rats with GN lesions. After pairing with LiCl, GN rats developed normal conditioned odor aversions (Experiment 1B), whereas conditioned taste aversions were attenuated (Experiment 1A) or totally blocked (Experiment 1B). Potentiation of odor by taste after compound conditioning was evident in both control and GN rats, although GN lesions attenuated the effect slightly in Experiment 1B. In Experiment 2, normal rats were given compound conditioning to induce potentiated odor aversions and then given GN lesions prior to tests with the odor and taste components. Taste aversion retention was disrupted totally by GN ablation; potentiated odor aversions were retained by both groups, although the GN group extinguished faster. Gustatory neocortex ablations produced differential effects on odor and taste, disrupting taste memorial and associative processes but leaving odor conditioning and the potentiation of odor by taste processes relatively unaffected. Integrity of the GN apparently is not necessary for the acquisition or retention of potentiation odor aversions.

Infant rat pups (3-4 days of age) that received a single pairing of a novel odor (CS) with illness later responded to the CS with sustained accelerations in heart rate (HR); a different novel odor evoked deceleratory HR responses. Control pups responded to the CS and the second novel odor with cardiac deceleration. In a second experiment, rat pups that received three pairings of a novel odor with a cold (10 degrees C) temperature reinforcement displayed a similar pattern of HR responses, i.e., acceleration to the CS and deceleration to the novel odor. Cardiac response patterns are a useful measure of learning in infant mammals. The directional modulations of HR found in these experiments compare favorably with previous interpretations of "orienting" and "defensive" reactions derived from studies of HR responses in humans.

Spatial localization was studied in the Morris water maze. The task required rats to escape from cool water (made opaque by milk) by finding a submerged, invisible platform located at a fixed place within the room. The start point was varied randomly, and there was no local cues to indicate the position of the platform. After training, the platform was moved. Rats subjected to central cholinergic receptor blockade with atropine sulfate were compared with normal rats and rats receiving peripheral cholinergic blockade with atropine methylnitrate. The controls for the use of search strategies, as compared with spatial mapping, were a group of blind rats and a group of rats for which the platform was moved from trial to trial. Measures of escape latency, swim distance, initial heading error, posttrial rearing on the platform, and search strategy after platform displacement revealed that the control rats and the atropine methylnitrate rats used a spatial mapping strategy to locate the platform. The atropine sulfate treated rats adopted a search strategy like that of the blind rats and the rats for which the platform was randomly moved: Their escape latency and swimming distance decreased across trials, including reversal trials, but their initial heading errors remained unchanged. The results support the idea that central cholinergic systems are important for spatial mapping, which demands the use of distal visual cues, but not for spatial localization, which requires other search strategies and possibly the use of proximal tactile, kinesthetic, and visual cues. Consistent with this idea, certain features of the atropine sulfate treated rats' behavior also suggested a novel explantation for some aspects of atropine stereotypies.

Studies have shown hippocampal rhythmic slow activity (H-RSA) to reflect both learning and memory processes across a variety of species and conditioning procedures. In order to investigate these relations further. H-RSA was manipulated by medial septal (MS) stimulation directly before training rats for light/dark discrimination in a T-maze. Rats that had H-RSA increased learned the discrimination significantly faster than those that had H-RSA blocked and control rats. In addition, increase in H-RSA before training was found to correlate with speed of learning. The evidence of this study is consistent with results of other studies showing septal-hippocampal interaction during learning. The results also support the view that H-RSA may be a neurophysiological representation of learning and memory processes.

Sodium-deficient rats display an appetite for solutions that humans judge as salty tasting whether or not the solutions contain sodium salts. When offered a choice between a pair of sodium salts, sodium-deficient rats generally preferred the more salty tasting. They tended to do the same for a pair of non-sodium salts and for a pair of sodium and non-sodium salts. The results show that human psychophysical judgments of saltiness are a good predictor of the choices that rats will make when sodium deficient--the more salty, the more preferred. The data support the thesis that the appetite of the sodium-deficient rat is not for sodium but for a salty taste.

In male Betta splendens, aggressive behavior is drastically attenuated following telencephalon ablation. Because instrumental training and Pavlovian conditioning experiments with intact fish have suggested that associative factors may play an important role in the performance of agonistic behaviors, the effect of ablation on instrumental learning and Pavlovian conditioning was studied. In Experiment 1, ablation had no effect on the learning of the instrumental tunnel-swimming response reinforced by mirror presentation (i.e., viewing a conspecific), although the mirror presentations in yoked-control groups elicited fewer responses in ablates than in normal and sham-operated control fish. Yoked controls further established that instrumental responding was maintained by the reinforcement contingency and was not merely the result of increased motor activity. Experiment 2 studied Pavlovian conditioning of the components of the agonistic display. Unconditioned fin erection, gill erection, and tail beating (i.e., unconditioned responses, URs) to the mirror US all were less frequent in ablates than in normals or shams. Of these, only gill cover erection showed evidence of true conditioning (i.e., conditioned responses; CRs) in which responses to the conditioned stimulus (CS) are due to the pairings of CS and US (unconditioned stimulus). However, ablates suffered no impairment of conditioned gill erections. Ablates performed fewer fin erections to the CS; however, fin erection responses were not due to CS-US pairings but were attributable to pseudoconditioning. These results are related to hypotheses postulating the involvement of learning mechanisms in ablation-produced deficits and normal aggressive behavior.