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Results for “Avoidance Learning”

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PubMed1991

Cholinergic drugs reverse AF64A-induced impairment of passive avoidance learning in rats.

The cholinergic neurotoxin AF64A was administered to rats in order to produce learning impairment to test the effect of cholinergic drugs. Seven days after receiving an intracerebroventricular injection of AF64A (2.5-7.5 nmol), rats were subjected to one-trial passive avoidance acquisition and tested 24 h later. Learning was significantly impaired at 3.75 nmol AF64A, a dose at which significant reduction in acetylcholine level and choline acetyltransferase and acetylcholinesterase activity in the hippocampus was observed but changes in monoamine levels in the hippocampus, general behavior, or sensory sensitivity were not observed. Arecoline (4 mg/kg, IP) and physostigmine (0.1 mg/kg, IP) significantly decreased the learning impairment produced by AF64A (3.75 nmol) when given before the acquisition of passive avoidance learning but not when given after the acquisition or before the 24 h retention test. These drugs and oxotremorine (0.1 mg/kg, IP) given immediately after the acquisition, however, improved passive avoidance retention when the interval between the acquisition and the test was shortened to 1 h. These results indicate that the impairment of learning in AF64A-treated rats is caused by a memory retention deficit and suggest that such impairment can be effectively ameliorated by cholinergic drugs.

Animals↗

PubMed1998

Signaled two-way avoidance learning using electrical stimulation of the inferior colliculus as negative reinforcement: effects of visual and auditory cues as warning stimuli.

The inferior colliculus is a primary relay for the processing of auditory information in the brainstem. The inferior colliculus is also part of the so-called brain aversion system as animals learn to switch off the electrical stimulation of this structure. The purpose of the present study was to determine whether associative learning occurs between aversion induced by electrical stimulation of the inferior colliculus and visual and auditory warning stimuli. Rats implanted with electrodes into the central nucleus of the inferior colliculus were placed inside an open-field and thresholds for the escape response to electrical stimulation of the inferior colliculus were determined. The rats were then placed inside a shuttle-box and submitted to a two-way avoidance paradigm. Electrical stimulation of the inferior colliculus at the escape threshold (98.12 +/- 6.15 (A, peak-to-peak) was used as negative reinforcement and light or tone as the warning stimulus. Each session consisted of 50 trials and was divided into two segments of 25 trials in order to determine the learning rate of the animals during the sessions. The rats learned to avoid the inferior colliculus stimulation when light was used as the warning stimulus (13.25 +/- 0.60 s and 8.63 +/- 0.93 s for latencies and 12.5 +/- 2.04 and 19.62 +/- 1.65 for frequencies in the first and second halves of the sessions, respectively, P < 0.01 in both cases). No significant changes in latencies (14.75 +/- 1.63 and 12.75 +/- 1.44 s) or frequencies of responses (8.75 +/- 1.20 and 11.25 +/- 1.13) were seen when tone was used as the warning stimulus (P > 0.05 in both cases). Taken together, the present results suggest that rats learn to avoid the inferior colliculus stimulation when light is used as the warning stimulus. However, this learning process does not occur when the neutral stimulus used is an acoustic one. Electrical stimulation of the inferior colliculus may disturb the signal transmission of the stimulus to be conditioned from the inferior colliculus to higher brain structures such as amygdala.

Acoustic Stimulation↗

PubMed1988

Running-wheel avoidance learning in rats (Rattus norvegicus): effects of contingencies and comparisons of different strains.

In Experiment 1, we showed that active- and passive-avoidance responding in a running wheel was learned because of the avoidance contingency. In Experiment 2, strain differences among four commercially bred rats were assessed in an active-avoidance paradigm. Wistar, Donryu, and Fischer rats learned faster than Sprague-Dawleys. In Experiment 3, learning in a multiple active/passive avoidance schedule was examined, and both components of this task were learned. This multiple schedule was used to investigate strain differences in selectively bred rats in Experiments 4 and 5. Tsukuba low-emotional (TLE) rats responded more than Tsukuba high-emotional (THE) rats in both components. However, discrimination of passive components was better in THE than in TLE rats. Syracuse high-avoidance rats were superior in the active component, whereas Syracuse low-avoidance rats showed superior performance in the passive component.

Animals↗

PubMed2002

Carryover effects associated with the single-trial passive avoidance learning task in the young chick.

The single-trial passive avoidance task is a useful procedure for examining learning and memory in the young chick. However, it has recently been suggested that discrepant results reported by different laboratories are due to differences in training procedure. The present study investigated a number of parameters surrounding the passive avoidance task, using day-old White Leghorn, Black Australorp cockerels. The results suggested that presentation of a water-dipped bead immediately after the aversive bead significantly altered retention levels. In addition, when the water-dipped bead was presented after the aversive bead, chicks failed to discriminate between beads for a period of 10 min following exposure to the aversant experience. A novel variant of the passive avoidance procedure, involving pretraining with a water-dipped red bead, training with an aversant-coated red bead, and testing with a dry red bead, was evaluated. A measure of avoidance was calculated using all three trials. It is suggested that the use of a single bead, measured both before and after the training experience and using both aversant- and water-trained controls, results in the most concise characterization of memory-related phenomena in the chick which is not contaminated by a carryover effect from the aversive training experience to the nonaversive bead.

Animals↗

PubMed1985

Genotype-environment interaction in passive avoidance learning of the paradise fish (Macropodus opercularis).

Passive dark avoidance conditioning and effects of the presence and absence of a fish-like dummy on the training process were studied in four inbred strains of paradise fish. Strain differences were found in the shuttle activity during habituation trials, and in the sensitivity to the mild electric shock punishment. The presence or absence of the dummy in the punished dark side of the shuttle box had a genotype-dependent effect on the measures taken during the conditioning process. The statistical analysis of the learning curves revealed differences in the way the strains varied in the different environments, i.e. genotype--environment interaction components of variances were identified. The results are discussed in the light of previous investigations and their implication in further genetic analysis.

Animals↗

PubMed1997

Intrahippocampal infusion of interleukin-6 impairs avoidance learning in rats.

AIM: To study the effect of intrahippocampal infusion of interleukin-6 (IL-6) on active avoidance in rats and the possible involvement of nitric oxide (NO). METHODS: Using a shuttle-box model, the effects of bilaterally intrahippocampal infusion of IL-6 3.2, 16, and 80 ng as well as sodium nitroprusside (SNP) 400 ng on active avoidance were studied on d 8 after administration. The levels of nitrite as an index of NO in the hippocampus were detected using a fluorometric assay 24 h after infusion of IL-6 3.2 or 80 ng. RESULTS: IL-6 16 and 80 ng impaired the acquisition performance of active avoidance by prolonging the latency of avoidance in training, but not the retention performance in testing. IL-680 ng and SNP 400 ng also resulted in a marked impairment in acquisition performances by decreasing the rate of avoidance, but not in retention performances. IL-680 ng markedly elevated the nitrite levels from 10.6 +/- 0.7 in control rats to 13.6 +/- 2.0 (nmol/g wet wt) (P < 0.01). IL-6 3.2 ng had no effect on active avoidance nor on nitrite levels. CONCLUSION: Intrahippocampal infusion of IL-6 impaired learning acquisition of active avoidance in rats.

Animals↗

PubMed1970