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At least 19 recordsLinked to original sources
PubMed1998

A new look at an old task: advantages and uses of sickness-conditioned learning in day-old chicks.

In sickness-conditioned learning, animals become ill after sampling a new substance and develop an aversion that is expressed as avoidance of that substance in subsequent presentations. We examined the parameters of a one-trial, nongustatory, sickness-conditioned learning task in day-old chicks. Chicks pecked a bead and were made ill by i.p. injection of lithium chloride (LiCl). Both 0.5 and 1.0 M LiCl (0.1 ml) produced reliable avoidance at test. Chicks injected with LiCl between 15 and 45 min after training avoided the bead at test, whereas those injected within 5 or 10 min or more than 45 min after training did not. Avoidance was present until 24 h posttraining and absent after 48 h. Therefore, robust learning of the sickness-conditioned learning task occurs in one trial without the need for gustatory cues, and memory for the task lasts at least 24 h. Uses of this task to study memory formation in the day-old chick are discussed.

Animals↗
PubMed2004

Associative change in the representations acquired during conditional discriminations: further analysis of the nature of conditional learning.

Three experiments with rats investigated how the associative strengths of the representations that underlie conditional learning change when they are conditioned in compound. The results of each experiment suggest that the representation whose associative strength is most discrepant from the asymptote supported by the outcome of the trial undergoes the greatest change in associative strength. These results parallel those from simple Pavlovian conditioning (e.g., R. A. Rescorla, 2000). are inconsistent with unique-cue and configural accounts of conditional learning, and support a connectionist analysis of learning in which a "winner-takes-all" rule applies to the hidden units that can be activated and acquire associative strength at a given point in time.

Analysis of Variance↗
PubMed1999

Lesions of the intermediate medial hyperstriatum ventrale impair sickness-conditioned learning in day-old chicks.

Lesion studies show that the intermediate medial hyperstriatum ventrale (IMHV), a forebrain visual association area in chicks, is involved in learning and memory for one-trial passive avoidance and imprinting. We examined the effects of IMHV lesions in a one-trial, nongustatory, sickness-conditioned learning task. This task is similar to passive avoidance and imprinting because all three tasks require the chick to remember visual cues in order to respond correctly. However, sickness-conditioned learning differs from imprinting and passive avoidance because it uses sickness as the aversive stimulus and there is a longer conditioned stimulus-unconditioned stimulus interval (30-min delay compared to seconds). Bilateral IMHV lesions given 24 h before training impaired the ability of the chicks to avoid a bead associated with sickness produced by lithium chloride injection, as did pretraining unilateral left or right IMHV lesions. Post-training IMHV lesions given 1 h after training did not impair avoidance of the test bead in the sickness-conditioned learning task. However, lesioned chicks showed generalized avoidance of all test beads. The pretraining lesion results are similar to those found in imprinting and passive avoidance learning; however, the effects of unilateral IMHV lesions differed. Post-training lesion effects are similar to those found in passive avoidance learning. We propose that both left and right IMHV are necessary for sickness-conditioned learning and that post-training IMHV lesions impair the ability of the chick to learn or remember the association between the color of the bead and the aversive consequences of LiCl injection.

Age Factors↗
PubMed1985

Cross-species embryonic septal transplants: restoration of conditioned learning behavior.

Embryonic septal and hippocampal tissue from mice was transplanted between species into the brains of adult rat hosts as cell suspensions. Deficits in the ability to learn a conditioned, hippocampally mediated, forced alternation behavior, which were caused by a bilateral transection of the fornix-fimbria pathway, were ameliorated in the septal transplant recipients. The successful performance of the task was correlated to the density index of acetylcholinesterase in the hippocampal section.

Acetylcholinesterase↗
PubMed2003

Transfer effects and conditional learning in rats with selective lesions of medial septal/diagonal band cholinergic neurons.

The authors examined visual-spatial conditional learning with automated touchscreen tasks in male Long-Evans rats with selective lesions of medial septal/vertical limb of diagonal band (MS/VDB) cholinergic neurons produced by 192 IgG-saporin. Performance on a conditional task, in which 1 of 2 centrally displayed stimuli directed the rat to respond to an illuminated panel on the left or right, depended on training history: Control rats with experience on other visual tasks performed better than MS/VDB-lesioned rats with similar training histories, whereas this effect was reversed in naive rats. This difference appears to reflect transfer effects present in the control rats that are absent in the MS/VDB-lesioned rats. These findings may suggest that MS/VDB cholinergic neurons play a particular role in the transfer of behavioral experience and flexibility of application of behavioral rules in memory, rather than a role in conditional learning per se.

Animals↗
PubMed1991

On the hippocampus and learned conditional responding: effects of aspiration versus ibotenate lesions.

To study the possible involvement of the hippocampus in learned conditional responding, rats with aspiration lesions of the hippocampus and others that had the hippocampus removed with ibotenic acid were trained on concurrent Pavlovian conditional and nonconditional discriminations. In agreement with the results reported by Ross et al. (1984), animals that had the hippocampus removed with aspiration were unable to learn the conditional discrimination, but learned the simple nonconditional discrimination without difficulty. In contrast, rats that had the hippocampus removed with ibotenic acid did not differ from controls in learning either discrimination. Furthermore, transfer test results were consistent with the hypothesis that ibotenate-lesioned rats performed conditional operations to solve the conditional discrimination problem. Histological analysis indicated that the ibotenate lesions resulted in the removal of the hippocampus and dentate gyrus with minimal involvement of other structures. In aspiration hippocampal animals there was less overall damage to the hippocampus, but there was also extensive damage to the axons passing in alveus and fimbria, together with bilateral loss of cells in the subicular complex, the cingulate gyrus, and the cortex. Since rats with ibotenate lesions had more complete removal of the hippocampus, yet learned both discriminations, the impaired conditional responding found in aspiration hippocampals must be due to extrahippocampal damage.

Animals↗
PubMed1990

Interhemispheric transfer of visuomotor conditional learning via the anterior corpus callosum of monkeys.

Two experiments examined interhemispheric transfer of learning across the anterior corpus callosum in monkeys (Macaca fascicularis). The animals learned a series of visuomotor conditional discrimination problems for food reward. Within each problem the animals were first trained using one hand to make the motor responses, and were then required to use the opposite hand in order to test for intermanual transfer of the initial learning. In Exp. 1, a group of animals with surgical section of the entire corpus callosum and anterior commissure showed a complete absence of intermanual transfer of learning. A second group, in which only the anterior commissure and the posterior part of the corpus callosum were sectioned, leaving the anterior corpus callosum intact, showed good intermanual transfer. Thus, intermanual transfer in the second group represented interhemispheric information transfer via the anterior portions of the corpus callosum. However, in Expt. 2, normal intermanual transfer was seen in a group of animals in which the anterior corpus callosum alone had been sectioned. We conclude that the anterior corpus callosum can mediate interhemispheric transfer of visuomotor conditional learning, but is not the only available route for such transfer in the present task.

Animals↗
PubMed1974

The biphasic effect of small doses of tranylcypromine on the spontaneous motor activity and learned conditioned behaviour in rats.

Tranylcypromine (TCP), a monoamine-oxidaone inhibitor with amphetamine-like property, has at first a depressant effect and 5 h later a stimulating effect on sponataneous motor activity and learned conditioned behaviour. This latter effect can be demonstrated by means of a modified conditioned avoidance response schedule and a specific time-schedule interval. While the depressant effect of tranylcypromine may be due to the initial increase of brain serotonin caused by this drug, its delayed stimulating effect is, very likely, related to norepinephrine brain increase occurring a few hours after TCP administration.

Animals↗
PubMed1995

Role of stimulus ambiguity in conditional learning.

Three experiments using rats and the conditioned emotional response procedure examined the notion that when a conditioned stimulus (CS) is paired with a reinforcer (US), that CS must be ambiguous if the CS-US association is to become the target of conditional control. CS ambiguity was manipulated by varying whether the CS had been preexposed prior to conditioning. In Experiments 1 and 2, it was demonstrated that a cue that accompanied pairings of a CS and shock acquired conditional control over the CS-shock association when that CS had been preexposed, but not when it was novel. The measure of conditional control in Experiments 1 and 2 was the ability of the (conditional) cue to enhance responding to the target CS. Experiment 3 used a blocking procedure to show that this enhancement reflected an amplification of the target CS's effective associative strength. These findings extend existing knowledge of the conditions required for conditional cue formation.

Animals↗
PubMed1988

Inferotemporal-frontal disconnection and fornix transection in visuomotor conditional learning by monkeys.

The first 2 experiments examined the ability of monkeys (Macaca fascicularis) to learn a series of visuomotor conditional discrimination problems for food reward. In each discrimination problem there were 2 visual stimuli, which were different from those in any previous discrimination problem. Each trial within a problem presented either one visual stimulus or the other, and the stimulus indicated which of 2 motor responses, tap or hold, was correct; the motor responses were defined in such a way as to be mutually exclusive. Successive problems were each trained to a criterion of correct performance. In the first experiment, it was found that fornix transection did not impair monkey's learning rate in this task. This result contrasts with previous results showing an impairment of learning rate following fornix transection in visuo-motor conditional discriminations in which the 2 motor responses were differentiated from each other by their spatial position or direction. The present result shows that the earlier demonstrated impairments are specific to spatial responses. In the second experiment, learning rate in the present task was found to be impaired by the combination of a unilateral inferotemporal ablation, contralateral to the hand used in the task by the animal, with a transection of the anterior corpus callosum. This result suggests that cortico-cortical interaction between the inferotemporal area and the frontal lobe contralateral to the hand in use is necessary for efficient learning in this task. The third experiment examined simultaneous 2-choice visual discrimination learning in the animals which had participated in experiment 2. In contrast to the results of Expt. 2, learning rate in this task was unimpaired. Experiment 3 shows that the impairment observed in Expt. 2 is not a general impairment of visual learning.

Animals↗
PubMed2000

Selective associations in day-old chicks: when do CS traces become available for sickness-conditioned learning?

Barber and colleagues (T. A. Barber, A. M. Klunk, P. D. Howorth, M. F. Pearlman, & K. E. Patrick, 1998; T. A. Barber, M. F. Pearlman & K. E. Patrick, 1995) showed that male domestic chicks would not peck a bead presented 15 or more min before a lithium chloride (LiCl) injection, but would peck a bead presented less than 15 min before a LiCl injection. In 4 experiments, the authors (a) confirmed their initial observation, (b) showed that the effect is not due to retrograde amnesia produced by LiCl, and (c) confirmed that memories less than 15 min old are available for other types of learning.

Age Factors↗
PubMedDate not supplied

Conditional learning in aged rats: evidence of hippocampal and prefrontal cortex impairment.

Groups of normal old rats and young adult rats were administered a test of conditional discrimination learning in which different visual stimuli were associated with responses to different levers. Initially, rats were tested in a zero-delay condition in which they selected their responses in the presence of the conditional stimuli. They were later tested at 5- and 15-s delays between stimulus presentation and the appearance of the levers. Old rats were impaired in learning the basic conditional discrimination, a test thought to be sensitive to frontal lobe dysfunction. Age differences increased with the length of the interval, revealing a time-dependent memory loss that was attributed to impaired hippocampal function.

Aging↗
PubMed1984

Hippocampectomy disrupts acquisition and retention of learned conditional responding.

The effects of bilateral hippocampal and neocortical lesions were examined on acquisition and retention of classically conditioned responses based on (a) simple associations, (b) a nonconditional discrimination, and (c) a conditional discrimination in the same subjects. Results showed that combined hippocampal and neocortical damage permanently prevented (within the limits tested) both acquisition and retention of learned behavior based on the conditional discrimination but had no effect on behaviors based on the nonconditional discrimination or simple associations. Neocortical lesions alone had no effect on either conditional or nonconditional discriminative responding, but they did temporarily disrupt acquisition and retention of behavior dependent on CS-CS (two conditioned stimuli) associations. Neither lesion affected learned behaviors mediated by CS-US (conditioned stimulus and unconditioned stimulus) associations. Thus, results showed that hippocampal damage selectively disrupted learned conditional behaviors and also revealed that central nervous system control of conditional discrimination performance, within-compound associations, and CS-US associations is mediated by different neural mechanisms.

Animals↗
PubMed2001

Perirhinal cortex and place-object conditional learning in the rat.

The present study examined whether excitotoxic lesions of the perirhinal cortex can affect acquisition of a place-object conditional task in which object and spatial information must be integrated. Testing was carried out in a double Y-maze apparatus, in which rats learned a conditional rule of the type, "In Place X, choose Object A, not Object B (A+ vs. B-); in Place Y, choose Object B, not Object A (A- vs. B+)." Perirhinal cortex lesions significantly impaired acquisition of this task while sparing performance of an allocentric spatial memory task performed in a radial arm maze. Perirhinal cortex lesions also had no apparent effect on a 1-pair object discrimination task performed in the double Y maze or on retention and acquisition of 4-pair concurrent discrimination problems performed in a computer-automated touch screen testing apparatus. The results suggest that, although the perirhinal cortex and hippocampus can be functionally dissociated, their normal mode of operation includes the integration of object and spatial information.

Animals↗