Successive Discrimination Learning Research Articles

Short-term availability of adult-born neurons for memory encoding

Adult olfactory neurogenesis provides waves of new neurons involved in memory encoding. However, how the olfactory bulb deals with neuronal renewal to ensure the persistence of pertinent memories and the flexibility to integrate new events remains unanswered. To address this issue, mice performed two successive olfactory discrimination learning tasks with varying times between tasks. We show that with a short time between tasks, adult-born neurons supporting the first learning task appear to be highly sensitive to interference. Furthermore, targeting these neurons using selective light-induced inhibition altered memory of this first task without affecting that of the second, suggesting that neurons in their critical period of integration may only support one memory trace. A longer period between the two tasks allowed for an increased resilience to interference. Hence, newly formed adult-born neurons regulate the transience or persistence of a memory as a function of information relevance and retrograde interference.

Successive and conditional discrimination learning in pigs

We studied the ability of pigs to discriminate tone cues using successive and conditional discrimination tasks. Pigs (n = 8) were trained in a successive discrimination Go/No-Go task (Experiment 1) to associate a Go-cue with a reward at the end of a runway and a No-Go-cue with the absence of reward. Latency to reach the goal-box was recorded for each cue-type. Learning of a conditional discrimination task was compared between low-birthweight (LBW, n = 5) and normal-birthweight (NBW, n = 6) pigs (Experiment 2) and between conventional farm (n = 7) and Göttingen miniature (n = 8) pigs (Experiment 3). In this active-choice task, one cue signalled a response in a right goal-box was correct and a second cue signalled a response in a left goal-box was correct. Cues were differentially rewarded. The number of sessions to learn the discrimination and number of correct choices per cue-type were recorded. In Experiment 1, four out of eight pigs showed learning on the task, that is, a higher latency to respond to the No-Go-cue, within 25 sessions. In Experiment 2, eight out of 11 pigs learned the discrimination within 46 sessions. LBW learners learned faster than NBW learners. In Experiment 3, all 15 pigs learned the task within 16 sessions. Göttingen miniature pigs learned faster than conventional farm pigs. While some methodological issues may improve the Go/No-Go design, it is suggested that an active-choice task yields clearer and more consistent results than one relying on latency alone.

Lateral hyperstriatal lesions disrupt simultaneous but not successive conditional discrimination learning of pigeons (Columba livia).

Lateral hyperstriatal lesions disrupt simultaneous but not successive conditional discrimination learning of pigeons (Columba livia).

Lateral hyperstriatal lesions disrupt simultaneous but not successive conditional discrimination learning of pigeons (Columba livia).

In 2 experiments we explored the effects of lateral versus medial laminar lesions of the hyperstriatum in pigeons (Columba livia); medical lesions were largely confined to the hyperstriatum accessorium, and lateral lesions to the hyperstriatum dorsale and hyperstriatum ventrale. In Experiment 1, lateral, but not medial, lesions disrupted acquisition of a simultaneous conditional discrimination; both medial and lateral lesions disrupted reversal of the discrimination. The reversal deficits of the medial and lateral groups were quantitatively similar, and both groups showed exaggerated positional responding. In Experiment 2, neither medial nor lateral lesions disrupted acquisition of a successive conditional discrimination. We conclude that lateral hyperstriatal damage does not obtain a general disruption of conditional learning; we speculate that the lateral hyperstriatum may play a critical role in configural learning.

Learning and transfer of identity-difference relationships by infants

Seven-month-old infants were presented three successive two-choice discrimination learning problems in which the stimuli were pairs of toys. On each trial, one pair of two identical toys and one pair of two different toys were presented. The infants were reinforced for fixating the positive pair by hearing a tape-recorded story. The relationship (either identity or difference) among the members of the positive pair was constant for the first two problems, and the percentage of total fixation time directed to the positive pairs increased over trials. Infants for whom the positive intrapair relationship was reversed for Problem 3 experienced an immediate decrease in their level of performance, whereas no such decrement occurred for the others. These results were interpreted as indicating that the infants had learned to attend and respond to intrapair relationships.

CS memory after trace conditioning

Two experiments investigated successive discrimination learning in rats. Of central interest was the influence of the interval between the reinforced stimulus (S+) and the reinforcer (shock) on discriminative performance. Experiment 1 demonstrated that when shock immediately followed the S+ the discrimination was formed rapidly—subjects quickly came to show conditioned responding exclusively during the S+. However, when there was a 30-s trace interval between the S+ and shock the discrimination was only poorly formed, and conditioned responding occurred on both S+ and nonreinforced (S−) trials. In Experiment 2 subjects received concurrent training on a visual and an auditory discrimination. For one discrimination the S+ was immediately followed by shock and for the second discrimination there was a trace interval between the reinforced cue and shock. The former discrimination was acquired more readily than the latter. Implications of these results for contemporary theories of discrimination learning are explored and parallels between these results and the phenomena of contrast and of “marking” are examined.

Effects of two ACTH analogs on successive odor discrimination learning in rats

Olfactory discrimination learning has been shown to provide a powerful tool to investigate the mechanisms involved in the formation, storage and retrieval of information in rodent CNS. In the present study we tested the effects of two ACTH analogs, which were previously reported to influence the processes of learning and memory, on various olfactory learning tasks. The ACTH(4–9) analog HOE 427 produced an apparent increase in storage of olfactory information as shown by the difficulty experienced by the animals to rapidly reverse their behavioral responses to previously learned odors. Similarly, the ACTH (4–9) analog ORG 2766 appears to enhance the storage of olfactory information when administered either before or after the learning trials. These data are consistent with the notion that ACTH and related analogs facilitate performance in a variety of learning tasks. In addition, our results suggest possible mechanisms by which some neuroactive peptides might modulate learning and memory processes in the CNS.

Olfaction and the "data" memory system in rats.

A set of studies was conducted to characterize the memory system involved in successive olfactory discrimination learning in rats. Two odors emanated from different arms of a radial maze; one of the arms contained a water reward. After training on four or five pairs of odors (20 trials per day), rats learned to discriminate the members of a new pair in 5-10 trials. Experiments in which either member of the pair was compared with a novel cue indicated that the rats learn both positive and negative odors, rather than simply ignoring the negative cue. The memories for the odors were apparently persistent, and no evidence for retroactive interference from subsequent training was obtained. Training on 30 pairs did not result in any slowing of subsequent learning, which suggest that the capacity of the memory system for odors is substantial. In a second group of experiments, we tested whether rats distinguish between odors by identifying unshared subcomponents or instead treat odors in a gestalt (i.e., unitary) fashion. Animals trained on three component odors with two in common did not recognize the elements that were unshared when these were presented by themselves. Even when one of the two shared components was combined with the differentiating component into a cue (i.e., two thirds of the original three-component odor), the new cue was treated as a novel odor. However, inclusion of a previously learned simple odor in a complex odor did affect the learning of that odor.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of early postnatal gonadal steroids on the successive conditional discrimination reversal learning in the rat

In the present study the existence of sex differences in the acquisition, retraining and reversal of a successive conditional discrimination learning (Experiment 1) and the role of the early postnatal gonadal steroids on these discrimination tasks (Experiment 2) were investigated. In Experiment 1 two groups of experimentally naive rats (males and females) were exposed to a black-white successive conditional discrimination task in a T-maze. No sex differences were found in the acquisition or retraining. However, in the reversal phase females made fewer errors and reached the discrimination criterion (90% of correct choices) sooner than males. In Experiment 2, the absence of sex differences in the acquisition or retraining phases and the existence of sexual dimorphism in the reversal period were confirmed. In addition, female androgenization and male orchidectomy, on day one after birth, reversed the direction of the sex differences found in the successive conditional discrimination reversal learning.

Time-dependent effects of posttraining intrahippocampal injections of corticosterone on retention of appetitive learning tasks in mice

In previous studies we suggested that corticosterone may modulate hippocampal functioning during memory formation. To test this assumption, we studied the effects of posttrial administration of corticosterone (1 μg) injected bilaterally in the hippocampus. The treatment was applied at different time intervals after the learning session and the retention session took place 24 h later. Using appetitive operant conditioning tasks in a Skinner box, we found that the posttrial treatment 1) did not affect the retention of a continuously reinforced schedule, 2) improved the retention of a successive discrimination learning task, and 3) was still effective when given 3 h after the acquisition of this task, but not after 6 h. Taken together, the results suggest that corticosterone modulates the hippocampal mechanisms involved in behavioral suppression during memory formation.

An experimental study of by-products of successive discrimination learning in the pigeon

Four experimental groups and a control group, of five pigeons each, were trained to successively discriminate a vertical amber line from one oriented either 30 or 60 deg to the right. Depending on group, pecks were intermittently reinforced by either 2.5 or 5.0 sec access to the food hopper. During discrimination, the subjects were provided a second response key, a peck upon which provided a 5-sec time-out (TO) from either the positive or the negative stimulus. Frequency of response on both the TO key and the discrimination key was monitored throughout. After the discrimination training, all subjects were given a postdiscrimination generalization test. Although peak shift was not obtained, the results support the hypothesis that by products of successive discrimination learning are functions of magnitude of S+ reinforcement and degree of S+/S− separation. It was concluded that the results are consistent with a conflict theory of by-products of discrimination learning.

The feature-positive effect and sign-tracking behavior during discrimination learning in the rat

Feature-positive (FP) and feature-negative (FN) successive discrimination learning was investigated in the rat. When a discrete, visual element serving to differentiate the discriminanda belonged to S+ (FP), rats acquired the discrimination more rapidly than when it formed a part of S− (FN). During the course of training, FP rats developed a tendency to direct their responding toward the differentiating feature in S+ while FN rats shifted their responding away from this element in S−. These findings were discussed in terms of the conceptions of stimulus-reinforcer relations and “sign-tracking” behavior.

Effects of the lateral septum and latent inhibition on successive discrimination learning.

Damage to the lateral nucleus of the septum in the rat resulted in atypical learning to a previously meaningless stimulus. Nonreinforced preexposure to a stimulus normally makes more difficult subsequent use of that stimulus for learning. The effect of this preexposure on learning is termed latent inhibition and was demonstrated in sham operated animals. Rats in which the lateral septum was damaged demonstrated a paradoxically smaller learning deficit in the presence of a conditioned stimulus that was previously presented without reinforcement, when compared to the performance of both septal lesioned rats no receiving nonreinforced preexposure and sham operates receiving preexposure. The interaction of nonreinforced preexposure and lateral septal lesions can be explained using a proposed sensitization hypothesis.

Drug effects on successive discrimination learning in young chickens

Chicks were trained to avoid pecking either a red or a blue bead in a one-trial avoidance task by coating one bead with methyl anthranilate. They avoided the aversant bead on retention tests 10 to 180 min or 24 hr after learning, but not the neutral bead. Intracranial administration of ouabain or cycloheximide (CXM) 5 min before learning resulted in decay in retention after 10 and 30 min respectively following learning, discrimination being effective prior to those times. In a second experiment, chicks were trained on three physically distinct beads, two of which were made aversive during the learning period, the training trials separated by an hour. Saline, ouabain, or CXM were administered immediately before training on one or other test bead. Saline-treated chickens retained memory of both aversive beads on retention trials 180 min later. CXM- and ouabain-treated chickens showed loss of memory for the bead associated with the drug but showed retention of the task which was not associated with the drug.

Differential effects of chlordiazepoxide on simultaneous and successive brightness discrimination learning in rats.

Chlordiazepoxide (CDP) at a dose of 20 mg/kg, i.p. was found to exert a marked disruptive effect on black-white successive discrimination learning in rats, while this effect failed to be obtained on black-gray simultaneous discrimination. Since trials to the learning criterion were found almost equal for saline rats on both successive and simultaneous discrimination tasks, the differential inhibitory effects of CDP could not be accounted for in terms of differences in difficulties of the two tasks. It is suggested that present results might be interpreted in terms of the hypotheses (a) that CDP produces a deficit in the integration of relevant stimulus cues when they were presented across trials or (b) that CDP has a disinhibitory effect in that inhibition of dominant response (positional preference) patterns is weakened by the drug, in a manner similar to effects observed in hippocampectomized animals.

Some effects of a discrete trial procedure on differentiation learning by Japanese monkeys

Employing newly developed equipment, which permitted presentation of discriminative stimuli and the response manipulandum separately, the present study reexamined the results ofMcClearn's (1957) study on differentiation learning. When a discrete trial procedure analogous toMcClearn's was used, the subjects (two Japanese monkeys;Macaca fuscata fuscata) persisted in responding on S- trials, replicatingMcClearn's results. However, when a free operant procedure was used, in which the response manipulandum was continually available, the subjects made few responses during S- trials and showed almost complete differentiation. It was concluded that the discrete presentation of the manipulandum itself has some obstructive effects on differentiation, or successive discrimination learning.

An analysis of the relationship between behavioral contrast and responding to S− in successive discrimination learning

Ten pigeons were given extended training with VI 60-sec reinforcement contingent upon keypecking at a 555-nm stimulus in an otherwise darkened chamber with white noise present. After attainment of response rate stability, 30 sessions of successive discrimination training were run, with VI 60-sec reinforcement still signaled by the stimulus conditions indicated above, while an unilluminated response key, a houselight and a 1000-Hz tone signaled extinction. Most subjects showed little tendency to respond to S−, yet all but one subject clearly showed positive behavioral contrast. The magnitude of the contrast effect was not systematically related to either the absolute level or to the pattern of responding during the nonreinforced stimulus.

Form preferences in successive discrimination learning of young chicks.

In four experiments the effects of form and orientation pecking preferences of 1- and 3-day old Vantress X Arbor Acre chicks on successive discrimination learning were determined, using heat reinforcement. Major findings were as follows: (a) The young chick has both circle and verticle orientation pecking preferences that are present during at least the first 3 days after hatching; (b) when either of these preferred cues is the nonreinforced cue, the young chick has difficulty in learning not to respond to it but learns quickly not to respond to an unpreferred cue (e.g., triangle and horizontal oriented dots or bar); and (c) these pecking preferences can be modified by heat reinforcement, and the effects of this conditioning is evidenct in subsequent extinction and retention tests. The main conclusion from these experiments is that form and orientation preferences, like brightness and color preferences, are important developmental constraints on conditioning of the young chick.

Position distinctiveness and successive discrimination learning

This experiment tested the prediction that increased spatial separation of discriminanda would facilitate successive discrimination learning. Eight pigtailed monkeys were trained concurrently on two successive discrimination problems, one with a small and the other with a large separation of cues. Better performance was associated with the larger cue separation.

Transfer of training following discrimination learning with two reinforced responses

Pigeons were given errorless discrimination training between chromatic stimuli with a specific reinforced response associated with each discriminative stimulus. These Ss subsequently acquired a successive go/no-go auditory discrimination (utilizing one response class) faster than Ss given single stimulus training. These results are more compatible with an explanation of transfer of training in successive operant discrimination learning based on general attention than one based on withholding responses.