Biomedical subjects

Ruth M Colwill

Publications and source records attributed to Ruth M Colwill.

4 recordsLinked to original sources

PubMed2006

Effect of US identity on elimination and recovery of autoshaped responding with explicitly unpaired and degraded contingency extinction procedures.

The depressive effects of noncontingent and explicitly unpaired food unconditioned stimuli (USs) and the recovery from those effects on autoshaped responding were examined in a series of experiments with pigeons. In Experiments 1 and 2, responding to a keylight conditioned stimulus (CS) previously paired with food was depressed equally by explicitly unpaired presentations of either that same food or a different food. Furthermore, responding recovered equally following removal of the explicitly unpaired foods. In contrast, Experiments 3 and 4 showed that noncontingent presentations of a food US depressed responding more to a keylight CS paired with that same food than to a keylight CS paired with a different food. Moreover, removal of the noncontingent foods led to complete recovery but more rapid extinction of responding to the same keylight relative to the different keylight. The implications of these results for understanding the mechanisms underlying depression and recovery of responding following degraded contingency and explicitly unpaired extinction procedures are discussed.

Animals↗

PubMed2006

Passage of time leaves response-outcome associations intact.

The effect of the passage of time on the association between an instrumental response and its outcome was examined in three experiments with rats using outcome devaluation. In Experiments 1 and 2, rats were initially trained to make one pair of instrumental responses for different outcomes (e.g., lever press-->pellets and chain pull-->sucrose). Then, after a delay of several weeks, a second pair of responses for those different outcomes (e.g., nose poke-->pellets and handle pull-->sucrose) was trained in Experiment 1 but not in Experiment 2. One of the outcomes was then devalued and the responses were tested in extinction. There was no evidence that the passage of time eliminated the sensitivity of a response to a change in the value of its outcome. Experiment 3 used the same design as Experiment 1 to examine the effect of the passage of time on extinguished instrumental responses. First, one pair of responses was trained with different outcomes and then extinguished prior to the training and subsequent extinction of a second pair of responses. After retraining both pairs of responses with a polycose outcome, one of the original outcomes was devalued. Each pair of responses was then tested in extinction. The results of the extinction tests revealed no evidence that the passage of time removed the sensitivity of an extinguished response to devaluation of its original outcome. These findings are consistent with other reports that the response-outcome association survives various response elimination techniques.

Animals↗

PubMed2005

Visual discrimination learning in zebrafish (Danio rerio).

Three experiments demonstrated visual discrimination learning in zebrafish (Danio rerio). In each experiment, zebrafish were given a choice between two visually distinct arms of a T-maze. Choice of one stimulus was always followed by a food reward, but choice of the other stimulus was not rewarded. Different colored sleeves fitted around the arms of the T-maze were used in Experiments 1 (green and purple) and 2 (red and blue). The stimuli used in Experiment 3 were white sleeves lined with horizontal or vertical black stripes. In all three experiments, zebrafish acquired a significant preference for the stimulus that led to a food reward. Experiments 1 and 2 also showed that zebrafish could learn a reversal of the discrimination. Finally, the effect of discontinuing food rewards was examined after reversal training in Experiment 2 and after initial discrimination training in Experiments 1 and 3. Non-reinforcement led to a decrease in correct responding in Experiments 2 and 3 independent of stimulus identity, but to an asymmetrical pattern of responding in Experiment 1. The median latency to make a choice response decreased over the course of acquisition in all three experiments; during extinction, median response times did not change at all in Experiment 1 and increased only very slightly in Experiment 2, but showed a substantial increase in Experiment 3. The implications of these results for the zebrafish as a model system for genetic studies of learning and memory are discussed.

Animals↗

PubMed2005

Acquisition and extinction of facilitation in the C57BL/6J mouse.

Acquisition, extinction, and transfer of facilitation were explored in a series of experiments with C57BL/6J mice. With a procedure in which an auditory target was followed by food only in the presence of a visual facilitator, Experiments 1-4 showed that the facilitator promoted magazine entries to the auditory target. This enhancement effect was eliminated by training the facilitator as a conditioned inhibitor (Experiments 1 and 3B). Enhancement was also reduced by nonreinforced presentations of the facilitator in a discrimination procedure (Experiment 1) and by simple nonreinforcement of the facilitator (Experiments 2, 3A, and 4). In contrast to the results obtained with a facilitator, simple nonreinforcement of an inhibitor, a visual cue that had signaled when an auditory target would not be reinforced, did not reduce its ability to modulate responding to that target (Experiment 4). However, both the facilitator and the inhibitor were found to transfer their modulatory effects to other targets (Experiment 4). Finally, mice demonstrated no evidence of differential responding on a biconditional discrimination procedure in which one auditory target (A1) was reinforced in the presence of one visual stimulus (L1) but not in the presence of another (L2), and a different auditory target (A2) was reinforced in L2 but not in L1 (Experiment 5). The implications of these results for analysis of the function of a facilitator are discussed.

Animals↗