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T R Schachtman

Publications and source records attributed to T R Schachtman.

12 recordsLinked to original sources
PubMed1992

Effects of acute swim stress on LiCl-induced conditioned taste aversions.

The present study examined the effects of a 5-min period of swim stress experienced between a flavor (saccharin) and illness (LiCl) on conditioned taste aversion learning. Experiment 1 obtained a stress-induced attenuation of learning. Experiment 2 replicated the findings of Experiment 1, and also obtained a similar attenuation when stress was administered 30 min prior to the saccharin presentation. Experiment 3 examined the effects of swim stress either 15 min or 90 min after the LiCl had been administered. It was found that swim stress 15 min after LiCl significantly attenuated CTA, but swim stress 90 min after LiCl did not. These results are discussed with regard to current views of the relationship between external events and conditioned taste aversions.

Animals↗
PubMed1992

Behavioral and physiologic effects of inapparent wound infection in rats.

There is a common notion that rats are resistant to postoperative wound infection because many recover from surgery performed under nonsterile conditions. As a result, nonaseptic surgical techniques are used commonly in rat surgery. Our aim was to determine if these techniques cause wound infection and, if so, whether or not the infection, inapparent to casual observation, creates measurable changes in rat physiology and behavior. Rats subjected to craniotomies or laparotomies and inoculated with 10(8) Staphylococcus aureus or Pseudomonas aeruginosa or sterile saline were tested for open-field activity, freezing behavior, home-cage behavior score, and wheel-running activity. Physiologic indices included lactate dehydrogenase, blood glucose, plasma fibrinogen, complete blood counts, wound bacterial counts and histology scores, body temperature, and body weight. Although no clinical signs were detected by postoperative observation, rats inoculated with bacteria were significantly less active in the open field and the duration of freezing behavior was shorter. Plasma fibrinogen, serum glucose, total white blood cell counts, and wound histology scores were significantly altered in the bacteria-inoculated rats. These findings underscore the need for sterile techniques in rat surgery to avoid confounding experimental data.

Animals↗
PubMed1990

The effects of stress on the development of immunological memory following low-dose antigen priming in mice.

Observable stress effects on immune responses may be a function of the quantitative and qualitative characteristics of the stressor, and the outcome measurement of immunity. Further, the effects of stress on humoral immunity, in particular, may be sensitive to the concentrations of antigen used to elicit a response. We have studied the effects of footshock stress during the time of priming with low concentrations of antigen on the secondary response to another low dose of antigen. The secondary humoral immune response of C3H/HeJ mice to the protein antigen keyhole limpet hemocyanin was examined following footshock, exposure to the apparatus without shock, or exposure to the home cage. Footshock reproducibly depressed the IgG anti-KLH response, and the effect on the IgM response was sporadic. Initially, footshock was administered for 7 days before and 7 days after priming with low amounts of antigen. Subsequent studies demonstrated that a single footshock session delivered 24 h after priming could suppress the IgG anti-KLH response.

Animals↗
PubMed1989

Voluntary consumption of cyclophosphamide by Mrl mice.

Fluid-deprived, lupus-prone Mrl-lpr/lpr and congenic Mrl +/+ mice were provided with a single drinking bottle containing varying concentrations of cyclophosphamide (CY) dissolved in chocolate milk. Eighteen- and 20-week-old Mrl-lpr/lpr males with manifest symptoms of autoimmune disease voluntarily consumed more of the CY solution than Mrl +/+ mice of the same age after 1 week of 1 hr/day exposures. The volume of CY-laced chocolate milk consumed was sufficient to attenuate lymphadenopathy and the elevated anti-DNA antibody titers in these animals. When testing began before the development of manifest symptoms of autoimmune disease, there were no differences between the two substrains. These results are consistent with the hypothesis that behavioral processes can act to correct homeostatic imbalances within the immune system.

Animals↗
PubMed1988

Testing response generation rules.

Robbins (1988) reported data that he viewed as inconsistent with Miller and Schachtman's (1985a) comparator hypothesis of conditioned response generation. Here we explain why we do not find his experiments a compelling test of the comparator hypothesis. We also briefly review other studies that tested the same predictions of the comparator hypothesis that Robbins examined. We conclude that there is considerable evidence that following excitatory or inhibitory conditioning with a target conditioned stimulus (CS) and unconditioned stimulus (US), extinction of other cues that were present during CS training ordinarily increases excitatory responding and decreases inhibitory responding to the CS. However, consistent with Robbins's conclusion, there is scant evidence that after CS-US training, enhancing the associative value of other cues that were present during CS training influences excitatory or inhibitory responding to the CS. The implications of these conclusions for the comparator hypothesis as an explanation of differences in acquired behavior and as a heuristic tool are considered.

Animals↗
PubMed1987

Mechanisms underlying retarded emergence of conditioned responding following inhibitory training: evidence for the comparator hypothesis.

The comparator hypothesis posits that conditioned responding is determined by a comparison at the time of testing between the associative strengths of the conditioned stimulus (CS) and stimuli proximal to the CS at the time of conditioning. The hypothesis treats all associations as being excitatory and treats conditioned inhibition as the behavioral consequence of a CS that is less excitatory than its comparator stimuli. Conditioned lick suppression by rats was used to differentiate four possible sources of retarded responding to an inhibitory CS. These include habituation to the unconditioned stimulus (US), latent inhibition to the CS, blocking of the CS-US association by the conditioning context, and enhanced excitatory associations to the comparator stimuli. Prior research has demonstrated the first three phenomena. Therefore, we employed parameters expected to highlight the fourth one--the comparator process. In Experiment 1, our negative contingency training was shown to produce a conditioned inhibitor that passed inhibitory summation and retardation tests. In Experiment 2 we found transfer of retardation from an inhibitory CS to a novel stimulus when the location where retardation-test training occurred was excitatory, which is indicative of contextual blocking and/or comparator effects. In Experiment 3, extinction of the conditioning context was found to attenuate retardation regardless of whether extinction occurred before or after the CS-US pairings of the retardation test. This indicates that much of the present retardation was due to the comparator process rather than to contextual blocking. Experiment 4 demonstrated that habituation to the US did not contribute to retardation in the present case. Collectively, these studies suggest that retardation following inhibitory training can be explained without recourse to any of the traditional mechanisms of conditioned inhibition.

Animals↗
PubMed1987

The comparator hypothesis of conditioned response generation: manifest conditioned excitation and inhibition as a function of relative excitatory strengths of CS and conditioning context at the time of testing.

In the present research water-deprived rats were used in a conditioned lick suppression paradigm to test and further develop Rescorla's (1968) contingency theory, which posits that excitatory associations are formed when a conditioned stimulus (CS) signals an increase in unconditioned stimulus (US) likelihood and that inhibitory associations develop when the CS signals a decrease in US likelihood. In Experiment 1 we found that responding to a CS varied inversely with the associative status of the context in which the CS was trained and that this response was unaltered when testing occurred in a distinctively dissimilar context with a different conditioning history, provided associative summation with the test context was minimized. These results suggest that manifest excitatory and inhibitory conditioned responding is modulated by the associative value of the training context rather than that of the test context. In Experiment 2 it was demonstrated that postconditioning decreases in the associative value of the CS training context reduced the effective inhibitory value of the CS even when testing occurred outside of the training context. Moreover, this contextual deflation effect was specific to the CS training context as opposed to any other excitatory context. Collectively, these studies support the comparator hypothesis, which states that conditioned responding is determined by a comparison of the associative strengths of the CS and its training context that occurs at the time of testing rather than at the time of conditioning. This implies that all associations are excitatory and that responding indicative of conditioned inhibition reflects a CS-US association that is below (or near) the associative strength of its comparator stimulus. It is suggested that response rules which go beyond a monotonic relation between associative value and response strength can partially relieve learning theories of their explanatory burdens, thereby allowing for simpler models of acquisition.

Animals↗
PubMed1986

Retrieval variability: sources and consequences.

A memory model that differentiates between active traces (ongoing electrochemical neural transmission) and passive traces (chemical/structural modification of neurons) is briefly outlined. Evidence suggests that new information is initially encoded as a passive representation within a fraction of a second, leaving little opportunity for retroactive interference with storage processes. Instead, it appears that retroactive interference results from disruption of post-acquisition processing which is necessary for subsequent retrieval. Using this hybrid cognitive-physiological framework, we examine possible sources of associative performance deficits. A distinction is made between similarity interference (arising from the content similarity of the target and interfering traces) and processing interference (arising from the competition between the two traces for use of a limited capacity processor). Both types of interference can act proactively or retroactively, and the similarity-processing and proactive-retroactive dimensions are viewed as orthogonal to the question of whether information is permanently lost or merely subject to a reversible retrieval failure. When reminder techniques (pretest cuing) are used, numerous instances of memory failure commonly identified as "acquisition failures" are found to be reversible without the occurrence of relevant new learning. This literature review constitutes the greater part of the paper. It is concluded that many memory failures are due at least in part to retrieval failure. Consideration of potential retrieval processes in light of the studies that are reviewed argues for the expansion of the initial active-passive trace distinction to three types of traces. In addition to active traces, these include two distinct types of passive traces, i.e., a small content-addressable reference catalog with innately defined dimensions that is used to locate more detailed passive traces, and a large capacity store of detailed passive traces that is location-addressable. The latter type of passive trace presumably is laid down almost instantaneously as events occur, i.e., in real time, whereas the reference catalog type of passive trace, which is used to address the detailed traces, is established somewhat after the sequence of events is complete. Hence, the reference catalog trace is more vulnerable and results in retrieval failure when it is disrupted.(ABSTRACT TRUNCATED AT 400 WORDS)

Amnesia↗
PubMed1985

A retrograde gradient for disruption of a conditioned aversion to drinking cold water by ECS administered during the CS-US interval.

Rats were used to examine the effects, upon a conditioned aversion to cold drinking water, of electroconvulsive shock (ECS) delivered during the delay between cue and unconditioned stimulus. An injection of LiCl (US) 30 min after ingestion of novel cold water (CS) produced a reliable aversion to the cold water. ECS given immediately following the ingestion of cold water substantially attenuated this aversion. An orderly decrease in the attenuation of the aversion was observed when ECS was delayed 5, 10 or 20 min after offset of the cold water cue. The results indicate that ingestive cue aversions can be formed without electrochemical neural-transmission-based representation of the cue being maintained during the CS-US interval. The differential effectiveness of ECS suggests that this agent retroactively interferes with processing of the ingestive cue.

Amnesia↗
PubMed1985

Blocking but not conditioned inhibition results when an added stimulus is reinforced in compound with multiple pretrained stimuli.

Conditioned barpress suppression by rats was used to explore the associative status of an initially neutral stimulus that was reinforced in simultaneous compound with two independently pretrained conditioned excitors. In contrast to the Rescorla-Wagner model, which predicts that the target stimulus (X) will be inhibitory following such A+/B+/ABX+ training, the present study found no evidence that X acquired inhibitory associative strength. Rather, the pretrained stimuli merely served to block conditioned excitatory responding to the target stimulus.

Animals↗
PubMed1983

Attenuation of experimental retrograde amnesia through pretraining administration of a dissimilar amnestic agent.

Experiment 1 found that pretraining administration of electroconvulsive shock (ECS) attenuated ECS-induced amnesia of one-trial passive avoidance training in rats. Similarly, pretraining injections of cycloheximide (CXM) attenuated the amnestic effects of CXM at training. Experiment 2 demonstrated the ability of pretraining ECS to attenuate CXM-induced amnesia and pretraining CXM to attenuate ECS-induced amnesia. These studies join others in observing comparable behavioral effects of ECS-like amnestic agents and antimetabolite-like amnestic agents despite their different means of primary action. Collectively, these studies support the view that the two families of amnestic agents produce amnesia through a common mechanism.

Animals↗