Biomedical subjects

Daniel S Wheeler

Publications and source records attributed to Daniel S Wheeler.

8 recordsLinked to original sources

PubMed2006

Recency-to-primacy shift in cue competition.

Three experiments were conducted using a lick-suppression preparation with rats to determine whether temporal and physical context shifts modulate the effectiveness of 2 sequentially trained blocking stimuli. Experiment 1 ascertained that it is possible to obtain blocking by conditioning rats to react to a target cue using 2 different blocking cues, each trained with a single-phase blocking paradigm. Experiment 2 showed that the more recently trained blocking stimulus was more effective (i.e., showed a recency effect) when testing was conducted immediately after training, but a long retention interval attenuated blocking by the most recently trained blocking stimulus and increased blocking by the initially trained blocking stimulus (i.e., a recency-to-primacy shift). This shift from recency to primacy affected in Experiment 2 by varying the retention interval was replicated in Experiment 3 by changing the physical context between training and testing. Taken together, the results indicate that the effectiveness of sequentially trained competing stimuli follows the same recency-to-primacy shift rule that is seen in traditional interference phenomena.

Animals↗

PubMed2006

Generalization decrement in human contingency learning.

An association between a cue and an outcome will generalize to a similar novel cue to some extent, but not completely. Learning theorists refer to the discrepancy between responding elicited by the original cue and the novel cue as a generalization decrement. Two experiments used a contingency learning task with human participants to compare the size of a generalization decrement between configurations of cues that were altered by adding or subtracting compositional elements. The results suggest that adding elements to a configuration can produce a generalization decrement, but removing elements produces a more robust generalization decrement. Furthermore, the generalization decrement caused by adding elements was not likely to be caused by competing orienting responses. The results are used to contrast Pearce's (1987, 1994) and Wagner's (2003) models of stimulus generalization.

Cues↗

PubMed2005

An extended comparator hypothesis account of superconditioning.

Three conditioned taste aversion experiments with rats investigated superconditioning. In each experiment, alternate exposures of 2 flavor compounds with a common element (i.e., AB/AS) were administered to establish an inhibitory relationship between the 2 unique elements, B and S, and prior to testing, S was paired with lithium chloride (LiCl). In Experiment 1, pairings of a neutral cue (X) with S in compound with B after the AB/AS exposures resulted in superconditioning between X and S. Extinction of the common element (A) just before the S-LiCl pairing attenuated both the inhibitory relationship between B and S (Experiment 2) and superconditioning between X and S (Experiment 3). These observations suggest that superconditioning consists of enhanced performance rather than enhanced associative acquisition.

Adjuvants, Immunologic↗

PubMed2005

Recovery from blocking between outcomes.

Contemporary associative learning research largely focuses on cue competition phenomena that occur when 2 cues are paired with a common outcome. Little research has been conducted to investigate similar phenomena occurring when a single cue is trained with 2 outcomes. Three conditioned lick suppression experiments with rats assessed whether treatments known to alleviate blocking between cues would also attenuate blocking between outcomes. In Experiment 1, conditioned responding recovered from blocking between outcomes when a long retention interval was interposed between training and testing. Experiment 2 obtained recovery from blocking between outcomes when the blocking outcome was extinguished after the blocking treatment. In Experiment 3, a recovery from blocking between outcomes occurred when a reminder stimulus was presented in a novel context prior to testing. Collectively, these studies demonstrate that blocking of outcomes, like blocking of cues, appears to be caused by a deficit in the expression of an acquired association.

Analysis of Variance↗

PubMed2004

Outcome pre- and postexposure effects: retention interval interacts with primacy and recency.

Effects of outcome-alone pretraining and posttraining exposure were investigated in conditioned suppression experiments conducted within a sensory preconditioning preparation with rats. Experiment 1 found that interference by outcome postexposure was stronger than that by outcome preexposure, suggesting a recency effect. Experiment 2 found that after a long retention interval, outcome preexposure produced more interference than outcome postexposure, suggesting a shift from recency to primacy with increasing retention interval. Experiment 3 showed that presentation of a priming stimulus that had been embedded within the earlier phase of treatment also caused a shift from recency to primacy. These results suggest that, at least in a sensory preconditioning paradigm, retrievability of outcome-alone exposure memory is an important determinant of any outcome-alone exposure effect.

Animals↗

PubMed2004

Interaction of retention interval with CS-preexposure and extinction treatments: symmetry with respect to primacy.

Imposition of a retention interval between cue-outcome pairings and testing can alleviate the retardation of conditioned responding induced by pretraining exposure to the cue (i.e., the CS-preexposure effect). However, recent studies have reported an enhanced effect of CS-preexposure treatment with longer retention intervals (De la Casa & Lubow, 2000, 2002; Lubow & De la Casa, 2002). In a series of conditioned barpress suppression studies with rats, we examined the effects of imposing a retention interval just prior to testing following either CS-preexposure (cue alone before cue-outcome pairings) or extinction (cue alone after cue-outcome pairings) treatments. Experiment 1 replicated in a different preparation recent reports of CS-preexposure treatment effects increasing with longer retention intervals. Experiment 2 showed that spontaneous recovery of stimulus control of behavior after extinction can be obtained with the same parameters as those used to observe the augmented effect of CS-preexposure treatment. In Experiment 3, both the augmented effect of CS-preexposure treatment and spontaneous recovery from extinction were found when we used, in place of a retention interval, an associative priming manipulation.

Animals↗

PubMed2003

Massive preexposure and preexposure in multiple contexts attenuate the context specificity of latent inhibition.

Latent inhibition, which refers to attenuated responding to a conditioned stimulus (CS) after CS-unconditioned stimulus (CS-US) pairings as a result of CS-alone presentations prior to the pairings, is often attenuated if preexposure and conditioning occur in different contexts (i.e., it is context specific). Here we report two conditioned lick suppression experiments, using rat subjects, that examined whether manipulations known to attenuate the context specificity of extinction could also eliminate the context specificity of latent inhibition. Context specificity of latent inhibition was eliminated when the CS was preexposed in multiple contexts (Experiment 1) and when the CS was massively pre-exposed in the training context alone (Experiment 2). These results and their practical implications are discussed in the framework of contemporary theories of latent inhibition.

Animals↗

PubMed2002

Iron deficiency in rats decreases acquisition of and suppresses responding for cocaine.

Iron deficiency impairs nigrostriatal and mesolimbic dopamine systems by causing decreased densities of D(1) and D(2) receptors and the dopamine transporter in the terminal fields, caudate-putamen and nucleus accumbens. Iron deficiency also causes deficits in dopamine-related pharmacological indices, e.g., deficits in locomotor stimulation by cocaine and locomotor inhibition by raclopride. Based on this knowledge, we hypothesized that iron deficiency would have a major impact on cocaine self-administration. Male Sprague-Dawley rats were fed an iron-deficient diet starting at weaning (Day 21) and continuing throughout the experiment. At 57-58 days of age, all animals had catheters implanted surgically into the jugular vein. Approximately 2 weeks later, all animals were trained to lick an empty spout for intravenous cocaine, delivered by infusion pump at 0.33 mg/kg. During the course of training, all animals acquired intravenous cocaine self-administration, however, the course of acquisition was significantly slower for the iron-deficient animals. When tested for responding on a progressive ratio (PR) schedule, the control animals maintained a constant number of infusions, whereas the responding of the iron-deficient animals fell off sharply. When the dose of cocaine was decreased, control, but not iron-deficient adjusted the amount administered by increasing the number of infusions. Finally, the failure to respond by the iron-deficient animals was not simply due to a failure to lick (i.e., a motor impairment), because both the iron-deficient and the control animals emitted approximately 1000 licks/20 min session when given free access to a palatable 0.1 M sucrose solution. Taken together, the data show that severe iron deficiency early in life can diminish the capacity of cocaine, but not sucrose to reinforce behavior. The question raised by this research thus, is whether iron deficiency alters hedonic-like responses only to dopamine-related behaviors and the degree to which willingness to "work" contributes to the effect.

Animals↗