Biomedical subjects

Martha Escobar

Publications and source records attributed to Martha Escobar.

8 recordsLinked to original sources

PubMed2003

Proactive interference between cues trained with a common outcome in first-order Pavlovian conditioning.

The nature of interference between cues (X, A) trained apart with a common outcome (O; an unconditioned stimulus) was explored by assessing proactive interference in first-order Pavlovian conditioning (i.e., A-O, X-O, resulting in attenuated responding to X). Three lick-suppression studies were conducted with water-deprived rats. Posttraining extinction of the interfering cue (A) attenuated proactive interference (Experiment 1), which mirrors the observation that extinction of the competing cue can reduce competition between cues trained together (e.g., recovery from overshadowing). Proactive interference was also attenuated with manipulations known to attenuate interference between outcomes trained apart (e.g., counterconditioning), namely reminder cues (Experiment 2) and renewal (Experiment 3). The findings suggest that similar processes underlie interference between cues trained apart, between cues trained together, and between outcomes trained apart.

Animals↗

PubMed2003

Latent inhibition in human adults without masking.

Latent inhibition refers to attenuated responding to Cue X observed when the X-outcome pairings are preceded by X-alone presentations. It has proven difficult to obtain in human adults unless the preexposure (X-alone) presentations are embedded within a masking (i.e., distracting) task. The authors hypothesized that the difficulty in obtaining latent inhibition with unmasked tasks is related to the usual training procedures, in which the preexposure and conditioning experiences are separated by a set of instructions. Experiment 1 reports latent inhibition without masking in a task in which preexposure and conditioning occur without interruption. Experiments 2 and 3 demonstrate that this attenuation in responding to target Cue X does not pass a summation test for conditioned inhibition and is context specific, thereby confirming that it is latent inhibition. Experiments 3 and 4 confirm that introducing instructions between preexposure and conditioning disrupts latent inhibition.

Adult↗

PubMed2003

Temporal integration and temporal backward associations in human and nonhuman subjects.

Two experiments are reported that demonstrate temporal integration of independently acquired temporal relationships, including backward associations, in both human (Experiment 1) and nonhuman (rats, Experiment 2) subjects. The experiments were designed and analyzed in the framework of the temporal coding hypothesis (e.g., Matzel, Held, & Miller, 1988; Savastano & Miller, 1998) as a strategy toward illuminating the use of temporal information and assessing the existence of temporal backward associations. Both experiments provided evidence of retrieval of associations to an event that was expected to occur prior to the moment in time at which a stimulus was presented (i.e., backward associations). In addition, Experiment 1 constitutes the first controlled demonstration of temporal integration by human subjects.

Adult↗

PubMed2003

Timing in retroactive interference.

Retroactive interference is conventionally viewed as attenuated retrieval of a target association due to the training of a second association between training and testing of the target association. In three experiments in which water-deprived rats were used as subjects, we manipulated the durations of the time between cue termination and outcome onset (Experiment 1), the durations of the target and the interfering cues (Experiment 2), and the durations of the outcome used during target and interfering training (Experiment 3). Greater interference was consistently observed between associations bearing a high degree of similarity in their temporal structure, which suggests that interference occurs between complex representations that encode not only the physical attributes of the stimuli, but also their temporal characteristics.

Animals↗

PubMed2002

Associative interference between cues and between outcomes presented together and presented apart: an integration.

In recent years, 'stimulus competition' in the study of acquired behavior has referred exclusively to (a) associative competition between cues trained in compound (e.g. overshadowing and blocking). Rarely cited are older experiments cast in the verbal learning tradition, now complemented with data from humans and rats in Pavlovian preparations, that demonstrate (b) competition between cues separately trained with a common outcome (i.e. proactive and retroactive interference). Similarly neglected are numerous examples of (c) competition between outcomes separately trained with a common cue within the verbal learning literature (also proactive and retroactive interference) as well as within the Pavlovian literature (i.e. counterconditioning). Recent data demonstrate (d) competition between outcomes trained in compound, thereby completing the four cells of a 2x2 matrix (competing stimuli trained together vs. trained apart and the competing stimuli being cues or outcomes) which highlights the ubiquitous nature of associative stimulus interference/competition. Most contemporary theories of acquired behavior can account for the phenomena in one or at most two cells of this matrix. Whether a common mechanism underlies the phenomena in all four cells of the matrix is currently unclear, but until such time as data preclude a common mechanism, parsimony encourages efforts to develop a model that encompasses all four cells. Here we offer a tentative model that addresses all four cells, albeit with two processes.

Journal Article↗

PubMed2002

Associative deficit accounts of disrupted latent inhibition and blocking in schizophrenia.

Latent inhibition (attenuated responding to a signal due to signal-alone presentations preceding the signal-outcome pairings) and blocking (attenuated responding to Signal B due to Signal A being paired with the outcome prior to pairings of an AB compound with the outcome) are reportedly absent in acute schizophrenics. The common assumption that these phenomena reflect the normal functioning of attention and the observation that rats administered low doses of amphetamine show a similar disruption has resulted in the development of an animal model of attentional dysfunction in acute schizophrenia. Here, we selectively review the experimental and clinical literature concerning latent inhibition and blocking, their disruption in acute schizophrenia, and the current status of this model. We conclude that the construct validity of the model is compromised if latent inhibition and blocking are viewed in attentional terms because experimental data indicate both phenomena can be better understood in associative terms. We favor a framework in which disruption of latent inhibition and blocking in acute schizophrenics is viewed as an inability to compare and express stored representations (i.e. associative performance deficit). This change of perspective does not undermine the potential value of the model, but rather suggests that the nature of its validity should be reconsidered.

Animals↗

PubMed2002

A comparison between elemental and compound training of cues in retrospective revaluation.

Associative learning theories assume that cue interaction and, specifically, retrospective revaluation occur only when the target cue is previously trained in compound with the to-be-revalued cue. However, there are recent demonstrations of retrospective revaluation in the absence of compound training (e.g., Matute & Pineño, 1998a, 1998b). Nevertheless, it seems reasonable to assume that cue interaction should be stronger when the cues are trained together than when they are trained apart. In two experiments with humans, we directly compared compound and elemental training of cues. The results showed that retrospective revaluation in the elemental condition can be as strong as and, sometimes, stronger than that in the compound condition. This suggests that within-compound associations are not necessary for retrospective revaluation to occur and that these effects can possibly be best understood in the framework of general interference theory.

Association Learning↗

PubMed2002

Latent inhibition and contextual associations.

Attenuated responding to a conditioned stimulus (CS) after preexposure to that CS (latent inhibition) has traditionally been attributed to reductions in CS associability. Alternatively, CS-context associations formed during CS preexposure later interfere with the acquisition or expression of CS-outcome associations. Three lick suppression experiments with rats contrasted these accounts. Presumably, exposure to the context attenuates the CS-context association without altering CS associability. With a fixed amount of CS preexposure, latent inhibition decreased with increasing context exposure during or after (but not before) CS preexposure. When the ratio of context preexposure duration to CS preexposure was fixed, latent inhibition increased with CS preexposure. These results suggest that latent inhibition is a direct function of the strength of CS-context associations formed during preexposure.

Animals↗