Biomedical subjects

Mauricio R Papini

Publications and source records attributed to Mauricio R Papini.

11 recordsLinked to original sources

PubMed2006

Appetitive latent inhibition in rats: preexposure performance does not predict conditioned performance.

Nonreinforced preexposure to a conditioned stimulus impairs subsequent conditioning with that stimulus. The goal of these studies was to assess the extent to which acquisition performance could be predicted from preexposure performance using a correlational approach. For both preexposure and autoshaping, four measures of performance were computed, including overall average lever pressing, lever pressing in the initial session, percentage change in lever pressing, and slopes. These measures were correlated in a large sample of rats trained in an autoshaping situation. None of the three measures of autoshaping performance was consistently predicted by any of the three measures of preexposure performance. These results are consistent with the view that latent inhibition is not reducible to long-term habituation.

Animals↗

PubMed2006

Administration of corticosterone after the first downshift trial enhances consummatory successive negative contrast.

Rats given access to a 32% sucrose solution and then downshifted to a 4% solution exhibit less contact with the sipper tube than unshifted controls always given access to 4% solution. This phenomenon, called consummatory successive negative contrast, was facilitated in Experiment 1 by a post-trial injection of corticosterone (3 mg/kg) administered immediately after the first downshift trial. Experiment 2 demonstrated that this facilitatory effect of post-trial corticosterone does not occur when administered 3 hr after the first downshift trial. These results support the hypothesis that corticosterone strengthens an aversive emotional component elicited by the surprising downshift in reward magnitude during the initial downshift trial.

Analysis of Variance↗

PubMed2006

Effects of housing on consummatory successive negative contrast in rats: wire-bottom cages versus polycarbonate tubs.

In consummatory successive negative contrast, rats that have had experience drinking 32% sucrose solution drink significantly less 4% sucrose solution than rats that have drunk only 4% solution. This contrast effect occurs reliably when rats are housed in wire-bottom cages, but it occurs significantly less frequently when rats are housed in polycarbonate tubs. Although it is unclear what causes these differences among housing conditions, the present study underscores the impact that housing conditions outside the domain of the training environment can have on behavioral outcomes.

Animal Husbandry↗

PubMed2005

Opioid receptors modulate recovery from consummatory successive negative contrast.

Three experiments explored the role of the opioid system in consummatory successive negative contrast. In Experiment 1, rats treated with the nonspecific opioid-receptor antagonist naloxone (2mg/kg) exhibited increased suppression after a shift from 32% to 6% sucrose solution (32-->6), relative to 6-->6 unshifted controls. A similar but shorter effect was observed with the delta-opioid receptor antagonist naltrindole (1mg/kg). In Experiment 2, naloxone increased suppression after a more conventional 32-->4 sucrose shift. In Experiment 3, rats classified as expressing slow recovery from contrast (after a 32-->4 sucrose downshift) were more sensitive to naloxone in an activity test than fast-recovery rats. Whereas it was previously known that contrast was reduced by the extrinsic administration of opioid agonists, the effects reported here with antagonists provide the first evidence that the opioid system is intrinsically engaged by situations involving surprising reward loss.

Animals↗

PubMed2005

Selective effects of the delta-opioid receptor agonist DPDPE on consummatory successive negative contrast.

Two experiments explored the role of the opioid system in a situation involving a surprising reduction in reward magnitude: consummatory successive negative contrast. Rats received access to 32% sucrose solution (preshift Trials 1-10) followed by 4% solution (postshift Trials 11-15). Independent groups received an injection of either the vehicle or the delta-receptor agonist [D-Ala2-,N-Me-Phe4,Gly-ol] enkephalin (DPDPE; 24 microg/kg). DPDPE attenuated the contrast effect when injected before Trial 11 but not when injected before Trial 12. An additional experiment showed that the attenuating effect of partial reinforcement on the recovery from contrast was reduced by DPDPE injections administered before nonreinforced preshift trials.

Analgesics, Opioid↗

PubMed2004

Lesions of the medial pallium, but not of the lateral pallium, disrupt spaced-trial avoidance learning in goldfish (Carassius auratus).

The effects of telencephalic lesions of the medial pallium (MP) and lateral pallium (LP) of goldfish on avoidance learning were studied in a two-way, shuttle response, spaced-trial avoidance conditioning situation. Animals received one trial per day, a training regime that permits the assessment of avoidance learning in the absence of stimulus carry-over effects from prior trials. Control and LP-lesioned goldfish exhibited significantly faster avoidance learning than MP-lesioned animals. These results suggest that the MP, but not the LP, is responsible for the widely described deficits in avoidance learning after lesions of the entire telencephalon. The proposal of a functional similarity between the fish MP and the mammalian amygdala, known to be involved in fear conditioning, suggests a conservative phylogenetic role of this area in avoidance learning.

Animals↗

PubMed2003

Involvement of the telencephalon in spaced-trial avoidance learning in the goldfish (Carassius auratus).

Goldfish (Carassius auratus) received escape-avoidance training in a shuttle-response situation at a rate of a single trial per day. Widely spaced training evaluates the ability of a discriminative stimulus to control an avoidance response in the absence of stimulus carry-over effects from prior recent trials. In Experiment 1, master goldfish exhibited significantly faster avoidance learning than yoked controls. The results suggest that the shuttle response was instrumentally acquired. Experiment 2 demonstrated a significant deficit in the acquisition of avoidance behavior following ablation of the telencephalon. The implications of spaced-trial, telencephalon-dependent avoidance learning, as demonstrated in these experiments for the first time, are discussed in the context of comparative research on instrumental learning in goldfish. These results provide further support for the hypothesis that the fish telencephalon contains an emotional system that is critical for fear conditioning.

Animals↗

PubMed2003

Comparative psychology of surprising nonreward.

The surprising or unexpected omission of an appetitive reinforcer has at least two effects: An allocentric effect according to which the organism updates knowledge about the environment, and an egocentric effect that allows the organism to learn about its own emotional reaction to the change. This egocentric effect (traditionally called frustration) is correlated to activation of the hypothalamic-pituitary-adrenal axis, can be modulated by treatment with anxiolytics, and is expressed in terms of behavioral changes that have an emotional component (e.g., agonistic behavior). It is hypothesized that all vertebrates share the mechanisms underlying the allocentric effect, but only mammals possess the mechanisms underlying the egocentric effect. It is further argued that frustrative mechanisms evolved in early mammals from those underlying fear conditioning.

Amphibians↗

PubMed2003

Appetitive latent inhibition in rats: now you see it (sign tracking), now you don't (goal tracking).

Latent inhibition (LI), the retardation of Pavlovian acquisition after nonreinforced preexposure to the conditioned stimulus, is a popular paradigm for studying basic attentional and memory processes from both behavioral and neurobiological perspectives. It is argued that whether LI emerges depends on the behavioral measure used to index conditioning. An experiment with rats demonstrates that stimulus preexposure retards the development of sign-tracking responses directed at the stimulus, but not the development of goal-tracking responses directed at the site of food delivery. These results are consistent with models that explain LI in terms of a deficit in retrieval.

Animals↗

PubMed2002

Pattern and process in the evolution of learning.

A century after E. L. Thorndike's (1898) dissertation on the comparative psychology of learning, the field seems ready for a reassessment of its metatheoretical foundations. The stability of learning phenotypes across species is shown to be similar to that of other biological characters, both genotypic (e.g., Hox genes) and phenotypic (e.g., vertebrate brain structure). Moreover, an analysis of some current lines of comparative research indicates that researchers use similar strategies when approaching problems from either an ecological view (emphasizing adaptive significance) or a general-process view (emphasizing commonality across species). An integration of learning and evolution requires the development of criteria for recognizing and studying the divergence, homology, and homoplasy of learning mechanisms, much as it is done in other branches of biological research.

Adaptation, Psychological↗

PubMed2002

Aftereffects of the surprising presentation and omission of appetitive reinforcers on key-pecking performance in pigeons.

The reinforcement-omission effect (ROE), also known as frustration effect, refers to greater response strength immediately after nonreinforcement (N) than reinforcement (R). The ROE was traditionally interpreted as transient invigoration after N induced by primary frustration. Pigeons demonstrate similar ROEs whether outcomes are surprising (partial R) or expected (discrimination training) in runway (Experiment 1) and Skinner box situations (Experiments 2-3). Variations in the interval between N and the opportunity to respond indicate that the ROE results from an aftereffect of food consumption (Experiment 4). Increasing reinforcer magnitude increased the after-R effect, without modifying the after-N function (Experiment 5). These results are reviewed in the context of comparative research on spaced-trial successive negative contrast and related phenomena that have failed to appear in experiments involving nonmammalian vertebrates.

Animals↗