Effects of selective antagonism or depletion of the cholinergic system on visual discrimination performance in rats.

A two-lever simultaneous visual discrimination task was used to study the effects on performance in Long-Evans rats of the muscarinic antagonists scopolamine (0.0125, 0.05, 0.

Shifting behavior: an analysis of response patterns of Parkinson patients in discrimination learning.

Parkinson patients often show decreased performance on what is generally referred to as "shift tasks." This does not necessarily imply that Parkinson patients have problems with shifting, since task performance reflects not only shifting but also other factors. Using a discrimination learning task, we analyzed response patterns to determine the decision rules used.

Apomorphine-susceptible and apomorphine-unsusceptible Wistar rats differ in novelty-induced changes in hippocampal dynorphin B expression and two-way active avoidance: a new key in the search for the role of the hippocampal-accumbens axis.

The present study examines two characteristic traits of the hippocampus in apomorphine-susceptible (APO-SUS) and apomorphine-unsusceptible (APO-UNSUS) Wistar rat lines. Since hippocampal mossy fibers contain among others dynorphin B as transmitter, a radioimmunoassay was used to analyze the hippocampal dynorphin B expression in response to novelty in these lines. Dynorphin B expression at the end of the baseline condition was greater in APO-SUS rats than in APO-UNSUS rats, while exposure to novelty decreased and increased the dynorphin B expression in APO-SUS and APO-UNSUS rats, respectively.

Haloperidol affects stimulus-dependent strategies and not reward-dependent strategies.

In order to investigate effects of haloperidol on response strategies, rats were confronted with an unsolvable discrimination problem after being injected with haloperidol (0.1 mg/kg, IP) or its solvent. The results showed that haloperidol-treated rats displayed systematic behaviour to a lesser degree than the control rats.

Problem-solving behaviour in apomorphine-susceptible and unsusceptible rats.

Pharmacogenetically selected apomorphine-susceptible (APO-SUS) and apomorphine-unsusceptible (APO-UNSUS) rats were trained in a discrimination learning paradigm. After the initial discrimination task was solved, reinforcement contingencies were reversed. No differences between APO-SUS and APO-UNSUS animals were found in the rate of learning.