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Results for “Reversal Learning”

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At least 991 records · Page 55Linked to original sources
PubMed1997

Differential roles of monkey striatum in learning of sequential hand movement.

To study the role of the basal ganglia in learning of sequential movements, we trained two monkeys to perform a sequential button-press task (2x5 task). This task enabled us to examine the process of learning new sequences as well as the execution of well-learned sequences repeatedly. We injected muscimol (a GABA agonist) into different parts of the striatum to inactivate the local neural activity reversibly. The learning of new sequences became deficient after injections in the anterior caudate and putamen, but not the middle-posterior putamen. The execution of well-learned sequences was disrupted after injections in the middle-posterior putamen and, less severely, after injections in the anterior caudate/putamen. These results suggest that the anterior and posterior portions of the striatum participate in different aspects of learning of sequential movements.

Animals↗
PubMed1981

Effects of restriction of maternal uterine blood supply on postnatal conditioning of heart rate and behavioral development in dogs.

An examination was made of the heart rate responses during aversive classical conditioning of 5- to 6-week-old Labrador puppies exposed to restricted maternal uterine blood supply during gestation. The direction of the heart rate responses of the treated puppies was consistently decelerative, whereas nontreated controls showed both decelerations and accelerations. The absence of accelerative heart rate changes, combined with the observed depression of base level heart rate and attenuated emotional behavior in the experimental animals relative to controls suggests that uterine blood supply insufficiency may have impaired normal autonomic development in utero.

Animals↗
PubMed2004

Bidirectional links in the network of multiplication facts.

In three experiments, we tested the hypothesis that activation of multiplication operand nodes (e.g., 3 and 8) can occur through presentation of their product (e.g., 24). In Experiments 1 and 2 we found activation of the operands when the product was presented as a cue in a number-matching task. In Experiment 3, activation also occurred in a parity-matching task, where the product (24) was not relevant to the parity matching on its operands (3 and 8). We concluded that bidirectional links exist among the operands and their product for multiplication problems and these links can be activated in a purely stimulus-driven manner. We suggest this may constitute the basis for the solution of simple divisions by mediation through the complementary multiplication facts.

Adult↗
PubMed1986

Synthesis of rat brain DNA during acquisition of an appetitive task.

We have examined the incorporation of [3H-methyl]thymidine into DNA extracted from several brain regions of rats learning a reverse handedness task, of control rats allowed to use their preferred paw, and of control rats left in their home cages. In learning animals, decrements in percent incorporation were observed in the visual cortex, remaining brain, hippocampus and entorhinal cortex. In the latter two regions less marked decreases were present in the active control group. No variation occurred in the sensory-motor cortex. In learning rats the specific radioactivity of neuronal DNA was markedly decreased in the hippocampus and remaining brain. In the former region, a less marked decrease was present in active control rats. In subcellular fractionation studies it was observed that decreases in DNA specific radioactivity prevailed in the mitochondrial fraction isolated from the hippocampus and visual cortex of learning rats. Brain radioactive DNA was widely distributed among fractions differing in their degree of repetitiveness. Its pattern of distribution did not coincide with that of bulk DNA and differed significantly among behavioural groups. The results suggest a non random origin of newly-synthesized brain DNA and its involvement in learning.

Animals↗
PubMedDate not supplied

A search for residual behavioral effects of trichloroethylene (TCE) in rats exposed as young adults.

Trichloroethylene (TCE) is an organic solvent with robust acute effects on the nervous system, but poorly documented long-term effects. This study employed a signal detection task (SDT) to assess the persistence of effects of repeated daily inhalation of TCE on sustained attention in rats. Adult male Long-Evans rats inhaled TCE at 0, 1600, or 2400 ppm, 6 h/day for 20 days (n=8/group) and began learning the SDT 3 weeks later. Rats earned food by pressing one retractable response lever in a signal trial and a second lever in a blank (no signal) trial. TCE did not affect acquisition of the response rule or performance of the SDT after the intertrial interval (ITI) was changed from a constant value to a variable one. Increasing the trial presentation rate reduced accuracy equivalently in all groups. Injections of ethanol (0, 0.5, 1.0, 1.5 g/kg ip) and d-amphetamine (0, 0.1, 0.3, 1.0 mg/kg sc) systematically impaired performance as functions of drug dose. d-Amphetamine (1.0 mg/kg) reduced P(hit) more in the 2400-ppm TCE group than in the other groups. All rats required remedial training to learn a reversal of the response contingencies, which TCE did not interfere with. Thus, a history of exposure to TCE did not significantly alter learning or sustained attention in the absence of drugs. Although ethanol did not differentially affect the TCE groups, the effect of d-amphetamine is consistent with solvent-induced changes in dopaminergic functions in the CNS. Calculations indicated power values of 0.5 to 0.8 to detect main effects of TCE for the three primary endpoints.

Anesthetics, Inhalation↗
PubMed2002

Hippocampal lesioned rats are able to learn a spatial position using non-spatial strategies.

In the last two decades, many experiments have demonstrated that the hippocampus plays a role in the learning and processing of spatial and contextual information. Despite these demonstrations, some recent publications have indicated that the hippocampus is not the only structure involved in spatial learning and that even after hippocampal lesions, rats can perform spatial tasks. However, it is not well established whether animals with hippocampal dysfunction still have some spatial learning capacities or develop non-spatial solutions; these may require lengthier acquisition training. We now report the effects of conventional, dorsal hippocampal ablation on rats' performance on the water maze. We tested rats using a short (4 days) versus a long (16 days) acquisition period. We demonstrated that animals with dorsal hippocampal lesions have some residual capacity for learning the localization of a hidden escape platform in a pool during both a reference memory task and a working memory task. The animals with dorsal hippocampal lesions learned to escape at a fixed location, but only with extended training. It is suggested that these animals used non-spatial strategies to compensate for a spatial memory impairment. The results are discussed with respect to the experimental procedure and the strategy applied by the lesioned rats.

Animals↗
PubMed2004

Phosphodiesterase inhibition by sildenafil citrate attenuates the learning impairment induced by blockade of cholinergic muscarinic receptors in rats.

We examined whether treatment with sildenafil citrate (the active compound of Viagra), a cyclic nucleotide phosphodiesterase type 5 inhibitor (PDE5), would reverse the learning impairment induced by cholinergic muscarinic (mACh) receptor blockade [0.75 mg/kg scopolamine HCl, intraperitoneal (i.p.) injections]. Rats were pretrained in a one-way active avoidance of foot shock in a straight runway and the next day received 15 training trials in a 14-unit T-maze. Performance in this maze paradigm requires accurate responding to avoid mild foot shock and has been shown to be sensitive to aging and to impairment in central cholinergic systems. Intraperitoneal (i.p.) injections of scopolamine or saline and sildenafil or vehicle were given 30 and 15 min before training, respectively. The combined treatment conditions were as follows: saline+vehicle (control), scopolamine (0.75 mg/kg)+vehicle, and scopolamine (0.75 mg/kg)+sildenafil (1.5, 3.0, or 4.5 mg/kg). Behavioral measures of performance included deviations from the correct pathway (errors), run time from start to goal, shock frequency, and duration. Statistical analysis revealed that scopolamine impaired maze performance and that sildenafil (3.0 mg/kg) significantly attenuated this impairment in a dose-dependent manner. These results suggest that sildenafil citrate may serve as a cognitive enhancer for therapeutic treatment of cholinergic dysfunction in age-related cognitive decline and Alzheimer's dementia (AD).

3',5'-Cyclic-GMP Phosphodiesterases↗