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At least 811 records · Page 45Linked to original sources
PubMed1988

Hippocampal system dysfunction and odor discrimination learning in rats: impairment or facilitation depending on representational demands.

The performance of normal rats and that of rats with hippocampal system damage were compared on acquisition of different versions of the same two-odor discrimination task that placed different encoding and representational demands on memory. Rats with fornix lesions were impaired when explicit comparisons among multiple odor cues and differential response choices were encouraged. However, when odor-cue comparison was hindered and explicit cues for response choice were eliminated, rats with fornix lesions out performed normal animals. The results support an hypothesis that the hippocampal system is critical to a memory representation based on encoding relations among multiple percepts, and other brain systems support performance adaptations based on encodings of stimuli individually.

Animals↗
PubMed1984

Interocular transfer of pattern discrimination learning in chicks.

A previous study found that chicks pecking a key for heat did not show interocular transfer of a pattern discrimination, indicating that the monocularly acquired discrimination was stored as a unilateral engram which was not available to the untrained eye/hemisphere system. In the present study, chicks were trained monocularly on a pattern discrimination and tested for interocular transfer exactly as in the previous experiment, except that a correct pecking response was reinforced by presentation of food. There was good interocular transfer of the discrimination under these conditions. These results are interpreted as indicating that the biological relevance of a learning situation influences the extent of interocular/interhemispheric communication of information. In addition to the findings with respect to transfer, the present study revealed some unexpected laterality effects. Chicks trained first through the right eye (left hemisphere) learned the pattern discrimination faster and showed more savings during the interocular transfer test than chicks trained first through the left eye (right hemisphere). These findings are discussed in terms of possible hemispheric specialization and asymmetry of interhemispheric communication in the avian brain.

Animals↗
PubMedDate not supplied

Preserved performance by cerebellar patients on tests of word generation, discrimination learning, and attention.

Recent theories suggest that the human cerebellum may contribute to the performance of cognitive tasks. We tested a group of adult patients with cerebellar damage attributable to stroke, tumor, or atrophy on four experiments involving verbal learning or attention shifting. In experiment 1, a verb generation task, participants produced semantically related verbs when presented with a list of nouns. With successive blocks of practice responding to the same set of stimuli, both groups, including a subset of cerebellar patients with unilateral right hemisphere lesions, improved their response times. In experiment 2, a verbal discrimination task, participants learned by trial and error to pick the target words from a set of word pairs. When age was taken into account, there were no performance differences between cerebellar patients and control subjects. In experiment 3, measures of spatial attention shifting were obtained under both exogenous and endogenous cueing conditions. Cerebellar patients and control subjects showed similar costs and benefits in both cueing conditions and at all SOAs. In experiment 4, intra- and interdimensional shifts of nonspatial attention were elicited by presenting word cues before the appearance of a target. Performance was substantially similar for cerebellar patients and control subjects. These results are presented as a cautionary note. The experiments failed to provide support for current hypotheses regarding the role of the cerebellum in verbal learning or attention. Alternative interpretations of previous results are discussed.

Aged↗
PubMed2000

Oral administration of adrafinil improves discrimination learning in aged beagle dogs.

Aged beagle dogs were trained on either a size or intensity discrimination task 2 h following treatment with either 20 mg/kg of adrafinil or a placebo control. Training continued until the dogs reached a predetermined criterion level of performance, or failed to acquire the task after 40 sessions. The treatments and tasks were then reversed, with both the test order and treatment order counterbalanced. Thus, half of the animals were first tested on the intensity discrimination, and half of these were first tested under adrafinil. Treatment with adrafinil produced significant improvement in learning, as indicated by a decrease in both errors and trials to criterion. An effect of adrafinil on motivation may partially account for these findings; however, adrafinil did not significantly affect response latency. Adrafinil is believed to serve as an alpha-1 adrenoceptor agonist. The improved learning may also result from enhancement of vigilance due to facilitation of noradrenergic transmission in the central nervous system.

Administration, Oral↗