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Results for “Reversal Learning”

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At least 937 records · Page 52Linked to original sources
PubMed1997

The recognition memory deficit caused by mediodorsal thalamic lesion in non-human primates: a comparison with rhinal cortex lesion.

Two earlier studies found that rhinal cortex ablations in the monkey (Macaca fascicularis) impaired delayed matching-to-sample (DMS) when the stimuli in the experiment came from a large population of possible stimuli, but not when the stimulus population was small, while uncinate fascicle section had no effect on DMS whatever the stimulus population size. The mediodorsal thalamus receives a large projection from the rhinal cortex, and has been implicated in recognition memory performance. We trained monkeys preoperatively in delayed matching-to-sample with large and small stimulus populations, exactly as in the earlier studies, then examined the effect of bilaterally ablating the medial portion of the mediodorsal thalamic nucleus. Mediodorsal lesion impaired postoperative delayed matching-to-sample performance with a large stimulus set, but had no effect on performance of DMS with a small stimulus population. In comparison with the earlier data from rhinal cortex lesions with the same methods, wherever a deficit was seen in the rhinal-lesioned animals the mediodorsal thalamic nucleus-lesioned animals showed a smaller deficit. We conclude that other efferents from the rhinal cortex, possibly those to the adjacent inferior temporal cortex, enable better performance in the mediodorsal thalamic nucleus-lesioned animals than in the animals with rhinal cortex ablation.

Animals↗
PubMed1979

Children's memory for orientation in the absence of external cues.

Some have interpreted children's reliance on external visual cues as evidence that they are unable to use internal cues for orientation. This hypothesis was examined in experiment 1, where 24 preschoolers were tested on left-right, vertical-horizontal, and mirror-image oblique discriminations under essentially context-free conditions. Subjects succeeded on all discrimination problems and performed equally well on vertical-horizontal and mirror-image oblique discriminations. Thus, preschoolers can use an internal frame of reference to code orientation. Experiment 2 contrasted children's performance under context-free conditions with their ability to discriminate orientation in the presence of external visual cues. Children who had discriminated left-right oblique and nonoblique mirror-image forms in experiment 1 failed to so discriminate in experiment 2. This result is discussed in terms of a breakdown in the ability to use internal cues when external visual cues are available.

Child, Preschool↗
PubMedDate not supplied

[Effect of neuroleptics on the retraining of rats to change the direction of the avoidance response in a Y-shaped maze].

The ability of rats to alter the direction of avoidance response in a Y-shaped labyrinth was determined. Chlorpromazine (1 mg/kg) and haloperidol (0.1 mg/kg) facilitated re-training of the animals but produced lengthening of the latent reaction periods. Smaller doses of chlorpromazine (0.5 mg/kg) and of haloperidol (0.05 mg/kg) improved the ability of rats to alter the direction of avoidance and did not affect the latency of responses. Such an action of the neuroleptics exerted mainly on animals initially difficultly amenable to re-training.

Animals↗
PubMed2004

Studies of learning and problem solving in two species of Australian marsupials.

This article reviews the authors' recent work with two species of Australian marsupials on several learning and conditioning experiments. The quokka (Setonix brachyurus) is a cat-sized herbivorous wallaby that inhabits offshore islands around south-western Australia. The fat-tailed dunnart (Sminthopsis crassicaudata) is a mouse-sized carnivorous marsupial that inhabits much of inland Australia. Both species were successful in learning simple discriminations, learning sets and reversal sets. Quokkas and dunnarts were also tested on two configural discrimination tasks: transverse patterning and negative patterning; only the dunnarts successfully solved these tasks. Dunnarts were also the only species to show one-trial learning in reversal set training. Dunnarts may be particularly useful subjects in future studies of brain-behavior relationships, since these animals have some interesting neuroanatomical features, demonstrate a wide range of fast learning abilities, and as pouch young, can be accessed during early developmental stages.

Animals↗
PubMed2002

Post-training reversible inactivation of hippocampus reveals interference between memory systems.

A post-training reversible lesion technique was used to examine the effects of neural inactivation of the dorsal hippocampus on place and response learning. Male Long-Evans rats trained in one of two versions of a water plus-maze task received post-training intra-hippocampal infusions of the local anesthetic drug bupivacaine (0.75% solution, 0.5 microl), or saline. Post-training intra-hippocampal infusions of bupivacaine attenuated acquisition of the place task and enhanced acquisition of the response task. Delayed (2-h) post-training infusions of bupivacaine did not affect retention in either task. The findings demonstrate (1) enhanced learning after reversible hippocampal lesions that is independent of treatment influences on non-mnemonic factors, and (2) inactivation of the dorsal hippocampus during the post-training memory consolidation period is sufficient to enhance response learning.

Analysis of Variance↗
PubMed1999

Spatial cognition in rhesus monkeys: male superiority declines with age.

Twelve young (4-7 years of age) and 14 old (20-27 years of age) male and female rhesus monkeys were tested on seven cognitive tasks. Males and females performed similarly on tasks of object memory and executive function, but young males outperformed young females on a spatial memory task (Delayed Recognition Span Test) that requires the identification of a new stimulus among an increasing array of serially presented stimuli. This superior level of spatial ability in young males declined sharply with age, so that old males did not perform significantly better than old females. These findings in the nonhuman primate suggest that biological rather than sociocultural factors underlie the sex differences in cognition and their diminution with age.

Aging↗
PubMed1998

Combined stimulation of the glycine and polyamine sites of the NMDA receptor attenuates NMDA blockade-induced learning deficits of rats in a 14-unit T-maze.

The present study examined the effects of multi-site activation of the glycine and polyamine sites of the NMDA receptor on memory formation in rats learning a 14-unit T-maze task. The competitive NMDA receptor antagonist, (+/-)-3-(2-carboxypiperazine-4-yl)-propyl-1-phosphonic acid (CPP, 9 mg/kg), was used to impair learning. The objectives were two-fold: (1) to investigate the effects of independent stimulation of the strychnine-insensitive glycine site or the polyamine site; (2) to investigate the effects of simultaneous activation of these two sites. Male, Fischer-344 rats were pretrained to a criterion of 13 out of 15 shock avoidances in a straight runway, and 24 h later were trained in a 14-unit T-maze that also required shock avoidance. Prior to maze training, rats received intraperitoneal (i.p.) injections of saline, saline plus CPP, CPP plus the glycine agonist, D-cycloserine (DCS, 30 or 40 mg/kg), CPP plus the polyamine agonist, spermine (SPM, 2.5 or 5 mg/kg), or CPP plus a combination of DCS (7.5 mg/kg) and SPM (0.625 mg/kg). Individual administration of either DCS or SPM attenuated the CPP-induced maze learning impairment in a dose-dependent manner. However, the combined treatment with both DCS and SPM completely reversed the learning deficit at doses five-fold less than either drug given alone. These findings provide additional evidence that the glycine and polyamine modulatory sites of the NMDA receptor are involved in memory formation. Furthermore, the potent synergistic effect resulting from combined activation of the glycine and polyamine sites would suggest a stronger interaction between these two sites than previously considered, and might provide new therapeutic approaches for enhancing glutamatergic function.

Animals↗