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J M Pearce

Publications and source records attributed to J M Pearce.

At least 73 records · Page 4Linked to original sources
PubMed1997

The distribution of lithium in rat brain and muscle in vivo by 7Li NMR imaging.

The regional distribution of lithium (Li) in vivo was determined on a relative basis in the brain and muscle of rats by 7Li NMR imaging. Both high resolution 7Li NMR spectroscopy and atomic absorption spectrophotometry were performed on extracts of brain and muscle tissue from the same rats. The average in vivo results were generally in good agreement with the corresponding average in vitro results, despite the relatively low signal-to-noise ratio of the in vivo images. There was good agreement between the two in vitro methods of analysis, both on average and for individual animals. Significant differences were found in vivo among Li concentration ratios for the various brain regions and muscle by 7Li imaging, as well as by the in vitro methods.

Animals↗
PubMed1997

Interaction between piloting and beacon homing by rats in a swimming pool.

In three experiments, rats in a swimming pool were trained to find a submerged platform with a beacon attached to it. For some rats this beacon unambiguously identified the location of the platform; for others the beacon was made ambiguous by placement of an identical beacon in a different part of the pool. Test trials, in the absence of the platform and the beacons, revealed more persistent searching near the original location of the platform if the beacon attached to the platform had been ambiguous. These results show that learning about the location of the platform, with regard to cues that lie beyond the pool, is influenced by the extent to which an animal can find the platform by relying on other cues. The final experiment shows that this interaction between cues is influenced by an animal's prior experience.

Animals↗
PubMed1997

Partial reinforcement in appetitive Pavlovian conditioning with rats.

Four experiments examined the effects of a partial reinforcement schedule on extinction using appetitive Pavlovian conditioning. Extinction was slower after partial than after continuous reinforcement when the schedules were administered to different groups (Experiment 1). The opposite result was found in Experiments 2 and 3 when both schedules were presented to the same group in the same context. When the schedules were presented to the same group in different contexts, then extinction was again slower after partial reinforcement (Experiment 3). Experiment 4 demonstrated that a change of context facilitates extinction to a greater extent after conditioning with a partial reinforcement schedule than with a continuous one. The results are explained by assuming that the nonreinforced trials of a partial reinforcement schedule create an internal state that serves as a contextual cue.

Analysis of Variance↗
PubMed1997

Sudden death due to disseminated cryptococcosis in a child with leukemia in remission.

Cryptococcus neoformans typically causes an insidious illness with symptoms related to meningitis or to lung involvement. This is the first reported sudden death due to cryptococcosis, which occurred in a child with leukemia that was in remission. The child had suddenly looked seriously ill and cried with abdominal pain and then died within 25 minutes. Disseminated cryptococcal infection of the lungs, heart, and pancreas was an unexpected finding at autopsy. This clinical experience raises the question whether fungal infections should now be considered in immunosuppressed patients who have an apparent septic collapse.

Abdominal Pain↗
PubMed1996

Sigmund Freud.

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History, 19th Century↗
PubMed1996

Acquisition of conditioned inhibition in rats is impaired by ablation of serotoninergic pathways.

The effects of chronically ablating the serotoninergic inputs to various regions of the rat brain on the ability to solve a feature-negative discrimination was measured. After intracerebroventricular administration of the specific neurotoxin 5,7-dihydroxytryptamine, the rats exhibited an impaired capacity to solve such a discrimination, irrespective of whether auditory or visual stimuli were used. Further behavioural analysis revealed that this effect was not due to a reduced capacity to form excitatory associations, since both groups responded equally to reinforced stimuli. By contrast, the lesion more likely resulted in a failure to endow the non-reinforced stimuli with inhibitory properties. This suggestion was supported by the observation that, in a retardation test, the conditioned inhibitor aroused less inhibition in the lesioned group than in vehicle-injected controls. Furthermore, the conditioned inhibitor failed to pass a summation test in lesioned animals, again indicating that their hampered ability to master the discrimination was the result of an impairment in the formation of inhibitory associations. It is concluded that destruction of central 5-hydroxytryptamine-containing pathways impairs the functioning of brain areas underlying inhibitory associative learning.

5,7-Dihydroxytryptamine↗