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C T Johnson

Publications and source records attributed to C T Johnson.

41 records · Page 3Linked to original sources
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Depressed excitability and integrated EEGs following hippocampal afterdischarges.

Rats with chronic hippocampal electrode implants had afterdischarges induced with electrical stimulus intensities of 115, 200, and 800% of a previously determined threshold. Afterdischarge duration, postictal EEG depression duration, and the duration of postictal electrical hypoexcitability were assessed. After discharge duration varied inversely with stimulus intensity as did the duration of postictal hypoexcitability. However, the duration of postictal EEG depression increased with stimulus intensity. This dissociation between postictal neuroexcitability and EEG depression is discussed in terms of possible underlying cholinergic mechanisms.

Animals↗
PubMedDate not supplied

Recognition memory test: validity in diffuse traumatic brain injury.

This study evaluated the validity and clinical utility of the Recognition Memory Test (RMT) as a measure of memory in severe traumatic brain injury (TBI). RMT scores for 86 TBI inpatients were related to injury severity, lesion location, and other memory indices. Only recognition memory for words (RMW) was significantly (p<0 01) related to duration of posttraumatic amnesia and a measure of "day to day" memory. Both RMT subtests showed expected modality-specific relationships with other clinical memory tasks. Patients with normal CT and right sided CT lesions tended to be more frequently impaired on recognition memory for faces (RMF) than RMW.

Journal Article↗
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Disruption of learned and spontaneous alternation in the rat by trimethyltin: chronic effects.

Trimethyltin (TMT) is a known neurotoxin which produces behavioral anomalies including hyperactivity, aggressiveness, perseveration, and learning deficits. These dysfunctions appear to be related to a severe loss of neurons in the hippocampal formation of the TMT-treated rat. In order to assess the effect of TMT exposure upon spontaneous and learned alternation, male Long-Evans rats were pretested for reinforced spontaneous alternation and then treated with either 7 mg/kg of TMT [( CH3]3SnCl) or the 0.9% NaCl vehicle. After treatment these groups were further subdivided and half of each group was tested in a "T" maze for reinforced spontaneous alternation while the remainder was tested for learned alternation. The TMT-treated rats uniformly ran faster on the second choice of reinforced spontaneous alternation tests than did controls. In addition, the TMT-treated rats made fewer alternations than controls, regardless of whether or not only successful alternations were being reinforced. These results are discussed in light of the known neurobehavioral consequences of TMT exposure.

Animals↗