Biomedical subjects

C J Oswald

Publications and source records attributed to C J Oswald.

5 recordsLinked to original sources

PubMed2001

Involvement of the entorhinal cortex in a process of attentional modulation: evidence from a novel variant of an IDS/EDS procedure.

Novel behavioral assays were used to assess the role of the entorhinal cortex in modulating attention to components of stimulus compounds. In Stage 1, rats received discrimination training with compounds constructed from 3 dimensions (auditory, visual, and tactile); in each compound the combination of components from 2 dimensions (e.g., auditory and visual) were relevant to the solution of the discrimination, and the remaining dimension (e.g., tactile) was irrelevant. In Stage 2, rats received a different discrimination in which the relevant dimensions were either congruent (auditory and visual) or incongruent (auditory and tactile) with those that were relevant in Stage 1. Sham-operated rats acquired the congruent discrimination more rapidly than the incongruent discrimination--a finding indicative of a process of attentional modulation--whereas rats with excitotoxic lesions of the entorhinal cortex acquired both discriminations equally readily.

Animals↗

PubMed2001

Excitotoxic lesions of the hippocampus leave sensory preconditioning intact: implications for models of hippocampal function.

Learning about contextual cues is markedly disrupted in rats with hippocampal lesions. One analysis of this disruption is that it reflects a general failure to form associations between the elements of complex events. A straightforward prediction of this analysis is that sensory preconditioning will be disrupted by hippocampal lesions. This prediction was assessed by presenting rats with flavored solutions composed of 2 elements (A and X) before X was paired with an injection of the emetic, lithium chloride. A subsequent test revealed that rats were less willing to consume Solution A than they were to consume a control solution, B. This was true of rats with sham lesions and those with excitotoxic lesions of hippocampus. These findings fail to support the proposition that the hippocampus-dependent deficit in contextual conditioning is due to a general disruption to the process of associating the elements of complex events.

Animals↗

PubMed2000

Identifying cortical inputs to the rat hippocampus that subserve allocentric spatial processes: a simple problem with a complex answer.

A consideration of the cortical projections to the hippocampus provides a number of candidate regions that might provide distal sensory information needed for allocentric processing. Prominent among the input regions are the entorhinal cortex, the perirhinal cortex, the postrhinal cortex, and the retrosplenial cortex. A review of these sites reveals the surprising fact that in spite of their anatomical connections, removal of the perirhinal and postrhinal cortices has little or no effect on spatial tasks and hence does not functionally disconnect the hippocampus. Extensive retrosplenial lesions have only mild effects, and even lesions of the entorhinal cortex only partially mimic the effects of hippocampal lesions upon tests of spatial memory. In contrast, studies using c-fos imaging support the involvement of the entorhinal, postrhinal, and retrosplenial cortices, but not the perirhinal cortex. It is argued that there exist multiple aspects of spatial memory, and this is reflected in the multiple routes by which cortical information can reach the hippocampus. One consequence is that lesions in a single site often have surprisingly mild effects on standard spatial tests.

Afferent Pathways↗

PubMed2000

The effects of combined lesions of the subicular complex and the entorhinal cortex on two forms of spatial navigation in the water maze.

The role of the subicular complex and entorhinal cortex (SUB-EC) in spatial learning was examined in 2 water maze experiments. In Experiment 1, rats had to locate a hidden platform that was always a fixed distance and direction from an intramaze landmark. Each day, the landmark and platform were moved to a new location. Both control and SUB-EC-lesioned rats learned to locate the platform equally readily during training. However, the control group was impaired in locating the platform when the visual extramaze cues were concealed, whereas the lesioned group was unaffected by this manipulation. In Experiment 2, the lesioned rats were impaired in finding a hidden platform that was in a fixed place in the water maze and showed no evidence of having learned its location in a probe test. These results suggest that damage to the SUB-EC impairs the integration of geometric information but spares a more general navigational-directional strategy.

Animals↗

PubMed2000

Disruption of comprehension by the meaning of irrelevant sound.

This study investigates the claim that the disruption of comprehension by irrelevant sound is qualitatively different from that of short-term memory for order. Both meaningful and meaningless speech disrupted the comprehensive aspect of the task, but the effect of meaningful speech was significantly greater. Both rehearsal and semantic processing, which are involved in reading comprehension, seem to be susceptible to disruption by irrelevant meaningful speech. The study provides some evidence to suggest that the presence of meaning in the irrelevant sound in creases disruption of performance in cognitive tasks that also call upon processing of meaning.

Humans↗