Biomedical subjects
Publications and source records attributed to J Olds.
This review of 43 cases of infective endocarditis (IE) treated at a large Iowa community hospital reveals an incidence of 9 cases per 22,000 annual admission. IE is most likely to occur in an elderly male with non-specific symptoms and signs and involvement of the mitral valve infected with streptococci.
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In Experiment 1, groups of hippocampal and control rats learned a simultaneous discrimination habit and were subsequently tested for its retention under variable contextual conditions. All groups recalled the discrimination response to an equally high level when testing conditions were constant throughout, but the hippocampal group showed impaired memory when contextual stimuli at recall testing did not conform to those of original learning. Experiment 2 indicated that the hippocampal impairment was not simply the result of introducing novel stimuli. In Experimental 3, animals were administered a reversal learning task with contextual stimuli varied between the two tests. The typically observed impairment of hippocampal animals on this task was reduced by contrasting contextual conditions. The data are seen to support a contex-tetrieval interpretation of hippocampal function.
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In behaving rats, unit activity recorded from the ventral tegmentum and from the reticular formation was monitored during classical conditioning. Rewarding electric stimulation of the medial forebrain bundle was used as the unconditioned stimulus (UCS). Only those cells possessing prior responses to the conditioned stimulus (CS) changed their responses as a result of conditioning. Responses recorded from cells which were driven by both the auditory CS and the brain shock UCS were significantly more often changed than those driven by the CS alohe. These data show that the auditory and brain shock fields of influence interact in at least some brain regions prior to conditioning and that pairing the two kinds of stimuli is more likely to influence auditory responses recorded from these regions than those recorded elsewhere. It is possible to imagine that the intersection of the two fields is a sine qua non of conditioning and that the two prior actions caused the change by interacting at or near the recording point.
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The aim is to find some switches in the brain and to characterize them if possible as either temporary and requiring some reverberatory process or as more stable and structural. There were five assumptions involved; (a) that the very large population of neurons in the brain could be effectively sampled in a limited set of experiments; (b) that a middle kind of electrodes could direct themselves to a sufficiently stable single unit population to permit extended conditioning experiments: (c) that averaging could be used to eliminate the effects of all unwanted variables that were not correlated with the main auditory signals: (d) that latency mapping would permit the tracing of a signal even through the multiple-channeled pathways of the brain (and would help us to identify switching points; (e) that a middle kind of conditioning (not Pavlovian entirely nor Slinner experiment with the clear CS of a Pavlovian one...