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Biomedical subjects

R B Glassman

Publications and source records attributed to R B Glassman.

At least 19 recordsLinked to original sources
PubMed1994

Behavioral effects of SI versus SII cortex ablations on tactile orientation-localization and postural reflexes of rats.

Ten rats were observed, before and after selective unilateral ablation of the SI and/or SII cortical area, for the ability to turn toward tactile stimuli to head, limbs, or trunk. Placing and hopping postural reflexes were also observed. SI damage caused greater contralateral deficits than SII damage in all these behavioral measures; combined ablation of SI plus SII caused the greatest contralateral deficits in all measures. Partial recovery of all behaviors was observed during six postoperative test sessions, spanning 2 months. In contrast to these rats, cats studied in earlier experiments in this laboratory had shown a double dissociation, with SI damage followed by contralateral deficits in posture and movement but not passive touch, and damage to SII plus subjacent cortex by contralateral deficits in passive touch but only very small deficits in posture and movement. In other species comparisons, normal rats oriented as vigorously as do cats to tactile cues and, like cats, showed tactile responsiveness in orientation-localization greater rostrally than caudally. In both species wrong-way orientations were occasionally observed during the early postoperative period following the largest unilateral lesions. Unoperated albino rats oriented much less readily than do unoperated cats toward appetitive auditory or visual cues signaling availability of food. An accompanying theoretical review paper further examines the nature of passive and active touch in terms of these and other comparative findings.

Animals↗
PubMed1994

Behavioral specializations of SI and SII cortex: a comparative examination of the neural logic of touch in rats, cats, and other mammals.

In what ways do passive touch and active touch require particular properties of cortical physiology? Because it is not easy to make predictions "bottom up" from neurophysiology and anatomy to behavior, there have been surprises in studying behavioral deficits following selective ablations of SI versus SII. For example, in earlier research on cats, unilateral ablation of SI unexpectedly had no effect on passive touch but did cause contralateral losses in posture and movement; it was ablation of SII plus subjacent cortex that led to contralateral losses in passive touch. In contrast, in a recent experiment with rats unilateral ablation of either SI or SII caused contralateral losses both in touch and postural reflexes. Some of the literature on dogs, monkeys, and humans suggests similarities with cats. To better understand these comparative findings, the following theoretical factors are considered: the degree of diffuseness versus specificity in brain input-output relations demanded or permitted by a behavior, the spatial and temporal scales of a behavior, the species' degree of encephalization, the need for stimulus generalization or functional equivalence of movements, and the relative sizes and sensitivities of different parts of the body. Hypotheses are also offered about why the evolution in rats of shortened forelimbs and increased vibrissal function may have entailed a peculiar compromise between active and passive touch and between functions of SI and SII.

Animals↗
PubMed1994

Spatial working memory score of humans in a large radial maze, similar to published score of rats, implies capacity close to the magical number 7 +/- 22.

To compare the working memory (WM) capacity of humans to rats, we tested humans with a 17-arm radial maze and, in a follow up experiment, with a 13-arm radial maze. Both mazes were 15.2 meters in diameter, painted on a grassy field. In one version of the 13-arm experiment, we required a concurrent nonsense vocalization to impede subjects' use of language to remember locations. Subjects were instructed to choose arms of the radial maze unsystematically--as rats generally appear to do--and to visit the end of each arm only once. In additional procedures, we tested working memory capacity in a verbal task that is more analogous to the radial maze than is the typical ordered recall test. Subjects were asked to try to recite a sequence of 17 numbers (i.e., 18 through 34) or letters (A through Q) in unsystematic order, with no repeats. In another experiment subjects recited 13 numbers (14-26) or letters (A-M). In all tests, subjects were allowed only as many responses as there were distinct items (17 or 13, respectively). Average correct-response (nonrepeat) scores were 14.4 for the 17-arm maze and 14.1 for both of the verbal 17-item tests; these scores are close to the reported score for rats in a 17-arm radial maze. Average scores were between 10.8 and 11.4 in all of the 13-item maze and recitation tasks.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Human performance with a seventeen-arm radial maze analog.

Results using radial mazes suggest rats may have a greater short-term memory (STM) capacity than the human "magical number seven." We examined spatial STM in humans using a radial maze analog drawn on paper. Subjects were instructed to lift, in "random" order, each of 17 cardboard flaps arranged radially around a center point. Fifteen undergraduate subjects, tested seven trials a day on 2 consecutive days, averaged 15.4 correct choices per trial. Thus, humans perform equally well on a 17-arm radial maze analog as rats do on a 17-arm radial maze, suggesting comparable spatial STM capacities, and perhaps homologous brain substrates for these tasks, in these two species.

Adult↗
PubMed1987

An hypothesis about redundancy and reliability in the brains of higher species: analogies with genes, internal organs, and engineering systems.

The phenomena of behavioral resistance to massive brain damage and behavioral recovery from brain damage suggest there is redundancy in neural tissue. This paper uses basic concepts from probability theory and reliability engineering, as a first step toward more rigorously establishing the plausibility of the redundancy hypothesis. Exponential effects in the relevant formulas lead to results that are intuitively surprising. Thus, within a broad range of parametric assumptions related to lifespan and number of neurons or neural subsystems, it appears that the human brain may be at least twice as large as it would have to be for short-term survival. Simple reliability models suggest that redundancies are in parallel connections of smallest subsystems, such as individual neurons. Other implications of the basic formulas concern the relation between backed-up subsystem reliability and lifetime usage frequency for each subsystem, and the evolution of approximately equal allocation of lifetime reliability among components of a system. In addition, the paper briefly reviews more complex reliability engineering approaches. Redundancy as a reason for neural mass action is compared to other theoretical reasons for mass action in sensorimotor function and learning. Relationships of the present hypothesis to other theories of recovery from brain damage and to theories of regressive trophic phenomena in ontogeny are briefly discussed; it is suggested that as stages of ontogeny progress, both redundancy and flexibility in simpler behavioral functions are traded away for a larger, more differentiated repertoire of complex functions and memories.

Animals↗
PubMed1982

Failure to find electrophysiological correlates of chronic neuroleptic-induced oral dyskinesias in cats: somatosensory and substantia nigra evoked potentials, electroencephalogram, and caudate spindles.

Each of nine cats was prepared with 30 chronically implanted stainless steel gross electrodes in cortex, basal ganglia and other brain structures. Measurements were taken for 0.5-11.5 months of baseline, chronic daily administration of chlorpromazine, and withdrawal. In most cases there was also a second cycle of drug administration and withdrawal. Although we observed dramatic, persistent increases in licking behavior, suggestive of tardive dyskinesia, consistent correlated patterns were not observed in somatosensory or substantia nigra evoked potentials, electroencephalogram, or spindling evoked in cortex by caudate stimulation.

Animals↗
PubMed1980

Oral dyskinesia in brain-damaged rats withdrawn from a neuroleptic: implication for models of tardive dyskinesia.

Rats with ablated frontal sensorimotor cortex and one with ablated sensorimotor connections to forebrain showed more vacuous chewing movements following 6-week chronic administration of a neuroleptic than did occipitally damaged rats or normal controls who were treated in the same way. The effect was still present 1 month after withdrawal. It was not clearly enhanced by subsequent treatments. Other behaviors (e.g., walking, rearing, or grooming) were not similarly affected by drug withdrawal. Additional results of terminal probes with amphetamine, apormorphine, and haloperidol are described, including movements labeled 'sham eating', observed only in frontal rats given apomorphine (AP). The results are interpreted in terms of a Jacksonina model of levels of brain organization; such a model may be applicable to tardive dyskinesia, seen in many schizophrenic patients who are maintained on neuroleptics for long periods.

Amphetamine↗
PubMed1977

Does the brain actively maintain itself?

All living systems have special mechanisms for combatting entropy; however, the brain has dimensions of organized complexity beyong those manifest in the anatomical structure and physiology of the rest of the body. Reasons are given in support of the notion that the brain therefore must have a special, intrinsic "homeostatic" system for its information bearing structures, and, further, that slow electroencephalographic activity has properties which might make it useful for such an order-maintaining function. Recovery from brain damage is hypothesized to be a byproduct of this process, which may involve a cruder sort of information processing than occurs with such functions as perception and learning. Synchronized EEG activity may be adequate to handle this sort of information processing. Speculations are offered about possible mechanics, on the neuronal level, of slow wave participation in plasticity; for example, one such suggestion is based on findings that electrical fields can influence cellular orientation. The methodology of discovering the distribution within the brain of the hypothetical maintenance system is discussed briefly.

Animals↗
PubMed1976

A neural systems theory of schizophrenia and tardive dyskinesia.

Some systems ideas applied to individual persons are used to try to explain symptoms of schizophrenia and a syndrome of uncontrolled fragments of movement which sometimes occurs as a side effect of chronic, antipsychotic drug therapy. The behavior of normal organisms may be conceptualized in three echelons of control, with each successively higher echelon organizing, by selective disinhibition, semiautonomous, spontaneous fragments of activity which comprise the next lower echelon. It is hypothesized that schizophrenia involves a deficiency of inhibition by the frontal cortex, first echelon, on the corpus striatum, second echelon. This results first in insufficiently integrated fragments of behavior, and second in premature associative linkages among active elements. First echelon control develops as a normal person matures and gradually loses some of the playful activities of childhood. It is hypothesized that by disrupting certain aspects of activity in the corpus striatum, neuroleptic drugs reduce schizophrenic symptoms but also reduce the capacity of the second echelon to inhibit and integrate the smaller behavioral fragments wired into lower parts of the brain, third echelon. This results in uncontrolled movements. Though many researchers already favor the hypothesis that neuroleptic drugs act on the corpus striatum, the broader theory presented here is new and depends in large part on general living systems considerations. Emphasis is on conceptual decomposition of the integrated behavior of a whole organism into less complex subsystems. Individually, these have neither too much nor too little complexity to yield a plausible model. Some experimental predictions and predictions about possible therapies are made from the theory.

Corpus Striatum↗