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Biomedical subjects

B L Malamut

Publications and source records attributed to B L Malamut.

7 recordsLinked to original sources
PubMed1992

Memory in a case of bilateral thalamic infarction.

The role of individual structures within the diencephalon for memory functioning is unknown. We present anatomic localization of lesions and a longitudinal neuropsychological profile of a young man who had a bilateral diencephalic stroke in the interpeduncular profundus arterial territory. MRI localized the lesions to the mamillothalamic tracts and inferior thalamic peduncle. The amnesia was characterized by severe impairment in explicit recall of new facts and events, while word-completion priming and remote memory were intact. We suggest that the memory deficit results from a disconnection of the diencephalon from the medial temporal region.

Adult↗
PubMed1989

Memory during subclinical hippocampal seizures.

We performed neuropsychological testing in 2 patients during subclinical hippocampal seizures recorded with depth electrodes. Neither subject showed impairment of consciousness, orientation, motor skills, or verbal fluency. The rapidity of recall of a well-learned word list was impaired in 1 subject during ictal fast spiking in the left hippocampus. Subclinical seizure activity may be responsible for a portion of the memory deficits found in patients with epilepsy.

Adult↗
PubMed1988

Dissociation of the effects of inferior temporal and limbic lesions on object discrimination learning with 24-h intertrial intervals.

Monkeys with bilateral ablations of the inferior temporal cortical area TE were trained on a visual discrimination task thought to measure non-cognitive habit formation. The task consisted of 20 object discriminations presented concurrently, but at the rate of only one trial on each per day; successive trials on a given discrimination were thus separated by 24-h intertrial intervals. Performance on this task by the animals with TE lesions was compared to that of both normal control monkeys and monkeys that had sustained bilateral removals of the amygdala and hippocampus. In contrast to the latter animals, which learned the 24-h intertrial interval task about as quickly as the normal controls, monkeys with area TE removals were markedly impaired. Taken together with earlier findings demonstrating that ablation of area TE impairs visual recognition memory, the present results suggest that area TE contributes not only, like limbic structures, to a cognitive memory system, but also, unlike limbic structures, to a non-cognitive habit system. Evidence is reviewed suggesting that this latter system may involve a corticostriatal circuit.

Animals↗
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↗
PubMed1977

Computer assisted tomography of focal cerebral radiation necrosis in the monkey.

The right occipital lobe in a series of pubescent monkeys was exposed to 3500 rads of orthovoltage radiation in a single dose. Sixteen to 38 weeks later the irradiated region broke down, rather abruptly. The visual evoked response, funduscopic photography, cerebral spinal fluid determinations for protein and lactic dehydrogenase, and computer assisted tomography (CAT) were used to anticipate and reflect the breakdown in neural tissue. CAT scanning demonstrated the two main effects of focal delayed radiation necrosis in this model (in a representative monkey): pronounced vasogenic edema from a break in the blood brain barrier, and contralateral hydrocephalus from brain distortion with obstruction of cerebral spinal fluid circulation. These findings were confirmed by postmortem examinations.

Animals↗