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Biomedical subjects

B L Malamut

Publications and source records attributed to B L Malamut.

13 recordsLinked to original sources
PubMed1997

Outcome after temporal lobectomy in bilateral temporal lobe epilepsy.

We determined how noninvasive presurgical data relate to prognosis after temporal lobectomy in patients with independent bilateral temporal lobe (IBTL) complex partial seizures on the intracranial electroencephalogram (EEG). Between 1986 and 1994, 28 patients had IBTL seizures on intracranial EEG. Fifteen of these 28 patients underwent temporal lobectomy and 13 were not offered surgery. Of the 15 patients who had surgery, 10 patients became seizure-free. Magnetic resonance imaging (MRI) and the Wada test were the only variables associated with a seizure-free outcome. Seven of 10 seizure-free patients had a lateralized Wada result or the presence of unilateral hippocampal sclerosis, whereas none of the patients with persistent seizures had either of these findings. Variables not found to be predictive of a seizure-free outcome included location of scalp interictal spikes, degree of seizure-onset laterality, presence of early epilepsy risk factor, duration of epilepsy, and full-scale intelligence quotient. We conclude that MRI and the Wada test provide information of prognostic value in patients with bilateral temporal seizures independent of intracranial EEG data.

Adolescent↗
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↗
PubMed1984

Monkeys with combined amygdalo-hippocampal lesions succeed in object discrimination learning despite 24-hour intertrial intervals.

Monkeys with combined amygdalo-hippocampal removal show severe impairments on visual memory tasks after delays of only a minute or two, yet they learn visual discrimination habits about as quickly as normal animals with intertrial intervals of the same duration. In an attempt to resolve this discrepancy between abnormally rapid forgetting and successful retention, tests were conducted to determine whether discrimination learning would be prevented in animals with limbic lesions if intertrial intervals lasted 24 hr. The results showed that as long as the lesion did not encroach on inferior temporal cortex, the operated animals could acquire concurrent sets of 20 object discrimination habits at the same rate as normal animals, in an average of about 10 trials per set. The findings suggest that learning and retention processes are divisible into a mechanism for memory formation that is dependent on the limbic system and a mechanism for habit formation that is not.

Amygdala↗
PubMed1980

Local cerebral glucose utilization in newborn and pubescent monkeys during focal motor seizures.

The [14C]deoxyglucose method was used to determine the rate of local cerebral glucose utilization (LCGU) in newborn and pubescent monkeys during focal motor seizures induced by injecting penicillin into the face-hand area of the right motor cortex. Seizures were studied in 3 newborn and 6 pubescent monkeys, and 3 newborn and 4 pubescent monkeys were used as controls. In controls, the pattern of glucose utilization within structures of the sensorimotor system was quite differenet at the two age levels; newborns showed far less activity, especially in the neocortex and striatum. In the monkeys with seizures, the unilateral increase in LCGU relative to the controls was greater in newborn than in pubescent monkeys except in the cerebral and cerebellar cortices. The increased glucose utilization in cortical and subcortical structures of the newborns was ipsilateral to the discharging lesin and lacked the well-defined pattern seen in the pubescent monkeys. In general, newborn brain was capable of supporting a focal motor seizure but lacked the precise clinical and electrographic expressions or efficient energy metabolism that accompany maturation of the brain at puberty.

Animals↗
PubMed1980

Propagation of focal motor seizures in the pubescent monkey.

The rate of local cerebral glucose utilization was determined for quantification of energy metabolism in macrostructures of the sensorimotor system during propagation of focal motor seizures in 24-month-old monkeys. The rate was measured in 4 control animals and in 4 monkeys each with seizures limited to the contralateral face, seizures of the contralateral face and upper extremity, and bilateral expression of seizures. Glucose utilization increased significantly, primarily unilaterally, with propagation. The increase was greatest in the sensory and motor cerebral cortices, putamen, and globus pallidus, was somewhat less in sensory and motor thalamic relay nuclei, and was least in the cerebellar cortex.

Animals↗
PubMed1980

Effects of manipulation of the sensorimotor system on focal motor seizures in the monkey.

During focal motor seizures induced by injecting penicillin into the face-hand area of the right motor cortex of 24-month-old monkeys, the sensorimotor system was manipulated by three methods. Elimination, by a paralytic agent, of proprioceptive input from contracting muscles and joints did not alter the electrographic expression of the seizure or the pattern of local glucose utilization in cortical or subcortical components of the sensorimotor system. An overall increase in the rate of energy metabolism occurred in the paralyzed monkeys with electrographic seizures. Cryogenic destruction of up to 90% of the ipsilateral ventral caudal globus pallidus had no effect on electrographic or clinical expression of the seizure. Electrical stimulation of the ipsilateral ventral caudal globus pallidus caused reproducible maximum expression of electrographic and clinical seizure phenomena for the 90-second duration of the stimulus.

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↗
PubMedDate not supplied

Verbal and figural recognition memory: task development and age associations.

The goal of the present study was to develop and validate parallel tests of verbal and figural delayed-recognition memory with similar task demands and difficulty levels. Such tasks would allow examination of age differences and longitudinal age changes in visual recognition memory for two types of stimuli, activate divergent neural systems, and allow us to use the same procedures within the confines of functional neuroimaging as those we use in standard neuropsychological administration. The tasks introduced here include a delay between target presentation and test phase, are matched in difficulty, and yield moderate levels of performance. Individual and group differences in task performance were examined in 80 cognitively normal men and women in two older age groups: 60 to 69 and 70 to 85. Accuracy averaged 74% in both tasks, with lower performance in the oldest age group. Although accuracy was equivalent between tasks, subjects had a more liberal response bias in the figural than verbal task. Performance on the new recognition-memory tests was significantly related to Benton Visual Retention Test (BVRT; Benton [1963]. New York: The Psychological Corporation) and California Verbal Learning Test (CVLT; Delis, Kramer, Kaplan, & Ober [1987]. New York: The Psychological Corporation) performance measures. The absence of floor or ceiling effects, wide range of individual variability, and demonstrated concurrent validity of the present tasks suggest their potential utility in functional neuroimaging studies and in the early detection of cognitive decline.

Acoustic Stimulation↗