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Biomedical subjects

C L Wilson

Publications and source records attributed to C L Wilson.

At least 109 records · Page 6Linked to original sources
PubMed1985

Human medial temporal-lobe stimulation disrupts both formation and retrieval of recent memories.

Disrupting medial temporal-lobe (MTL) activity for less than a second, either during the initial presentation of a complex scene or when it is presented again 1 min later, severely impairs recognition at the second presentation. MTL disruption during both presentation and recognition periods produces further impairment. These results are not consistent with views limiting MTL function solely to encoding or solely to retrieval mechanisms.

Amygdala↗
PubMed1984

Habituation of human limbic neuronal response to sensory stimulation.

Hippocampal, parahippocampal gyrus, and amygdalar neuronal responses to visual and acoustic stimuli were analyzed during trains of several hundred stimulus repetitions as part of an investigation of sensory pathways to medial temporal lobe structures in complex-partial epilepsy patients who were being monitored with depth electrodes. Ten percent of more than 500 single and multiple units tested were responsive to simple sensory stimuli. The majority of the responsive units were recorded in the posterior parahippocampal gyrus (HG) during visual stimulation. Although neurons in pes hippocampi (PH; Ammons's horn) were also responsive to photic stimuli, no visually responsive units were found in amygdala. Very few units were responsive to acoustic stimuli, and these were found only in PH and amygdala, and not in HG. Significant trends of increase or decrease in response amplitude during trains of stimuli were found in all acoustically responsive units. Significant trends of visual response amplitude increase or decrease were found in 20% of PH units, and in 44% of HG units. Mean latencies of acoustically responsive units were longer than those of visually responsive units, and latencies of PH sensory units showing decremental response were longer than nondecremental PH units. Rate of response decrement was usually linear for acoustic responses and exponential for visual responses. The response dynamics of medial temporal lobe neurons are compared with those described in the animal limbic system and are related to habituation of human sensory evoked scalp potentials.

Acoustic Stimulation↗
PubMed1983

Visual receptive fields and response properties of neurons in human temporal lobe and visual pathways.

Recordings were made from depth electrodes placed in medial temporal and occipital lobes for the localization of seizure foci in patients with medically intractable psychomotor epilepsy. Electrodes were located in the amygdala and at three rostrocaudal levels of the hippocampal formation including the posterior hippocampal gyrus, which lies medial to the portion of the geniculostriate pathway which passes through the temporal lobe. 1. Approximately 10 per cent of single units recorded from microelectrodes chronically implanted in medial temporal sites were visually responsive. Some of the units in the posterior hippocampal gyrus displayed receptive field characteristics similar to those reported in lower primates, including circular or linear shape, monocular or binocular response, variable (1 to 10 deg) receptive field size, retinotopic organization and sustained or transient response. 2. Visually responsive units were also recorded from lateral geniculate nucleus, pulvinar nucleus and occipital cortex, and their basic response form and latencies compared with the short latency visually responsive cells in medial temporal lobe. 3. The heterogeneity of receptive field characteristics in the medial temporal lobe is consistent with the existence of more than one visual input to this region, while their retinotopic relationship differentiates these receptive fields from those of units studied in the inferior temporal lobe of lower primates. 4. Properties of visual pathways in this region are discussed in relation to several types of temporal lobe function and to memory. Recordings from these neurons offer a rare opportunity for comparison of central visual response properties and receptive field characteristics of humans with those reported in animal studies.

Adult↗
PubMed1983

Energy accounting.

Explore the source record for details and available documents.

Conservation of Energy Resources↗
PubMed1982

Asymmetry and ventral course of the human geniculostriate pathway as determined by hippocampal visual evoked potentials and subsequent visual field defects after temporal lobectomy.

Twenty-two patients with psychomotor epilepsy were implanted with depth electrodes along the axis of the mesial temporal lobe to identify an operable unilateral epileptic focus. Neuronal and field potentials were recorded in response to diffuse retinal illumination and clear short-latency responses were found in parahippocampal gyrus. These visual afferents in the mesial temporal lobe are assumed to be both from subcortical and cortical visual areas. There was a clear asymmetry in the ventral trajectory of the geniculostriate pathway as evidenced by asymmetric neuronal and field potential responses to brief flashes in right vs. left hippocampal gyrus and confirmed by a corresponding partial visual field deficit following therapeutic anterior temporal lobectomy. These results demonstrate that there is a retinotopic organization of fibers in the human geniculostriate pathway and that this pathway may have considerable variability in the anterior and ventral course these fibers take through the temporal lobe. These findings adequately account for the presence of direct projections from geniculate to hippocampal cortex and for unexpected hemianopsias with standard resections of the temporal lobe when there is a deviant detour of the geniculostriate pathway.

Dominance, Cerebral↗
PubMed1982

Brain generators of evoked potentials: the late (endogenous) components.

Locating the synapses which generate endogenous potential components recorded at the scalp would permit some aspects of the neural activity directly underlying cognition to be probed non-invasively. Knowing which synapses are functioning abnormally in certain neurological and psychiatric diseases may suggest rational treatment strategies aimed at local brain regions. Although it is not possible to localize the generating synapses using scalp topography, large potentials can be recorded in the hippocampal formation during the same task conditions which evoke scalp endogenous potentials. Phase-reversal of these hippocampal potentials over short distances, accompanied by changes in simultaneously recorded unit-activity, indicates that they are generated locally. Demonstration that they volume-conduct to the scalp would, however, require observation of lesion effects, and recordings from other candidate structures, as well as a realistic model for propagation.

Afferent Pathways↗
PubMed1981

Aversion to the reinforcer differentially affects conditioned reinforcement and instrumental responding.

Rats were trained to press a bar for sucrose solution delivered by a dipper; they then received pairings of sucrose and lithium chloride (LiCl) in the home cage and were tested for bar pressing. In the first and second experiments, the conditioned aversion to sucrose had no effect on unreinforced bar pressing in the test, but the aversion reduced bar pressing reinforced either by sucrose or by the operation of the empty dipper. In the third and fourth experiments, presses during training were reinforced by sucrose only in the presence of an audiovisual discriminative stimulus; in the test, the aversion to sucrose reduced pressing reinforced by the discriminative stimulus, but the aversion had no effect on unreinforced pressing in either the presence or the absence of the discriminative stimulus. Thus, pairings of sucrose and LiCl reduced the reinforcing value of sucrose and also of a stimulus previously paired with sucrose, but they had no effect of an instrumental response previously reinforced by sucrose or on the discriminative properties of a stimulus paired with sucrose.

Animals↗
PubMed1980

A circuit for safe diagnostic electrical stimulation of the human brain.

An electronic circuit for controlled electrical stimulation of the human brain has been designed to optimize safety in charge transfer from electrodes to brain and to eliminate the likelihood of unwanted currents from the neurostimulator resulting from component failure. The circuit schematics feature the following designs: (1) a highly accurate and versatile rate generator 0.5 p.p.s. to 99 in increments of 0.5 p.p.s., (2) symmetrically-biphasic lead and lag pulses of 100 musec duration, (3) photo-isolated driver amplifiers with accurate waveform, reproduction, (4) true biphasic passive-current regulators driven by an isolated battery supply voltage for switch-selectable currents of 0.25 to 5 ma or variable current regulation, (5) accurate current and voltage waveform monitors that isolate the stimulating electrodes from the monitors, and (6) capacity-coupled outputs to guarantee no net D.C. component at the end of each biphasic pulse. Relay-switching circuits are also shown that allow sequential stimulation and recording from one or several electrodes. This neurostimulator has been in use for over two years without evidence of electrolytic damage at identifiable electrode tips. The utility of simultaneous stimulation of several different electrodes at safe charge levels is described.

Amygdala↗
PubMed1979

Cytochemical and biochemical identification of lysosomes in Cryptococcus neoformans.

Normaski optics, fluorescence and electron microscopy were employed to demonstrate the occurrence of lysosomes in capsulated, enztmatically decapsulated, and dewalled cells of a human isolate of Cryptococcus neoformans. Fluorescent studies, using acridine orange as a lysosomal indicator, revealed the presence of variously sized, spherical, reddish-orange fluorescing bodies. Electron microscopy studies demonstrated the presence of acid phosphatase (AP), a lysosome marker enzyme, in single-membrane bound organelles. Lysosomes were removed from dewalled cells and separated by differential centrifugation on ficoll gradients. That fraction indicating the highest assay for AP was centrifuged at high speed, and the resulting pellet was fixed for electron microscopy and stained by the Gomori procedure for AP. Sections of the pellets revealed AP stained vesicles of the same size range as those within intact cells.

Cryptococcus↗
PubMed1979

Surgical treatment of anomalous left coronary artery from pulmonary artery: follow-up in teenagers and adults.

To determine which method of surgical therapy might be optimal for patients with anomalous left coronary artery from the pulmonary artery (ALCAPA), a follow-up study was performed. Twenty-nine teenagers and adults who had ALCAPA diagnosed during life at age 13 years or older were identified mainly by literature search. Recent follow-up was obtained on all. Thirteen treated by ALCAPA ligation alone (Group A), were followed a mean of 9.2 years postoperately (range 1 to 15 years). There was no operative mortality. Three Group A patients died suddenly; a mean of five years (range 2 to 7 years) postoperatively. Sixteen patients treated by simultaneous ALCAPA ligation and saphenous vein graft (SVG) from aorta to left coronary artery (Group B) were followed a mean of five years (range 0 to 11 years) with one intraoperative death and no late mortality. Using the generalized Wilcoxon test for single censored samples, there was no significant difference in survival at any postoperative year when comparing both Groups A and B. The late appearance of sudden death in three Group A patients and no late deaths in Group B patients suggests that ligation and SVG, or its equivalent, may be the therapy of choice.

Adolescent↗
PubMed1978

Recurrent atrial fibrillation with nausea and vomiting.

Atrial fibrillation occurred twice during episodes of severe nausea and vomiting in a previously healthy 40-year-old male with new onset of Meniere's syndrome (tinnitus, vertigo, deafness). No organic cause was identified to explain the arrhythmia. Holter monitoring, maximal treadmill stress testing, and sinus node recovery times were normal. Intense vagal stimulation, subsequent bradycardia, and dispersion of atrial tissue refractory period is the likely explanation for this arrhythmia.

Atrial Fibrillation↗