Biomedical subjects
Publications and source records attributed to J C Lynch.
A case of brain abscess treated non surgically is reported. Complete clinical and radiological resolution is demonstrated. The authors conclude that in selected patients conservative management of focal intracerebral infection may obviate the need for surgical intervention.
A case of temporary cortical blindness following cerebral angiography is presented and discussed. The etiology of this rare complication is not completely understood. Probably the blindness is secondary to the direct effect of the contrast medium in the blood-brain-barrier in the striate cortex.
Optokinetic nystagmus (OKN) was induced in six monkeys by rotation of a full field drum. After unilateral lesions of the inferior parietal lobule and prestriate cortex (IPL-PS lesion), three monkeys had diminished velocity of slow components when the drum rotated toward the side of the lesion. OKN slow components appeared normal when the drum rotated in the opposite direction, while fast components appeared normal in both directions. The severity of the slow component deficit was greater at higher rates of stimulus rotation than at lower ones. Recovery occurred within 7-10 days for two monkeys; no recovery was evident after 2 weeks for the third. Subsequent bilateral IPL-PS lesions in two of these monkeys reduced OKN slow phase velocity in both directions. Two monkeys with unilateral lesions limited to the inferior parietal lobule (IPL lesions) had only very mild and transient deficits lasting 1-3 days. Bilateral IPL lesions also produced only slight OKN deficits. One monkey had a lesion which destroyed most of the lateral striate cortex of one hemisphere and had no discernable OKN deficit. These results demonstrate that, in contrast to earlier reports, lesions of parieto-occipital cortex in monkeys produce deficits which are qualitatively similar to, although of shorter duration than, those OKN deficits which commonly are associated with posterior parietal damage in humans.
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In North America there are two disjunct forms of grayling, Montana and arctic, which have been separated for approximately 75,000 to 100,000 years. Electrophoretic analysis of thirty-six protein loci in these forms has revealed: (1) levels of gene duplication comparable to other salmonids, (2) a level of heterozygosity similar to other salmonids, (3) a fast and a slow evolving set of proteins, and (4) no obvious relationship between genetic variability and enzyme function. The genetic divergence between these populations may warrant subspecific designations for these two forms.
1. Experiments were made on the cortex of the inferior parietal lobule in 10 hemispheres of six alert, behaving monkeys. The electrical signs of the impulse discharges of single cortical cells were recorded as the monkeys executed tasks requiring them to fixate stationary visual targets, track those which moved slowly, and to make saccadic movements to foveate those which suddenly jumped from one locus to another within the field of view. A total of 907 neurons of area 7 were identified in terms of their physiological properties, particularly the correlation of their activity with the oculomotor components of these behavioral acts of directed visual attention; 480 of these were located by cytoarchitectural layer. Most identifiable cells of area 7 are visuomotor neurons, in a special and conditional sense. Their discharge frequencies increase before and during those steady fixations and movements of the eyes which secure and maintain foveation of objects, but only if the visual targets engaged are linked by a strong motivational drive; in our experiments, one between thirst and the light whose dimming the animal has learned to detect for liquid reward. We have identified and studied three major classes of neurons in area 7. 2. The visual fixation neurons (57%) accelerate discharge synchronously with fixation of a visual object the animal desires. The incremented discharge continues until reward, but then declines abruptly even when there is no immediate shift of the line of gaze. Fixation neurons are relatively inactive during those casual fixations by which the animal insepcts the surrounding environment. Mist fixation neurons subtend gaze fields limited to one quadrant or half of the total gaze field. The sum of the gaze fields of the fixation neurons in one hemisphere is weighted moderately toward the contralateral side. Fixation cells also discharge during slow pursuit movements in any direction so long as the movement stays within the gaze field of the neuron under study. About 40% of fixation cells are suppressed before and during saccadic movements of the eyes to a new target within the gaze field of the fixation cell. Those suppressed are located preferentially in layer V of the cortex. Suppression is maximal for saccades directed contralaterally to the hemisphere under study. 3. Visual tracking neurons are active during oculomotor pursuit of slowly moving visual objects, not during steady fixations. They show a marked directional but no laterality relation, and are suppressed before and during a visually evoked saccade superimposed on the smooth pursuit movement. The rate of discharge is a flat function of tracking speed so that these cells do not appear to emit signals which specify the speed of smooth pursuit movements. 4. The saccade neurons are active before and during visually evoked saccadic movements of the eyes but not before spontaneous saccades, no matter whether made in light or near darkness. The discharge of saccade neurons leads the eye movement by as much as 150 ms (mean, 73 ms)...
Experiments were made on the posterior parietal association cortical areas 5 and in 17 hemispheres of 11 monkeys, 6 M. mulatta and 5 M. arctoides. The electrical signs of the activity of single cortical cells were recorded with microelectrodes in waking animals as they carried out certain behavioral acts in response to a series of sensory cues. The behavioral paradigms were one for detection alone, and a second for detection plus projection of the arm to contact a stationary or moving target placed at arm's length. Of the 125 microelectrode penetrations made, 1,451 neurons were identified in terms of the correlation of their activity with the behavioral acts and their sensitivity or lack of it to sensory stimuli delivered passively; 180 were studied quantitatively. The locations of cortical neurons were identified in serial sections; 94 penetrations and 1,058 neurons were located with certainty. About two-thirds of the neurons of area 5 were activated by passive rotation of the limbs at their joints; of these, 82% were related to single, contralateral joints, 10% to two or more contralateral joints, 6% to ipsilateral, and 2% to joints on both sides of the body. A few of the latter were active during complex bodily postures. A large proportion of area 5 neurons were relatively insensitive to passive joint rotations, as compared with similar neurons of the postcentral gyrus, but were driven to high rates of discharge when the same joint was rotated during an active movement of the animal...
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
The distribution of pulvinar neurons that project to the lateral intraparietal area (LIP) and area 7a, two subregions of the inferior parietal lobule in monkeys, was determined using small injections of retrogradely transported fluorescent dyes. Both LIP and 7a received the majority of their thalamic input from contiguous but distinct zones within the medial pulvinar nucleus. Thalamocortical cell bodies that projected to LIP were arranged in a dense, horizontally oriented cluster that was sandwiched between two similar clusters of neurons that projected to 7a. There was minimal overlap of the respective clusters. LIP also received an appreciable input from the dorsal half of the lateral pulvinar nucleus, but tracer placements in 7a resulted in only occasional labeled neurons in the lateral pulvinar.
The actual and preferred methods of continuing medical education (CME) on diabetes were determined from a telephone survey of a stratified random sample of over 600 primary care physicians in Pennsylvania. A response rate of 73% was obtained. Journal articles were identified as the leading source of information that affected practice behavior related to diabetes. However, no single journal was read by a majority of physicians, and information provided in diabetes journals reached fewer than 10% of primary care physicians. Local educational programs and programs offered by hospitals were the preferred choices for continuing medical education. When reported patterns of care for diabetic patients were compared with published standards of care, no statistical differences were found between physicians who had and physicians who had not attended a CME course. To be most effective, CME courses should be intensive and may need to be presented locally to reach the widest possible audience.