Showing papers on "Somatosensory system published in 1968"

Somatosensory evoked responses in multiple sclerosis patients with varying sensory loss

Abstract: IT IS GENERALLY ACCEPTED that symptoms in multiple sclerosis are produced by blocked or impaired nerve conduction across areas of demyelination. Charcot' was the first to suggest such impaired or slowed conduction as the basic pathophysiology of this disease, yet few investigators have attempted to demonstrate this mechanism in man or in lower animals. McDonald,2 Meyer? and Hall,4 each using different methods to produce experimental demyelination of central and peripheral axons, have only recently derived experimental evidence that supports Charcot's earlier speculations. Our own interests have been with the use of the somatosensory cortical evoked response in multiple sclerosis patients. I t has been previously shown and confirmed in our own laboratory that the somatosensory evoked response is abnormal in disease states in which there is impairment of position or vibration sense or both. Since these deficits are frequently present in multiple sclerosis, it was felt appropriate to use this type of evoked response as a means of assessing subcortical conduction phenomena in these patients.

Somatomotor and Somatosensory: Median Nerve Stimulation in Man

Abstract: SINCE 1947, when Dawson 1 described a method which made it possible to record somatosensory evoked cortical potentials from the human scalp by means of a computeraveraging technique, there has been considerable interest in the broader applications of these methods. Recent studies by Bickford and associates 2 have focused attention on the occurrence of evoked motor responses in association with the more classical potentials of cortical origin. Widespread myogenic responses, below movement threshold, to sound and to photic stimulation have been described and have been named the "sonomotor response" and the "photomotor response," respectively. The contaminating effect that these potentials can have on evoked responses recorded from the scalp and the difficulties of their separation have already been stressed. This report describes the myogenic potentials resulting from median nerve stimulation and illustrates how these responses also may contaminate scalp-recorded somatosensory evoked responses. 3 In addition, studies undertaken to

A single unit analysis of trigeminal projections to bulbar reticular muclei of the rat

Abstract: The lateral bulbar reticular formation of anesthetized rats was explored with microelectrodes in order to compare the response and field characteristics of its somatosensory cells with properties of units located in the adjacent spinal trigeminal complex. Responses were evoked in the cells using natural and electrical stimulation of the skin. Neurons in the reticular nuclei tended to exihibit long latencies, low folowing capacities and large receptive fields. On the other hand, trigeminal complex cells generally revealed opposite characteristics, more typical of primary sensory structures, such as short latencies, high following capacities and punctate-to-small fields. The distinction between the regions was emphasized by additional qualities which were peculiar to the reticular neurons: Bilateral peripheral representation, into very coarse mechnical stimulation. In amny respects, the data indicate that the lateral reticular formation is intimately involved in the mediation of facial pain. They also support the view that it participated in this function by regulating the flow of nocioceptive activity from receptive mechanisms of the skin to the lemniscal pathway.

An investigation of pyramidal tract cells in the somatosensory cortex of the rat

Abstract: 1. An electrophysiological study has been made of pyramidal tract (PT) cells in the somatosensory cortex of the rat; the axons of the cells were shown to project either to the dorsal column nuclei or to the corticospinal tract. 2. The corticospinal axons had conduction velocities of 7·6-10·8 m/sec. and therefore must have belonged to the large population of PT axons with relatively small diameters. 3. PT cells constituted almost a quarter of the units encountered; they were distributed throughout the forepaw area within the deeper layers of the cortex. 4. The sizes of the receptive fields of PT cells varied widely and did not differ significantly from those of non-PT cells. 5. The latencies of PT cell discharges following peripheral stimulation showed less variation than those of non-PT cells though the mean latencies were identical. 6. Most PT cells could be driven from the periphery and exhibited spontaneous activity in addition; they therefore function to maintain a continuous control over the somatosensory input to the brain which can be increased whenever the skin is stimulated.

The specific somatosensory system and dyskinesia.

Abstract: SEVERAL hypotheses have been proposed for the mechanism of abnormal movements, with the greatest emphasis placed upon the role of central structures. 1-3 While the importance of muscle afferents has also been stressed, 4 little attention has been paid to other peripheral receptors. However, observations made during a series of stereotactic thalamotomies suggest that impulses transmitted over the specific somatosensory pathways are also concerned in dyskinesia. Materials and Methods Cortical and subcortical potentials evoked by transcutaneous electrical stimulation of the median nerve were recorded during 42 stereotactic thalamotomies in patients with dyskinesia. The cortical responses were detected by pin electrodes placed in the scalp, and the depth responses by concentric, bipolar, Teflon insulated, stainless steel electrodes with an outer diameter of 1.4 mm and tip separation of 0.5 mm. An averaging computer was used to retrieve the evoked potentials. 5 The electrodes were directed toward nucleus ventralis posterior lateralis

Discharges from somatosensory cortical neurons as an index of after-phenomena

Abstract: The latent period of the s ingle-uni t response in the p r imary project ion zone of the somatosensory cor tex of a cat anesthet ized with Nembutal to e l ec t r i ca l s t imulat ion of fore l imb ne rves does not exceed 60 r e se t , and the spike response of the neuron ends not l a te r than 100 msec after application of the s t imulus. Somet imes , bes ides thei r immedia te par t ic ipat ion in the response to s t imulat ion, cor t ica l neurons exhibit secondary responses associa ted with st imulation. This paper desc r ibes p roper t i es of these secondary responses and d i scusses their possible physiological s ignificance.