Showing papers on "Somatosensory system published in 1974"

The Physiology of the Vestibular Nuclei

Abstract: The experiments of Goltz (1870), Mach (1873), Breuer (1891), Ewald (1892), Barany (1907) and Steinhausen (1931, 1933) can be considered as a very important first step in the development of the physiology of the vestibular system. They established a theory of the mechanics of the peripheral vestibular sensory mechanisms which is still basically valid today. The various sensory cells in the peripheral vestibular sensory organ serve as receptors for linear and angular accelerations about different axes, thus providing a three dimensionally organized sensory system for orientation in space. Various other sensory systems such as the visual, somatosensory and acoustic apparatus combine with the vestibular organs in assuring a high sensitivity for the adjustment of the body in space. Part of this regulation is achieved by means of interaction in the vestibular nuclei which integrate the activity of the various vestibular receptors as well as the activity of other sensory structures which converge directly or indirectly on the vestibular neurones. As the vertebrates developed from lower to higher forms other sensory systems such as the somatosensory and visual systems became more and more important in the regulation of posture; however, the vestibular nuclei still remain an important integrative structure that deserves the interest of anatomists as well as physiologists.

Somatotopically organized inputs from fore- and hindlimb areas of sensorimotor cortex to cerebellar Purkynĕ cells.

Abstract: The patterns of convergence of nerve and cortical inputs representing the forelimb and hindlimb were studied in Purkyně cells of the cat. The most important inputs to Purkyně cells of the pars intermedia come from peripheral nerves and the areas of the sensorimotor cortex concerned with the same limb. In lobule V, the forelimb nerve and cortical inputs are dominant, while in lobules III and IV the hindlimb inputs are dominant. Lobules IVa–Va represent a zone of hindlimb-forelimb overlap, with the nerve and cortical inputs making parallel transitions from the hindlimb dominance of IVa to the forelimb dominance of Va. Furthermore, within the nerve and cortical projections to the pars intermedia, mossy fiber and climbing fiber systems have similar projection patterns. In addition to the hindlimb-forelimb overlap in lobules IVa–Va, nearly half (44%) of the Purkyně cells throughout lobules III, IV, and V of the pars intermedia respond with weak or moderate responses to cortical or nerve inputs from the non-dominant limb, some of which are clearly important physiologically.

Somatosensory cortical involvement in responses to noxious stimulation in the cat.

Abstract: The experiment examines the role of the cerebral cortex in regulating responses to noxious stimulation by studying the effects of cortical ablations in cats on escape from electric shock applied to the foot pads. The latency of escape as a function of shock intensity was measured before and after bilateral ablations of various portions of the cat's somatosensory cerebral cortex. Ablations of the second somatosensory cerebral cortex significantly increased the escape response threshold. If the sulci bordering this region were included in the ablation, the threshold increase was greater and longer-lasting. Ablations of the primary somatosensory cortex increased latencies at most intensities of electric shock, but did not change the response thresholds. Ablations of both primary and second somatosensory cortex increased response thresholds and response latencies. None of these ablations altered the responses, however, if the cat had been overtrained for six to seven months prior to surgery. The results suggest that the second somatosensory region and the sulci bordering the second somatosensory region in the cat cerebral cortex are involved in responses to noxious stimulation.

Sympathetic Skin Nerve Activity and Skin Temperature Changes in Man

Abstract: Simultaneous recordings of skin temperature and efferent sympathetic impulse activity in cutaneous nerve fascicles were made in two healthy subjects and in one patient with paraplegia due to a transverse lesion of the spinal cord at the level of the first lumbar segment. In the patient the recordings were made below the level of the lesion in a skin area deprived of sensibility but with preserved temperature responses to indirect heating and cooling. The sympathetic nerve activity showed the same characteristics both in the paraplegic patient and in the healthy subjects. Evoked changes in sympathetic nerve activity were followed by changes in skin temperature of the same type in all three subjects. The demonstration of concomitant changes in evoked sympathetic nerve activity in a peripheral nerve and in skin temperature in the corresponding skin area strongly supports the concept that the cutaneous thermoregulatory vasomotor response (CTVR), is a consequence of changes in efferent sympathetic nerve activity. The results demonstrate that loss of somatic sensation and voluntary motor function can be combined with a functionally intact efferent sympathetic pathway below the level of a “complete” lesion of the spinal cord.

Use of sensory recombination and somatosensory deafferentation techniques in the investigation of sensory-motor integration.

Abstract: Sensory rearrangement and somatosensory deafferentation experiments are being employed in this laboratory, both singly and in combination, as complementary research strategies for elucidating the role of direct sensory feedback in the learning and performance of various categories of movement.In deafferentation experiments on adolescent monkeys, we found that movements of almost all types can be learned and performed in the absence of guidance from the periphery. Moreover, recent work with primate infants deafferented on the first day of life has demonstrated that somatosensory feedback and spinal reflexes are also not necessary, after birth, for the ontogenetic development of most types of movement performed by the forelimbs.Sensory rearrangement studies with human subjects were directed at examining prism adaptation as a learning phenomenon. One experiment showed that, in controlling the rate of performance of an operant response, decreases in the amount of lateral displacement of vision could be used a...

Relations of Peripheral Action Potentials and Cortical Evoked Potentials to the Magnitude of Sensation

Abstract: The magnitude of sensation is related to the stimulus according to Stevens’ psychophysical “power” law Ψ = k(φ − φ 0) n . Peripheral action potentials and central electric responses have both been examined for a possible parallelism. According to Mountcastle, somatosensory receptors impose the power law on the number or the frequency of impulses in the primary sensory neurons and higher-order neurons respond linearly to this input. Davis, however, found poor correspondence in auditory nerve of guinea pig, using number of active fibers as the measure.

Sensory and Perceptual Functions in the Cerebral Palsied. III. Some Visual Perceptual Relationships.

Abstract: The relationships between specific aspects of peripheral ocular defects and perceptual deficits were investigated in a cerebral palsied population. The groups included 60 spastics, 60 athetoids and a control group of 60 non-neurologically impaired subjects. Subjects were equally grouped in age ranges of 7 to 9, 10 to 12, 13 to 15, 16 to 18 and 19 to 21. Sexes were equally represented. The visual system evaluation included measures of refractive error, amblyopia, binocular fusion, muscle balance, rotational abnormalities, visual acuity, visual fields, examination of the cornea and lens for opacification, and checking of the optic nerve, retinal vessels and macula for disease. The sensory and perceptual tests included somatosensory measures, stereognosis, depth perception, limb localization, cross-modality pattern discrimination and concept formation. An estimate of intelligence was obtained by administering the non verbal Full Range Picture Vocabulary Test. Our findings suggest that cerebral palsied children and young adults vary greatly in the nature and extent of their visual system defects and that those who are identified as spastics show qualitatively and quantitatively more defects than the athetoids. The pattern of significant correlations between visual and perceptual deficits differs for the spastic and athetoid groups, perhaps reflecting the presumed differences in loci of central nervous system damage. The correlations between performance on limb localization and specific visual defects are consistent with Luria's postulation of sensory analyzers, in this instance, the visual kinesthetic analyzer.

The Effects Of Cerebellar Stimulation On the Averaged Sensory Evoked Responses in the Cat

Abstract: Although photic, auditory and somatosensory evoked responses can be recorded on the cerebellum (Snider & Stowell, 1944), and stimulations of the cerebellum can produce evoked responses in the sensory areas of the cerebral cortex (Henneman, Cooke, & Snider, 1950), it is not clearly understood what effect, if any, the cerebellum might have on the perception of sensory information at the cerebral cortical levels. Vague sensations have, however, been produced by stimulating with chronic depth electrodes in the cerebellum of awake humans (Nashold & Slaughter, 1969).

Unit responses of the somatosensory cortex of the waking cat to stimulation of the ventro-posterolateral thalamic nucleus

Abstract: Unit responses in the primary somatosensory projection cortex to stimulation of the ventro-posterolateral thalamic nucleus were investigated by extra- and intracellular recording in chronic experiments on cats. Short-latency spike responses of 71.3% of recorded neurons appeared after not more than 4 msec. It is concluded that activation of neurons in this area of the cortex is chiefly monosynaptic and disynaptic. Besides participating in the initial response to the stimulus, one-quarter of the neurons generated after-discharges 120–314 msec later. These after-discharges are based on rebound after IPSPs and additional synaptic activation. Initial inhibition may appear 1.5 msec after stimulation of the ventro-posterolateral nucleus, evidence against the participation of recurrent collaterals in the formation of these IPSPs.

SOMATOSENSORY SYSTEM. Vol. 2 of HANDBOOK OF SENSORY PHYSIOLOGY

Abstract: NEUROLOGY OF EAR, NOSE AND THROAT DISEASES By Charles H. Edwards. (Pp. 305; £6.) Butterworths: London. 1973. I have enjoyed reading this little book. It is always rewarding to learn from a colleague who has made a special study of a branch of neurology in which one feels ignorant. But it is infuriating to find major deficiencies in exactly those areas where it is useful to have a book at one's elbow. Surely one would expect to find, in a book with this title, detailed information about audiometry and loudness recruitment in neurological diagnosis. Bell's palsy is doubtfully otological, but at least one should find the best of electrodiagnostic work referred to and some guidance on the indications for surgery. Are any of the widely marketed drugs of proven value in Meniere's disease? I still do not know. This book could be so valuable. Perhaps a new edition would fill the gaps and give a better bibliography and index.

Disturbance and restoration of functions after division of spinal afferent pathways in the cat

Abstract: The possibility and degree of recovery of motor and sensory functions in cats were studied after one-stage or two-stage bilateral division of the posterior columns and spinocervical tracts at the cervical level. Blocking the afferent inflow along these systems led to severe and prolonged disturbances of sensation and motor activity and was accompanied by a sharp decrease in nociceptive sensation. Weak (6–8 V) electrical stimulation of the skin of the limbs, which evoked a primary response of maximal amplitude in intact waking animals, evoked no electrical response in the somatosensory cortex of the chordotomized animals. However, on increasing the intensity of stimulation by 2, 3, or more times, low-amplitude negative waves with a spike latency of about 15 msec, together with slow late waves, were recorded in foci of maximal activity of the cortex. Recovery of motor activity and, to some extent, of proprioception was observed 2–4 months after injury; responses to tactile stimulation were not restored. In the course of compensatory reconstruction evoked activity in the somatosensory cortex did not recover. It is concluded that the recovery of motor activity in cats after injury to the afferent systems of the spinal cord can take place despite a considerable defect of somatic sensation.