Showing papers on "Somatosensory system published in 1978"

Nociceptive responses of neurons in medial thalamus and their relationship to spinothalamic pathways

Abstract: 1. An extracellular study of the cat medial thalamus has revealed four types of somatosensory neurons. These were located primarily in the n. parafascicularis, n. subparafascicularis, and n. centralis lateralis; none were found in the n. centrum medianum. There was no functional segregation of neurons within each nucleus or between nuclei. Each type of neuron had large and often bilateral receptive areas. No somatotopic organization of neurons was found within the medial thalamus. 2. Noxious (N) and noxious-tap (NT) neurons comprising 72% of the sample (78 of 109 total) were considered to be nociceptive. N cells responded exclusively to noxious mechanical stimulation of skin, muscle fascia, tendons, and joints, and to direct stimulation of A-delta- and C-fiber groups in cutaneous, articular, and muscle nerves. NT cells responded to noxious and tap stimulation in a differential manner and to stimulation of the entire spectrum of A- and C-fibers. N and NT cells accurately signaled the duration of noxious mechanical stimulation. Their nociceptive responses were also graded as a function of both noxious stimulus intensity and the number of activated A-delta- and C-fibers. Stimulation of A- and C-fibers evoked, respectively, an inital burst and a late burst of discharges. A brief period of inhibition intervened between the initial and late bursts of NT cells. Prolonged afterdischarge was often observed following noxious natural stimulation or stimulation of A-delta- and C-fibers. The phenomenon of discharge "windup" was observed during iterative stimulation of C-fibers. 3. Tap (T) neurons (10%) responded only to brisk but innocuous taps applied to skin or underlying tissue. These cells were driven only by activation of A-alpha- and A-beta-fibers. The response to such stimulation was seen as an initial burst of discharges followed by an inhibitory period. 4. Inhibited (I) neurons (18%) had resting discharges that were inhibited by noxious stimuli and stimulation of A-beta- and C-fiber groups. 5. The results obtained from monitoring the peripherally evoked responses of nociceptive N and NT neurons before and after selective lesions of the spinal cord strongly suggested that the spinothalamic tracts were the only spinal projections mediating A- and C-fiber input to these cells. Each spinothalamic tract apparently carried information originating from both sides of the body.

Fundamentals of sensory physiology

Abstract: 1 General Sensory Physiology, Psychophysics- 11 Basic Concepts in General Sensory Physiology- 12 Relation Between Stimulus and Behavior Conditioned Reflex- 13 Measurement of the Intensity of Sensations Psychophysics- 14 Spatial, Temporal, and Affective Aspects of Sensation- 2 Somatovisceral Sensibility- 21 Mechanoreception- 22 Proprioception- 23 Thermoreception- 24 Visceral Sensibility- 3 Neurophysiology of Sensory Systems- 31 Transformations of Stimuli in Receptors- 32 Sensory Functions of the CNS - a Survey- 33 Properties and Operation of Sensory Neurons and Aggregates of Neurons- 34 The Somatosensory System: Spinal Cord, Ascending Pathways, and Brain Stem- 35 The Somatosensory System in Thalamus and Cortex- 36 The Sensory System in the Light of Information Theory- 4 Nociception and Pain- 41 The Qualities and Components of Pain- 42 Neurophysiology and Psychophysics of Pain- 43 Pathophysiology of Pain Special and Abnormal Forms of Pain- 44 Factors that Affect Pain Pain Therapy- 5 Physiology of Vision- 51 The Eye- 52 Psychophysics of Visual Perception- 53 Neurophysiology of Vision- 54 Eye Movements and Sensorimotor Integration in Vision- 6 Physiology of Hearing- 61 Anatomy of the Ear- 62 Auditory Performance- 63 Functions of the Middle and Inner Ears- 64 The Auditory Nerve and the Higher Stations of the Auditory Pathway- 7 Physiology of the Sense of Equilibrium- 71 Anatomy and Physiology of the Peripheral Organ- 72 Central Nervous Basis of the Sense of Equilibrium- 8 Physiology of Taste- 81 Morphology of the Organs of Taste Subjective Taste Physiology- 82 Objective Taste Physiology- 9 Physiology of Olfaction- 91 The Olfactory Mucosa Peripheral Mechanisms of Olfactory Reception- 92 Subjective Olfactory Physiology Central Connections- 10 Thirst and Hunger: General Sensations- 101 Thirst- 102 Hunger- 11 Suggested Reading- 12 Answer Key- 13 Subject Index

Short-latency somatosensory evoked potentials.

Abstract: • Short-latency components of the somatosensory evoked potential (SEP) were studied in 20 subjects who had median nerve stimulation using knee, forehead, and ear reference recordings. Six potentials were identified (P10, P12, P14, N19, P20, P23). Potential P10 seems to originate in the brachial plexus, P12 most likely is generated in dorsal column nuclei and medial lemniscus, P14 is probably thalamic in origin but is frequently bilobed and may have a second generator source, and N19 may originate in sensory radiation or cortex. The origin of P20 is unclear, and P23 appears to be generated in the contralateral somatosensory cortex. Clinically, we recommend using right, left, and bilateral median nerve stimulation at 4 Hz. Intensity of stimulus should produce at least a small thumb twitch. It was only with knee reference recording that all early potentials were seen.

Sensory and behavioral properties of neurons in posterior parietal cortex of the awake, trained monkey.

Abstract: Neurons in posterior parietal cortex of the awake, trained monkey respond to passive visual and/or somatosensory stimuli. In general, the receptive fields of these cells are large and nonspecific. When these neurons are studied during visually guided hand movements and eye movements, most of their activity can be accounted for by passive sensory stimulation. However, for some visual cells, the response to a stimulus is enhanced when it is to be the target for a saccadic eye movement. This enhancement is selective for eye movements into the visual receptive field since it does not occur with eye movements to other parts of the visual field. Cells that discharge in association with a visual fixation task have foveal receptive fields and respond to the spots of light used as fixation targets. Cells discharging selectively in association with different directions of tracking eye movements have directionally selective responses to moving visual stimuli. Every cell in our sample discharging in association with movement could be driven by passive sensory stimuli. We conclude that the activity of neurons in posterior parietal cortex is dependent on and indicative of external stimuli but not predictive of movement.

Removal of whiskers in young rats causes functional changes in cerebral cortex

Abstract: SENSORY deprivation or deafferentation has been shown to result in a variety of changes within the mammalian central nervous system (CNS)1,2. Although the majority of the studies have been anatomical in nature, recordings from cells in the visual cortex have shown that functional modifications also occur as a consequence of a deprived or abnormal visual experience in early life3–6. Moreover, alterations in neural responses are found in the somatosensory system7–9 following removal of input from the hind leg. We report here functional changes in the rat cortex resulting from early destruction of the whiskers. The region of the rat cortex receiving the sensory input from the whiskers contains aggregations of cells known as barrels and these aggregations do not develop if the corresponding whiskers are destroyed soon after birth10–13. We have found that such whisker removal also causes the associated cortical cells to become functionally reconnected with regions of the face surrounding the whiskers.

Cytoarchitecture and thalamic connectivity of third somatosensory area of cat cerebral cortex.

Abstract: 1. The third somatosensory area (SIII) was identified in the cat cerebral cortex by the recording of surface potentials evoked by deflection of a single contralateral mystacial vibrissa. A small amount of tritiated leucine was then injected at the center of the focus of evoked activity and, after a suitable survival period, the brain was prepared for autoradiography. 2. As defined by the presence of an autoradiographic injection, the SIII focus lay in a cytoarchitectonic field characterized in particular by the presence of very large pyramidal cells in layer V and corresponding to area 5a of Hassler and Muhs-Clement (24). 3. The terminal ramifications of corticothalamic cells, as outlined by axoplasmically transported label, formed clustered aggregations in the medial division of the posterior group of thalamic nuclei (Pom) and not in the ventrobasal complex (VB). This part of Pom is known to receive fibers from the spinal cord. 4. Injections of horseradish peroxidase primarily affecting area 5a retrogradely labeled cells in Pom but not in VB. 5. Injections of isotope in the two other foci of vibrissa-evoked activity usually recorded in each brain were invariably found to label a part of area 3b of the first somatosensory area (SI) in the case of the more anterior focus. The second focus sometimes lay in area 2 of SI and sometimes in the second somatosensory area (SII).

Some Anatomical Bases of Cortical Somatotopic Organization

Abstract: The evoked potential method was used to define the cortical visual, auditory and somatosensory areas in the mouse. Two somatotopic representations (SmI and SmII) were found which in general conform to

Development of Cutaneous Sensory Receptors Birds

Abstract: In recent studies, refined physiological and cytological techniques have permitted a number of precise observations to be made on the structure of peripheral cutaneous sensory receptors in vertebrates and their role in somatic sensation (for reviews, see Cauna, 1962; Quilliam and Armstrong, 1963, 1966; Polacek, 1966; Munger, 1971; Andres and During, 1973; Goglia, 1973; Schwartzkopff, 1973; Iggo, 1974; Andres, 1974).

Effect of Ethanol on Neuronal Activity in The Parietal Association Cortex of Alert Monkeys

Abstract: The effect of alcohol was studied in alert monkeys on the cellular mechanisms of the posterior parietal association cortex, a region that normally participates in visuo-spatial co-ordination of hand movements. In thirty-two experiments, the effects of intracardiac administration of ethanol were monitored by the intracortical multiple-unit recording technique. Alcohol produced rhythmic groupings of the spontaneous impulse activity; the rhythm was accentuated by closing the eyes. The dominant frequency of this rhythm (3.5 to 1 Hz) correlated inversely with the blood alcohol level. Three groups of response types were studied in Brodmann's area 7. At 8 of 12 recording sites, a close correlation was observed between the monkey's reaching accuracy and the magnitude of integrate multineuronal responses to reaching with the contralateral arm under visual guidance, or to grasping an object. Half of the 10 recording sites which were activated by complex visual stimulation also showed a close correlation with the behavioural action of alcohol. Least sensitive to alcohol were somatosensory responses; only 3 of 10 of such recording sites were influenced by moderate doses of alcohol. Larger doses producing coma increased the proportion of responses blocked by alcohol, whereas no effects were observed in the adjacent primary somatosensory cortex. Our results show that the posterior parietal association cortex is very sensitive to the action of alcohol. Moreover, these findings support the theory that the action of alcohol in various parts of the central nervous system depends on the complexity of synaptic contacts to the location under study.

Long-term effects of partial limb amputation in man.

Abstract: Ten patients with amputation of part of one arm have been studied electrophysiologically. In each patient the ulnar nerve was stimulated electrically in the amputation stump and at a corresponding level in the intact limb. Control observations were also made on 15 normal subject. In the partially-amputated (PA) limbs the amplitudes of the centripetal ulnar nerve compound action potentials, after maximal stimulation of fast-conducting fibres, were markedly reduced in comparison with the results in control limbs. A small decrease in the mean impulse conduction velocity was observed in the population of PA limbs. In comparison with control observations, stimulation of the ulnar nerve in a PA limb evoked responses in the contralateral somatosensory cortex which were significantly diminished. Simulation of PA limbs caused reflex excitation and inhibition of triceps motoneurones similar to that observed in control subjects. In the intact limbs of the amputees, however, inhibition was reduced, possibly as a consequence of overuse. It is concluded that the receipt of an input from the periphery is essential for the functional integrity of most motor and sensory nerve axons, and probably for fibres in the dorsal column-medial lemniscus pathway.

Labyrinthine and somatosensory convergence upon vestibulospinal neurons.

Abstract: In awake cats cells forming the lateral (LVST) and medial (MVST) vestibulospinal tracts were identified by employing antidromic stimulation of the spinal cord. Neuronal responses to bilateral vestibular, forelimb, hind-limb, and neck electrical nerve stimulation were analysed. Extracellular recording in the vestibular nuclei was performed via a glass micropipette saturated with Fast Green, to aid in later histological tract identification.The number of cells projecting to cervical and lumbar regions in the dorsal and ventral division of Deiters' nucleus did not differ significantly. An unexpectedly large number of MVST units was found in the descending nucleus. Some MVST units projected to the lumbar cord but in both the medial and descending nuclei, projections to the cervical cord were in majority. Almost all spinal projecting vestibular neurons received labyrinthine input and more than half received somatosensory input. The units could be separated into several populations on basis of excitatory and in...

Labyrinthine and somatosensory convergence upon vestibulo-ocular units.

Abstract: The vestibular nuclei were investigated in 18 adult cats. Vestibulo-oculo-motor neurons were identified by antidromic stimulation of the ascending medial longitudinal fasciculus (MLF). The neurons were subjected to various stimuli: vestibular, neck, forelimb and hindlimb nerve stimulation on both sides. The recording was extracellular with micropipettes containing Fast Green. Only the medial and the superior vestibular nuclei were found to project to the MLF. All projecting units had input from the labyrinths. Excitatory response latencies to ipsi-lateral labyrinth stimulation never exceeded 3 msec. Both excitatory and inhibitory response latencies could be distributed into different categories. The majority of the neurons did not receive a somatosensory input, and surprisingly few convergent units could be seen. Peripheral somatosensory information apparently plays a minor role in vestibulo-ocular relations.