Showing papers on "Somatosensory system published in 1985"

The rat nervous system

Abstract: Vasculature O.U. Scremin, Cerebral Vascular System. Spinal Cord and Peripheral Nervous System C. Molander and G. Grant, Spinal Cord Cytoarchitecture. A. Ribeiro-da-Silva, Substantia Gelantinosa of Spinal Cord. G. Grant, Primary Afferent Projections to the Spinal Cord. D.J. Tracey, Ascending and Descending Pathways in the Spinal Cord. G. Gabella, Autonomic Nervous System. Brainstem and Cerebellum C.B. Saper, CentralAutonomic System. G. Holstege, The Basic, Somatic, and Emotional Components of the Motor System in Mammals. B.E. Jones, Reticular Formation: Cytoarchitecture, Transmitters, and Projections. A.J. Beitz, Periaqueductal Gray. G. Aston-Jones, M.T. Shipley, and R. Grzanna, The Locus Coeruleus, A5 and A7 Noradrenergic Cell Groups. J.H. Fallon and S.E. Loughlin, Substantia Nigra. J.B. Travers, Oromotor Nuclei. G. Holstege, B.F.M. Blok, and G.J. ter Horst, Brain Stem Systems Involved in the Blink Reflex, Feeding Mechanisms, and Micturition. T.J.H. Ruigrok and F. Cella, Precerebellar Nuclei and Red Nucleus. J. Voogd, Cerebellum. Forebrain R.B. Simerly, Anatomical Substrates of Hypothalamic Integration. W.E. Armstrong, Hypothalamic Supraoptic and Paraventricular Nuclei. B.J. Oldfield and M.J. McKinley, Circumventricular Organs. R.L. Jakab and C. Leranth, Septum. D.G. Amaral and M.P. Witter, Hippocampal Formation. G.F. Alheid, J.S. de Olmos, and C.A. Beltramino, Amygdala and Extended Amygdala. L. Heimer, D.S. Zahm, and G.F. Alheid, Basal Ganglia. J.L. Price, Thalamus. K. Zilles and A. Wree, Cortex: Areal and Laminar Structure. Sensory Systems D.J. Tracey and P.M.E. Waite, Somatosensory System. P.M.E. Waite and D.J. Tracey, Trigeminal Sensory System. W.D. Willis, K.N. Westlund, and S.M. Carlton, Pain. R. Norgren, Gustatory System. J.A. Rubertone, W.R. Mehler, and J. Voogd, The Vestibular Nuclear Complex. W.R. Webster, Auditory System. A.J. Sefton and B. Dreher, Visual System. M.T. Shipley, J.H. McLean, and M. Ennis, Olfactory System. Neurotransmitters G. Halliday, A. Harding, and G. Paxinos, Serotonin and Tachykinin Systems. S.E. Loughlin, F.M. Leslie, and J.H. Fallon, Endogenous Opioid Systems. L.L. Butcher, Cholinergic Neurons and Networks. O.P. Ottersen, O.P. Hjelle, K.K. Osen, and J.H. Laake, Amino Acid Transmitters. Development S.A. Bayer and J. Altman, Neurogenesis and Neuronal Migration. S.A. Bayer and J. Altman, Principles of Neurogenesis, Neuronal Migration, and Neural Circuit Formation. Subject Index.

Inferior olivary neurons in the awake cat: detection of contact and passive body displacement

Abstract: We have recorded from 306 neurons in the inferior olive of six alert cats. Most of the cats were trained to perform a simple task with the forelimb. We observed the neural responses to a wide variety of cutaneous and proprioceptive stimuli, as well as responses during spontaneous and learned active movements. Neurons responsive to somatosensory stimulation were found in all parts of the inferior olive, and they were roughly evenly divided between those responsive to cutaneous stimulation and those responsive to proprioceptive stimulation. In the dorsal accessory olive all neurons were responsive to somatosensory stimulation. In the medial accessory nucleus 88% and in the principal olive 74% of cells were responsive to somatosensory stimulation. Cells responsive to cutaneous stimulation usually had small receptive fields, commonly on the paw. These cells had low-threshold responses to one or more forms of cutaneous stimulation and typically fired one spike at the onset of the stimulus on 80% or more of stimulus applications. Cells responsive to proprioceptive stimulation most commonly responded to passive displacements of a limb. These cells were often very sensitive, responding to linear displacements of less than 1 cm in one specific direction. No cells in our sample responded reliably during active movement by the animal. Only 21% of cells responding to passive proprioceptive stimulation showed any modulation during active movement, and the modulation was weak. Likewise, cells responsive to cutaneous stimulation generally failed to respond when a similar stimulus was produced by an active movement by the animal. Exceptions to this were stimuli produced during exploratory movements or when the receptive field unexpectedly made contact with an object during active movement. Electrical stimulation applied in the inferior olive failed to evoke movements or to modify ongoing movement. Our results are consistent with the hypothesis that inferior olivary neurons function as somatic event detectors responding particularly reliably to unexpected stimuli.

Microstimulation of the primate neostriatum. II. Somatotopic organization of striatal microexcitable zones and their relation to neuronal response properties.

Abstract: Sensorimotor response properties of neostriatal neurons were characterized in conjunction with assessments of the motor effects of intrastriatal microstimulation in unanesthetized rhesus monkeys. Neuronal activity and microexcitability were assessed at 250- to 500-micron intervals and, in some cases, at 25- to 100-micron intervals. The results are based on the functional characterization of 878 putamen and 224 caudate neurons and analysis of the effects of microstimulation at each of these recording sites. Recording/stimulation sites were located between stereotaxic planes A6 and A22 in 81 microelectrode tracks from three monkeys. A total of 443 (50.4%) putamen neurons showed discrete responses to the sensorimotor examination. Of neurons with sensorimotor responses, 232 (52.4%) showed increased rates of discharge in relation to both active and passive movements of specific body parts. An additional 193 (43.6%) cells increased their rates of discharge only during the monkey's active movements of specific body parts. The remaining 18 (4.0%) cells appeared to respond exclusively to passive somatosensory stimulation. The sensorimotor response areas of putamen neurons ranged in size from an entire limb to a single joint. Putamen neurons were somatotopically organized throughout the rostrocaudal extent of the nucleus. Neurons with sensorimotor response areas involving the leg were located in the dorsolateral putamen, those with orofacial representations were located ventromedially, and those with arm representations were located in an intermediate position. Microstimulation evoked discrete movements of individual body parts at 21.6% of the 878 putamen sites. Over 95% (181/190) of the effective sites were located within the central half of the rostrocaudal extent of the putamen, between stereotaxic planes A10 and A17. The pattern of somatotopic organization revealed by microstimulation was the same as that derived from sensorimotor response properties of putamen neurons. Moreover, a close correspondence was observed between the movements evoked from a given SMZ and the functional properties of local neurons. In contrast to the results obtained in the putamen, none of the 224 stimulation sites in the caudate nucleus was microexcitable, and only 17 (7.6%) of the caudate neurons had definable sensorimotor response properties. This is consistent with the view that the primate putamen, by virtue of its anatomic connections with the sensorimotor and premotor cortical fields, is more directly involved in motor functions, whereas the caudate nucleus, by virtue of its connections with cortical "association" areas, is involved in more complex behavioral functions.

Electrical sources in human somatosensory cortex: identification by combined magnetic and potential recordings

Abstract: Magnetic fields and electrical potentials produced by neuronal activity have different properties that can be used for the identification of electrical sources in the human brain. Fields and potentials occurring 20 to 30 milliseconds after median nerve stimulation in human subjects were compared in order to investigate the sources of evoked potential components that have been attributed by different investigators to the thalamus or thalamocortical afferents, to separate radial sources in somatosensory cortex and motor cortex, or to a tangential source in somatosensory cortex. The magnetic and potential wave forms were highly similar in morphology, and their spatial distributions were centered over sensorimotor cortex, were dipolar in shape, and differed in orientation by approximately 90 degrees; distances between the minimum and maximum of the magnetic distributions were about 60 percent of those of the potential distributions. These results cannot be accounted for by thalamic sources or radial cortical sources alone, but are consistent with a tangential source in somatosensory cortex, with an additional smaller contribution from radial sources.

Optical mapping of electrical activity in rat somatosensory and visual cortex

Abstract: We have investigated the use of optical methods for monitoring neuron activity in mammalian cortex. The cortex was stained with a voltage- sensitive dye and fluorescence was simultaneously measured from 124 areas using a photodiode array. Optical signals were detected in rat somatosensory cortex in response to small whisker movements and in visual cortex in response to light flashes to the eye. Relatively large signals were obtained during focal interictal epileptiform discharges induced by bicuculline. The measuring system had a time resolution of milliseconds and a spatial resolution of a few hundred micrometers. Simultaneous, multi-site optical recordings of activity may provide a new and potentially powerful method for studying function and dysfunction in mammalian cortex.

Induction of functional retinal projections to the somatosensory system.

Abstract: Optic axons can be induced to form permanent, retinotopic connections in the auditory (medial geniculate, MG) and somatosensory (ventrobasal, VB) nuclei of the Syrian hamster thalamus; this occurs when the principal targets of retinofugal axons are ablated in newborn hamsters and alternative terminal space is created by partial deafferentation of MG or VB1–3. The experimentally induced retinal projection to the somatosensory nucleus occurs by the stabilization of an early, normally transient projection4–5. The present study was undertaken to determine whether the anomalous, stabilized retino-VB projection is functional. Newborn hamsters were operated on to produce permanent retino-VB projections and when the animals were mature, neurophysiological recordings were made in the cortical targets of VB, the first and second somatosensory cortices (SI and SII, respectively). Visual stimulation within well-defined receptive fields reliably evoked multi-unit responses in SI and SII of operated, but not normal hamsters. The representations of the visual field in SI and SII showed a partially retinotopic organization. These results demonstrate that optic tract axons can form functional synapses in the thalamic somatosensory nucleus, and suggest that neural structures which normally process information specific to one sensory modality have the potential to mediate function for other modalities.

The second sensory area in humans: evoked potential and electrical stimulation studies.

Abstract: A patient with intractable seizures originating from a right frontal focus was evaluated for surgical treatment. This evaluation was carried out using a chronically implanted array of 96 stainless steel electrodes 1 cm apart and covering the perirolandic and frontal areas. Somatosensory evoked potentials and electrical stimulation of the subdural electrodes localized the primary sensory hand area. Evoked potentials of identical waveform but of lower amplitude and 2.4 ms longer latency were recorded in the inferior frontal gyrus immediately anterior to the face area of the motor strip. Electrical stimulation of that area elicited: (1) a "paralyzing" feeling in the left arm and face; (2) inhibition of rapid alternating movements of left fingers, left hand, and tongue; (3) inability to maintain a strong voluntary muscle contraction of the left hand or tongue; and (4) speech arrest. This appears to be the first report of a secondary sensory area in humans demonstrated by both electrical stimulation and evoked potential studies. Electrical stimulation showed that the secondary sensory area overlapped an area of complex motor control, suggesting that the secondary sensory area provides direct sensory feedback information for appropriate motor integration.

A comparative analysis of the development of the primary somatosensory cortex: interspecies similarities during barrel and laminar development.

Abstract: The development of the barrels and layers II-V was examined in Nissl-stained preparations of the primary somatosensory cortex in six species- hamster, mouse, rat, gerbil, rabbit, and guinea pig–that have increasingly longer gestation periods. The barrels and layers II-V begin to differentiate postnatally during the first week postpartum in the hamster, mouse, rat, and gerbil; perinatally in the rabbit; and ∼4 weeks prenatally in the guinea pig. The structure of the barrels and layers II-V is similar at the onset of their differentiation in each species, even though there are interspecies differences in the mature structure of the barrels and layer V. The rate of the initial differentiation of the barrels and layers II-V is also similar in each species, even though there are considerable interspecies differences in the duration of the preceding period of development. In each species, layer V begins to differentiate first from the cortical plate and, within 1 or 2 days, contains sublayers that eventually disappear in the rabbit and guinea pig. About 3 days after the initial differentiation of layer V, layers II-IV begin to differentiate, seemingly simultaneously, causing the cortical plate to have a trilaminar appearance. Barrels are first evident just before the appearance of the trilaminar plate in hamsters; concomitant with the trilaminar plate in mice, rats, and guinea pigs; and just after the trilaminar plate in gerbils and rabbits. Septa appear 1 or 2 days after the barrels except in rabbits, which never have septa. Barrel maturation proceeds rapidly after the initial appearance in all species except the hamster, in which continued maturation seems to be delayed until the appearance of the trilaminar plate. The barrels in immature rats and rabbits become more prominent than they will eventually be in the adults. Our results indicate a close and rapid developmental affilation between layers II-V, especially layers II-IV, that seems quite separate from the development of layers I and VI. However, barrel development and differentiation of layers II-IV seem to be closely, but independently initiated. Secondary remodeling occurs in layer V and the barrels of some species.

Depression of cortical somatosensory evoked potentials by nitrous oxide

Abstract: The effects of the inhalation of50% nitrous oxide on somatosensory evoked potentials during a fentanyf-oxygen anaesthetic technique for central nervous system surgery were evaluated. The latency and amplitude of the first cortical wave were obtained using conventional somatosensory techniques with median or posterior tibialnerve stimulation. Data were collected before and after the inhalation of 50% nitrous oxide in oxygen introduced at the conclusion of the surgical procedure. The addition of nitrous oxide was associated with consistent decreases in the amplitude of somatosensory evoked potentials, but with no significant changes in latency. Since no electrical, physiological, or surgical event was associated with these changes, the results suggest that they were attributable to nitrous oxide per se.

Spinal cord monitoring. Electrophysiological measures of sensory and motor function during spinal surgery

Abstract: Various recording methods were tested in 60 patients who underwent scoliosis surgery to find the most suitable technique for the spinal cord monitoring and to elucidate the neuroanatomic relationship of the evoked potentials recorded by these methods. Responses were recorded from the scalp and spine after stimulation of the tibial nerve or the spinal cord. The potentials from electrodes placed over the muscles and the tibial nerve after stimulation of the spinal cord were also recorded. Epidurally recorded spinal evoked potentials after stimulation of the tibial nerve generally consisted of two major negative peaks, NI and NII, and subsequent multiple waves. NI may be mediated through the spinocerebellar tract, and NII is most likely mediated through the dorsal column. The polyphasic waves are probably conducted through the slower sensory ascending pathways. The potentials recorded from the muscle after spinal cord stimulation may be mediated through the motor tract. Various recording techniques described in this study were mutually complimentary in confirming the results of tests recorded in the technically difficult environment of the operating room. In general, spinal cord stimulation recorded from the scalp or the spine was superior to peripheral nerve stimulation in yielding better defined responses. If the potential recorded from the muscle after stimulation of the spinal cord is indeed mediated through the motor pathway, this would be useful to assess motor function during surgery.

Vibration and muscle contraction affect somatosensory evoked potentials.

Abstract: We recorded potentials evoked by specific somatosensory stimuli over peripheral nerve, spinal cord, and cerebral cortex. Vibration attenuated spinal and cerebral potentials evoked by mixed nerve and muscle spindle stimulation; in one subject that was tested, there was no effect on cutaneous input. Presynaptic inhibition of Ia input in the spinal cord and muscle spindle receptor occupancy are probably the responsible mechanisms. In contrast, muscle contraction attenuated cerebral potentials to both cutaneous and muscle spindle afferent volleys; central mechanisms modulating neurons in the dorsal columns nuclei, thalamus, or cerebral cortex are probably responsible.

Responsiveness of ventrobasal thalamic neurons after suppression of S1 cortex in the anesthetized rat

Abstract: Corticofugal influences on the responses of ventrobasal (VB) thalamic neurons to repetitive stimuli were studied in anesthetized rats by suppressing primary somatosensory (S1) electrocortical activity with topically applied lidocaine. Effective concentrations of lidocaine were confined to S1 and immediately adjacent cortex and suppressed evoked S1 responses and corticofugal discharges. Suppression of S1 cortex reduced the average number of spikes discharged by 83 VB neurons in response to each of 25 electrical somatic stimuli delivered at frequencies ranging from 1 to 50 Hz. Of 20 units studied both before and after S1 suppression, 14 (70%) showed a similar reduced response to repetitive stimuli. Cortical suppression produced no consistent changes in spontaneous activity, somatic stimulus threshold, response latency, or size of receptive field. There was no significant difference in the effect of cortical suppression on the responsiveness of 8 VB neurons to repetitive medial lemniscal, as compared to somatic, stimuli. We conclude that, in the anesthetized rat, S1 corticofugal activity facilitates somato-sensory transmission to VB neurons and that this facilitation is mediated, at least in part, by corticothalamic neurons.

Cerebral somatosensory potentials evoked by muscle stretch, cutaneous taps and electrical stimulation of peripheral nerves in the lower limbs in man

Abstract: Somatosensory cerebral evoked potentials were recorded in man to natural forms of somatosensory stimulation of the lower extremity including stretching of the muscle tendons, tapping on muscle bellies and tapping on cutaneous surfaces. These potentials were compared with those evoked by electrical stimulation of peripheral nerves measuring the amplitudes and latencies of the evoked potential components and defining the effects of stimulus variables on these parameters. Spinal cord potentials could only be detected to electrical stimuli. Mechanical stimulation of tendons and muscle bellies evoked scalp potentials at latencies earlier than those evoked by electrical stimulation of the peripheral nerve and by cutaneous stimulation at the same level of the leg. Muscle receptors, most probably muscle spindles, are the source of the short latency components obtained by the stretching of tendons and tapping on muscle bellies. The proximal location of these receptors as well as very rapid spinal conduction account for the latency difference. The potentials were larger to electrical stimulation of nerve trunks than to mechanical stimulation of tendons or skin, suggesting the asynchronous activation of a smaller number of fibres by the latter. Individuals with the largest potentials to one form of stimulation usually had the largest potentials to the other modes of stimulation. The use of physiological stimuli such as muscle stretch to test the transmission in specific neural pathways might be useful in investigating the processing of relatively selective afferent volleys using noninvasive evoked potential recordings.

Sequential activation of neurons in primate motor cortex during unrestrained forelimb movement.

Abstract: We trained monkeys to perform an unrestrained, reaching movement of the arm. Electromyogram (EMG) recordings of forelimb muscles revealed sequential activation, proximal to distal, of muscle groups involved in the task. The delay in onset of EMG activity between proximal (shoulder and elbow) and distal (wrist and finger) muscles was approximately 60 ms. We identified the neurons in the forelimb area of the contralateral motor cortex as controlling particular joints by previously defined criteria involving responses to somatosensory stimulation and effects of intracortical microstimulation. Many cells discharged prior to the onset of EMG activity acting on the appropriate joint, whereas others began firing at a later phase of the movement. The population of all proximal cells altered discharge patterns approximately 60 ms earlier than the population of distal cells. A small percentage of cells showed an initial inhibitory change in discharge frequency, and this inhibition typically occurred prior to the excitatory changes seen in the majority of cells. The results are discussed in terms of the "nested-zone" model of the forelimb motor cortex. The data support one of the predictions of this model, namely that discharges of identified cells within the cortical zones are causally related to voluntary movement at appropriate forelimb joints.

Diversity among Purkinje cells in the monkey cerebellum.

Abstract: A monoclonal antibody (B1) produced against rat embryonic forebrain membranes shows specific and striking immunohistochemical staining of Purkinje cells in the monkey cerebellum in a pattern of broad parasagittal alternating bands of cells either possessing or lacking the B1 antigen. In addition, the neurons of the deep cerebellar nuclei and some neurons of the motor cortex and of the spinal cord also contain the B1 antigen. Neurons with the B1 antigen were also seen in the somatosensory cortex, the vestibular and cochlear nuclei, and the retina.

Vibrissae tactile stimulation: (14C) 2-deoxyglucose uptake in rat brainstem, thalamus, and cortex.

Abstract: The right mystacial vibrissae of awake, adult rats were stroked at 4–6 times/second and brain regions which increased (14C) 2-deoxyglucose (2DG) uptake were mapped autoradiographically. The ventral parts of the ipsilateral spinal trigeminal nuclei pars caudalis (Sp5c), pars interpolaris (Sp5i), pars oralis (Sp5o), and the principal trigeminal sensory (Pr5) nuclei were activated. The lateral part of the ipsilateral facial (VII) nucleus (the region which innervates the vibrissae muscles) was also activated possibly via excitatory, trigeminal (Sp5c, Sp5i, Sp5o, Pr5) sensory afferents. A number of regions were activated contralateral to the sensory stimulus. Discrete patches of (14C) 2DG uptake occurred in deep layers of the superior colliculus (SCsgp). Dorsolateral and dorsomedial parts of the ventrobasal nucleus (VB), and posterior, dorsolateral parts of the reticular nucleus (R) of thalamus were activated, along with broad portions of the primary somatosensory cortex (SI) and second somatosensory cortex (SII). Though all layers of SI and SII cortex increased 2DG uptake, VB thalamic afferents to layers IV and Vc-Vla presumably accounted for the greater activation of these cortical layers during repetitive sensory stimulation of the vibrissae (RSSV). Activation of the above structures fits well with known anatomical data. However, the pattern of activation during RSSV was very different from that previously described during vibrissae motor cortex stimulation (VMIS). RSSV and VMIS both produced similar repetitive movements of all the mystacial vibrissae. However, only a few overlapping brain regions were activated during both RSSV and VMIS. These RSSV-VMIS overlap zones included Sp5o; rostral Sp5i; lateral VII; SCsgp; ventrobasal-posteromedial and ventrobasal-ventrolateral zones in thalamus; and a rostral region of SI probably anterior to the Woolsey vibrissae barrelfield in the dysgranular somatosensory (SI) cortex. Since RSSV and VMIS would both be expected to activate vibrissae proprioceptors, we have hypothesized that vibrissae proprioceptive input was processed in part in the RSSV-VMIS overlap zones. Convergence of motor-sensory inputs and other types of processing could have also occurred in these overlap zones.

The structure of the brainstem and cervical spinal cord in lungless salamanders (family plethodontidae) and its relation to feeding.

Abstract: We present an HRP study of the sensory tracts and motor nuclei associated with feeding (especially use of the tongue) in plethodontid salamanders (mainly Batrachoseps attenuatus, Bolitoglossa subpalmata, Desmognathus ochrophaeus, Eurycea bislineata, and Plethodon jordani). The nerves studied are VII (ramus hyomandibularis only), IX, X, XI, the first spinal nerve (hypoglossus), and the second spinal nerve. Two types of sensory projections are universally found in the brainstem: superficial somatosensory projections of VII, IX, and X, and deeper visceral sensory projections of IX and X to the fasciculus solitarius. The first spinal nerve and the spinal accessory nerve (XI) have no sensory projections, but the second spinal nerve has typical projections along the dorsal funiculus of the spinal cord. The motor nuclei of VII ramus hyomandibularis, IX, and X form a combined nucleus situated at the level of the IX/X root complex. The nucleus of the first spinal nerve is well separated from the combined nucleus and is situated rostral and caudal to the obex. The rostral part of the motor nucleus of the second spinal modestly overlaps that of the first. The motor nucleus of the spinal accessory nerve is more or less restricted to the region of the second spinal nerve. Its fibers leave the brain through the last root of the IX/X complex and the related ganglion. Bolitoglossine and nonbolitoglossine differ in the architecture of the spinal nuclei. Two distinct types of motor neurons occur in spinal nuclei of nonbolitoglossine species–some of those with tongue projection–but only one type is found amongthe tongue-projecting bolitoglossine group.