Showing papers on "Somatosensory system published in 1990"

Postural strategies associated with somatosensory and vestibular loss.

Abstract: This study examines the roles of somatosensory and vestibular information in the coordination of postural responses. The role of somatosensory information was examined by comparing postural responses of healthy control subjects prior to and following somatosensory loss due to hypoxic anesthesia of the feet and ankles. The role of vestibular information was evaluated by comparing the postural responses of control subjects and patients with bilateral vestibular loss. Postural responses were quantified by measuring 1) spatial and temporal characteristics of leg and trunk EMG activation; 2) ankle, knee, and hip joint kinematics, and 3) surface forces in response to anterior and posterior surface translations under different visual and surface conditions. Results showed that neither vestibular nor somatosensory loss resulted in delayed or disorganized postural responses. However, both types of sensory deficits altered the type of postural response selected under a given set of conditions. Somatosensory loss resulted in an increased hip strategy for postural correction, similar to the movement strategy used by control subjects while standing across a shortened surface. Vestibular loss resulted in a normal ankle strategy but lack of a hip strategy, even when required for the task of maintaining equilibrium on a shortened surface. Neither somatosensory nor vestibular loss resulted in difficulty in utilizing remaining sensory information for orientation during quiet stance. These results support the hypothesis that cutaneous and joint somatosensory information from the feet and ankles may play an important role in assuring that the form of postural movements are appropriate for the current biomechanical constraints of the surface and/or foot. The results also suggest that vestibular information is necessary in controlling equilibrium in a task requiring use of the hip strategy. Thus, both somatosensory and vestibular sensory information play important roles in the selection of postural movement strategies appropriate for their environmental contexts.

Vestibular neurones in the parieto‐insular cortex of monkeys (Macaca fascicularis): visual and neck receptor responses.

Abstract: 1. One hundred and fifty-two vestibularly activated neurones were recorded in the parieto-insular vestibular cortex (PIVC) of four awake Java monkeys (Macaca fascicularis): sixty-two were tested systematically with visual stimulation and seventy-nine were tested with various somatosensory stimuli. With very few exceptions all vestibular neurones tested responded to visual and somatosensory stimulation, therefore being classified as polymodal vestibular units. 2. A most effective stimulus for all fifty-eight visually activated PIVC units was movement of a large structured visual pattern in an optimal direction. From forty-four units responsive to a horizontally moving optokinetic striped drum, twenty-nine were activated with optokinetic movement in the opposite direction to the activating vestibular stimulus ('synergistic' response), thirteen were activated optokinetically and vestibularly in the same direction ('antagonistic' responses) and two were biphasic. The gain of the optokinetic response to sinusoidal stimulation (average 0.28 (impulses s-1) (deg s-1)-1 at 0.2 Hz, 56 deg amplitude) was in a range similar to that of the vestibular gain at low frequencies. At 1 Hz some units only showed weak optokinetic responses or none at all, but the vestibular response was still strong. 3. With different 'conflicting' or 'enhancing' combinations of optokinetic and vestibular stimulation no generalized type of interaction was observed, but the responses varied from nearly 'algebraic' summation to no discernible changes in the vestibular responses by additional optokinetic stimuli. With all visual-vestibular stimulus combinations the responses to the vestibular stimulus remained dominant. 4. The optokinetic preferred direction was not related to gravitational coordinates since the optokinetic responses were related to the head co-ordinates and remained constant with respect to the head co-ordinates at different angles of steady tilt. 5. Almost all PIVC units were activated by somatosensory stimulation, whereby mainly pressure and/or movement of neck and shoulders (bilateral) and movement of the arm joints elicited vigorous responses. Fewer neurones were activated by lightly touching shoulders/arms or neck, by vibration and/or pressure to the vertebrae, pelvis and legs. 6. A most effective somatosensory stimulus was sinewave rotation of the body with head stationary. The gain of this directionally selective neck receptor response was in the range of vestibular stimulation. Interaction of vestibular and neck receptor stimulation was either of a cancellation or facilitation type.(ABSTRACT TRUNCATED AT 400 WORDS)

Behaviorally contingent property of movement-related activity of the primate putamen.

Abstract: 1. In this study, the movement-related activity of putamen neurons was investigated in behaving monkeys. The objective of the study was to examine whether the activity occurring in phase with body movements is directly related to the movement per se by encoding movement parameters or whether it is dependent on the circumstances in which the movement is performed. 2. Sensorially triggered arm movements were used as a behavioral task. A sequence of three visually triggered repetitive flexion-extensions of the elbow joint across the target were followed by the delivery of a juice reward. 3. There are two classes of putamen cells: type I, with tonic spontaneous discharges (2-7 Hz) and broad extracellularly recorded action potentials, and type II, with very low spontaneous discharge rate (less than 1 Hz). The movement-related phasic discharges occur exclusively in type II cells. 4. The movement-related activity of type II cells is classified into two contrasting types of cells: type IIa that exhibit burst discharges preceding the first movement of a sequence of repetitive arm or orofacial movements but that are almost inactive during succeeding movements, and type IIb that show movement-locked burst discharges with one-to-one correspondence. The somatotopic location of the cells was identified by microstimulation and/or sensory responses to passive somatosensory manipulation of the periphery. 5. The activities of type IIa cells occur with a short and fairly constant latency after the visual trigger stimulus and cease as soon as the sequence of the learned movements is initiated. In the condition in which the monkey attended to the visual trigger stimulus without initiating learned movements and waited for the delivery of juice reward at a fixed time after the stimulus, type IIa cells exhibited slight but consistent phasic discharges after the visual stimulus with short latency. This indicates that the type IIa cells have a visuomovement property. The type IIb cells, on the other hand, have a longer latency of activity after the visual trigger than type IIa cells and do not have the visuomovement property. 6. The type IIa cells change their activity pattern depending on whether the direction of initial movement is predictable before the trigger stimulus or not. 7. The activities of type IIa cells in the arm area of the putamen precede the electromyogram (EMG) of prime mover muscles by greater than 100 ms on average, whereas most type IIb cells are activated after the EMG during a learned arm-movement task.(ABSTRACT TRUNCATED AT 400 WORDS)

Electrophysiological studies of acetylcholine and the role of the basal forebrain in the somatosensory cortex of the cat. ii, cortical neurons excited by somatic stimuli

Abstract: 1. Of the sample of 322 neurons located in somatosensory cortex and tested for their responsiveness to somatic stimulation, 91 (28%) responded to stimuli applied to the skin. The majority were located in the middle cortical layers. Each of the cells subjected to tests with glutamate and acetylcholine (ACh) was rapidly adapting to cutaneous stimuli, giving a response at the onset of skin indentation and sometimes after the stimulus withdrawal. 2. Of the 30 cells tested by pairing basal forebrain (BF) stimulation with cutaneous stimulation. 18 (60%) displayed enhanced responses to the same cutaneous stimulus after the pairing. These effects lasted for greater than 5 min in 17 cases, persisting for as long as the cell was studied, sometimes greater than 1 h. 3. The enhanced responsiveness to cutaneous stimuli could not be reversed by atropine, but in each of the 11 cells where atropine was administered while the BF stimulus was paired with the skin stimulus, the pairing produced no enhancement. 4. We conclude that pairing a BF stimulus with a cutaneous stimulus leads to long-term facilitation of the responsiveness of the cortical neuron subjected to this treatment and that this effect is mediated by the release of acetylcholine from BF cholinergic neurons that act on muscarinic receptors found on neurons in the somatosensory cortex.

Areal and laminar organization of corticocortical projections in the rat somatosensory cortex.

Abstract: The present study examines patterns of connectivity between the primary somatosensory cortex of the rat (SI) and surrounding cortical areas also implicated in the processing of somatosensory information. The impetus for the study was the recent reports of major differences in the organization of cortex lateral and caudal to the SI in two other rodent species; the mouse (Carvell and Simons, '86: Somatosens. Res. 3:213-237; '87: J. Comp. Neurol. 265:409-427) and the grey squirrel (Krubitzer et al., '86: J. Comp. Neurol 250: 403-430). Corticocortical connections between the somatosensory areas of the rat parietal cortex were examined by using the combined retrograde and anterograde transport of horseradish peroxidase as well as the retrograde transport of fluorescent tracers. Tracer injections were made into different locations within SI and dysgranular cortex as well as into more lateral regions of parietal cortex. The tangential patterns of distribution both of callosal connections and of cytochrome oxidase activity together provided points of reference in determining the relation between injection sites and the resultant patterns of label. The results indicate that two distinct somatosensory areas, SI and the dysgranular cortex, are interconnected with a further lateral somatosensory area referred to as the second somatosensory area (SII). These projections are organized in a topographic fashion, which we interpret as evidence for a single representation of the body surface in SII. The three somatosensory areas each exhibit unique laminar patterns of ipsilateral corticocortical projection neurons and terminations. In SI, projection neurons are found mainly in layers II, III, and Va, and terminations are largely restricted to the infragranular layers. In the dysgranular cortex, projection neurons and terminations are found in all layers except layer I in which only terminal label is detectable and layer Vb in which notably fewer neurons are labelled. In SII, projection neurons and terminations are found in all layers except layer I and are particularly dense in lower layer III and layer IV. Further, whereas the laminar and areal distributions of ipsilateral and contralateral corticocortical projections largely overlap in both SI and the dysgranular cortex, in SII they tend to be areally segregated. Neurons projecting bilaterally to both ipsilateral and contralateral somatosensory cortex were equally rare in all three somatosensory areas. These results are discussed in relation to the organization of SII in other rodent species, and it is concluded that in the rat, like the mouse, cortex lateral and caudal to SI contains a single representation of the body surface.

Interhemispheric transfer of plasticity in the cerebral cortex

Abstract: Each half of the body surface is represented topographically in the contralateral cerebral hemisphere. Physiological data are presented showing that homotopic regions of primary somatosensory cortex are linked such that plasticity induced in one hemisphere, in the form of receptive field expansion brought about by a small peripheral denervation, is immediately mirrored in the other hemisphere. Neurons which display the plasticity show no responsiveness to stimulation of the ipsilateral body surface. This suggests that the pathways and mechanisms mediating this transfer are specific to the role of maintaining balance, or integration, between corresponding cortical fields.

Output pathways from the rat superior colliculus mediating approach and avoidance have different sensory properties.

Abstract: Neuroanatomical studies have demonstrated that the two major descending pathways from the superior colliculus arise from regionally segregated, distinct, cells of origin. Stimulation and lesion studies have implicated the crossed descending tecto-reticulo-spinal projection in approach movements towards novel stimuli whereas the ipsilateral pathway appears to be involved in the control of avoidance and escape-like behaviours. The present electrophysiological study attempted to characterise the sensory properties of antidromically identified cells of origin of these pathways in anaesthetised rats. We found that the contralaterally projecting predorsal bundle (PDB) efferents were primarily somatosensory while the ipsilateral cuneiform (CNF) projection was primarily visual. PDB cells, mainly found in the intermediate layers, responded principally to vibrissal stimulation with their overlying visual fields optimally stimulated by small dark moving objects in the lower rostral and lateral field. In contrast, most CNF cells were located rostromedially, with the greatest contribution from visual cells responsive to stimuli in the upper rostral field. A significant proportion of these showed no response to small moving dark discs but fired vigorously to ‘looming’ stimuli. Ethological considerations suggest that these are appropriate stimulus characteristics for a system controlling approach and avoidance behaviour in an animal such as the rat where predators generally appear from above and prey is found on the ground.

Receptive-field changes induced by peripheral nerve stimulation in SI of adult cats.

Abstract: 1. Receptive fields (RFs) of neurons in the primary somatosensory (SI) cortex were defined before, during, and after electrical stimulation of myelinated fibers in the dorsal cutaneous branch of the ulnar nerve in adult pentobarbital sodium-anesthetized cats. 2. This stimulation resulted in an approximately threefold increase of SI multiunit RF sizes. Substantial changes were first recorded within 1-2 h of stimulation. RFs typically enlarged continuously over a several-hour stimulation period, then stabilized. 3. RF-area increases were observed within both the forepaw and hindpaw representational zones in the SI cortex contralateral to the stimulated forepaw nerve. RF sizes did not increase in the ipsilateral SI body surface representation or in sham-stimulation control animals. 4. Preliminary studies indicate that stimulation-induced changes can be halted and often reversed by the intravenous administration of the opiate antagonist naloxone. 5. These observations suggest a global naloxone-sensitive modulatory system that operates on large-diameter afferent inputs in the cat somatosensory system. The increases in RF size occur under nerve-stimulation conditions similar to those that result in the generation of widespread analgesia (Chung et al. 1984a,b; Gamble and Milne 1986; Toda and Ichioka 1978).

Development of sensory systems in mammals

Abstract: THE VISUAL SYSTEM: Prenatal Development of Visual System Structures Behavioral Analysis of Visual Development The Role of Experience in Visual Development THE AUDITORY SYSTEM: Development of Auditory System Structures Experiential Factors in Auditory System Development THE VESTIBULAR SYSTEM: Development of the Vestibular System THE SOMATOSENSORY SYSTEM: Peripheral Alteration and Somatosensory Development THE CHEMICAL SENSES: Olfactory Development Taste Development DEVELOPMENT OF SENSORY SYSTEMS IN OVERVIEW: Summary of Epigenic and Experiential Contributions Underlying Formation of Sensory Systems in Mammals Conclusions.

Oscillatory activity of single units in a somatosensory cortex of an awake monkey and their possible role in texture analysis.

Abstract: Neuronal activity was extracellularly recorded in the cortex of an awake monkey (Macaca fascicularis). Single units displaying oscillatory firing patterns were found in the upper bank of the lateral sulcus in a region where most of the neurons responded to somatosensory stimuli. The spectral energies of the oscillating activity were distributed in a trimodal fashion--0-15, 15-50, and 80-250 Hz--with the most common frequencies around 30 Hz. The oscillatory activity was not affected by anesthesia, but it was often reduced by tactile stimulation or self-initiated movements. Analysis of the spike trains suggests that the majority of oscillatory activity was intrinsically generated by the neurons. A neural model of texture analysis is offered based on a corticothalamic phase-locked loop. The newly identified oscillators play a key role in this model. The relevance of the model to physiological, anatomical, and psychophysical data, as well as testable predictions, are discussed.

Contribution of somatosensory information to perception of the visual vertical with body tilt and rotating visual field

Abstract: This study was designed to explore the role of somatosensory information from the trunk in the perception of the visual vertical. Twelve normal subjects and 1 subject with no somatosensory function below the neck attempted to set a line to the true vertical in the sitting and lying positions, first with a static visual background and then with rotation of the background about the line of sight. The absence of somatosensory information did not affect accuracy when the subjects were in the upright position. When lying horizontally, all control subjects experienced a substantial perceived tilt of the vertical in the direction of body tilt (the Aeffect), but, in contrast, the subject lacking somatosensory function exhibited a small but consistent apparent tilt of the vertical in the opposite direction (theE effect). This finding is discussed in relation to two competing hypotheses regarding the mechanisms subserving apparent displacement of the subjective vertical in tilted subjects.

Single unit analysis of the human ventral thalamic nuclear group. Activity correlated with movement.

Abstract: During neurosurgical operations for the relief of movement disorders, single thalamic neurons (n = 107) were identified with activity which was related to verbally cued active movements (movement-related cells). The activity of each neuron was examined during different contralateral movements in order to determine the movement which was associated with the most consistent and pronounced change in firing rate (the optimal response). The optimal response was determined by analysis of histograms of neuronal activity which were constructed by using the onset of EMG activity to synchronize successive repetitions of the active movement. Movement-related cells exhibited optimal responses associated with such movements as making a fist, extension or flexion of the wrist, flexing or extending the elbow, pointing with the entire upper extremity, extending the tongue and lifting the leg. Most movement-related cells recorded in a single parasagittal plane in an individual patient had optimal responses related to movements involving the same part of the body. Movement-related cells were classified into those that were activated in response to somatosensory stimulation (combined cells, n = 20) and those which were not (voluntary cells, n = 87). Combined cells were activated in advance of EMG activity during active movement and so could be distinguished from cells responding only to sensory stimulation (sensory cells). Movement-related cells (combined and voluntary cell types) were located anterior to sensory cells and tended to show a mediolateral somatotopic organization parallel to that of sensory cells with cutaneous receptive fields. Combined cells responded to somatosensory stimulation of the same part of the body as that involved in the active movement related to the optimal response of the cell. Combined cells responding to passive movements of a joint always had their optimal response during active movement about the same joint. The activity of combined cells during parkinsonian tremor may clarify the role of sensory feedback in tremor.

Ablations of areas 3b (SI proper) and 3a of somatosensory cortex in marmosets deactivate the second and parietal ventral somatosensory areas.

Abstract: Partial ablations of specific parts of cortical areas 3b (SI proper) and 3a in marmosets were found to render somatotopically equivalent parts of two other cortical somatosensory fields, the second somatosensory area (SII) and the parietal ventral area (PV), unresponsive to peripheral stimulation. Microelectrode recordings in anesthetized marmosets first established the responsiveness and locations of the representations of body parts, including the hand in areas 3a and 3b, SII, and in some cases PV. The hand representations in areas 3a and 3b were then removed by aspiration. Immediately afterwards, additional recordings established that regions of SII and PV that formerly represented the hand were no longer responsive to cutaneous stimulation of the hand (or any other skin surface). Other parts of these fields, representing parts of the body other than the hand, remained responsive to stimulation of the previously effective receptive fields. We conclude that SII and PV depend on inputs (either direct or indirect) from areas 3a and 3b for their activation.

Sensory properties and afferents of the N. dorsolateralis posterior thalami of the pigeon

Abstract: According to previous studies, the avian n. dorsolateralis posterior thalami (DLP) receives visual and somatosensory afferents. While some authors (e.g., Gamlin and Cohen: J. Comp. Neurol. 250:296-310, '86) proposed a distinction between a visual caudal (DLPc) and a somatosensory rostral (DLPr) part, other authors (e.g., Wild: Brain Res. 412:205-223, '87) could not confirm such a differentiation. The aim of the present experiment was to study with physiological and anatomical methods the proposed parcellation of the DLP into various components dealing with different modalities. The physiological properties of the DLP of the pigeon were analysed with extracellular single unit recordings. With the same approach, neurons of the n. dorsalis intermedius ventralis anterior (DIVA), a somatosensory relay nucleus in the dorsal thalamus, were also analysed. The afferents of the DLP were studied by using anatomical tract tracing techniques with retrograde and anterograde tracers. The sensory properties of DLP cells revealed that somatosensory, visual, and auditory modalities affect the neuronal firing frequency in this nucleus. All three modalities were present throughout the full caudorostral extent of the DLP. Cells recorded in DIVA responded nearly exclusively to somatosensory stimulation. Unlike the DLP, single units in DIVA generally had smaller receptive fields encompassing only one extremity. The analysis of afferent connections of the DLP by using injections of retrograde and anterograde tracers (HRP, WGA-HRP, Fast Blue, and Rhodamine-beta-isothiocyanate) demonstrated extensive projections from the nuclei gracilis et cuneatus (GC) and more sparse projections from the nucleus tractus descendens trigemini (TTD), and the nucleus cuneatus externus (CE). Brainstem afferents of the DLP came from different vestibular nuclei, various areas of the brainstem reticular formation, and the optic tectum. Prosencephalic afferents originated in the n. posteroventralis thalami (PV), the n. ventromedialis posterior thalami (VMP), the n. dorsalis intermedius ventralis anterior (DIVA), and the nucleus reticularis superior pars dorsalis and ventralis (RSd and RSv). Telencephalic afferents of the DLP came from the hyperstriatum accessorium (HA) and a group of cells at the borderline between the hyperstriatum intercalatus superior (HIS) and the hyperstriatum dorsale (HD). The somatosensory afferents of the DLP probably originate from the GC, TTD, and CE, whereas it is likely that the visual input is mediated by the optic tectum. The anatomical source for the acoustic input is unclear. The very long latencies of auditory DLP neurons make it likely that the acoustic input originates at least partly in the reticular formation.(ABSTRACT TRUNCATED AT 400 WORDS)

Focal Alzheimer's disease.

Abstract: Alzheimer9s disease is characterized by relative sparing of primary sensory and motor cortex and a lack of sensory or motor symptomatology. We report a case of presenile onset dementia accompanied by a slowly progressive hemi-paresis. Autopsy examination showed severe pathologic involvement of somatosensory cortex with neuritic plaques and neurofibrillary tangles, in addition to degeneration of the nucleus basalis and locus ceruleus. Neurochemical and immunocytochemical studies showed a moderate cortical cholinergic deficiency with normal somatostatin-like immunoreactivity and a profuse immunostaining of somatosensory cortex with the Alz-50 antibody. These unusual features emphasize that Alzheimer9s disease is extremely variable in its clinical symptomatology, pathologic distribution, and neurochemical dimensions.

Somatosensory evoked potentials in rat cerebral cortex before and after middle cerebral artery occlusion

Abstract: We recorded somatosensory evoked potentials in pentobarbital-anesthetized rats before and after middle cerebral artery occlusion. Trigeminal (vibrissae), median (forelimb), and sciatic (hind limb) nerve stimuli produced consistent, robust, and sharply localized responses in the trigeminal, forelimb, and hind limb regions of the somatosensory cortex of 18 rats. These regions are situated at sequentially greater distances from the center of infarcts produced by middle cerebral artery occlusion. In eight rats, occlusion 1-2 mm below the rhinal fissure abolished somatosensory evoked potentials in all three cortical region within minutes. Positive wavelets preceding the primary cortical response were also diminished by the occlusion, suggesting that ischemia affected the thalamocortical white matter. Four of these eight rats did not show histologically apparent ischemic involvement of the hind limb cortical region at 3 hours after occlusion; sciatic nerve evoked potentials recovered substantially in all four rats, and the amplitudes exceeded baseline (129 +/- 30% at 1 hour, 173 +/- 33% at 3 hours) in three of the four rats. Three of the eight rats did not have gross ischemic involvement of the forelimb cortical region; median nerve evoked potentials recovered fully in all eight rats, but the amplitudes did not exceed baseline. All eight rats had evidence of ischemic damage in the trigeminal cortex; no rat showed full recovery in this region, and all but one had trigeminal evoked potentials that were less than 20% of baseline amplitudes by 3 hours after occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Efferent neurons and suspected interneurons in S-1 forelimb representation of the awake rabbit: receptive fields and axonal properties.

Abstract: 1 Receptive-field properties of antidromically identified efferent neurons within the cutaneous forelimb representation of primary somatosensory cortex (S-1) were examined in fully awake rabbits Efferent neurons studied included callosal neurons (CC neurons, n = 52), ipsilateral corticocortical neurons (C-IC neurons, n = 48) that project to or beyond the second somatosensory cortical area (S-2), and corticofugal neurons of layer 5 (CF-5 neurons, n = 97) and layer 6 (CF-6 neurons, n = 59) that project to and/or beyond the thalamus 2 An additional class of neurons was studied that was not activated antidromically from any stimulus site, but which responded synaptically to electrical stimulation of the ventrobasal (VB) thalamus with a burst of three or more spikes at frequencies of 600 to greater than 900 Hz Most of these neurons also responded synaptically to stimulation of S-2 and the corpus callosum The action potentials of these neurons were much shorter (mean = 045 ms) than those of efferent neurons (mean = 095 ms) Such properties have been associated with interneurons found throughout the central nervous system, and these neurons are thereby referred to as suspected interneurons (SINs) 3 CF-5 neurons differed from CC, C-IC, and CF-6 neurons in their spontaneous firing rates, axonal properties, and receptive-field properties Whereas CF-5 neurons had a mean spontaneous firing rate of 55 spikes/s, CC, C-IC, and CF-6 neurons had mean values of less than 1/s Axonal conduction velocities of CF-5 neurons were much higher (mean = 1292 m/s) than either CC (mean = 215 m/s), C-IC (mean = 131 m/s), or CF-6 (mean = 253 m/s) neurons A decrease in antidromic latency (the "supernormal" period) that was dependent on prior impulse activity was seen in the great majority of CC, C-IC, and CF-6 neurons but was either minimal or absent in CF-5 neurons of comparable conduction velocity A higher proportion of CF-5 neurons (98%) responded to peripheral sensory stimulation than did either CC (75%), C-IC (71%), or CF-6 (51%) neurons CF-6 and C-IC neurons that did not respond to sensory stimulation had significantly lower axonal conduction velocities and spontaneous firing rates than those that responded to such stimulation 4 Cutaneous receptive fields were seen in most neurons that could be driven by peripheral stimulation(ABSTRACT TRUNCATED AT 400 WORDS)

Modulation of somatosensory evoked responses in the primary somatosensory cortex produced by intracortical microstimulation of the motor cortex in the monkey.

Abstract: Previous studies have shown that the amplitude of somatosensory evoked potentials is diminished prior to, and during, voluntary limb movement. The present study investigated the role of the motor cortex in mediating this movement-related modulation in three chronically prepared, awake monkeys by applying low intensity intracortical microstimulation (ICMS) to different sites within the area 4 representation of the arm. Air puff stimuli were applied to the contralateral arm or adjacent trunk at various delays following the ICMS. Somatosensory evoked potentials were recorded from the primary somatosensory cortex, areas 1 and 3b, with an intracortical microelectrode. The principal finding of this study was that very weak ICMS, itself producing at most a slight, localized, muscle twitch, produced a profound decrease in the magnitude of the short latency component of the somatosensory evoked potentials in the awake money. Higher intensities of ICMS (suprathreshold for eliciting electromyographic (EMG) activity in the “target” muscle, i.e. that muscle activated by area 4 stimulation) were more likely to decrease the evoked response and produced an even greater decrease. The modulation appeared to be, in part, central in origin since (i) it preceded the onset of EMG activity in 23% of experiments, (ii) direct stimulation of the muscle activated by ICMS, which mimicked the feedback associated with the small ICMS-induced twitch, was often ineffective and (iii) the modulation was observed in the absence of EMG activity. Peripheral feedback, however, may also make a contribution. The results also indicate that the efferent signals from the motor cortex can diminish responses in the somatosensory cortex evoked by cutaneous stimuli, in a manner related to the somatotopic order. The effects are organized so that the modulation is directed towards those neurones serving skin areas overlying, or distal to, the motor output.

Visual and somatosensory processing in the macaque temporal cortex: the role of 'expectation'.

Abstract: The somatosensory and visual properties of cells in a polymodal region of temporal cortex were studied in 4 awake behaving macaque monkeys. When stimulated passively and out of sight, cells with tactile responses were found to have very large receptive fields covering most of the body surface and an apparent lack of selectivity for size, shape or texture of the tactile stimulus. These properties are equivalent to those described for the anaesthetized preparation (Bruce et al. 1981). Our study revealed that tactile responses were influenced by the degree to which stimuli could be ‘expected’. Tactile stimulation arising from active exploration of novel surfaces produced vigourous neuronal responses but equivalent stimulation of the skin arising when the monkey contacted ‘expected’ surfaces such as itself or items with which it had become familiar produced no responses. The responses of cells to active or passive tactile stimulation were attenuated when the monkey could see the objects causing the stimulation. For cells responsive to more than one sensory modality, visual and somatosensory responses were associated in a compatible manner. Cells responsive to the onset of touch were selective for the sight of objects moving towards the monkey, whereas cells selective for the offset of touch were responsive to the sight of movements away from the monkey.

From neuron to action : an appraisal of fundamental and clinical research

Abstract: 1: Motor.- Adaptations and Learning of Arm Movements.- Emergent Issues in the Control of Multi-joint Movements.- Looking Where the Action Is: Negative DC Shifts as Indicators of Cortical Activity.- Negative DC Shifts of the Supplementary and Motor Area Preceding and Accompanying Simultaneous and Sequential Finger Movements.- DC Potential Shifts and Regional Cerebral Blood Flow Reveal Frontal Cortex Involvement in Human Visuomotor Learning.- Event-Related Slow Potentials Recorded from Cortex and Depth of the Human Brain.- Cortical DC-Shifts Related to Sustained Sensory Stimulation and Motor Activity.- Coordination Between Posture and Movement in Parkinsonism and SMA Lesion.- Feedback Mechanisms Controlling Skeletal Muscle Tone.- Significance of Carbonic Anhydrase in the Function of Skeletal Muscle.- 2: Oculomotor and Equilibrium.- Holding the Eye Still After a Saccade.- Do the Pretectum and Accessory Optic System Play Different Roles in Optokinetic Nystagmus?.- Excitatory and Inhibitory Mechanisms Involved in the Dynamic Control of Posture During the Vestibulospinal Reflexes.- Motion Perception with Moving Eyes.- Does the System for Smooth-Pursuit Eye Movements Rely on a Neuronal Representation of Target Motion in Space?.- Optokinetic and Smooth-Pursuit Response After Adaptive Modification of the Vestibulo-Ocular Reflex.- The Detection of Motion by the Vestibular System.- Role of Neck and Visual Afferents for Self and Object Motion Perception in Labyrinthine Defective Subjects.- The Coordination Between the Lid and Eye During Vertical Saccades.- Ocular Pursuit of Sinusoidally Moving Targets: Is There a Sine Wave Generator in the Brain?.- The Role of Visual Feedback and Preprogramming for Smooth Pursuit Eye Movements: Experiments with Velocity Steps.- Positional Nystagmus of Benign Paroxysmal Type (BPPN) due to Cerebellar Vermis Lesions: Pseudo-BPPN.- Two Forms of Head-Shaking Tests in Vestibular Examination.- 3: Sensory and Cognitive.- The Parietal Visual System and some Aspects of Visuospatial Perception.- Focal Thalamocortical Rhythms as Indicators of Attentive States in the Cat.- The Sensory Neuron - Where the Action Begins.- Parallel and Complementary Organization of Cortical Eye Movement Control and Visual Perception.- Stages of Somatosensory Processing Revealed by Mapping Event-Related Potentials.- On Ideation and "Ideography".- Movement Detection and Figure-Ground Discrimination.- Influence of Complex Visual Stimuli on the Regional Cerebral Blood Flow.- DC Shifts in the Human Brain: Their Relationship to the CNV and Bereitschaftspotential.- Probability Mapping of EEG Changes due to the Perception of Music.- Program Generator Revisited: The Role of the Basal Ganglia in Language and Communication.- From Articular Nociception to Pain: Peripheral and Spinal Mechanisms.- 4: Evolution.- The Evolution of Cerebral Asymmetry.- Science, Man and Meaning.- Information and Efficiency.- A Critical Consideration of Kornhuber's Concept of the Brain-Mind Problem.- Brain, Mind, Freedom: Beyond Metatheory, Nearer to Reality.- Neuroethological Foundations of Human Speech.- Cricket Neuroethology: A Comparative Approach to the Nervous System.- Hierarchies of Structure-Function Relationship in the Neurosciences.- Evolution and Phylogenetic Diversification of Chemical Messengers.- 5: Synaptic and Elementary Processes.- Cascade-Type Reentrance: The Major Connectivity Principle of the Neocortex.- Peripheral Axotomy Challenges the Central Motor Neuron and its Cellular Microenvironment.- Frequency and Amplitude Codes of Neuronal Signals.- Balance and Imbalance of Transsynaptic Neurotransmission as Conditions for Normal and Pathological Behaviour: Examples Only.- Behavioural Pharmacology of Brain Glutamate.- Effects of CO2 on Neuronal Functions.- The R-Wave Biography of a Brain Potential.- The Proton-Activated Sodium Current: Activation Conditions in Mammalian Central Neurons.- The Impact of Advanced Computing on Medicine.- Biomagnetic Measuring Technique: State of the Art and Prospects for the Future.- 6: Neurological Sciences I (Psychiatry).- Advances in Schizophrenia Research.- Cognitive Basic Symptoms of Thought, Perception and Action in Idiopathic Psychoses and Limbic System.- Phenomenological Aspects and the Measurement of Negative or Basic Symptoms in Schizophrenia.- Evoked Brain Potentials and Psychometric Data in Children at Risk for Schizophrenia.- The Order of EEG Activity of Schizophrenic Patients and the Influence of Haloperidol and Biperidene on the EEG Order of Healthy Subjects.- Progress in Neuropsychopharmacology: The Use of Thymosthenic Substances in Schizophrenia.- Dopamine D2 - Receptors in Post-mortem Human Brains from Schizophrenic Patients.- Phencyclidine - A Challenge to Schizophrenia Research.- Neurotoxic Metabolites of Tyrosine/Dopamine in Cerebrospinal Fluid and Serum of Normal Men and Neurological Patients: A Sign of the Activity of free Oxygen Radicals?.- Searching for New Antiischemic Compounds: Theoretical and Practical Aspects.- Experimental Intracerebral Hematoma and Treatment with Flunarizine in Rats.- "Normal" Alcohol Consumption and Well-Being: Relationship Between Reduction of Alcohol Consumption and Changes in Well-Being.- "Normal" ("Social") Daily Alcohol Consumption, Arterial Hypertension, Glucose Tolerance, Plasma Insulin, C Peptide, GGT, S-Adenosylmethionine, Plasma Lipids and Obesity: Insulin Receptor Damage and Mediators Versus Repair Mechanism of Toxic Alcohol Effects.- EEG Signs of a Disturbed Voluntary Process Prior to Voluntary Movements in Schizophrenia.- 7: Neurological Sciences II (Neurology and Neurosurgery).- The Role of the Magnification Factor in the Recovery Process of Visual Field Defects After Retrogeniculate Lesions.- Oxygen Free Radicals and Radical Scavengers in Neurology.- Immunotherapy in Multiple Sclerosis: Current Status and Future Prospects.- Effective Treatment of Multiple Sclerosis with Cyclophosphamide with Little Side Effects.- Neurogenesis and Pathogenesis of Glia: Immunological Studies.- Paired Stimuli in the Diagnosis of Peripheral and Central Nervous Diseases.- Early Speech Education: An Epidemiologic Study.- Hope for a Drug Treatment in Acute Stroke.- The Essence of Aphasia - Disturbed Control of Language Production, e. g. in Phonemic Paraphasia: A Quantitative Comparison of Spontaneous Speech in Aphasia and Dementia.- Planning Strategies of Intracranial Microsurgery.- What Can Neurosurgery Do in 19887.- Transcranial Doppler Evaluation of Cerebral Hemodynamics in Carotid Artery Occlusions.- Sonography Through the Anterior Fontanelle in Newborns: An Efficient Method for Screening Pre- and Perinatal Lesions.- The Severity of Convulsive Behaviour in Rats: Disinhibitory Effects of Cortical Lesions.- Electrophysiology of Myotonias and Periodic Paralyses.- Protection Against Sudden Infant Death: Home Monitoring of All Infants During the First Year of Life by Means of the Baby protector.- EEG Spectra and Evoked Potentials to Words in Apallic Patients.

Sensory and cognitive event-related potentials in myalgic encephalomyelitis.

Abstract: Myalgic Encephalomyelitis (ME) is a form of post viral fatigue syndrome resulting in myalgia and fluctuating fatiguability. Symptoms reflecting central nervous system dysfunction are common and include muscle weakness, headache, sensory disturbances, poor short term memory and impairment of concentration. In view of the fact that sensory and cognitive disturbances are experienced by many patients objective evidence was sought with multi-modality sensory evoked potentials and auditory event-related cognitive potentials in a group of ME patients both with and without the enteroviral antigen, VP1 test positive. The auditory brainstem, median nerve somatosensory and pattern reversal checkerboard visual potentials were normal for all 37 patients tested. In contrast to the sensory potentials significant differences in the mean latencies of the cognitive potential N2 and P3 were found. Reaction times were also significantly prolonged but the performance in terms of error was not significantly affected. No significant difference emerged in any of the parameters for the VP1 test. P3 was abnormal in latency or amplitude in 36% of the VP1 positive patients for the frequency discrimination task and 48% for the more difficult duration discrimination task. The abnormalities indicate attentional deficits in some patients and slower speed of information processing in others. The prolonged latencies observed in these patients have not been observed in patients with depression in many other studies.

Acute Effects of Total or Partial Digit Denervation on Raccoon Somatosensory Cortex

Abstract: The immediate effects of total or partial denervation of single digits (0-16 hr after nerve transection) on primary somatosensory cortex were studied electrophysiologically. Comparisons of response properties and cortical somatotopy were made between intact raccoons and four groups of raccoons with transection of some or all of the nerves innervating the fourth or fifth digit. Animals with all four digital nerves cut (amputation of the digit) were most different from normal. Approximately half of the penetrations in the affected cortical region showed inhibitory responses to stimulation of adjacent skin regions. These consisted of a strong response to stimulus offset and/or a suppression of spontaneous activity during indentation. Since these responses were substantially different from those recorded several months after digit amputation, additional changes in connectivity and synaptic strength must occur with chronic denervation. These inhibitory responses were not seen in animals with one, two, or three nerves cut per digit. In the animals with partial denervation of a digit, the greatest disruption occurred when both ventral nerves to the glabrous skin were transected. This yielded cell clusters with abnormally large receptive fields, disruptions in somatotopic organization, and a decreased occurrence of low-threshold responses. If only one nerve to glabrous skin was transected, there was less change, even if it was combined with transection of both nerves to hairy skin. These results suggest that the release of inhibitory responses in a cortical digital region by amputation is prevented by the retention of even one ventral nerve. None of the denervation conditions produced large nonresponsive areas of cortex, which would have indicated a loss of all inputs.

Effects of MK-801 on recovery from sensorimotor cortex lesions.

Abstract: Histologic evidence suggests that drugs acting as noncompetitive antagonists at the N-methyl-D-aspartate receptor can have beneficial or pathologic effects on central nervous system neurons. In the present experiments we examined the effects of MK-801 on recovery of behavioral function after unilateral lesions in the rat somatic sensorimotor cortex. In the first experiment, rats with unilateral sensorimotor cortex lesions were given either MK-801 (1 mg/kg) or saline 12-16 hours after surgery. Additional injections were given on postoperative days 2, 4, and 6. Behavioral tests measured somatosensory asymmetries (i.e., bilateral tactile stimulation tests) and forelimb placing. After creation of sensorimotor cortex lesions, rats showed an ipsilateral somatosensory bias and an impairment in placing the contralateral forelimb. Rats treated with MK-801 recovered slightly faster than saline-treated animals as measured by a bilateral tactile stimulation test (p less than 0.05). In contrast, there was no significant difference between the groups in the recovery of forelimb placing. In a second experiment, rats with sensorimotor cortex lesions were treated with a single injection of MK-801 after behavioral recovery. Twenty hours after the MK-801 injection, rats with sensorimotor cortex lesions showed a reinstatement of the placing deficits. The impairment endured for at least 7 days after injection. These behavioral data support the idea that MK-801 can have either beneficial or detrimental effects when administered after brain damage.

Callosal projections in rat somatosensory cortex are altered by early removal of afferent input.

Abstract: During the first postnatal week, the distribution of callosal projection neurons in the rat somatosensory cortex changes from a uniform to a discontinuous pattern. To determine if this change is influenced by afferent inputs to the somatosensory cortex, the effect of both early unilateral infraorbital nerve section and unilateral removal of the dorsal thalamus on the distribution of callosal projections in rat somatosensory cortex was examined. One month after either of the above manipulations at birth, the tangential distribution of callosal projections in the somatosensory cortex was examined using the combined retrograde and anterograde transport of horseradish peroxidase. Both manipulations alter the distribution of callosal projection neurons and terminations in the somatosensory cortex. After infraorbital nerve section, the distribution of callosal projections is altered in the contralateral primary somatosensory cortex. The abnormalities observed are consistent with the altered distribution of thalamocortical projections. In addition, consistent abnormalities were observed in the pattern of callosal projections of the second somatosensory area of both hemispheres. Most notably, they are absent in a portion of the region that contains the representation of the mystacial vibrissae and sinus hairs in this area. Thalamic ablation resulted in highly aberrant patterns of callosal projections in the somatosensory cortex on the operated side, where abnormal bands and clusters of callosal projections were observed in apparently random locations. These results are interpreted as evidence that both peripheral and central inputs influence the maturational changes in the distribution of callosal projection neurons.

Electrodiagnostic features of the Guillain‐Barré syndrome The relative sensitivity of different techniques

Abstract: We compared the diagnostic sensitivity of somatosensory evoked potentials (SEPs) and F waves with peripheral motor and sensory nerve conduction studies in 15 patients with the Guillain-Barre syndrome. All 4 types of studies were performed on 44 nerves (17 median, 12 ulnar, and 15 lower extremity). In the lower extremities, we used the peroneal nerves for all types of study except peripheral sensory conduction studies, which were performed on the sural nerve. We detected abnormalities by peripheral motor conduction studies in 33 of 44 nerves, by F waves in 31, by SEPs in 23, and by peripheral sensory conduction in 17. The cumulative sensitivity increased with the testing of multiple nerves by motor nerve conduction, sensory nerve conduction, and F-wave studies, but not with multiple SEPs. F-wave studies were significantly more sensitive than SEPs in identifying abnormalities. Thus, the recording of SEPs is indicated for diagnosis of the Guillain-Barre syndrome only if peripheral nerve conduction and F-wave studies are normal.