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Results for “Sensorimotor Cortex”

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At least 199 records · Page 11Linked to original sources

PubMed1991

The effect of gangliosides upon recovery of aspartate/glutamatergic synapses in striatum after lesions of the rat sensorimotor cortex.

Changes in neuronal uptake of glutamate/aspartate were studied in the striatum after unilateral destruction of the sensorimotor cortex and injection of GM1 ganglioside. A 75% decrease of uptake of [3H]D-aspartate in the striatum ipsilateral to the cortical lesion was detected at 10 days postlesion compared to the contralateral striatum. We have demonstrated that injection of gangliosides during 10 days returned the uptake of [3H]D-aspartate to control level and compensated loss of the synapses in the striatum after the cortical lesion and thereby can prevent aberrant axonal overgrowth in the contralateral striatum.

Animals↗

PubMed1977

The effect of lesions of the sensorimotor cortex and the capsular pathways on servo responses from the human long thumb flexor.

Lesions of the sensorimotor cortex, or of the capsular pathways beneath it, caused (with one exception out of 14 cases) diminution "r loss of the servo responses in the thumb, which are based on the long-latency stretch reflex. When not absent the long-latency stretch reflex tended to be late in onset. When absent it was often replaced by a large early reflex response at spinal latency. In general the results are consistent with the transcortical theory of the long-latency stretch reflex for the thumb, but, in detail, they indicate that the theory will require elaboration.

Adult↗

PubMed1991

Two transient potassium currents in layer V pyramidal neurones from cat sensorimotor cortex.

1. Two transient outward currents were identified in large pyramidal neurones from layer V of cat sensorimotor cortex ('Betz cells') using an in vitro brain slice preparation and single-microelectrode voltage clamp. Properties of the currents deduced from voltage-clamp measurements were reflected in neuronal responses during constant current stimulation. 2. Both transient outward currents rose rapidly after a step depolarization, but their subsequent time course differed greatly. The fast-transient current decayed within 20 ms, while the slow-transient current took greater than 10 s to decay. Raised extracellular potassium reduced current amplitude. Both currents were present in cadmium-containing or calcium-free perfusate. 3. Tetraethylammonium had little effect on the slow-transient current at a concentration of 1 mM, but the fast-transient current was reduced by 60%. 4-Aminopyridine had little effect on the fast-transient current over the range 20 microM-2 mM, but these concentrations reduced the slow-transient current and altered its time course. 4. Both transient currents were evoked by depolarizations below action potential threshold. The fast-transient current was evoked by a 7 mV smaller depolarization than the slow-transient current, but its chord conductance increased less steeply with depolarization. 5. Voltage-dependent inactivation of the fast-transient was steeper than that of the slow-transient current (4 vs. 7 mV per e-fold change), and half-inactivation occurred at a less negative potential (-59 vs. -65 mV). The activation and inactivation characteristics of each current overlapped, however, implying the existence of a steady 'window current' extending over a range of approximately 14 mV beginning negative to action potential threshold. 6. The fast-transient current displayed a clear voltage dependence of both its activation and inactivation kinetics, whereas the slow-transient current did not. Recovery of either current from inactivation took about 1 s near -70 mV. The recovery of the slow-transient current became faster with hyperpolarization. 7. The contribution of each transient current to repolarization of the action potential was assessed from pharmacological responses. Blockade of calcium influx had little or no effect on the rate of action potential repolarization, whereas the selective reduction of either transient current caused significant slowing of repolarization. 8. We conclude that Betz cells possess at least two transient potassium currents, each a member of the rapidly expanding family of voltage-gated potassium currents that have been identified in various cell types.(ABSTRACT TRUNCATED AT 400 WORDS)

4-Aminopyridine↗

PubMed1987

Anomalous rectification in neurons from cat sensorimotor cortex in vitro.

The ionic mechanisms underlying anomalous rectification in large neurons from layer V of cat sensorimotor cortex were studied in an in vitro brain slice. The anomalous rectification was apparent as an increase of slope conductance during membrane hyperpolarization, and the development of anomalous rectification during a hyperpolarizing current pulse was signaled by a depolarizing sag of membrane potential toward resting potential (RP). Voltage-clamp analysis revealed the time- and voltage-dependent inward current (IAR) that produced anomalous rectification. IAR reversal potential (EAR) was estimated to be approximately -50 mV from extrapolation of linear, instantaneous, current-voltage relations. The conductance underlying IAR (GAR) had a sigmoidal steady-state activation characteristic. GAR increased with hyperpolarization from -55 to -105 mV with half-activation at approximately -82 mV. The time course of both GAR and IAR during a voltage step was described by two exponentials. The faster exponential had a time constant (tau F) of approximately 40 ms; the slow time constant (tau S) was approximately 300 ms. Neither tau F nor tau S changed with voltage in the range -60 mV to -110 mV. The fast component constituted approximately 80% of IAR at each potential. Both IAR and GAR increased in raised extracellular potassium [( K+]o) and EAR shifted positive, but the GAR activation curve did not shift along the voltage axis. Solutions containing an impermeable Na+ substitute caused an initial transient decrease in IAR followed by a slower increase of IAR. Brain slices bathed in Na+-substituted solution developed a gradual increase in [K+]o as measured with K+-sensitive microelectrodes. We conclude that GAR is permeable to both Na+ and K+, but the full contribution of Na+ was masked by the slow increase of [K+]o that occurred in Na+ substituted solutions. Chloride did not appear to contribute significantly to IAR since estimates of EAR were similar in neurons impaled with microelectrodes filled with potassium chloride or methylsulfate, whereas, ECl (estimated from reversal of a GABA-induced ionic current) was approximately 30 mV more positive with the KCl-filled microelectrodes. Extracellular Cs+ caused a reversible dose- and voltage-dependent reduction of GAR, whereas intracellular Cs+ was ineffective. The parameters measured during voltage clamp were used to formulate a quantitative empirical model of IAR.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMedDate not supplied

[The effect of opioid neuropeptides on the cholino- and adrenoreactivity of the sensorimotor cortex cells in rats].

The effect of two neuropeptides, dalargine and betaendorphine, on cholino- and adrenoreactivity of sensorimotor cortex cells has been studied in immobilized rats in acute experiments. Subcutaneous administration of the peptides led to redistribution of cells according to the type of their reaction and to changes in intensity of neuronal reactions to the applied neurotransmitters. The observed changes in chemoreactive properties of cortical neurons under the influence of the neuropeptides may play a certain part in the processes of learning and memory.

Acetylcholine↗

PubMed1993

Modal gating of Na+ channels as a mechanism of persistent Na+ current in pyramidal neurons from rat and cat sensorimotor cortex.

The kinetic behavior of brain Na+ channels was studied in pyramidal cells from rat and cat sensorimotor cortex using either the thin slice preparation or acutely isolated neurons. Single-channel recordings were obtained in the cell-attached and inside-out configuration of the patch-clamp technique. Na+ channels had a conductance of about 16 pS. Patches always contained several Na+ channels, usually 4-12. In both preparations, long depolarizing pulses revealed two distinct patterns of late Na+ channel activity following transient openings. (1) Na+ channels displayed sporadic brief late openings sometimes clustered to "minibursts" of 10-40 msec. These events occurred at a low frequency, yielding open probability (NPo) values below 0.01 (mean = 0.0034). (2) In the second gating mode, an individual Na+ channel in the patch failed to inactivate and produced a burst of openings often lasting to the end of the pulse. This behavior was observed in about 1% of depolarizations. Shifts to the bursting mode were usually confined to a single 400 msec pulse, but rarely occurred during two or more consecutive pulses applied at 2 sec intervals. Sustained bursts did not require preceding transient openings to occur since they were also observed during slow depolarizing voltage ramps. The similar incidence of inactivation failures in cell-attached versus inside-out recordings suggests that the bursting mode is a property of the channel and/or adjacent membrane-bound structures. Calculations indicate that brief late openings and rare sustained bursts suffice to generate a small but significant whole-cell current. Since the Na+ channels mediating early, brief late, and sustained openings were identical in terms of their elementary electrical properties, we propose that the fast and the persistent Na+ currents of cortical pyramidal cells are generated by an electrophysiologically uniform population of Na+ channels that can individually switch between different gating modes.

Animals↗

PubMed1992

Coherent 25- to 35-Hz oscillations in the sensorimotor cortex of awake behaving monkeys.

Synchronous 25- to 35-Hz oscillations were observed in local field potentials and unit activity in sensorimotor cortex of awake rhesus monkeys. The oscillatory episodes occurred often when the monkeys retrieved raisins from a Klüver board or from unseen locations using somatosensory feedback; they occurred less often during performance of repetitive wrist flexion and extension movements. The amplitude, duration, and frequency of oscillations were not directly related to movement parameters in behaviors studied so far. The occurrence of the oscillations was not consistently related to bursts of activity in forearm muscles, but cycle-triggered averages of electromyograms revealed synchronous modulation in flexor and extensor muscles. The phase of the oscillations changed continuously from the surface to the deeper layers of the cortex, reversing their polarity completely at depths exceeding 800 microns. The oscillations could become synchronized over a distance of 14 mm mediolaterally in precentral cortex. Coherent oscillations could also occur at pre- and postcentral sites separated by an estimated tangential intracortical distance of 20 mm. Activity of single units was commonly seen to burst in synchrony with field potential oscillations. These findings suggest that such oscillations may facilitate interactions between cells during exploratory and manipulative movements, requiring attention to sensorimotor integration.

Animals↗

PubMed2005

Primary sensorimotor cortex activation with task-performance after fatiguing hand exercise.

We have compared functional MRI signals in primary sensorimotor cortex (SM1) during a paced motor task of each hand before and after unimanual (right hand) fatiguing exercise. Our aims were to determine whether the degree of activation is different when a motor task is performed after a fatiguing exercise, and whether there are any differences in activation between movement of the fatigued and non-fatigued hands. There was a significant reduction in the number of voxels activated in SM1 in the hemisphere contralateral to movement of both the fatigued hand (38 +/- 5 pre-exercise versus 21 +/- 3 post-exercise; P<0.05) and the non-fatigued hand (32 +/- 4 pre-exercise vs 18 +/- 4 post-exercise; P<0.05). There was no significant difference in the magnitude of the functional magnetic resonance imaging signal before or after exercise, however, the variance increased significantly after exercise (6.0 +/- 0.5 pre-exercise vs 7.3 +/- 0.6 post-exercise; P<0.01). Reduced functional activation in SM1 may reflect increased variability in the activation rather than a reduction in activation of cortical motor networks after fatigue.

Adult↗

PubMed1990

Functional subdivisions of the rat somatic sensorimotor cortex.

The behavioural impairments and subsequent recovery were studied in rats with circumscribed unilateral lesions in the somatic sensorimotor cortex (SMC). Lesions were made in the caudal forelimb region (CFL), the rostral forelimb region (RFL), the anteromedial cortex (AMC) or the hindlimb area. Rats with damage in the CFL produced a deficit in placing the forelimb contralateral to the lesion during exploratory locomotion on a grid surface. Rats with AMC damage circled in the direction ipsilateral to the lesion. Lesions in the CFL or AMC produced an ipsilateral somatosensorimotor asymmetry on the bilateral-stimulation test (responding to adhesive patches placed on the contralateral forelimb was slower) that recovered in 7 days following AMC lesions or 28 days following CFL lesions. Finally, RFL lesions produced an ipsilateral asymmetry on the bilateral-stimulation task that was more severe and enduring (recovery in 60 days). After behavioral recovery, the effects of an additional lesion placed in the homotopic contralateral cortex were examined (two-stage bilateral lesion). Rats receiving two-stage bilateral lesions in the RFL or CFL responded slower to tactile stimulation of the forelimb contralateral to the second lesion. In the case of CFL-damaged rats, placing deficits also appeared contralateral to the most recent injury. In contrast, rats receiving two-stage bilateral AMC lesions did not exhibit behavioral asymmetries following the second lesion. These results provide evidence to suggest that subdivisions of the rat SMC can be distinguished with lesion/behavioral experiments. Moreover, a comparison of the effects of unilateral and two-stage bilateral lesions may help in the parcellation of the rat SMC into functionally distinct subareas and provide a basis for studying the processes of recovery and maintenance of function following brain damage.

Animals↗

PubMedDate not supplied

[Connections of the representational area of the distal section of the forelimb in the rat sensorimotor cortex].

Using horseradish peroxidase, studies have been made on the distribution of retrogradely labeled nervous cells in the sensorimotor cortex of rats. The enzyme was injected into electrophysiologically identified zone of representation of the distal part of the forelimb in areas S2 and S1. It was found that this zone in S2 contains afferent connections mainly from representation of the same extremity in S1 and only a few afferents from other areas of S1, S2 and M1 of the same hemisphere. Single labeled neurones were found in areas S2, S1 and M1 of the contralateral hemisphere. Representation of the forelimb in S1 receives mainly cortical afferents from the same region of S1 and from single cells of homologous zones S2 of the same and S1 of the contralateral hemisphere. Connections from S1 to S2 are more numerous than the opposite ones. In contrast to cats and monkeys, in rats afferent cortical fibers to zone S2 pass not only from the third layer, but also from the fifth and sixth layers of the cortex. It is suggested that during progressive development of the neocortex in mammals, the increase in the degree of separation of neurones (which give origin to corticofugal and cortical connections) among different layers of the cortex takes place.

Afferent Pathways↗

PubMed1985

An anterograde HRP-WGA study of aberrant corticorubral projections following neonatal lesions of the rat sensorimotor cortex.

Anterograde transport of horseradish peroxidase - wheat germ agglutinin (HRP-WGA) was used to examine the effect of unilateral neonatal ablation of the sensorimotor cortex on the remaining corticofugal projections to the midbrain in the rat. In unlesioned animals, the sensorimotor cortical efferents to the midbrain were entirely ipsilateral, terminal labeling being evident in the red nucleus, the midbrain reticular formation, the periaqueductal gray, the intermediate gray layer of the superior colliculus, the nucleus parafascicularis prerubralis and the perilemniscal area. Corticorubral fibers were seen to reach the midbrain through the thalamus or the cerebral peduncle. In the red nucleus, terminal labeling was essentially restricted to the parvocellular region. In neonatally lesioned adults, aberrant corticofugal fibers crossed the midline to terminate in the contralateral red nucleus, the midbrain reticular formation, the periaqueductal gray, the nucleus parafascicularis prerubralis and the intermediate gray layer of the superior colliculus. The aberrant projections maintained the topographic specificity of the normal ipsilateral projections. This was most evident in the corticorubral projection, where the aberrant contralateral fibers terminated in the parvocellular area of the red nucleus.

Aging↗

PubMed1997

Intra-operative localization of sensorimotor cortex by cortical somatosensory evoked potentials: from analysis of waveforms to dipole source modeling.

Intra-operative localization of sensorimotor cortex is of increasing importance as neurosurgical techniques allow safe and accurate removal of lesions around the central sulcus. Although direct cortical recordings of somatosensory evoked potentials (SEPs) are known to be helpful for cortical localization, source localization models can provide more precise estimates than subjective visual analysis. In addition to intra-operative analysis of waveforms and amplitudes of SEPs to median nerve stimulation in 20 neurosurgical patients, we used a spatiotemporal dipole model to determine the location of the equivalent dipoles consistent with the cortical distribution of the SEPs. The early cortical SEPs were modeled by 2 equivalent dipoles located in the postcentral gyrus. The first dipole was primarily tangentially oriented and explained N20 and P20 peaks. The second dipole was primarily radially oriented and explained P25 activity. We found consistent localization of the first dipole in the postcentral gyrus, which was always located within 8 mm of the central sulcus, with an average distance of 3 mm. This finding provides an objective basis for using the SEP phase reversal method for cortical localization. We conclude that dipole source modeling of the cortical SEPs can be considered as an objective way of localizing the cortical hand sensory area.

Adolescent↗

PubMed1997

Ethanol consumption following recovery from unilateral damage to the forelimb area of the sensorimotor cortex: reinstatement of deficits and prevention of dendritic pruning.

Unilateral injury to the forelimb-representation area of the sensorimotor cortex (FL-SMC) in adult rats results in use-dependent proliferation of dendritic processes, followed by partial pruning, of layer V pyramidal neurons of the contralateral homotopic cortex. In development, 'exuberant' growth of neurons is often followed by pruning, a process that has been associated with a glutamatergic-NMDA receptor mechanism. A related mechanism may play a role in injury-related pruning of dendrites in adults. The N-methyl-D-aspartate (NMDA) receptor antagonist MK801, administered throughout the pruning phase to adult animals with FL-SMC lesions, prevents dendritic pruning and disrupts behavioral recovery. Ethanol (ETOH) also acts as an NMDA receptor antagonist. It has been shown to reduce NMDA-active ion currents, inhibit NMDA-evoked electrophysiological responses, and decrease glutamate-binding in the hippocampus and cortex. ETOH also affects neuromorphology in the developing and adult cerebellum, hippocampus, and cortex. Ethanol's involvement with NMDA receptor function and its influence on dendritic morphology led us to examine its effect on dendritic pruning and behavioral recovery following unilateral FL-SMC lesions. Lesioned animals were exposed to moderate doses of ethanol in a liquid diet only during the period of dendritic pruning. As with MK801, ETOH prevented pruning and reinstated chronic behavioral asymmetries.

Animals↗

PubMedDate not supplied

Historical survey. The concept of a sensorimotor cortex: its later history during the twentieth century.

This paper continues the historical review on the concept of a sensorimotor cortex into the twentieth century. Paul Flechsig was probably the first to accept this concept after the turn of the century. Like Munk, he believed in an almost reflex-like unity between cortical sensory and motor function. With the help of his myelogenetic technique, Flechsig also demonstrated convincingly in the human brain that the two Rolandic convolutions receive a separate influx of thalamic afferents. Had this finding met with more attention, much experimental work by some of the distinguished later investigators might have proved to be unnecessary. Research has now reached a state when an early plausible explanation of the problem may be confidently expected.

Animals↗

PubMed1985

Properties of persistent sodium conductance and calcium conductance of layer V neurons from cat sensorimotor cortex in vitro.

Properties of the persistent sodium conductance and the calcium conductance of layer V neurons from cat sensorimotor cortex were examined in an in vitro slice preparation by use of a single microelectrode, somatic voltage clamp, current clamp, intra- and extracellular application of blocking agents, and extracellular ion substitution. The persistent sodium current (INaP) attained its steady level within 2-4 ms of a step change in voltage at every potential where it could be examined directly [to about 40 mV positive to resting potential (RP)]. Because of its fast onset INaP can be activated during a single excitatory postsynaptic potential (EPSP) and can influence the subsequent voltage time course and cell excitability. Application of a depolarizing holding potential greater than or equal to 20 mV positive to RP could inactivate spikes, thus allowing examination of INaP at voltages positive to spike threshold. At every potential where INaP was visible, it was mixed with a slow outward current. After depressing potassium currents with blocking agents, INaP could be observed during depolarizations to about 40 mV positive to RP where it is normally hidden by the larger outward currents. Indirect evidence suggests that INaP is present and large during prolonged depolarizations greater than 50 mV positive to RP. INaP was blocked by intracellular injection of the lidocaine derivative QX-314, as well as by extracellular tetrodotoxin (TTX). INaP was much more sensitive to QX-314 than was the height and rate of rise of the spike. This observation and the results in paragraph 3 above are best explained by separate INaP and spike sodium channels. After blockade of INaP and sodium spikes, Ca2+ spikes could be evoked only if potassium currents were first depressed. The Ca2+-dependent nature of the regenerative potentials was indicated by their disappearance when Co2+ or Mn2+ was substituted for Ca2+ in the perfusate and by the appearance of greatly enhanced potentials of similar form when Ba2+ was substituted for Ca2+. Ba2+ substitution greatly enhanced evoked and spontaneous synaptic potentials. Prolonged-plateau action potentials could be evoked in the presence of TTX and Ba2+. Ca2+ spike threshold was 30-40 mV positive to RP, which is significantly more positive than sodium spike threshold. Results of voltage clamp in the normal perfusate and in the presence of Ca2+-blockers or Ba2+ indicated that little or no Ca2+ conductance is activated in the voltage range 25 mV positive to RP where INaP is the dominant ionic current.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMedDate not supplied

["The avoidance" of the direct current application to the sensorimotor cortex (a computer-controlled experiment in rabbits)].

In a computer controlled experiment the electric activity of rabbits right sensorimotor cortex was recorded in the area of the excitation focus produced by the direct current (2 mcA) application. The current was switched on at the 5th, 10th and 15th minutes of experiment only in cases when the mean amplitude of the delta waves exceeded the baseline. The current was switched off at the mean amplitude of the delta waves exceeding the baseline level by 50%. After training some experiments (2-4), rabbits learned to change their functional state in such way that they "avoided" the action of the direct current.

Animals↗

PubMed1993

[The corticorubral projection in rats: topographic distribution of fibers arising from areas of the sensorimotor cortex functionally identified by microstimulation].

The combination of microstimulation and anterograde tracing techniques reveals that different regions of the sensorimotor cortex project to different sectors of the red nucleus (NR). V-FEF projects to the dorsolateral sector, JLT to the dorsal sector, RFL and CFL to the dorsomedial and medial sectors, respectively, and HL to the ventral and ventrolateral sectors. Moreover, the NR receives fibers from the 2 somatosensory cortical areas examined in this study. The vibrissae area projects to the dorsolateral sector and the hand area to the dorsomedial sector.

Animals↗

PubMedDate not supplied

Dynamics of interstimulus intervals in the activity of neurons of the sensorimotor cortex during the development of a food-procuring reflex in the rabbit.

The impulse activity of neurons of the sensorimotor cortex (SMC) during the formation of a food-procuring reflex in the rabbit, as well as in trained animals if reinforcement is discontinued and substituted, was investigated. In the process of training the neurons of the SMC acquire the capacity for anticipatory reactions. The sudden abolition and substitution of reinforcement elicits the appearance of activity which is characteristic for the process of discordance in the acceptor of the result of the action. Repeated substitutions lead to the appearance of activity which is characterized by a coordination process at the moment of the "recognition" of the substitution, despite the absence of food reinforcement.

Acoustic Stimulation↗