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Results for “Sensorimotor Cortex”

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PubMed1996

Intramembranous structure of the postsynaptic membrane in the rat sensorimotor cortex.

Intramembranous structure of the postsynaptic membrane of the axodendritic synapses in the rat sensorimotor cortex was examined by means of freeze-etching technique. Perforated and non-perforated aggregates of particles were found at the extracellular half (E-face) of the postsynaptic membrane. To study correlation between membrane structure and synaptic plasticity we compared size and particle packing density in both type aggregates of particles at the E-face of the postsynaptic dendritic spine membrane. The results are discussed in terms of plasticity on the synaptic contact zone (SCZ) at the postsynaptic membrane of the excitatory axospinous synapses.

Animals↗

PubMed1970

Thermosensitivity of neurons in the sensorimotor cortex of the cat.

Extracellular action potentials were recorded from 80 neurons in the sensorimotor cortex of the cat as brain temperature was varied by 4 degrees to 8 degrees C. The discharge rate of 37 percent of the neurons studied increased with increasing brain temperature. The discharge rate varied inversely with temperature in 11 percent of the neurons.

Action Potentials↗

PubMed1984

[Ultrastructural changes in the neurons of the sensorimotor cortex in rats under prolonged hypokinesia].

The authors studied the neuronal ultrastructure of the sensorimotor cortex of rats exposed to 90 days of hypokinesia and at different times after its withdrawal. During prolonged restriction of motor activity, dystrophic changes seen in the cortical neurons were most demonstrable. During the first week of the posthypokinetic period, the degree of dystrophic lesions was reduced and the signs of intracellular regeneration were fairly conspicuous. Three weeks after hypokinesia withdrawal the ultrastructure of most neurons returned to normal, with the structure abnormalities being still observed in individual cells.

Animals↗

PubMedDate not supplied

Changes in power and coherence of brain activity in human sensorimotor cortex during performance of visuomotor tasks.

Electrocorticograms (ECoG) were recorded using subdural grid electrodes in forearm sensorimotor cortex of six human subjects. The subjects performed three visuomotor tasks, tracking a moving visual target with a joystick-controlled cursor; threading pieces of tubing; and pinching the fingers sequentially against the thumb. Control conditions were resting and active wrist extension. ECoGs were recorded at 14 sites in hand- and arm-sensorimotor area, functionally identified with electrical stimulation. For each behavior we computed spectral power of ECoG in each site and coherence in all pair-wise sites. In three out of six subjects, gamma-oscillations were observed when the subjects started the tasks. All subjects showed widespread power decrease in the range of 11-20 Hz and power increase in the 31-60 Hz ranges during performance of the visuomotor tasks. The changes in gamma-range power were more vigorous during the tracking and threading tasks compared with the wrist extension. Coherence analysis also showed similar task-related changes in coherence estimates. In contrast to the power changes, coherence estimates increased not only in gamma-range but also at lower frequencies during the manipulative visuomotor tasks. Paired sites with significant increases in coherence estimates were located within and between sensory and motor areas. These results support the hypothesis that coherent cortical activity may play a role in sensorimotor integration or attention.

Epilepsy↗

PubMed2004

Fluoro-Jade and TUNEL staining as useful tools to identify ischemic brain damage following moderate extradural compression of sensorimotor cortex.

Cerebral ischemia was produced by moderate compression for 30 min of a specific brain area in the sensorimotor cortex of Sprague-Dawley rats. On day 1, that is 24 h after the transient sensorimotor compression, ischemia-exposed animals displayed a marked focal neurological deficit documented as impaired beam walking performance. This functional disturbance was mainly due to contralateral fore- and hind-limb paresis. As assessed by daily beam walking tests it was shown that there was a spontaneous recovery of motor functions over a period of five to seven days after the ischemic event. Using histopathological analysis (Nissl staining) we have previously reported that the present experimental paradigm does not produce pannecrosis (tissue cavitation) despite the highly reproducible focal neurological deficit. We now show how staining with fluorescent markers for neuronal death, that is Fluoro-Jade and TUNEL, respectively, identifies regional patterns of selective neuronal death. These observations add further support to the working hypothesis that the brain damage caused by cortical compression-induced ischemia consists of scattered, degenerating neurons in specific brain regions. Postsurgical administration of the AMPA receptor specific antagonist, LY326325 (30 mg/kg; i.p., 70 min after compression), not only improved beam walking performance on day 1 to 3, respectively but also significantly reduced the number of Fluoro-Jade stained neurons on day 5. These results suggest that enhanced AMPA/glutamate receptor activity is at least partially responsible for the ischemia-produced brain damage detected by the fluorescent marker Fluoro-Jade.

Animals↗

PubMed2002

Movement artefacts and MR BOLD signal increase during different paradigms for mapping the sensorimotor cortex.

BACKGROUND: The authors evaluated the impact of motion artefacts on presurgical mapping of the sensorimotor cortex with functional magnetic resonance imaging (fMRI). Different mapping paradigms were compared with regard to the frequency of motion artefacts and the resulting signal increase. METHOD: 94 surgical candidates with mass lesions near the central region were investigated using BOLD(1)-contrast T2(*) weighted multislice multi-echo EPI gradient echo sequences on a 1,5 T Philips Gyroscan. Three functional paradigms were performed: a) repetitive self-paced clenching of the hand to a fist (68 runs); b) repetitive finger-to-thumb opposition (46 runs); c) sensory stimulation by repetitive brushing of the palm (15 runs). Task-related haemodynamic changes were identified by statistical analysis with the Kolmogorov-Smirnov-test. MR signal increase in percent was calculated for each of the paradigms. Motion artefacts were rated on a scale from 1 to 3. FINDINGS: Severe motion artefacts occurred in 8 hand clenching runs and in 2 finger opposition runs. Artefacts were more pronounced in hand clenching than in finger opposition. There were no motion artefacts in any of the sensory stimulation runs. Concerning the percent MR signal change there was no significant difference between hand clenching and finger opposition (T-test: p>0,5) but a highly significant difference (p<0,0001) between both motor tasks and the sensory paradigm (hand clenching: 2.68+/-0.75; finger opposition: 2.76+/-0.79; sensory stimulation: 1.72+/-0.65). INTERPRETATION: Sensory stimulation causes by far less artefacts than motor paradigms but it also has to be considered less sensitive as it produces a smaller MR signal increase. Therefore in presurgical evaluation sensory stimulation should be kept in reserve for cases in whom motion artefacts are very likely to occur, i.e. patients with severe forms of paresis.

Adolescent↗

PubMed1992

Interaction of afferent impulses in the human primary sensorimotor cortex.

We recorded somatosensory evoked magnetic fields (SEFs) over the hand area of the primary sensorimotor cortex (SMI) in 6 healthy adults in 2 sets of experiments to study interaction of afferent impulses. In experiment 1, SEFs were elicited by contralateral median nerve (MC) stimuli presented alone and 40 msec after a conditioning stimulus to the contralateral ulnar (UC), ipsilateral median (MI) or contralateral tibial (TC) nerve. N20m, P30m and P60m deflections to MC stimulation were markedly attenuated by preceding UC stimulation whereas N40m was enhanced, and a novel P80m emerged. In contrast, MI or TC stimulation did not affect the responses to MC. In experiment 2, the time course of recovery of N20m to median nerve stimuli was studied after stimulation of the adjacent ulnar and of the same median nerve. The recovery curves were similar for both conditioning stimuli with nearly full recovery of N20m at 120 msec. The results indicate marked interaction of impulses from ipsilateral median and ulnar nerves in human SMI, but no evidence was found of interaction from the two hands or from ipsilateral hand and foot.

Adult↗

PubMed1993

Postnatal development of a persistent Na+ current in pyramidal neurons from rat sensorimotor cortex.

1. Whole-cell recordings were performed on acutely isolated pyramidal neurons from rat sensorimotor cortex 2 to 21 days postnatal to study the expression of a tetrodotoxin (TTX) sensitive, voltage dependent, persistent Na+ current (INaP) during different stages of postnatal development. 2. INaP was activated positive to about -60 mV and attained its peak amplitude between -40 and -35 mV. Activation of INaP did not require preceding activation of the transient Na+ current. 3. Peak INaP amplitudes showed a three-fold increase over the first three postnatal weeks, starting from 60.7 +/- 7.5 (SE) pA (n = 6) at postnatal day (P) 2-P5 and reaching 189.1 +/- 20.4 pA (n = 13) at P17-P21. 4. Measurements of peak INaP density, which took concomitant cell growth into account, revealed that a considerable current density already existed in very young neurons (P2-P5: 4.3 +/- 1.0 microA/cm2, n = 6) when compared with INaP density in early adult neurons (P17 - P21: 8.9 +/- 0.8 microA/cm2, n = 5). 5. Our data provide the first direct evidence for the presence of a significant INaP density during early postnatal development of neocortical neurons indicating that this current should play a role in the control of intrinsic excitability at this age.

Animals↗

PubMed1979

An autoradiographical study of the projections from the feline sensorimotor cortex to the brain stem.

Following an autoradiographical study on the projections from the feline sensorimotor cortex (representation of the limbs) to the brain stem, new projections to nucleus pretectalis posterior, the coerulear nuclei, nuclei corporis pontobulbares, nucleus intertrigeminalis, nucleus f, x and z of the vestibular nuclear complex, nucleus parvocellularis compactus, nucleus parasolitarius, nuclei insulae cuneati laterales, the nuclei of the raphé, nucleus reticularis lateralis and nucleus fastigii were found besides the well known projections to the tectal nuclei, the reticular formation, nucleus ruber, griseum pontis, the sensory trigeminal nuclei and the dorsal column nuclei. There was no evidence of projections to nucleus tractus solitarii. The amounts of radioactivity within the nuclei seem to be in favour of EM autoradiographical studies on the synaptology of these projections, apart from faintly labelled structures like most of the reticular nuclei, the sensory trigeminal nuclei, the coerulear nuclei and nucleus fastigii.

Animals↗

PubMed1975

Distribution and properties of commissural and other neurons in cat sensorimotor cortex.

Commissural, cortico-cortical and cortico-caudate neurons have been investigated in the primary sensorimotor cortex of the cat, using antidromic stimulation techniques, and histological identification of recording sites. These neurons are to be found in all cortical laminae except the first; commissural and cortico-cortical neurons were found to be commonest in laminae III and VI, whilst cortico-caudate neurons were most abundant on the border between laminae III and V, in motor areas. In sensory areas topographically identified as representing distal parts of limbs, commissural neurons are very rare, confirming neuroanatomical studies on the origin and termination of callosal fibres. The intracerebral neuronal projections investigated in this study had slow conduction velocities (less than 1 m/sec, up to about 10 m/sec). It was found that projections from area 6, whether commissural, cortico-caudate, or cortico-peduncular have slower conduction velocities than their counterparts from area 4. It is suggested that this is related to the type of motor control in which these two areas are involved (slowly-responding postural movements, as opposed to more rapid distal limb movements). No neurons were found which had both commissural (or cortico-cortical), and cortico-fugal projections.

Animals↗

PubMedDate not supplied

Characteristics of neuronal responses in the sensorimotor cortex of the cat to monaural and binaural stimulation.

The dependence of neuronal responses in the sensorimotor cortex (SMC) of the cat upon localization parameters of dichotically presented auditory signals was studied in acute experiments. Binaural stimulation was more effective than either monaural stimulation. It was shown that spatial-localization parameters of auditory-stimulus source such as interaural differences in intensity and time are reflected by the characteristics of neuronal responses in the SMC; moreover, in 67-88% of cases the most pronounced responses were observed for small, close to zero, temporal and amplitudinal interaural shifts. It was found that SMC neuronal background activity may be altered by signals simulating directed movement of the sound source in the horizontal plane.

Animals↗

PubMed1993

Response characteristics of subthalamic neurons to the stimulation of the sensorimotor cortex in the rat.

Responses of the subthalamic nucleus (STH) neurons to the stimulation of the sensorimotor cortex (Cx) were recorded in intact rats and in those which received lesions in the pallidum, the neostriatum, the brainstem, or the corpus callosum. Most of the STH units (78%) exhibited two excitatory peaks which were interrupted by a brief period of inhibition. Some of units which were located in the peripheral part of the STH tended to lack the brief inhibitory component and exhibited a long period of excitation. These excitations were followed by a long-lasting inhibitory period. Intracellular recording indicated that these responses were EPSPs interrupted by a short IPSP and a long period of disfacilitation of Cx inputs. A quinolinic acid lesion of the neostriatum and a knife cut of the brainstem failed to alter these responses, while an ibotenic acid lesion of the globus pallidus abolished the short inhibition seen in the midst on the excitation. Stimulation of contralateral Cx also evoked excitatory responses in the STH. The responses were completely eliminated by a parasagittal knife cut of the rostral part of the corpus callosum.

Animals↗

PubMed1998

Postnatal differentiation of firing properties and morphological characteristics in layer V pyramidal neurons of the sensorimotor cortex.

The maturational profile of the firing characteristics of 217 layer V pyramidal neurons of rat sensorimotor cortex, injected with biocytin for morphological reconstruction, was analysed by means of intracellular recordings made between postnatal day (P)3 and 22. Starting from the onset of the second postnatal week, the pyramidal neurons could be differentiated as adapting or non-adapting regular spiking on the basis of the presence or absence of spike frequency adaptation. The percentage of non-adapting regular spiking neurons was very high during the second postnatal week (53%) and progressively decreased with age, concurrently with the appearance of the new class of intrinsically bursting neurons (beginning of the third week) whose percentage progressively increased from 23%, found in P14-P16 rats, to 46% in adult rats. Non-adapting regular spiking neurons were found to share with intrinsically bursting neurons several physiological characteristics comprehending faster action potentials, more prominent effect of anomalous rectification and consistent depolarizing afterpotentials, that differentiated them from the adapting regular spiking neurons. Moreover, intrinsically bursting and non-adapting regular spiking neurons were characterized by a round-shaped distribution of basal dendrites and expanded apical dendritic arborization, that differentiated them from the adapting regular spiking neurons showing a simpler dendritic arborization. These morphological hallmarks were seen in immature intrinsically bursting neurons as soon as they became distinguishable, and in immature non-adapting regular spiking neurons starting from the onset of the second postnatal week. These findings suggest that a significant subpopulation of immature non-adapting regular spiking neurons are committed to becoming bursters, and that they are converted into intrinsically bursting neurons during the second postnatal week, as soon as the ionic current sustaining the burst firing is sufficiently strong. The faster action potentials in both immature non-adapting regular spiking and intrinsically bursting neurons suggest a higher density of Na+ channels in these neuronal classes: the maturational increase in Na+-current, namely of its persistent fraction, may represent the critical event for the conversion of the non-adapting regular spiking neurons into the intrinsically bursting ones.

Aging↗

PubMed1996

Synchronization of neurons during local field potential oscillations in sensorimotor cortex of awake monkeys.

1. The neural activity associated with 20- to 40-Hz oscillations in sensorimotor cortex of awake monkeys was investigated by recording action potentials of single and multiple units. At a given site, activity of many units became synchronized with local field potential (LFP) oscillations. Cycle-triggered histograms (CTHs) of unit spikes aligned on cycles of LFP oscillations indicated that about two thirds of the recorded units (n = 268) were entrained with LFP oscillations. On average, units had the highest probability of spiking 2.7 ms before peak LFP negativity, corresponding to a -27.6 degrees phase shift relative to the negative peak of the LFP. 2. The average relative modulation amplitude (RMA), defined as the ratio of amplitude of oscillatory component of CTH and the baseline multiplied by 100, was 45 +/- 27% (mean +/- SD). The RMAs of single units did not differ significantly from those of multiple units. 3. Phase shifts and RMAs did not vary systematically with the cortical depth of recorded units. 4. Autocorrelation histograms (ACHs) of entrained units exhibited clear 20- to 40-Hz periodicity if they were compiled with spikes that occurred during oscillatory episodes in LFPs. ACHs of spikes outside oscillatory episodes usually did not show periodicity. Global ACHs of all spikes typically showed weak or no evidence of periodic activity. 5. Cross-correlation histograms (CCHs) between pairs of units complied with all spikes, whether they occurred during or outside LFP oscillations, seldom revealed significant features (19 of 134 pairs or 14%). However, CCHs compiled with spikes that occurred during oscillatory episodes (OS-CCHs) had significant features in 67 of 134 pairs recorded ipsilaterally; in these 67 cases, units at both sites showed modulation in CTHs. 6. The latencies of the OS-CCH peaks (taking the medial unit as reference) were normally distributed about a mean of -0.5 +/- 13 ms. Normalized peak height of CCHs (peak/baseline x 100) was, on average, 14.3 +/- 11.2%. Peak latency and normalized peak amplitude did not change significantly with horizontal separation of recorded precentral pairs up to 14 mm. 7. Units in the left and right hemispheres could become synchronized during oscillations. Significant features in OS-CCH were detected in 22 of 42 pairs of units recorded bilaterally. The average peak latency was 0.2 +/- 8.0 ms and the average normalized peak amplitude was 10 +/- 8%. These parameters did not differ significantly from those for ipsilateral OS-CCHs. 8. Oscillations tended to affect both the temporal structure and net rate of unit firing. For each unit, the firing rate was clamped to a narrow range of frequencies during oscillatory episodes. The coefficient of variation (SD/mean) of firing rates was significantly reduced during oscillatory episodes compared with prior rates (P < 0.001, paired t-test). However, the overall mean firing rate of each unit during all oscillatory episodes did not differ from its average rate immediately before the episodes. Thus oscillatory episodes tended to clamp mean firing rates to the cells' average rates outside episodes. 9. The strength of synchronization between units during oscillatory episodes was unrelated to their involvement in the task. For pairs of precentral units recorded ipsilaterally, the probability of occurrence of significant features in the OS-CCH was slightly larger when both units of the pair were task related (33 of 56 pairs or 59%) than when only one unit was task related (20 of 39 pairs or 51%) or neither unit was task related (7 of 16 or 44%). However, these differences were not statistically significant. The magnitude of the correlation peak and the latency to peak were also not significantly different for the three cases. 10. These results suggest that units across wide regions can become transiently synchronized specifically during LFP oscillations, even if their spikes are uncorrelated during nonoscillatory periods.

Action Potentials↗

PubMed1983

[Dynamics of the oxygen tension in the hippocampus and sensorimotor cortex during the wakefulness-sleep cycle].

Recording of the PO2 dynamics in the hippocampus and sensorimotor cortex revealed that the level of PO2 changes rather easily and dramatically depending on emotional tension of the organism during different phases of sleep and wakefulness and being, probably, related to the functional shifts occurring in these structures. On the basis of the percentage of periodical constituents of the PO2 oscillations it may be concluded that the functional activity in the dorsal hippocampus is enhanced during active wakefulness and paradoxical phase of sleep (PS); while during passive wakefulness and slow sleep it is depressed. The maximum occurs in the PS and minimum--in the slow sleep.

Animals↗

PubMed1993

[Habituation and effects of protein synthesis blockers on neuronal activity in the cerebral sensorimotor cortex in rabbits].

The investigation of brain functions has been for many years an exciting and at the same time a very complex and enigmatic domain of research. In our experiments we followed the occurrence of habituation, a simple form of learning, during a peripheral light stimulation, in sensorimotor cortex neurons of rabbits. In the majority of the mature neurons habituation occurred with repeated light stimulations with same features, while in immature rabbits it was less frequently observed and was slower. Since in basic patterns of habituation and learning, cell protein plays a significant role, we followed the effects of protein synthesis blockers in the process of training and electrogenesis. Microiontophoretic application of actinomycin D and cyclohexamide compromised the occurrence of habituation in high number of registered neurons, while the application of a neurotransmitter, acetyl choline, promoted habituation in the sensorimotor brain cortex neurons of immature experimental animals.

Acetylcholine↗

PubMed1989

Role of the sensorimotor cortex in postural adjustments accompanying a conditioned paw lift in the standing cat.

The role of the sensorimotor cortex in the postural adjustments associated with conditioned paw lifting movements was investigated in the cat. Cats were trained to stand quietly on four strain gauge equipped platforms and to perform a lift-off movement with one forelimb when a conditioned tone was presented. The parameters recorded were the vertical forces exerted by the paws on each platform, the lateral and antero-posterior displacements of rods implanted on the T2, T12, L5 vertebrae as well as their rotation, and the EMG of triceps and biceps of both forelimbs. Before lesion, the postural adjustment consisted of a "non-diagonal" pattern where the CG was displaced laterally inside the triangle formed by the three remaining supporting limbs. Here a lateral bending of the thoracic column toward the supporting forelimb could be observed. The associated EMG pattern consisted of an early activation of the triceps lateral head in the moving limb which was probably responsible for the body displacement toward the opposite side, and a late biceps activation associated with the lift. In the supporting forelimb, a coactivation of the biceps and triceps was usually present. After contralateral sensorimotor lesion, the conditioned lifting movements were lost for 4-15 days after the lesion, before being subsequently recovered. The same lateral CG displacement and bending of the back was seen after lesion as before, which indicates that the goal of postural adjustment was preserved. However, the means of reaching it were modified.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1998

Isometric force-related activity in sensorimotor cortex measured with functional MRI.

Isometric force-related functional magnetic resonance imaging (fMRI) signals from primary sensorimotor cortex were investigated by imaging during a sustained finger flexion task at a number of force levels related to maximum voluntary contraction. With increasing levels of force, there was an increase in the extent along the central sulcus from which a fMRI signal could be detected and an increase in the summed signal across voxels, but these parameters were related in such a way that the signal from each voxel was similar for each level of force. The results suggest that increased neuronal firing and recruitment of corticomotor cells associated with increased voluntary isometric effort are reflected in an expansion of a relatively constant fMRI signal over a greater volume of cortex, rather than an increase in the magnitude of the response in a particular circumscribed region, possibly due to perfusion of an increase in oxygen-enriched blood over a wider region of the cortex.

Adult↗