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PubMedDate not supplied

[Transformation of the synaptic apparatus of the rabbit sensorimotor cortex following creation of a polarization dominant].

Ultrastructural transformations of axo-somatic and axo-dendritic synapses of the rabbit sensorimotor cortex were studied during: 1) polarization of the cortical surface with a DC anode and 2) the setting up of a polarization motor dominant. A comparison between the structural characteristics of the examined region of the cerebral cortex of the two groups of animals revealed transformations in the synaptic apparatus, which may be regarded as a result of the formation of a temporary connection: an increase in the number of axo-dendritic synapses with considerably thickened postsynaptic membranes; an increase in the number of axonic terminals with a concentration of synaptic vesicles and mitochondria content. The indicated changes were more pronounced in the deep layers of the sensorimotor cortex.

Animals↗

PubMed1990

[Ultrastructural research on the sensorimotor cortex in adult rats. I. Intranuclear inclusions in the neurons and astrocytes].

The morphological peculiarities of neurones and astrocytes in the sensorimotor cortex of mature (over 3 months) and elderly (over 24 months) rats were studied at electron microscopic level. Intranuclear inclusions are found in the nuclei of pyramidal neurones from the third and fifth layer. On the basis of their fine structure they could be grouped into the following types: 1. Filamentous bundles. 2. Filamentous crystalloids. 3. Granulofilamentous bodies. 4. Membrane-enclosed inclusions. 5. Combined intranuclear inclusions. Filamentous crystalloids are found in two varieties, composed of filaments with various diameter and way of arrangement. Membrane-enclosed bodies are formed as small vesicles or large vacuoles. Combinations from various types of inclusions in the nucleus of a neurone are discovered frequently. Only intranuclear inclusions of the type of membrane-enclosed bodies are observed in the nuclei of astrocytes. These bodies are found only in the nuclei of astrocytes of elderly animals. On the basis of the comparative analysis between ultrastructural characteristics and frequency of intranuclear inclusions in pyramidal neurones and astrocytes in sensorimotor cortex of mature and elderly rats their probable connection with age changes in the central nervous system is discussed.

Aging↗

PubMed2002

Caloric restricted male rats demonstrate fewer synapses in layer 2 of sensorimotor cortex.

Previous studies have demonstrated an age-related decline in the density of presumptive inhibitory synapses in layer 2 of rat sensorimotor cortex [J. Comp. Neurol. 439(1) (2001) 65]. Caloric restriction has been shown to ameliorate age-related deterioration in a variety of systems and to extend life span. The present study tested the hypothesis that caloric restriction would prevent the previously reported age-related synaptic decline. Accordingly, synaptic density in layer 2 of sensorimotor cortex was compared between 29-month-old male rats fed ad libitum and 29-month-old male rats that were caloric restricted (60% of ad libitum calories) from 4 months of age. In serial electron micrographs, the physical disector was used to determine the numerical density of presumptive excitatory and inhibitory synapses (those containing round or nonround vesicles, respectively) as well as that of neurons. Not only was the previously reported age-related decline in numerical density of presumptive inhibitory synapses not ameliorated by caloric restriction, the numerical density was significantly lower in caloric restricted than in ad libitum fed rats for total as well as for presumptive excitatory and inhibitory synapses. Analysis further revealed no difference in the numerical density of neurons in this region. Relating synapse density to neuron density as the ratio of synapses to neuron also demonstrated significantly fewer synapses per neuron in caloric restricted than in ad libitum fed old rats. Finally, synapse length was significantly less in caloric restricted rats. These results suggest that not only does caloric restriction fail to prevent the age-related decline in presumptive inhibitory synapses, it results in fewer presumptive excitatory synapses as well.

Aging↗

PubMedDate not supplied

[The dependence of the neuronal reactions of the sensorimotor cortex to a simultaneous complex stimulus on the level of the differentiation of its components].

On alert animals the change was studied of the neuronal activity of the sensorimotor cortical area of cats brain in dependence on the level of differentiation of the components of simultaneous heteromodal complex stimulus. According to the character of this dependence and a number of other parameters two groups of neurones were singled out in the sensorimotor cortex. It was shown that parameters of reactions of all recorded neurones of the sensorimotor cortex to the positive conditioned signal were the first established after consolidation of the animal conditioned motor activity. In the course of elaboration following parameters changed: expressiveness, intensity, duration and value of latency. Reactions of neurones of both groups to the inhibitory stimuli were stabilized only after consolidation of the habit of differentiation. Responses of the first group neurones changed only by the pattern of discharge, while the responses of the second group neurones could change by expressiveness of response, its sign, duration and value of latency. Oscillations of the differentiation level after finishing of the elaboration of inhibitory conditioned reactions affected only the responses of the second group neurones to complex components.

Acoustic Stimulation↗

PubMed1995

Ionic mechanisms underlying burst firing in pyramidal neurons: intracellular study in rat sensorimotor cortex.

In in vitro slices prepared from rat sensorimotor cortex, intracellular recordings were obtained from 107 layer V pyramidal neurons, subsequently injected with biocytin for morphological reconstruction. Of the 107 neurons, 59 (55.1%) were identified as adapting (45) or non-adapting (13) regular spiking neurons (RS), and 48 (44.9%) as intrinsically bursting (IB) neurons discharging with an initial cluster of action potentials, which tended to recur rhythmically in a subset of 19 cells. The block of IAR by extracellular Cs+ did not affect burst generation, but enhanced the tendency to reburst in IB neurons. A similar effect was induced by other procedures affecting K(+)-dependent post-burst hyperpolarization. In IB neurons Ca2+ spikes had a longer decay time than in RS neurons, however selective blockers of both low and high threshold Ca2+ conductances failed to impair bursting activity. On the contrary, the perfusion of the slices with 0.5-1 microM TTX suppressed bursting behaviour in a critical time interval preceding the complete block of Na(+)-dependent action potentials. It is concluded that the persistent Na+ current INAP is the most important intrinsic factor for the typical firing properties of IB neurons, while Ca2+ and K+ conductances appear to contribute towards shaping bursts and controlling their recurrence rate. The morphology, connectivity and physiological properties of adapting and non-adapting RS neurons are particularly suited to the processing of respectively phasic and tonic inputs, whereas the properties of IB neurons are consistent with their suggested role in cortical rhythmogenesis and in the pathophysiological synchronized activities underlying epileptogenesis.

Action Potentials↗

PubMed1997

Long-term potentiation and depression in layer III and V pyramidal neurons of the cat sensorimotor cortex in vitro.

Synaptic plasticity of the cat sensorimotor cortex was examined intracellularly in vitro. After tetanic stimulation of the white matter, layer III and V pyramidal neurons showed long-term potentiation (LTP) of EPSPs in high incidence without GABA(A) antagonist. The incidence and magnitude of LTP were very conspicuous in layer V cells. After an NMDA receptor antagonist application, the synaptic potentiation was blocked completely in layer III but not in layer V cells. Long-term depression (LTD) of the evoked EPSPs was also induced by the same stimulation in some layer III cells, where a transient hyperpolarization of the membrane potential was observed during tetanus.

2-Amino-5-phosphonovalerate↗

PubMed1992

[Reparative changes in the sensorimotor cortex of the offspring in moderate prenatal alcoholism].

Sensorimotor cortex of 21-, 30-, 60-day-old offspring given prenatally moderate alcohol (2 g/kg) manifested signs of compensatory type: double nerve and glial cells, open capillaries, nearby nerve and glial cell bodies with basal membrane of capillaries. Intracellular reparative processes in dystrophic neurons were observed: nuclear activation, hyperplasia of cytoplasmic organelles, hypertrophy of some of them. Reparative processes are more distinct in 30-day-old rat offspring In 60-day-old offspring a polymorphic pattern of cortical synapses ultrastructure was found. However, dystrophic changes of neurons and interneuronal connections still remain.

Animals↗

PubMed2004

Effect of transcranial DC sensorimotor cortex stimulation on somatosensory evoked potentials in humans.

OBJECTIVE: To study the after-effect of transcranial direct current stimulation (tDCS) over the sensorimotor cortex on the size of somatosensory evoked potentials (SEPs) in humans. METHODS: SEPs were elicited by electrical stimulation of right or left median nerve at the wrist before and after anodal or cathodal tDCS in 8 healthy subjects. tDCS was applied for 10 min to the left motor cortex at a current strength of 1 mA. RESULTS: Amplitudes of P25/N33, N33/P40 (parietal components) and P22/N30 (frontal component) following right median nerve stimulation were significantly increased for at least 60 min after the end of anodal tDCS, whereas P14/N20, N20/P25 (parietal components) and N18/P22 (frontal component) were unaffected. There was no effect on SEPs evoked by left median nerve stimulation. Cathodal tDCS had no effect on SEPs evoked from stimulation of either arm. CONCLUSIONS: Anodal tDCS over the sensorimotor cortex can induce a long-lasting increase in the size of ipsilateral cortical components of SEPs. SIGNIFICANCE: tDCS can modulate cortical somatosensory processing in humans and might be a useful tool to induce plasticity in cortical sensory processing.

Adult↗

PubMed1990

Thalamic projections to sensorimotor cortex in the newborn macaque.

In the present experiments thalamocortical projections to different functional areas of the newborn (or prematurely delivered) macaque's sensorimotor cortex were labeled using retrogradely transported fluorescent dyes. Several dyes were used in each animal to (1) enable the direct comparison of the soma distributions of different thalamocortical projections within thalamic space, and (2) identify by double labeling neurons shared between these distributions. The projection patterns in the newborn macaque were compared with those of the mature animal reported by Darian-Smith et al. (J. Comp. Neurol. 1990;298:000-000). The main observations were (1) all thalamocortical projections to the sensorimotor cortex of the mature macaque are well established by embryonic days 146-150, as was shown by labeling these pathways in infants delivered by cesarean section, (2) a significant number of thalamocortical neurons in the newborn were double-labeled following dye injections into different pre- or postcentral areas, and where the margins of the dye uptake zones were separated by 3-8 mm, and (3) extensive projections from the anterior pulvinar nucleus to the motor and premotor cortex, and to the supplementary motor cortex were labeled in the newborn macaque. Both the exuberant terminal arborizations, and the precentral pulvinar projections were diminished by the 6th postnatal month, and absent in the mature macaque. The role of epigenetic determinants of these postnatal events is briefly considered.

Afferent Pathways↗

PubMed2004

Coupling between "hand" primary sensorimotor cortex and lower limb muscles after ulnar nerve surgical transfer in paraplegia.

Previous neuroimaging evidence revealed an "invasion" of "hand" over "lower limb" primary sensorimotor cortex in paraplegic subjects, with the exception of a rare patient who received a surgical motor reinnervation of hip-thigh muscles by the ulnar nerve. Here, the authors show that a functional reorganization of cortico-muscular and cortico-cortical oscillatory coupling was related to the recovery of the rare patient, as a paradigmatic case of long-term plasticity in human sensorimotor cortex after motor reinnervation of paraplegic muscles. This conclusion was based on electroencephalographic and electromyographic data collected while the patient and normal control subjects performed isometric muscle contraction of the left hand or lower limb. Cortico-muscular and cortico-cortical coupling was estimated by electroencephalographic-electromyographic coherence and directed transfer function of a multivariate autoregressive model.

Adult↗

PubMed2006

Layer-specific properties of the persistent sodium current in sensorimotor cortex.

We evaluated the characteristics of the persistent sodium current (I(NaP)) in pyramidal neurons of layers II/III and V in slices of rat sensorimotor cortex using whole cell patch-clamp recordings. In both layers, I(NaP) began activating around -60 mV and was half-activated at -43 mV. The I(NaP) peak amplitude and density were significantly higher in layer V. The voltage-dependent I(NaP) steady-state inactivation occurred at potentials that were significantly more positive in layer V (V(1/2): -42.3 +/- 1.1 mV) than in layer II/III (V(1/2): -46.8 +/- 1.6 mV). In both layers, a current fraction corresponding to about 25% of the maximal peak amplitude did not inactivate. The time course of I(NaP) inactivation and recovery from inactivation could be fitted with a biexponential function. In layer V pyramidal neurons the faster time constant of development of inactivation had variable values, ranging from 158.0 to 1,133.8 ms, but it was on average significantly slower than that in layer II/III (425.9 +/- 80.5 vs. 145.8 +/- 18.2 ms). In both layers, I(NaP) did not completely inactivate even with very long conditioning depolarizations (40 s at -10 mV). Recovery from inactivation was similar in the two layers. Layer V intrinsically bursting and regular spiking nonadapting neurons showed particularly prolonged depolarized plateau potentials when Ca2+ and K+ currents were blocked and slower early phase of I(NaP) development of inactivation. The biexponential kinetics characterizing the time-dependent inactivation of I(NaP) in layers II/III and V indicates a complex inactivating process that is incomplete, allowing a residual "persistent" current fraction that does not inactivate. Moreover, our data indicate that I(NaP) has uneven inactivation properties in pyramidal neurons of different layers of rat sensorimotor cortex. The higher current density, the rightward shifted voltage dependency of inactivation as well the slower kinetics of inactivation characterizing I(NaP) in layer V with respect to layer II/III pyramidal neurons may play a significant role in their ability to fire recurrent action potential bursts, as well in the high susceptibility to generate epileptic events.

Action Potentials↗

PubMed2003

Magnetic source imaging contributes to the presurgical identification of sensorimotor cortex in patients with frontal lobe epilepsy.

OBJECTIVE: One of the primary goals of preoperative evaluation of patients considered to be candidates for epilepsy surgery is the delineation of eloquent cortex adjacent to the area of resection. The aim of this study is the functional localization of the sensorimotor cortex in relation to an epileptogenic frontal lobe lesion, thus enabling a more complete resection in these patients while minimizing the risk of postoperative neurological deficits. METHODS: Participating in this study were patients with epilepsy, diagnosed as being related to a left or right frontal lobe lesion. Magnetoencephalographic responses evoked by electrical stimulation of the left and right hand median nerve were localized using single time-point equivalent dipole (ED) modeling, taking into account the realistic shape of the head. Instead of relying on the primary component (N/P 20) of the somatosensory evoked magnetic fields (SEFs) in this study ED fits were obtained for each time-point of the somatosensory evoked responses. On a cortical rendering, the reconstructed dipoles were depicted relative to the anatomy obtained from 3D-magnetic resonance imaging. RESULTS: The results of single time-point ED analysis including all the components of the responses indicated that the sources underlying the SEFs are located at the borders of the central sulcus (CS). The opposite direction of the sources underlying, respectively, the primary and subsequent late component of the SEFs indicated distinct sources located at the opposite banks of the CS. These sources, therefore, might correspond to the sensory hand projection area and the primary motor area of the sensorimotor cortex. It appeared that the location of the EDs obtained for the SEFs of 4 of the 7 patients studied were asymmetric for the left and right hemisphere, probably because of a displacement of the sensorimotor areas relative to the CS. The systematic assessment of the dipole fits compared to brain anatomy confirmed that volume conduction changes due to the lesion were not responsible for these observed deviations, thus leaving as explanation space-occupying and neurophysiological changes due to the lesion.

Adolescent↗

PubMed2002

Localisation of the sensorimotor cortex during surgery for brain tumours: feasibility and waveform patterns of somatosensory evoked potentials.

OBJECTIVE: Intraoperative localisation of the sensorimotor cortex using the phase reversal of somatosensory evoked potentials (SEPs) is an essential tool for surgery in and around the perirolandic gyri, but unsuccessful and perplexing results have been reported. This study examines the effect of tumour masses on the waveform characteristics and feasibility of SEP compared with functional neuronavigation and electrical motor cortex mapping. METHODS: In 230 patients with tumours of the sensorimotor region the SEP phase reversal of N20-P20 was recorded from the exposed cortex using a subdural grid or strip electrode. In one subgroup of 80 patients functional neuronavigation was performed with motor and sensory magnetic source imaging and in one subgroup of 40 patients the motor cortex hand area was localised by electrical stimulation mapping. RESULTS: The intraoperative SEP method was successful in 92% of all patients, it could be shown that the success rate rather depended on the location of the lesion than on preoperative neurological deficits. In 13% of the patients with postcentral tumours no N20-P20 phase reversal was recorded but characteristic polyphasic and high amplitude waves at 25 ms and later made the identification of the postcentral gyrus possible nevertheless. Electrical mapping of the motor cortex took up to 30 minutes until a clear result was obtained. It was successful in 37 patients, but failed in three patients with precentral and central lesions. Functional neuronavigation indicating the tumour margins and the motor and sensory evoked fields was possible in all patients. CONCLUSION: The SEP phase reversal of N20-P20 is a simple and reliable technique, but the success rate is much lower in large central and postcentral tumours. With the use of polyphasic late waveforms the sensorimotor cortex may be localised. By contrast with motor electrical mapping it is less time consuming. Functional neuronavigation is a desirable tool for both preoperative surgical planning and intraoperative use during surgery on perirolandic tumours, but compensation for brain shift, accuracy, and cost effectiveness are still a matter for discussion.

Adolescent↗

PubMed1988

[Participation of calcium-dependent potassium conductance in the processes of membrane hyperpolarization of the pyramidal neurons in the sensorimotor cortex in the cat].

In acute experiments on immobilized cats intracellular injection of Ca+ decreased of IPSP and postburst hyperpolarization amplitudes in pyramidal neurons of the sensorimotor cortex. Intracellular injection of ethylene glycol tetraacetic acid had almost the same effect. This substance also reduced the late part of spike afterhyperpolarization, while the early part remained practically unchanged. It is concluded that Ca2+-dependent K+-conductance might play an important role in the genesis of IPSP, postburst and spike afterhyperpolarization in the membrane of pyramidal neurons of the cat sensorimotor cortex.

Action Potentials↗

PubMed1984

[Structural aspects of the development and formation of growth cones in the sensorimotor cortex and caudate nucleus in ontogeny].

The structural organization and formation of the growth cones were studied on the basis of differentiating neurons and processes of the sensorimotor cortex and the caudate nucleus of rats in ontogenesis. Vesicles have been shown to be the major structural unit of the pericarial growth cones and the growth cones of the processes in the cerebral formations studied. The growth cones of the caudate nucleus show more frequently both vesicles and some cytoplasmic organelles as compared with those of the sensorimotor cortex. The growth cones are maximally pronounced at the end of the first postnatal week when the intensive growth and development of the dendrite tree and the ramification of axon terminals are observed. Simultaneously with the formation of the growth cones, their degeneration occurs as well; the latter being noted in animals of all the age groups studied. The questions concerning the formation of the growth cones and the genesis of the vesicular components of these formations are discussed.

Aging↗

PubMed1975

The effects of graded forelimb afferent volleys on acetylcholine release from cat sensorimotor cortex.

1. The acetylcholine (ACh)-releasing system in the cerebral cortex of pentobarbital anaesthetized cats was investigated by examining the effect of graded afferent volleys in forelimb nerves on ACh release from the sensorimotor cortices contralateral and ipsilateral to the site of stimulation. 2. Cortical ACh release was determined by bio-assay of neostigmine-containing perfusates which had been in contact with the cortical surfaces for 5-10 min periods. 3. Afferent volleys, generated by stimuli that were effective in activating as many fibres of a fibre group as possible without stimulating fibres in the group with the next highest threshold for activation, were monitored from dorsal roots C7 or C8 before entering the spinal cord. 4. Stimulation of the deep (DR) and superficial (SR) radial nerves and the radial (R) nerve proximal to the junction of the DR and SR were effective in enhancing ACh release only when either group III or groups III and IV fibres were included in the afferent volley. 5. The rates of ACh release from the primary receiving area of the sensorimotor cortex contralateral to the site of stimulation did not differ from those from the same area of the ipsilateral sensorimotor cortex. 6. The pertinence of this data to the various hypotheses concerning the nature of the ACh-releasing pathways to the cerebral cortex is discussed.

Acetylcholine↗

PubMed1988

[Reorganization of the synaptic inputs of the sensorimotor cortex to the red nucleus after the destruction of the cerebellar nucleus interpositus in adult cats].

Responses of the red nucleus to neurons to stimulation of the ipsilateral sensorimotor cortex have been studied in acute cats with preliminary lesion of the contralateral cerebellar nucleus interpositus (exposition from two weeks to a year and longer period) by intracellular recording technique. Acceleration of the monosynaptic EPSPs rise testifying to formation of the terminal dendrosomatic sprouting of axons of the corticorubral neurons on proximal segments of the somatodendritic membrane of the red nucleus neurons was observed. Various division of the sensorimotor cortex were unequally involved in the process of reorganization of synaptic inputs on the level of individual red nucleus neurons.

Animals↗

PubMed2005

Characteristics of the development of the sensorimotor cortex in rats aged 7-8 days in roller cultures of free-floating brain slices.

The development and formation of the neuronal architectonics of organotypic structures of the sensorimotor cortex in rats aged 7-8 days were studied in roller cultures. Free-floating slices were cultured for 2-3 weeks. Serial paraffin sections of cultured tissue were stained with fast cresyl violet as described by Nissl. Initially planar sections of the cortex were found to change their configuration during the process of cultivation and were transformed into spherical structures, retaining the major histotypic features of cortical formations. Radially orientated pyramidal cells and fusiform neurons formed a cortical rudiment, not discriminated into layers, over the whole surface of the spherical tissue structures. In free-floating slices of the sensorimotor cortex of rats aged 7-8 days in roller cultivation, histogenetic processes continued, leading to the formation of histotypic cortical structures similar to the phylogenetically more ancient allocortical formations of the forebrain.

Animals↗