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PubMed1978

Convergence of cerebral inputs onto dentate neurons in monkey.

The patterns of convergence of inputs from different areas of the cerebral cortex and the peripheral nerves onto single dentate neurons was studied in cebus monkeys. Dentate neurons receive their strongest and most numerous inputs from the premotor and supplementary motor regions of area 6. The sensorimotor and frontal cortices have weaker projections to the dentate nucleus, while peripheral nerves and many other association cortical areas were found to be effective in influencing cells of the lateral cerebellum. Dentate cells that respond to stimulation of hindlimb regions of the sensorimotor cortex tend to receive their principal input from the supplementary motor area and medial premotor regions, while neurons responding to forelimb sensorimotor cortex tend to receive lateral premotor inputs. In addition there is a topographical organization within the ventral pole of dentate with the hindlimb represented in the anterior regions and the forelimb in the posterior regions. These results are compared with those of similar studies of interpositus and dentate neurons in cat and monkey. The differences between the afferent inputs to dentate and interpositus are consistent with the suggestion that the lateral cerebellum is involved in programming movement parameters before movement initiation while the intermediate zone is involved in up-dating the evolving movement.

Animals↗

PubMed1994

Inter-subject variability of cerebral activations in acquiring a motor skill: a study with positron emission tomography.

Cerebral structures activated during sequential right-hand finger movements were mapped with regional cerebral blood flow (rCBF) measurements by positron emission tomography (PET) in individual subjects. Nine healthy volunteers were examined twice; after initial learning and after practicing the finger movement sequence for more than 1 h. Task-specific activation sites were identified by statistical distributions of maximal activity and region size in rCBF subtraction images. A consistent task-specific activation in all nine subjects was detected in the contralateral sensorimotor cortex at an average movement rate of 3.2 Hz reached after practice. This corresponded to a significant increase of the mean rCBF in the left primary sensorimotor cortex in spatially standardised and averaged PET images. Additional task-specific activation sites detected by individual analysis were found in the lateral and medial premotor, parietal, and cingulate areas, and in subcortical structures including the basal ganglia of both cerebral hemispheres. These activations showed no or little spatial overlap from subject to subject, thus being obscured in the analysis of pooled data. The observed activity patterns were related to movement rate and accuracy in individual subjects. It is suggested that the rCBF changes associated with acquisition of a motor skill in individual humans may correspond to plasticity of sensorimotor representations reported in monkeys.

Adult↗

PubMed1976

[Spatial organization of the direct connections of the sensory-motor cortex with the rhombencephalon and spinal cord in cats].

The distribution and ultrastructure of terminals of corticofugal fibres in the cat hindbrain and spinal cord were examined by light and electron microscopy in various periods of experimental degeneration elicited by large or small sensorimotor cortex destructions. Using the Fink-Heimer technique, it is shown that the corticofugal projections in the dorsal column nuclei and in the spinal intermediate zone are somatotopically arranged. Even small restricted areas of sensorimotor cortex give two separate descending supraspinal systems. The fibres of the first system are distributed in the dorsolateral and dorsolmedial parts of the spinal intermediate zone, predominantly contralaterally. The fibres of the second system are distributed in the dorsolateral and ventromedial parts of the intermediate zone (bilaterally). Degenerating axo-somatic and axo-dendritic contacts contain spherical vesicles. The majority of degenerating axons in n. cuneatus are 0.5-1,5 mu in diameter. The data obtained are discussed in connection with the electrophysiological data on the mechanisms of the cortical control of the spinal cord neuronal activity.

Animals↗

PubMedDate not supplied

Coherence analysis of the electrical activity of the rabbit brain in the process of the formation of the polarization dominant.

It has been demonstrated by means of the method of spectral coherence analysis in rabbits, under conditions of a chronic experiment, that when a motor "dominant" reaction is still absent in the early stages of the dominant, interhemispheric asymmetry appears in the Coh spectra of the electrical activity of the sensorimotor cortex and the VPL nucleus of the thalamus. On the other hand, interhemispheric asymmetry appears in the Coh spectra of the electrical activity of the sensorimotor cortex and the CA3 field of the dorsal hippocampus only at the stage at which the motor "dominant" reaction is recorded. The asymmetry in the alpha and beta ranges of the frequencies in the Coh spectra of the biopotentials of the investigated regions, which coincides with the attainment of the motor "dominant" reaction, is associated with the processes of the organization of movement.

Animals↗

PubMed1994

Corticospinal axons and mechanism of target innervation in rat lumbar spinal cord.

The aim of the present study is to investigate the mechanism by which outgrowing rat corticospinal (CS) axons innervate their spinal gray target areas. This study was carried out with the use of anterogradely transported horseradish peroxidase or 1,1-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI) after application in the sensorimotor cortex of rat pups varying in age between 5 days postnatal (P5) and 10 days postnatal (P10). The CS axons of neurons situated in the sensorimotor cortex have reached the ventral most parts of the dorsal funiculus at mid-lumbar spinal cord levels at the fifth postnatal day (P5). After a waiting period of 2 days some CS fibers change their direction and directly enter the adjacent spinal gray target areas. One day later, i.e., P8, CS target innervation by the formation of collateral branches can be observed. Finally, the development of collaterals by interstitial budding from their parent axons appears to be the major, but not the exclusive, mechanism by which CS axons innervate the lumbar spinal gray matter target area.

Animals↗

PubMed2003

Cortical activations associated with auditorily paced finger tapping.

We investigated neuromagnetic responses during an auditorily paced synchronization task using a 122-channel whole-head neuromagnetometer. Eight healthy right handed subjects were asked to synchronize left and right unilateral finger taps to a regular binaural pacing signal. Synchronization of the right hand with an auditory pacing signal is known to be associated with three tap-related neuromagnetic sources localized in the contralateral primary sensorimotor cortex. While the first source represents the neuromagnetic correlate of the motor command the second one reflects somatosensory feedback due to the finger movement. The functional meaning of the third source, which is also localized in the primary somatosensory cortex is still unclear. On the one hand this source represents a neuromagnetic correlate of somatosensory feedback due to the finger tap. On the other hand it has been suggested that the function of this source could additionally represent a cognitive process, which enables the subject to monitor the time distance between taps and clicks. The aim of the present study was to elucidate the function of this source, which would fundamentally reform the meaning of the primary somatosensory cortex in the timing of movements with respect to external events. The data of the present study demonstrate that the three sources in the contralateral sensorimotor cortex are stronger related to the tap than to the click. This result contradicts the assumption of a cognitive process localized in the primary somatosensory cortex. Thus, activation in the primary somatosensory cortex most likely represents exclusively somatosensory feedback and no further cognitive processes.

Acoustic Stimulation↗

PubMed1981

Absence of seizures or mirror foci in experimental epilepsy after excision of alumina and astrogliotic scar.

In 15 rhesus monkeys (Macaca mulatta) made epileptic by the sensorimotor cortical injection of alumina, the roles of alumina and of "mirror foci" were investigated by serial surgical excisions of the granuloma, surrounding epileptic focus, and contralateral homotopic sensorimotor cortex. Electroencephalographic and electrocorticographic recordings documented foci and transmitted contralateral epileptic activity. After the granuloma was removed, seizures continued but without alumina. After the epileptic cortex was removed, no seizure activity remained and no contralateral independent foci occurred. These findings indicate that the epilepsy incident to alumina injection into the sensorimotor cortex in monkey is not dependent on the continual presence of alumina and is not associated with independent or "mirror foci."

Aluminum Hydroxide↗

PubMed2002

MEG responses during rhythmic finger tapping in humans to phasic stimulation and their interpretation based on neural mechanisms.

The phase-resetting experiment was applied to human periodic finger tapping to understand how its rhythm is controlled by the internal neural clock that is assumed to exist. In the experiment, the right periodic tapping movement was disturbed transiently by a series of left finger taps in response to impulsive auditory cues presented randomly at various phases within the tapping cycle. After each left finger tap, the original periodic tapping was reestablished within several tapping cycles. Influences of the disturbance on the periodic right finger tapping varied depending on the phase of the periodic right finger tapping at which each left finger tap was made. It was confirmed that the periodic tapping was disturbed not by the auditory cues but by the left finger taps. Based on this fact, in this paper each single left tap was considered as the stimulus, and the phase of the periodic tapping of the right index finger when the left tap was executed as the phase of the stimulus. Responses of the neural activities (magnetoencephalography, MEG), the tapping movement, and the corresponding muscle activities (electromyography) were simultaneously measured. Phase-resetting curves (PRCs) representing the degree of phase reset as a function of the phase of the stimulus were obtained both for the left sensorimotor cortex MEG response and for the right index finger tapping response. The shapes of both PRCs were similar, suggesting that the phase reset of the left sensorimotor cortex activities and that of the finger tapping rhythm were the same. Four out of eight subjects showed type-0 reset in Winfree's definition, and the others showed type-1 reset. For general limit-cycle oscillators, type-0 reset is obtained for relatively strong perturbations and type 1 for weak perturbations. It was shown that the transient response of MEG to the single left tap stimuli in type-0 subjects, where the phase was progressively reset, were different from those in type-1 subjects. Based on detailed analysis of the differences, a neural network model for the phase reset of the tapping rhythm is proposed.

Acoustic Stimulation↗

PubMed1982

Selective retrograde transport of D-aspartate in spinal interneurons and cortical neurons of rats.

Retrograde labeling of neuronal elements in the brain and spinal cord has been investigated by autoradiographic techniques following injections of D-[3H]aspartate (asp), [3H] gamma-aminobutyric acid (GABA) or horseradish peroxidase (HRP) in the medulla and spinal cord of rats. Twenty-four hours after D-[3H]asp injections focused upon the cuneate nucleus, autoradiographic labeling is present over fibers in the pyramidal tract, internal capsule and over layer V pyramids in the forelimb representation of the sensorimotor cortex. After [3H]GABA injections in the same nucleus no labeling attributable to retrograde translocation can be detected in spinal segments, brain stem or cortex. Conversely, injections of 30% HRP in the cuneate nucleus label neurons in several brain stem nuclei, in spinal gray and in layer V of the sensorimotor cortex. These observations give further support to the proposed existence of a selective retrograde transport of D-[3H]asp and are consistent with the available evidence which indicates that the corticodorsal column nuclei path use glutamate and/or aspartate as neurotransmitter(s). D-[3H]Asp injections focused on the dorsal horn at cervical segments label a fraction of perikarya of the substantia gelatinosa and a sparser population of larger neurons in laminae IV to VI for a distance of 3-5 segments above and below the injection point. No brain stem neuronal perikarya appear labeled following spinal injections of D-[3H]asp although autoradiographic grains overlie pyramidal tract fibers on the side contralateral to the injection. This labeling however has not been observed rostral to lower pontine levels nor over cortical neurons at any of the survival times used in the present experiments (6-72 h). As in cases with cuneate injections this pattern of labeling contracts with that obtained after spinal injections of either [3H]GABA or HRP. Although labeling of neocortical neurons has not been observed after spinal injections of D [3H]asp, possibly as a result of the length of corticospinal axons, retrograde labeling of these elements for at least some distance may be taken as suggestive of a special affinity of their terminals for glutamate and/or aspartate.

Animals↗

PubMed1990

Local as well as remote functional and metabolic changes after focal ischemia in cats.

Behavior and limb placing ability were analyzed acutely and subacutely (up to 21 days) following unilateral occlusion of the middle cerebral artery (MCA) in cats. Immediately following occlusion, all tested cats started to display a sequence of different behaviors, characteristic for 1) an ipsilateral inhibition of dopaminergic activity in the caudate nucleus (CN); 2) an inhibition of GABAergic activity in the reticular substantia nigra (SNR); 3) a stimulation of GABA receptors in the deeper layers of the colliculus superior (CSDL) (starting-time of these phases: about 4, 12 and 25 min, respectively). The latter behavior was also present subacutely. In addition, unilateral orofacial dyskinetic movements were observed acutely as well as subacutely. Contralateral limb placing was deficient in all cats 60 min postocclusion; it was at least partly restored subacutely. Twenty-one days after the occlusion, [14C]-2-D-deoxyglucose uptake was relatively reduced in the ipsilateral CN (especially in its posterior part), the ipsilateral SNR and the ipsilateral CSDL. The anterior CN appeared to be less affected than the posterior CN. Metabolism was relatively reduced in the sensorimotor cortex only in part of the tested cats. The data show that unilateral MCA occlusion produces consistent functional changes in all structures studied apart from the sensorimotor cortex, viz. the CN, the SNR and the CSDL.

Animals↗

PubMed2000

Functional MRI cerebral activation and deactivation during finger movement.

OBJECTIVE: To examine interhemispheric interactions of motor processes by using functional MRI (fMRI). BACKGROUND: Despite evidence of interhemispheric inhibition from animal, clinical, and transcranial magnetic stimulation (TMS) studies, fMRI has not been used to explore activation and deactivation during unilateral motor tasks. fMRI changes associated with motor activity have traditionally been described by comparing cerebral activation during motor tasks relative to a "resting state." In addition to this standard comparison, we examined fMRI changes in the resting state relative to a motor task. METHODS: Thirteen healthy volunteers performed self-paced sequential finger/thumb tapping for each hand. During fMRI data acquisition, four epochs were obtained; each comprised of 30 seconds of rest, 30 seconds of right hand activity, and 30 seconds of left hand activity. Resultant echoplanar images were spatially normalized and spatially and temporally smoothed. RESULTS: As expected, hand movements produced activation in the contralateral sensorimotor cortex and adjacent subcortical regions and, when present, the ipsilateral cerebellum. However, hand movement also produced a significant deactivation (i.e., decreased blood flow) in the ipsilateral sensorimotor cortex and subcortical regions, and when present, the contralateral cerebellum. Conjunction analysis demonstrated regions that are activated by one hand and deactivated by the contralateral hand. CONCLUSION: Unilateral hand movements are associated with contralateral cerebral activation and ipsilateral cerebral deactivation, which we hypothesize result from transcallosal inhibition.

Adult↗

PubMed2002

Serial MRI findings in a case of primary lateral sclerosis.

A patient with primary lateral sclerosis (PLS) underwent MRI 3 times over 8.5 years. These images demonstrate progressive atrophy of the premotor, parietal, and primary sensorimotor cortex, with sparing of the temporal lobe, occipital lobe, and cerebellum. The pattern of cerebral atrophy was clearly restricted but was more extensive than expected from sensorimotor cortex pyramidal cell loss described in literature autopsy reports of PLS. Cortical motor system degeneration in PLS, whether primary or secondary, may be more extensive than previously believed.

Atrophy↗

PubMedDate not supplied

[Effect of polarization of different levels of the visual and motor analyzers on instrumental conditioned reflexes in dogs].

Dogs with stabilized instrumental conditioned reflexes of tonic form to a bell and flickering light, exhibited a depression or complete inhibition of the reflexes after a short anode polarization of the lateral geniculate body (LGB). Polarization of the superior colliculi exerted a similar influence but to a lesser degree. Prolonged polarization of the visual cortex completely inhibited conditioned reflexes to light at the very first or second minute of its action. The degree of inhibition depended on the current intensity, the area of its action and the functional state of the animal. Polarization of the sensorimotor cortex resulted in a delay and often in complete inhibition of the instrumental reflexes. Polarization of the red nucleus also inhibited the reflexes. Evoked potentials recorded from the LGB, the superior colliculi and the visual cortex underwent considerable changes (decrease of the primary response and disappearance of the secondary response) after polarization of the sensorimotor cortex.

Animals↗

PubMed1991

Neurones with epileptiform discharge in the central nervous system and chronic pain. Experimental and clinical investigations.

Epileptiform discharge was recorded from neurons in the thalamic nuclei of chronic pain patients during stereotactic surgery. Hyperactive neurons showed regular firing of 3-5 trains of epileptic-like group discharges with a frequency of 4 to 5 Hz. As described by Lombard et al. (1979), we operated on the dorsal root unilaterally, sectioning C5 to Thl in male Wistar rats. One to three months after the operation, hyperactive neurons were examined in the contra-lateral thalamic nuclei (VP, zona incerta), and lemniscus medialis. The firing patterns and distribution of hyperactive neurons in these animals was very similar to those of humans. The hyperactive neuron was unaffected by electrical stimulation of the nucleus raphe dorsalis (NRD) and locus ceruleus (LC). Administration of phenytoin and diazepam reduced the firing. However, no effect was seen with valproic acid. During spreading depression of the sensorimotor cortex, a remarkable reduction was seen on the firing of thalamic hyperactive neurons. This suggested that hyperactive neurons of the thalamic nuclei received facilitory effects from the sensorimotor cortex with little influence from adrenergic or serotoenergic systems.

Animals↗

PubMed1989

Cerebral glucose utilization in rat brain during phenobarbital withdrawal.

The phenobarbital withdrawal syndrome in rats is characterized by tremors, arched back, weight loss and hyperactivity. This syndrome is shown to be associated with both general and localized increases in cerebral glucose utilization. An increase in glucose utilization (significant at the P less than or equal to 0.001 level) was observed in 72% of the 57 structures examined. Increases in glucose utilization of greater than or equal to 180% of control values were noted in structures associated with the motor system (columns in the frontal sensorimotor cortex, globus pallidus, dentate nucleus of the cerebellum and ovoid areas in the cerebellar vermis), thalamic nuclei (lateral and posterior), dorsal lateral geniculate, mammillary body, cingulate cortex, locus ceruleus, and cerebellar flocculus and paraflocculus. The structures showing the greatest increase in glucose utilization were cerebellar paraflocculus (257% of control), columns in the frontal sensorimotor cortex (247% of control) and ovoid areas in the cerebellar vermis (223% of control). Areas of the brain that have been described as cell body areas for serotonergic (raphe), noradrenergic (locus ceruleus), dopaminergic (substantia nigra, zona compacta) and GABAergic (globus pallidus) neurons also showed increases in glucose utilization. The pattern of cerebral glucose utilization accompanying the phenobarbital withdrawal syndrome in rats contrasts with that for morphine withdrawal and exhibits both similarities and differences with respect to ethanol withdrawal.

Animals↗

PubMed1996

Decreased neuronal nitric oxide synthase messenger RNA and somatostatin messenger RNA in the striatum of Huntington's disease.

The cellular abundance of neuronal nitric oxide synthase and somatostatin messenger RNAs was compared in the caudate nucleus, putamen and sensorimotor cortex of Huntington's disease and control cases. Neuronal nitric oxide synthase messenger RNA was significantly decreased in the caudate nucleus and putamen, but not in the sensorimotor cortex in Huntington's disease; the decrease in neuronal nitric oxide synthase messenger RNA became more pronounced with the severity of the disease. Somatostatin gene expression was significantly decreased in the dorsal putamen in Huntington's disease, but was essentially unchanged in all other regions examined. The density of neurons expressing detectable levels of neuronal nitric oxide synthase messenger RNA was reduced in the striata of Huntington's disease cases with advanced pathology; the density of neurons expressing detectable levels of somatostatin messenger RNA was similar in control and Huntington's disease cases. Neuropeptide Y-, somatostatin- and NADPH-diaphorase-positive neurons were consistently present throughout the striatum across all the grades of the disease. Neuronal nitric oxide synthase and NADPH-diaphorase activity (a histochemical marker for nitric oxide synthase-containing neurons) co-localize with somatostatin and neuropeptide Y in interneurons in the human striatum and cerebral cortex. Although the neurodegeneration associated with Huntington's disease is most evident in the striatum (particularly the dorsal regions), neuronal nitric oxide synthase/neuropeptide Y/somatostatin interneurons are relatively spared. Nitric oxide released by neuronal nitric oxide synthase-containing neurons may mediate glutamate-induced excitotoxic cell death, a mechanism proposed to be instrumental in causing the neurodegeneration seen in Huntington's disease. The results described here suggest that although the population of interneurons containing somatostatin, neuropeptide Y and neuronal nitric oxide synthase do survive in the striatum in Huntington's disease they are damaged during the course of the disease. The results also show that the reduction in neuronal nitric oxide synthase and somatostatin messenger RNAs is most pronounced in the more severely affected dorsal regions of the striatum. Furthermore, the loss of neuronal nitric oxide messenger RNA becomes more pronounced with the severity of the disease; thus implying a down-regulation in neuronal nitric oxide synthase messenger RNA synthesis, and potentially neuronal nitric oxide synthase protein levels, in Huntington's disease.

Aged↗

PubMedDate not supplied

[Intercentral relations of the electrical processes of the rabbit brain with a polarization dominant].

The dynamics of changes in intercentral relations of electrical activity of the sensorimotor and premotor zones of both hemispheres and the ventroposterolateral (VPL) nucleus of the left and right thalamus at formation of motor dominant under the action of the DC anode in the rabbit sensorimotor cortex was studied by the method of spectral-correlation analysis. It is shown that in the much less than dominant much greater than motor analyzer (the sensorimotor cortex and VPL) highly coherent connections of electrical processes are formed in the delta-range with conjugated lowering of biopotential connections between the structures of the motor analyzer of the much less than nondominant much greater than part of the brain. At the same time differently directed connections of electrical processes are formed between the structures of the motor analyzer, and between the premotor cortex and focus area. Thus, during formation of the much less than polarization much greater than dominant, a new structure of the intercentral relations of electrical processes is established not only in the much less than dominant much greater than but also in the other half of the brain.

Acoustic Stimulation↗

PubMedDate not supplied

Hypoxic hypoxia induces different biochemical changes in the cortex of the right and left hemispheres of rat brain.

The activity of acetylcholinesterase (AChE), adenylate cyclase (AC), 5'-nucleotidase (NT), Na+, K(+)-ATPase, as well as the contents of phospholipids (PL) and gangliosides (G) per mg of protein in homogenate, crude membrane (P2) fraction, and synaptosomes from the sensorimotor cortex of the right and left hemispheres of rat brain were analyzed under normal and hypoxic conditions. The authors found that under normal physiological conditions there are no significant differences of the studied parameters in homogenates of sensorimotor cortex from the right and left hemispheres. In P2 fractions, and especially in preparations of synaptosomes from the right and left cortex, differences in the activity of 5'-NT and AC were found. Hypoxia (pO2 = 7.8%) was shown to alter studied parameters (AChE, AC, Na+, K(+)-ATPase activity, and PL content) mainly in the right hemisphere.

5'-Nucleotidase↗