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At least 613 records · Page 34Linked to original sources
PubMed1996

[Functional imaging of the sensorimotor cortex using an ultra-fast MR imaging method].

UNLABELLED: The aim of this study was to assess changes in brain activity during a motor task and variable sensory stimulation using echo planar imaging, which represents the fastest clinically usefull imaging technique available. MATERIALS AND METHODS: The subjects of this study were 11 healthy-volunteers, 4 males and 11 females, with an average of 26.4 years. The subjects were instructed to tap the fingers of one hand as the motor task. Compressed air was applied 5 times a second as "simple" sensory stimulation. Simple figures were drawn on the subjects palm as "complex" sensory stimulation. In all cases, functional imaging was performed by T2*-weighted echo planar imaging (TE = 53 msec, TR = 3000 msec, flip angle = 90 degrees, matrix 64 x 64, FOV = 205 mm, slice thickness = 8 mm) alternately at rest and during the task (intervals: 30 sec). A total of 60 images was collected in 3 minutes. Images obtained by subtracting images at rest and during the task were analyzed. RESULTS AND DISCUSSION: Almost all subjects showed a transient signal increase in the contralateral paracentral region during simple sensory stimulation. Continuous signal increases in the contra- and/or ipsi-lateral para-central region were observed during complex sensory stimulation. Some exhibited signal increases in the parietal or frontal association cortex, but they disappeared when subject's attention was distracted during stimulation. All subjects displayed signal increases in the contralateral para-central region during the motor task. Some of them exhibited signal increases in the medial frontal area (supplementary motor area) and ipsilateral para-central region. These results suggest that the signal increases of functional MRI reflect not only simple reactions to stimulation but higher cerebral function as well.

Adult↗
PubMedDate not supplied

[The ensemble organization of the sensorimotor cortex in ontogeny].

Examination of sensomotor zone of the human brain cortex in human subjects (from newborns up to 20 year-olds) with yearly intervals revealed the presence of all neuroglia-vascular ensembles components without any relationship in composition by the moment of birth. Significant increase of the cortical layers and sublayers thickness, connected with growth of the volume of all type neurons and development of dendritic-axonic networks, vessels and glia were noted. Stair-like groups of neurons are present by the moment of birth, and so called racemose groups, the composition of which is diverse in different fields form by the age of three when vertical and horizontal contacts system grows more complicate and the astrocyte glia differentiates. The size of pyramidal neurons (Betz cells included), fusiform and stellate neurons increases by the age of six. By 10-12 years intraensemble, interensemble and transcortical contacts attain the high level of development. By 16-18 years ensemble organization of the cortex reaches the level, characteristic to adults in main parameters of its architectonics.

Adolescent↗
PubMedDate not supplied

[The biochemical characteristics of the sensorimotor cortex in right-handed, left-handed and ambidextrous rats].

The activity of acetylcholinesterase (AChE), 5'-nucleotidase (NT), adenylate cyclase (AC) in P2 fraction of sensory-motor cortex was studied in right-handed, left-handed and ambidexters rats on the 2-nd and 45-th day after revealing preferable forepaw at taking feedstuff out of horizontal tube (1 case, 10 presentations). By bilateral (averaging right and left hemispheres) values of AChE, NT and AC ambidexters differ from animals with absolute motor preference and right-handed rats differ from left-handed ones (2-nd day). In 1.5 month differences between ambidexter and animals with preferable extremity are revealed by NT and AC activity. Chemical brain asymmetry is revealed for ambidexters (AChE, 45-th day), right-handed rats (NT, 45-th day) and left-handed animals (AC, 2-nd day). Functional importance of biochemical characteristics studied is discussed.

5'-Nucleotidase↗
PubMedDate not supplied

Pathophysiology of sensorimotor cortex in cortical myoclonus.

We have studied greatly enhanced cortical responses to somatosensory stimuli [giant somatosensory evoked potential (SEP) or magnetic field (SEF)] and cortical activities preceding the myoclonus (premyoclonus spike) in patients with cortical myoclonus, using magnetoencephalographic (MEG) techniques. A P1m component of giant SEF was estimated as a dipole positioned on the postcentral gyrus in all giant SEFs. This indicates that abnormally enhanced responses to sensory stimuli originate from the sensory cortex. In most of the patients with cortical reflex myoclonus, a dipole for the premyoclonus spike was also localized on the postcentral gyrus, which suggests that abnormal activation of the sensory cortex produces the spontaneous myoclonus. In one patient with galactosialidosis, two dipoles, one on the postcentral and the other on the precentral gyrus, could reasonably explain the premyoclonus spike. In the other patient with cortical reflex myoclonus, the premyoclonus spike associated with jerks of the lower limb muscle was estimated to be one dipole on the superior frontal gyrus just anterior to the paracentral lobule. This suggests that both spontaneous myoclonus and enhanced long loop reflex are generated by abnormal activation of the motor cortex in this patient. In a patient with epilepsia partialis continua who had no long loop reflexes, the premyoclonus spike was demonstrated to be positioned on the precentral gyrus, which indicates that abnormal activation of the motor cortex causes the spontaneous myoclonus in this patient. Our MEG studies demonstrated that abnormalities of the sensory or motor cortices contribute differently to the generation of myoclonus in cortical myoclonus, despite the fact that the sensory cortex is the main contributor in most of them.

Electric Stimulation↗
PubMed1997

Mapping of the sensorimotor cortex: functional MR and magnetic source imaging.

PURPOSE: To assess the reliability and comparability of functional MR imaging and magnetic source imaging for mapping the somatosensory cortex. METHODS: Parallel studies were performed in eight volunteer subjects in whom both hemispheres were measured with the use of painless tactile stimulation of the tip of each index finger. Magnetic source imaging was performed using a 37-channel biomagnetometer; evoked magnetic fields were analyzed using the single-equivalent dipole representation to ascertain the neuronal source. Functional MR imaging was performed on a 1.5-T MR unit. Blocks of images during periods of rest and activation were acquired using gradient-echo echo-planar imaging. Correlation analysis identified pixels in which signal intensity correlated with the stimulus function. A subsequent requirement for spatial connectivity of activation was imposed to reduce the random occurrence of pixels satisfying the correlation criteria. RESULTS: Using temporal and spatial statistical criteria for activation, we found that functional MR imaging showed activation in 1 of 16 hemispheres. In three cases, this was accompanied by activity either frontally or ipsilateral to the stimulus. Magnetic source imaging showed parietal contralateral location in all 16 cases. Where successful localization was achieved with both methods, the separation between sources appeared to be between 1 and 4 cm. Functional MR imaging localizations tended to lie more superficially than the magnetic source imaging localizations. Performance of a simple motor task, rather than use of somatosensory stimulation, resulted in a cortical signal change detectable with a similar functional MR imaging approach in all cases, suggesting the more robust nature of this stimulus. CONCLUSIONS: Functional mapping of the somatosensory cortex can be achieved with functional MR imaging or magnetic source imaging. Functional MR imaging yields more spurious locations and fails to show localization more often. If neuronal signal propagation pathways are of interest, the temporal resolution of functional MR imaging alone may be inadequate. A combination of magnetic source imaging and functional MR imaging may allow improved sensitivity, fewer false-positive results, and high spatial and temporal resolution.

Adult↗
PubMed1997

[Age-related changes in the cytoarchitectonics of the human sensorimotor cortex].

The study of human brain sensomotor cortex architectonics within the period since birth up to 20 years with a year long intervals demonstrated that pyramidal neurons differentiation is most intensive in area 4p throughout the period since birth up to 6 months, in area 6p--up to one year and in area 6op--up to 2 years. Pyramidal neurons proportion in sublayer 3 increases significantly in all sensomotor cortex areas within the first postnatal year and its growth continues up to 15-16 years. In area 5 proportion of pyramidal neurons in areas studied undergoes the period of intensive growth up to one year, than it starts to increase by 6-7 years, and finishes its growth in areas 6 and 6op by 14 years and in area 4p--by 16 years.

Adolescent↗
PubMed1985

Is the hindlimb representation of the rat's cortex a 'sensorimotor amalgam'?

In the rat, the hindlimb representation of the sensorimotor cortex is characterized by the presence of large pyramids in the fifth layer and a dense granular layer ('sensorimotor amalgam'). The objective was to investigate in the rat, whether or not the efferent zones to the gastrocnemius muscle and the proprioceptive feedback projection from that muscle to the cortex are co-extensive. To this end, the proprioceptive zone was mapped by means of field potentials and single unit discharges evoked by controlled longitudinal displacements of the gastrocnemius tendon. The efferent zones to the gastrocnemius muscle were mapped by means of intracortical microstimulation (ICMS; less than 30 microA). The proprioceptive zone occupied a territory extending from 1.0 to 2.5 mm caudal to the bregma and from 2.0 to 3.0 mm lateral from the midline. The response properties were similar to those observed previously in area 3a of monkeys. For sinusoidal displacements threshold amplitude decreased with increasing stretch frequency. The modal value of response latency was 7 ms, the shortest latency 4 ms. The ICMS zone lay 0.5 to 1.5 mm caudal to bregma having an overlap of 0.5 mm with the proprioceptive region. The proprioceptive as well as the motor areas lay within the granular cortex, but overlapped only to a small extent.

Animals↗
PubMed2000

Neuromagnetic localization of CMV generators using incomplete and full-head biomagnetometer.

Contingent magnetic variation (CMV) data were recorded in three healthy male subjects using a 2 x 37 biomagnetometer system. The experiment was repeated for one of the subjects using a 151 whole-head biomagnetometer; the same auditory GO/NOGO choice reaction time paradigm as in the first experiment was used, extended to include repetitions of identical runs and additional control conditions. Magnetic field tomography was applied to the averaged data of each subject, for each run and condition (e.g., GO/NOGO). An independent estimate of the current density in the brain was obtained every few milliseconds. The slow components were emphasized by integrating the square of the current density vector, pixel by pixel, revealing in each subject activity in the auditory cortex, sensorimotor cortex, inferior prefrontal area, and posterior inferior parietal area. The intersubject variability was large, but looking across subjects the auditory and sensorimotor cortex (which were best covered by the two probes) were consistently identified in each subject as contributing to the generation of the early and late slow CMV components. These findings were confirmed by the whole-head single-subject experiment, in which slow activity was also identified in the supplementary motor area (SMA) and posterior cingulate cortex (PCC), areas very likely missed in the first experiment because of the limited view of the twin system. The PCC and particularly the SMA activations were substantially reduced when identical runs were repeated.

Adult↗
PubMed1994

NMDA receptors mediate amphetamine-induced upregulation of zif/268 and preprodynorphin mRNA expression in rat striatum.

The role of N-methyl-D-aspartate (NMDA) excitatory amino acid receptors in D-amphetamine (AMPH)-induced behavioral changes and increased expression of the nuclear transcription factors, c-fos and zif/268, and preprodynorphin (PPD) mRNA in various regions of rat forebrain was investigated with quantitative in situ hybridization histochemistry. Three hours after a single injection of AMPH (5 mg/kg, i.p.), the mRNA expression of zif/268, but not c-fos, in dorsal striatum (caudate nucleus) and cerebral cortex (sensorimotor cortex), and PPD mRNA in dorsal striatum, was upregulated. Pretreatment of rats with MK-801 (0.5 mg/kg, i.p.) attenuated AMPH-induced striatal and cortical expression of zif/268 mRNA and striatal expression of PPD mRNA, without affecting the behavioral alterations induced by AMPH. A similar, dose-dependent suppression of AMPH-induced zif/268 and PPD mRNA in striatum and cortex was also revealed after systemic administration of (+/-)-3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP) at doses of 5 and 10 mg/kg. CPP, only at the higher dose, slightly attenuated behavioral activity induced by AMPH. MK-801 and CPP (at higher dose) alone suppressed basal (constitutive) zif/268 mRNA levels in both striatum and cortex regions. No significant effect of either antagonist was found on constitutive expression of striatal PPD mRNA. These studies indicate that NMDA receptors mediate, at least in part, activation of zif/268 and PPD gene expression in striatum and sensorimotor cortex by a single injection of AMPH. Furthermore, NMDA receptor-mediated gene regulation more likely is involved in long-term neuronal plasticity to drug exposure than in acute drug effects since NMDA receptor antagonists had little or no effect on the acute behavioral actions of AMPH.

Animals↗
PubMed2001

Cortical activation in patients with functional hemispherectomy.

Functional hemispherectomy, a safe and effective therapeutical procedure in medically intractable epilepsy, offers the chance to investigate a strictly unilateral cortical activation in ipsilateral limb movement. We assessed the pattern of cortical activation in a group of patients following functional hemispherectomy. We measured regional cerebral blood flow (rCBF) in 6 patients postoperatively and 6 normal subjects with positron emission tomography using 15[O]H2O as a tracer. Brain activation was achieved by passive elbow movements of the affected arm. Analysis of group results and between-group comparisons were performed with statistical parametric mapping, (SPM96). In normal subjects brain activation was found contralaterally in the cranial sensorimotor cortex and the supplementary motor area and ipsilaterally in the inferior parietal cortex. In patients significant rCBF increases were found in the inferior parietal cortex, caudal sensorimotor cortex and the supplementary motor area ipsilaterally. The activation was weaker than in normal subjects. Compared with normal subjects patients showed additional activation in the premotor cortex, caudal sensorimotor cortex and the inferior parietal cortex of the remaining hemisphere. Less activation compared with normal subjects was found in the cranial sensorimotor cortex and the supplementary motor area. A functional network connecting the inferior parietal cortex, premotor cortex and the supplementary motor area as well as the existence of ipsilateral projections originating from these regions may explain why these areas are predominantly involved in reorganization confined to a single hemisphere.

Adult↗
PubMed2000

Effect of thyroid hormone deficiency on developmental expression of goalpha gene in the brain of neonatal rats by competitive RT-PCR and in situ hybridization histochemistry.

Goalpha is a guanine nucloetide-binding regulatory protein alpha subunit which is mainly distributed in the central nervous system, but it has not previously been reported how it is regulated by thyroid hormone in the brain of neonatal rat at transcriptional levels. In this report, we used quantitative competitive reverse transcriptional PCR to quantify the effects of TH deficiency on Goalpha gene expression in the brain of neonatal rat at mRNA levels. It was found that Goalpha mRNA levels in the brain of 14-day-old rats significantly increased over 3-fold after induction of perinatal hypothyroidism, and declined markedly after treatment of thyroxine replacement. In situ hybridization histochemistry was further employed to observe the time-course and spatial expression of Goalpha gene in the brain of neonatal rats affected by thyroid hormone deficiency during the developmental period. The data showed that perinatal hypothyroidism can enhance Goalpha mRNA levels in the temporal cortex, sensorimotor cortex, piriform cortex, amygdala, hippocampal CA1-4 subfields, dentate gyrus, arcuate nucleus (AR) and ventromedial hypothalamic nucleus (VMH) of hypothalamus, but not in the striate cortex, cingulate cortex, claustrum, caudate/putamen and thalamus in the brain of rat at 7-21 days post-partum. The results suggest that up-regulation of Goalpha gene expression may be one kind of common mechanism responsible for neurological deficits in some brain areas arising from thyroid hormone deficiency in the critical periods of neonatal rats.

Animals↗