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Results for “Sensorimotor Cortex”

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PubMed1995

Functional magnetic resonance imaging mapping of the sensorimotor cortex with tactile stimulation.

The purpose of this study is to compare tactile stimulation of the palm with voluntary movement of the fingers as paradigms for mapping the sensorimotor cortex in functional magnetic resonance imaging. In 22 subjects, 24 sets of functional magnetic resonance images were obtained with echoplanar acquisitions and cross-correlation image processing techniques. Two tasks were employed: a motor task in which subjects moved the thumb and index finger of one hand and a sensory task in which the palm was scratched by another person. The activation from the two tasks coincided entirely in 20 sets and partially in 3 sets. In one case, no activation was seen with the motor task. The study suggests that tactile stimulation of the palm is useful and reliable for mapping the sensorimotor cortex.

Adult↗

PubMedDate not supplied

The morphofunctional characteristics of neurons of the sensorimotor cortex of aged rabbits during the trace assimilation of rhythm.

The formation of trace rhythm assimilation (an analog of the conditioned reflex to time) by neurons of the sensorimotor cortex in response to prolonged (10-20 min) electrodermal stimulation of an extremity at a frequency of 0.5-1 or 2 Hz was investigated in awake adult (5-7 months), old (54-65 months), and very old (66-85 months) rabbits. The data of the spectral analysis of the impulse activity of 460 neurons showed aged-related differences in the formation of trace rhythm assimilation by neurons: it takes place after one to two series (1st to 2nd days of the experiment) in young animals; after two to four series of periodic stimulation (2nd to 3rd days of the experiment) in the old animals; in very old animals rhythmic stimulation essentially did not result in rhythm assimilation by cortical neurons. Quantitative and qualitative morphological changes in nerve and glial cells in the sensorimotor cortex of old rabbits as compared with young rabbits were identified. It is hypothesized that deviations in the course of mnestic processes observed in animals during aging may be associated with destructive phenomena in the neocortex during normal aging.

Aging↗

PubMed1993

Sensorimotor cortex projections to the ventrolateral and the dorsomedial medulla oblongata in the rat.

After small pressure injections of Fluorogold (FG), and Dextran-tetramethylrodamine (DR) into the dorsal motor nucleus of the vagus/nucleus of the solitary tract (DMV/NTS) and the rostral ventrolateral medulla (RVLM), respectively, retrograde FG-labelled cells were found mainly in the sensorimotor cortex; retrograde DR-labelled cells were located in the same cortical areas and in the prefrontal cortex. Double-labelled cells were also found in the sensorimotor cortical areas. These results provide evidence of direct projections from the sensorimotor cortex to the DMV/NTS and RVLM and suggest that somatic cortical areas directly control cardiovascular output during sensory and somatic processes.

Animals↗

PubMed1993

Rapid reliable measurement of lesion parameters for studies of motor recovery after sensorimotor cortex injury in the rat.

Measurement of the ability of rats to traverse a narrow elevated beam has been used to quantitate motor recovery after unilateral injury to the sensorimotor cortex. Lesion extent is an important variable to consider in studies of the effects of drugs on beam-walking recovery. However, traditional histologic evaluation precludes neurochemical measurements in brain tissue. The present study was carried out to determine how well the dimensions of the lesion measured at the surface of the brain correlate with subsequent motor recovery in comparison with standard histology. The maximum medial extent of the lesion (closest approximation of the lesion to the inter-hemispheric fissure) was correlated with subsequent recovery (Spearman r = 0.61, P = 0.02) whereas the lesion surface area was not correlated with recovery (Spearman r = 0.25, P = 0.30). This data compared favorably with measures that were dependent on histologic tissue preparation. Furthermore, measurements of surface lesion parameters were highly reliable (intra- and inter-observer reliability for lesion surface maximum medial extent and lesion surface area were r2 = 0.88, 0.96, 0.97, and 0.96, P = 0.0001, respectively). Lesion surface parameters provide a valid and reliable measure of lesion size and extent for studies of beam-walking recovery after injury to the sensorimotor cortex.

Animals↗

PubMed1998

A parametric analysis of the 'rate effect' in the sensorimotor cortex: a functional magnetic resonance imaging analysis in human subjects.

We studied the effects of different movement speeds of unimanual right hand movements on functional magnetic resonance signal changes in the sensorimotor cortex using echo planar imaging (EPI). Six healthy right-handed subjects were scanned at rest and while executing a finger tapping task with their right index finger. Movement frequency was visually paced at rates ranging from 0.5 to 5 Hz, separated by 0.5 Hz steps. The blood oxygen level dependent (BOLD) response within the left sensorimotor cortex was linearly and positively related to movement frequency. However, this relation holds (r2 = 0.91) only for movement frequencies faster than 1 Hz (1.5-5 Hz). For the slower frequencies there was an initial sharp increase of the BOLD response from 0.5 to 1 Hz followed by an activity drop for 1.5 Hz. These results are compatible with the idea that two different motor control modes are operative during slow or fast movements. During slow movements a computational demanding on-line feedback control mode is operative resulting in strong BOLD signals indicating extensive neural activity. During faster movements on the other hand a program-like motor control mode is operative resulting in less demanding neural computations. The amount of neural computation for the latter control mode increases with increasing movement speed.

Adult↗

PubMedDate not supplied

Location of the sensorimotor cortex: functional and conventional MR compared.

PURPOSE: To determine the value of functional MR imaging to supplement conventional MR imaging for locating the rolandic cortex. METHODS: Parasagittal MR images acquired in conjunction with functional MR images were reviewed. The central sulcus was identified on the MR images by conventional parcellation methods. In the functional MR images, the sensorimotor cortex (rolandic cortex) was identified by the activation secondary to finger and thumb movement or tactile stimulation of the palm. The location of the central sulcus and rolandic cortex was compared. RESULTS: In 18 of 23 studies, the central sulcus selected by anatomic criteria coincided exactly or approximately with the cortex activated by the motor or sensory tasks. In two cases of tumor, the rolandic cortex could be located by means of the activation, but the central sulcus was not identified because of severe distortion of anatomic landmarks. In two volunteers, the central sulcus identified by anatomic landmarks did not coincide with the activated cortex. CONCLUSION: This study demonstrates that functional imaging supplements anatomic imaging in locating the sensorimotor cortex. Functional MR imaging may be a useful adjunct to conventional MR imaging to determine noninvasively the proximity of eloquent brain to focal brain lesions.

Adult↗

PubMed2005

Short-lasting impairment of temperature perception by high frequency rTMS of the sensorimotor cortex.

OBJECTIVE: Repetitive transcranial magnetic stimulation (rTMS) has become a useful tool for investigating and even modulating human brain function. RTMS of the human motor cortex can produce changes in excitability that outlast the period of stimulation. To investigate the persistent effect of high-frequency rTMS of sensorimotor cortex (SM1) on somatosensory function. METHODS: We evaluated the thermal thresholds (cold and warm sensation) in 14 normal subjects before and after a short train of 5Hz rTMS over the SM1 or occipital cortex (OC). RESULTS: Threshold for cold perception was increased immediately after rTMS of the left SM1 and no effects at all were noticed after OC stimulation. There was a slight, not significant, increase of warm threshold immediately after the rTMS of the left SM1 and no effects at all were noticed after OC stimulation. CONCLUSIONS: High frequency rTMS over primary sensorimotor cortex seems to modulate sensory function related to thermal (cold) perception. SIGNIFICANCE: The method may be useful for both the study of normal human physiology of temperature perception and for rTMS based manipulation of brain plasticity in patients with sensory disturbances.

Adult↗

PubMed1997

d-Amphetamine attenuates decreased cerebral glucose utilization after unilateral sensorimotor cortex contusion in rats.

Unilateral contusion injury to the sensorimotor cortex causes, among other symptoms, a transient contralateral hindlimb hemiparesis in rats. A single i.p. 2 mg/kg dose of d-amphetamine (d-AMPH) 24 h after injury accelerates spontaneous recovery from this particular deficit. The mechanism(s) of spontaneous and d-AMPH enhanced recovery are unknown but alleviation of a neuronal depression has been proposed. This quantitative CMRglu study was designed to determine effects of cortical contusion injury and d-AMPH on CMRglu in cortical and subcortical structures. At 2 days after injury, CMRglu was significantly reduced compared to sham-operated controls only in structures ipsilateral to contusion. Affected structures included the caudate putamen, medial geniculate nucleus, lateral geniculate nucleus and the parietal cortex immediately posterior to injury. By 6 days post-contusion, the hypometabolism partially reversed in all structures. A single low dose of d-AMPH significantly alleviated the post-traumatic CMRglu reduction at 2 days after injury. Importantly, while this alleviation was not significant for any single structure, the main effect of treatment was highly significant. d-AMPH increased CMRglu at 2 days post-injury by 18-33% compared to contused/saline-treated rats. These results suggest that alleviation of neuronal metabolic depression may contribute to spontaneous and d-AMPH enhanced recovery.

Animals↗

PubMed2002

Dopamine modulation of activity of cat sensorimotor cortex neurons during conditioned reflexes.

The effects of iontophoretic application of dopamine and selective D1 or D2 dopamine receptor agonists and antagonists on impulse activity of neurons of the deep layers of the sensorimotor cortex of cat were investigated during performance of a conditioned paw movement task. The application of dopamine, Quinpirole (selective D2 receptor agonist) or SKF 38393 (selective D1 receptor agonist) increased both background (P<0.001) and evoked impulse activity (P<0.05 for selective agonists). Selective D2 and D1 receptor antagonists (Sulpiride and SKF 83566, respectively) both increased the latency of neural responses and significantly increased the latency of the conditioned paw movements (P<0.01). These data suggest that during natural physiological functions subcortical dopamine neurons provide facilitation of activity pyramidal neurons of sensorimotor cortex.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗

PubMed1986

Branched projections of cat sensorimotor cortex: multiple retrograde labeling via commissural corticocortical, decussated corticostriatal and undecussated corticostriatal axons.

The common origins and interrelationships of commissural corticocortical and descending corticostriatal projections were assessed by multiple retrograde labeling of neurons in the precruciate sensorimotor cortex of the cat. The major finding was that some of these neurons had axons that branched at least twice to send collaterals to contralateral cortical sites and bilateral subcortical sites in the caudate nucleus. Regardless of their collateralization, these axons originated mainly from pyramidal neurons of small-medium size located in cortical laminae III-V. A considerable component of the corticocortical and corticostriatal inputs derived from the same neurons. These fibers subserve both intra- and interhemispheric linkages of the sensorimotor cortex with itself and the basal ganglia.

Animals↗

PubMed2002

Extradural compression of sensorimotor cortex: a useful model for studies on ischemic brain damage and neuroprotection.

Behavioral and morphological changes were examined for up to 9 days after moderate cerebral ischemia caused by slow compression of a specific brain area in the sensorimotor cortex of Sprague-Dawley rats. Functional deficits after the cerebral ischemia were assessed by daily beam-walking tests, whereas morphological changes were verified using Nissl staining on day 1, 2, 3, 5, and 9, respectively. Rats exposed to cerebral ischemia displayed impaired beam walking performance. Mild hypothermia prevented both the compression-produced functional deficits and the brain damage. Younger (5 weeks) animals showed less neurological deficits than older (9 weeks) animals. Histological examination revealed a pronounced increase in the number of injured pyramidal neurons from day 1 to day 3 in the primarily damaged brain region. Between day 3 and day 5, the number of injured cells remained constant, whereafter there was a slow decline of thionin-positive neurons as examined on day 9. The noncompetitive NMDA receptor antagonist, dizocilpine (MK-801; 3 mg/kg, i.p.), did not alter the neurological impairment on day 1, but improved thereafter the rate of functional recovery and reduced the number of damaged cells. The AMPA receptor antagonist, LY326325 (15 or 30 mg/kg; i.p.), dose-dependently diminished the neurological deficits on day 1, enhanced the rate of recovery, and reduced the number of injured neurons over time. Our data suggest that short-lasting extradural compression of a well-defined brain area in the sensorimotor cortex is a highly reproducible model with a high success rate for the study of functional and morphological consequences after cerebral ischemia as well as for the evaluation of the therapeutic potential of novel, neuroprotective pharmacological agents.

Animals↗

PubMed1999

Movement-related glutamate levels in rat hippocampus, striatum, and sensorimotor cortex.

Changes in brain extracellular glutamate during movement stress were studied using in vivo microdialysis. Male Long-Evans rats were placed in a clear cylinder designed to elicit behavioral activation while undergoing microdialysis sampling from either the hippocampus, striatum or sensorimotor cortex. Glutamate levels were determined by high performance liquid chromatography with fluorescence detection in the dialysates taken before, during, and after exposure to the cylinder. Animals were in a behaviorally quiescent state before exposure to the cylinder, but they demonstrated increases in rearing, locomotion, and turning while in the cylinder. Dialysate glutamate levels were significantly enhanced in the samples taken while the rat was in the cylinder compared with samples taken before or after exposure to the cylinder. In a second study, rats were implanted with bilateral probes in the forelimb sensorimotor cortex, and one forelimb was immobilized by means of a plaster of paris cast. Glutamate, aspartate, serine, and taurine levels were quantified in casted animals. In casted animals, dialysate glutamate levels were lower on the side contralateral to the immobilized limb during both quiescence and movement stress. Aspartate and taurine, but not serine levels increased during movement stress in both the side contralateral and the side ipsilateral to the immobilized limb. These results suggest that there is extracellular overflow of glutamate and other neuroactive amino acids during spontaneous movement, and chronic disuse can suppress extracellular glutamate levels.

Amino Acids↗

PubMedDate not supplied

[Neurophysiological characteristics of the rat sensorimotor cortex in early motor deprivation and training].

Young rats, beginning with the age of 1 month, were kept in small size cages for 3 months, i.e., were exposed to 3-month motor deprivation. This exposure caused a modulating effect of a diminished activity of neuronal populations in the sensorimotor cortex which manifested as a prolongation of the latent periods of primary responses and recovery cycles of excitation of the neuronal populations generating the responses. The differences in the opposite changes in the sensorimotor cortex of the young animals that developed following prolonged deprivation and training of similar duration were seen in the parameters of excitation recovery cycles rather than in the latent periods. The reserve capabilities of the developing cortical structure associated with the modulation of excitation recovery cycles during training were 2.0-2.5 times greater than the dysfunctional changes in the same neuronal populations during motor deprivation. Both early motor deprivation and training did not influence the heterochronic development, emergence and subsequent attainment of the maximum amplitude of components of the testing primary response in the process of a gradual increase of the stimulus-to-stimulus interval.

Animals↗

PubMed1998

Functional image-guided surgery of intracranial tumors located in or near the sensorimotor cortex.

OBJECT: The purpose of this study was to evaluate the efficacy of noninvasive preoperative functional imaging data used in an interactive fashion in the operating room. The authors describe a method of registering preoperative functional magnetic resonance (fMR) imaging localization of sensorimotor cortex with a frameless stereotactic surgical navigation device. METHODS: The day before surgery, patients underwent blood oxygen level-dependent fMR imaging while performing a finger-tapping motor paradigm. Immediately afterward an anatomical stereotactic MR image was acquired. Raw fMR imaging data were analyzed offline at a separate workstation, and the resulting functional maps were registered to a high-resolution anatomical scan. The fused functional-anatomical images were then downloaded onto a surgical navigation computer via an ethernet connection. At surgery, the brain was exposed in the standard fashion, and the sensorimotor cortex was identified by direct cortical stimulation, the use of somatosensory evoked potentials, or both. This localization was then compared with that predicted by the registered fMR study. Thirteen procedures were performed in 12 patients. The mean registration error was 2.2 mm. The predicted location of motor and/or sensory cortex matched that found on intraoperative mapping in all 12 patients tested. Maximal tumor resection was accomplished in each case and no new permanent neurological deficits resulted. CONCLUSIONS: Compared with conventional brain mapping techniques, fMR image-guided surgery may allow for smaller brain exposures, localization of the language cortex with the patient under general anesthesia, and the mapping of multiple functional sites. The scanning equipment used in this method may be more readily available than for other functional imaging techniques such as positron emission tomography or magnetoencephalography.

Adult↗

PubMed2002

Insulin-like growth factor-1 does not ameliorate the age-related decline in presumptive inhibitory synapses in layer 2 of rat sensorimotor cortex.

Four old (29 months) Brown Norway x Fischer 344 (BN x F344) rats received intracerebroventricular infusion of insulin-like growth factor-1 (IGF-1) and four middle-aged (18 months) and four old (29 months) rats received infusion of saline for 28 days. Sensorimotor cortex containing layer 2 was blocked and processed for electron microscopy. Thin (700 A) and semithin (1 microm) sections were collected from the same anatomical space for quantification of synapses and neurons, respectively, using the physical disector. Numerical density (Nv) of presumptive inhibitory synapses in layer 2 of sensorimotor cortex has been reported to decline with age Poe et al., 2001; Brunso-Bechtold et al. [Brain Res. 872 (2000) 125]. Infusion of IGF-1 did not affect the density of synapses or neurons when old IGF-1 animals were compared with old saline animals.

Aging↗

PubMed2006

Transcranial magnetic stimulation over sensorimotor cortex disrupts anticipatory reflex gain modulation for skilled action.

Skilled interactions with new environments require flexible changes to the transformation from somatosensory signals to motor outputs. Transcortical reflex gains are known to be modulated according to task and environmental dynamics, but the mechanism of this modulation remains unclear. We examined reflex organization in the sensorimotor cortex. Subjects performed point-to-point arm movements into predictable force fields. When a small perturbation was applied just before the arm encountered the force field, reflex responses in the shoulder muscles changed according to the upcoming force field direction, indicating anticipatory reflex gain modulation. However, when a transcranial magnetic stimulation (TMS) was applied before the reflex response to such perturbations so that the silent period caused by TMS overlapped the reflex processing period, this modulation was abolished, while the reflex itself remained. Loss of reflex gain modulation could not be explained by reduced reflex amplitudes nor by peripheral effects of TMS on the muscles themselves. Instead, we suggest that TMS disrupted interneuronal networks in the sensorimotor cortex, which contribute to reflex gain modulation rather than reflex generation. We suggest that these networks normally provide the adaptability of rapid sensorimotor reflex responses by regulating reflex gains according to the current dynamical environment.

Adult↗

PubMed2001

Functional MRI detects posterior shifts in primary sensorimotor cortex activation after stroke: evidence of local adaptive reorganization?

BACKGROUND AND PURPOSE: Further recovery from stroke can occur late, long after the end of the apparent evolution of pathological changes. This observation and evidence obtained from functional imaging for altered patterns of activation after brain injury suggest that cortical reorganization may contribute to recovery. Here, we have tested for potentially adaptive reorganization in the primary sensorimotor cortex. METHODS: We used functional MRI to study brain activation with dominant hand movement in right-handed healthy control subjects (n=20) and in patients after subcortical ischemic infarcts causing mild to moderate right hemiparesis (n=8). The numbers of pixels activated above threshold and the geometric centers of activation clusters were determined. RESULTS: Although random-effects analysis identified some differences in activation maxima, similar regions of the brain were activated with sequential finger tapping in the patient and control groups. However, consistent with the heterogeneity in the locations, sizes, and times after the infarcts, patterns and magnitudes of activation showed some heterogeneity between patients. Nonetheless, for the group as a whole, there was a decreased motor cortex lateralization index (-0.1+/-0.7 in patients and 0.7+/-0.3 in control subjects, P=0.05). The geometric center of activation of the primary sensorimotor cortex activation cluster contralateral to the affected hand in patients was also shifted posteriorly (mean 12 mm, P<0.04) relative to that of the control subjects. To confirm the latter observation, the activation response with a simple hand-tapping task was examined in some of the subjects. With this task, there was also a trend (mean 10 mm, P=0.07) toward a more posterior activation in patients. CONCLUSIONS: These results confirm altered patterns of activation in the contralateral and ipsilateral primary sensorimotor cortices after recovery from strokes causing hemiparesis. These (and other changes) suggest that modulation of widely distributed parts of the cortical network for motor control may contribute to adaptations leading to functional recovery after stroke.

Acute Disease↗

PubMedDate not supplied

[Analysis of the layer distribution of transcallosal responses in the sensorimotor cortex of kittens in the 1st month of life].

In experiments on 23 kittens ageing between 1-30 days, anaesthetized by barbiturate and immobilized by diplacine, studies have been made on the distribution of transcallosal responses (TCRs) along the whole diameter of the sensorimotor cortex. In order to obtain more accurate data on localization of the sources and drains of extracellular current vertical component, a method of double graphic differentiation was used. It was shown that in 1-2-day kittens TCRs have a positive oscillation form throughout all the depth of recording. During the 1st week, TCRs from the cortical surface acquired a positive-negative configuration, remaining mostly positive in deeper layers. At this ontogenetic stage, the drain of positive-negative oscillation is focused in the layer I. In 2-3-week kittens, positive-negative potentials on the surface were transformed into negative-positive responses in deep layers. The drains of this deep negative component were localized in the layers III and V-VI. On the 4th week, positive-negative TCRs on the surface changed into negative-positive potentials at various depths depending on the spatial position of the recording point. The drain of deep-laid negative component in the focus of maximum activity was found in the layer V, out of its boundaries--in the layers II-III. Ontogenetic dynamics was revealed of current drains localization of both TCRs components in the sensorimotor cortex in new-born kittens.

Aging↗