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PubMed2002

The window of opportunity for administration of magnesium therapy following focal brain injury is 24 h but is task dependent in the rat.

The present study was conducted to establish the window of opportunity for the administration of a regimen of MgCl2 pharmacotherapy following focal injury to the brain. Rats were subjected to unilateral electrolytic lesions of the sensorimotor cortex (SMC) and administered a regimen of MgCl2 (1.0 mmol/kg) or 0.9% saline (1.0 ml/kg) beginning either 15 min, 8 h or 24 h after injury. Subsequent injections were administered 24 and 72 h after the initial treatment. Behavioral testing assessed recovery of function on several sensorimotor behaviors for 24 days following injury. The results of the present study suggest that treatment with a regimen of MgCl2 significantly facilitated recovery of function on the forelimb-->forelimb and vibrissae-->forelimb placing tests when administered 15 min, 8 h or 24 h after injury compared with saline-treated rats. Recovery of locomotor placing was significantly facilitated at 15 min and 8 h but not at 24 h compared with saline-treated rats. In addition, the ability of MgCl2 to limit neuronal loss in the ipsilateral ventral posterior lateral (VPL) nucleus of the thalamus was seen at only the 15-min treatment interval. These results suggest that the window of opportunity for MgCl2 pharmacotherapy is 24 h, task dependent and is much shorter for protecting neurons in the VPL.

Animals↗
PubMed2003

Correlation between cerebral reorganization and motor recovery after subcortical infarcts.

Our objective was to investigate correlations between clinical motor scores and cerebral sensorimotor activation to demonstrate that this reorganization is the neural substratum of motor recovery. Correlation analyses identified reorganization processes shared by all patients. Nine patients with first-time corticospinal tract lacuna were clinically evaluated using the NIH stroke scale, the motricity index, and the Barthel index. Patients were strictly selected for pure motor deficits. They underwent a first fMRI session (E1) 11 days after stroke, and then a second (E2) 4 weeks later. The task used was a calibrated repetitive passive flexion/extension of the paretic wrist. The control task was rest. Six healthy subjects followed the same protocol. Patients were also clinically evaluated 4 and 12 months after stroke. All patients improved significantly between E1 and E2. For E1 and E2, the ipsilesional primary sensorimotor and premotor cortex, supplementary motor area (SMA), and bilateral Broadmann area (BA) 40 were activated. Activation intensity was greater at the second examination except in the ipsilesional superior BA 40. Magnitude of activation was lower than that of controls except for well-recovered patients. E1 clinical hand motor score and E1 cerebral activation correlated in the SMA proper and inferior ipsilesional BA 40. Thus, we demonstrated early functionality of the sensorimotor system. The whole sensorimotor network activation correlated with motor status at E2, indicating a recovery of its function when activated. Moreover, the activation pattern in the acute phase (E1) had a predictive value: early recruitment and high activation of the SMA and inferior BA 40 were correlated with a faster or better motor recovery. On the contrary, activation of the contralesional hemisphere (prefrontal cortex and BA 39-40) and of the posterior cingulate/precuneus (BA 7-31) predicted a slower recovery.

Adult↗
PubMedDate not supplied

Sensorimotor control is impaired in dancers with functional ankle instability.

BACKGROUND: Factors potentially causing chronic instability after ankle inversion sprains have rarely been examined during the injuring movement. PURPOSE: To compare control of ankle movement during quiet stance and after inversion perturbation in chronically unstable ankles (n = 16) with healthy controls (n = 26). METHODS: Movement control was measured as magnitude of lateral ankle oscillation, using 3SPACE Fastrak during single leg stance (baseline oscillation) in two foot positions, flat and demi-pointe. In both positions, time to resume baseline oscillation after inversion perturbation (perturbation time) of 15 degrees for the flat foot and 7.5 degrees on demi-pointe was also determined. RESULTS: Baseline oscillation on demi-pointe was significantly smaller (P < 0.005) for the sprained group (2.5 +/- 0.5 mm) than for controls (4.0 +/- 2.3 mm). Perturbation time for the flat foot was significantly longer (P < 0.05) for the sprained group (2.2 +/- 0.4 seconds) than for controls (1.8 +/- 0.5 seconds). However, failure rate was higher (P < 0.05) among the sprained group than controls for perturbation with the foot flat and baseline oscillation on demi-pointe. CONCLUSIONS: Findings demonstrated altered sensorimotor control in chronically unstable ankles. Those sprainers who successfully completed the tasks minimized oscillation. The impairments in the sprained group may reflect deficits in either movement detection, peroneal muscle response, or both.

Adult↗
PubMed2002

Functional magnetic resonance imaging of the human sensorimotor cortex using a novel vibrotactile stimulator.

The purpose of this study was to investigate the fMRI response of the sensorimotor cortex to a vibration paradigm produced by a novel vibrotactile stimulator. Fifteen contiguous slices covering the sensorimotor cortex parallel to the anterior (AC) and posterior commissure (PC) line were obtained with echoplanar magnetic resonance imaging at 1.5T. Cortical activity in ten healthy subjects (20-45 years) was investigated during vibration (50 Hz) of the palm of the right hand and compared to a finger-to-thumb tapping paradigm. For the vibration paradigm a mechanically driven vibration head was mounted on the palm of the right hand. The new vibration device produces vibration frequencies (1-130 Hz) and displacement amplitudes (0.5-4 mm) suitable to elicit the tonic vibratory reflex. The fMRI measurement during vibratory stimulation revealed activation in the pre- and postcentral gyrus in all subjects. These activations were comparable to the finger-to-thumb tapping paradigm. The advantages of the new MR compatible vibration device include effective transmission of the stimulus and controlled vibration frequencies and intensities. These preliminary fMRI results indicate that vibration can be an alternative paradigm for the evaluation of sensory and motor functions in patients unable to perform active motor paradigms.

Adult↗
PubMed2001

Imaging in vivo brain-hormone interaction in the control of eating and obesity.

The field of neuroimaging has made great progress in the mapping of human brain function. In this article, we present a functional magnetic resonance imaging (fMRI) study on the hypothalamic regulation of satiety and its relationship with obesity. The fMRI techniques have been proven invaluable for analyzing changes in brain activity that are associated with most sensorimotor and cognitive functions. However, few studies have been successful in the delineation of the interaction between the central nervous system and the endocrine system, due to the lack of suitable mapping methods which can pinpoint the onset of changes in neuronal activity (e.g., those following eating or drug intake). We have recently introduced a new fMRI method known as temporal clustering analysis (TCA) for dynamically tracking the time course of brain activation. Along with simultaneous blood sampling for the circulating hormone levels, the fMRI techniques with TCA may provide an integrated view of the nervous and endocrine systems in vivo, and thus greatly enhance our understanding of the complex interplay between neural events and hormonal signals.

Cluster Analysis↗
PubMed1993

Motor learning.

Bilateral damage of the medial temporal lobe system prevents the formation of new declarative memories but leaves intact knowledge that was acquired before damage. For motor learning, no structure has been identified that plays a comparable role for the consolidation of motor memories. The deficits of motor learning are focal and show a similar allocation to the various sensorimotor subsystems, as do the corresponding non-mnemonic functions. The involvement of sensorimotor circuitries changes during motor learning so that association areas are preferentially activated in the early stages, and cerebello- and striato-motor-cortical loops are preferentially activated in the late stages of motor learning. Recent neuroanatomical and neurophysiological findings on the effects of brain lesions in human and non-human primates are discussed.

Animals↗
PubMed2000

Frequency dependence of the functional MRI response after electrical median nerve stimulation.

Localizing sensorimotor areas with high resolution functional MRI is of considerable interest for a wide range of medical applications from the preoperative planning of neurosurgical interventions to determining the course of neuroplastic reorganisation after brain lesions. We examined the effect of the stimulation frequency on the blood oxygen level dependent (BOLD) fMRI response and on perfusion weighted fMRI using electrical median nerve stimulation at 5, 15, 40, and 100 Hz. BOLD fMRI was performed using a single shot gradient echo EPI sequence to acquire 15 contiguous slices. For the qualitative flow sensitive studies, a single slice inversion recovery prepared spin echo echoplanar sequence (IR-SE EPI) was used. In the primary sensorimotor cortex, a linear increase of the fMRI-BOLD response, affecting both the number of activated pixels and the amplitude of the signal changes, was seen with increasing stimulation frequencies. The qualitative in-flow sensitive studies, using the IR-SE EPI sequence, indicate that the tissue perfusion also increases over the same range of frequencies. This implicates that larger fMRI responses can be obtained if electrical median nerve stimulation is performed at higher frequencies. The results are compared with electrophysiological data, which show a decrease of the early somatosensory evoked potentials at higher frequencies.

Adult↗
PubMed2006

A mouse model of sensorimotor controlled cortical impact: characterization using longitudinal magnetic resonance imaging, behavioral assessments and histology.

The present study establishes a new mouse model for traumatic brain injury (TBI), using an electromechanically driven linear motor impactor device to deliver a lateral controlled cortical impact (CCI) injury to the sensorimotor cortex. Lesion cavity size was measured, and inter-animal consistency demonstrated, at 14 days post injury. Qualitative information regarding damage progression over time was obtained by scanning with high field magnetic resonance imaging (MRI) at five time points following injury. Functional impairment and recovery were measured with the Rotarod, gridwalk and cylinder tests, and lesion cavity volume was measured post mortem with thionin-stained tissue sections. The study establishes the reliability of a linear-motor based device for producing repeatable damage in a CCI model, demonstrates the power of longitudinal MRI in studying damage evolution, and confirms that a simple battery of functional tests record sensorimotor impairment and recovery.

Animals↗
PubMedDate not supplied

[The effect of motor training on evoked sensorimotor cortex potentials in rats during ontogenesis].

Investigation into the influence of motor training on the functional activity of the rat sensorimotor cortex in ontogenesis has shown that three to four-month training, starting at the age of four weeks, leads to a statistically significant enhancement of sensorimotor cortex activity both by latencies and recovery cycles durations. A similar six to seven-month locomotor training produces the same statistically significant results. The differences in the shifts of functional activity after motor training observed between two age groups are not statistically significant. The probability of changes in the average definitive electrophysiological parameters of functional activity after motor training observed between two age groups are not statistically significant. The probability of changes in the average definitive electrophysiological parameters of functional activity of the sensorimotor cortex is suggested in rats aged more than a month, as a result of individual experience.

Animals↗
PubMed1998

Locomotor capacity attributable to step training versus spontaneous recovery after spinalization in adult cats.

Locomotor performance, hindlimb muscle activity and gait patterns during stepping were studied in step-trained and non-trained female, adult spinal cats. Changes in locomotor characteristics relative to prespinalization bipedal and quadrupedal stepping patterns were used to evaluate the effects of step training on the capacity to execute full weight-bearing stepping after spinalization. Step training consisted of full weight-bearing stepping of the hindlimbs at the greatest range of treadmill speeds possible at any given stage of locomotor recovery. In the initial stages of training the limbs were assisted as needed to execute successful steps. On the basis of two behavioral criteria, the maximum speed of treadmill stepping and the number of successful steps per unit time, the ability to step was at least 3 times greater in animals trained to step versus those allowed to recover spontaneously, i.e., the non-trained. The greater success in stepping was reflected in several physiological and kinematic properties. For example, the amplitude of electromyograph (EMG) bursts in the tibialis anterior (an ankle dorsiflexor), the amount of extension at the end of both the stance (E3) and swing (E1) phases of the step cycle, and the amount of lift of the hindlimb during swing were greater in step-trained than in non-trained spinal cats. The changes that occurred in response to training reflected functional adaptations at specific phases of the step cycle, e.g., enhanced flexor and extensor function. The improved stepping capacity attributable to step training is interpreted as a change in the probability of the appropriate neurons being activated in a temporally appropriate manner. This interpretation, in turn, suggests that step training facilitated or reinforced the function of extant sensorimotor pathways rather than promoting the generation of additional pathways. These results show that the capacity of the adult lumbar spinal cord to generate full weight-bearing stepping over a range of speeds is defined, in large part, by the functional experience of the spinal cord after supraspinal connectivity has been eliminated. These results have obvious implications with regards to 1) the possibility of motor learning occurring in the spinal cord; 2) the importance of considering "motor experience" in assessing the effect of any postspinalization intervention; and 3) the utilization of use-dependent interventions in facilitating and enhancing motor recovery.

Animals↗
PubMedDate not supplied

Influence of dominant motivation on the functional organization of auditory input to the sensorimotor cortex of the cat brain.

The results of experiments reviewed in this article demonstrate the possibility of the transformation of the frequency tuning of the auditory input into the sensorimotor cortex (SMC) of the cat under the influence of a dominant motivation. Similar changes took place in the parietal cortex (PC) but they were significantly less in absolute magnitude. The identified transformation of the frequency tuning of the auditory input into the SMC and the PC is in agreement with a change in the biological significance of the auditory signals of kittens for females in the period of lactation, and corresponds for each cat to the spectral composition of the vocalizations of its own kittens.

Acoustic Stimulation↗
PubMed1980

Reinnervation of the denervated striatum by substantia nigra transplants: functional consequences as revealed by pharmacological and sensorimotor testing.

Embryonic substantia nigra (SN) was transplanted to the neostriatum in adult rats subjected to a unilateral or serial bilateral destruction of the nigrostriatal dopamine (DA) pathway. The survival of the graft and the growth of DA-containing fibers from the graft into the host brain was studied by fluorescence histochemistry and micro-fluorometry. The motor asymmetry, and the contralateral 'sensory neglect' induced by a unilateral destruction of the nigrostriatal DA pathway, were monitored in the transplanted rats and in non-transplanted controls through repeated measurements of the amphetamine-and apomorphine-induced rotational behaviour, and through analysis of the rats performance in a number of sensorimotor tests. Finally, the development of aphagia and adipsia after a serial bilateral destruction of both nigrostriatal DA pathways were followed in rats bearing bilateral SN transplants and in lesioned non-transplanted controls. The results show that large parts of the dorsal neostriatum can be reinnervated by DA-containing axons from the intracortical transplant and that this new DA input can fully compensate for the amphetamine-induced motor assymmetry that resulted from the initial destruction of the innate nigrostriatal DA pathway. The fluorescence microscopical observations provide strong evidence that the compensation of the amphetamine-induced rotational response was specifically related to the re-establishment of a new DA input to the denervated neostriatum, and that the degree of rotational compensation was well correlated to the magnitude of ingrowth into the neostriatum. Subsequent surgical removal of the SN transplant reinstated the initial rotational behaviour. In sharp contrast to the marked compensation in motor asymmetry, the transplanted rats showed no tendency to recover in their sensorimotor performance. Thus, while the sensorimotor deficit had recovered in the control group a marked contralateral 'sensory neglect' remained in the transplanted animals. Furthermore, removal of the transplant produced a significant improvement in their sensorimotor performance within 3 days. In the bilaterally transplanted animals the presence of the transplants did not prevent the development of severe adipsia, aphagia and akinesia following the destruction of the remaining contralateral nigrostriatal pathway. In fact, the recovery from the consummatory deficits tended to be better in the lesioned control rats than in the transplanted ones. It is concluded that SN transplants reinnervation the dorsal part of the neostriatum are able to replace the innate SN in normalizing some aspects of the rats motor behaviour, while their sensorimotor deficits and deficits in consummatory behaviour were unaffected. It is suggested that this dissociation of transplant-induced recovery is due to the failure of the SN transplants to reinnervate those parts of the neostriatum which are most directly implicated in sensorimotor and consummatory behaviour.

Animals↗
PubMed2003

Reduced G(i) and G(o) protein function in the rat nucleus accumbens attenuates sensorimotor gating deficits.

Prepulse inhibition of the acoustic startle response (PPI) is a cross-species measure of sensorimotor gating, which is severely disrupted in patients with schizophrenia. PPI deficits can be produced in experimental animals by administration of selective D(2)-like dopamine receptor agonists in the nucleus accumbens (NAc). G proteins coupled to these receptors reportedly are altered in the NAc of patients with schizophrenia. Therefore, we sought to determine whether experimental inactivation of intracellular G proteins in the NAc alters PPI. In adult male Sprague-Dawley rats, baseline PPI was determined by presenting acoustic pulse stimuli (120 dB) alone or preceded 100 ms earlier by prepulse stimuli (3, 6 or 12 dB above 70 dB ambient noise). PPI disruption was assessed in the presence of quinpirole (0.0, 0.05, 0.1, 0.5 mg/kg, sc), and pertussis toxin (PTX; 0.05 microg/side) was then infused into the NAc bilaterally. Ten days later, quinpirole-mediated disruption of PPI was significantly reduced; neither PTX alone, nor heat-inactivated PTX had any effect on quinpirole-induced PPI reductions. PPI was significantly higher after PTX infusion upon moderate quinpirole challenge, suggesting that D(2)-like receptors were less effective. PTX treatment significantly reduced basal and dopamine-stimulated [35S]GTPgammaS binding in the NAc core and shell, and reduced G(i)(alpha) protein immunoreactivity in the NAc. The results suggest that PPI disruption mediated by D(2)-like receptor activation in the NAc depends on coupling to G(i) and G(o) proteins, alteration of which could cause sensorimotor gating deficits in schizophrenia.

Acoustic Stimulation↗
PubMed1995

Functional magnetic resonance imaging of sensory and motor cortex: comparison with electrophysiological localization.

Functional magnetic resonance (MR) imaging was performed using a 1.5-tesla MR system to localize sensorimotor cortex. Six neurologically normal subjects were studied by means of axial gradient-echo images with a motor task and one or more sensory tasks: 1) electrical stimulation of the median nerve; 2) continuous brushing over the thenar region; and 3) pulsed flow of compressed air over the palm and digits. An increased MR signal was observed in or near the central sulcus, consistent with the location of primary sensory and motor cortex. Four patients were studied using echo planar imaging sequences and motor and sensory tasks. Three patients had focal refractory seizures secondary to a lesion impinging on sensorimotor cortex. Activation seen on functional MR imaging was coextensive with the location of the sensorimotor area determined by evoked potentials and electrical stimulation. Functional MR imaging provides a useful noninvasive method of localization and functional assessment of sensorimotor cortex.

Adult↗
PubMed2003

Ipsilateral cortical activation during finger sequences of increasing complexity: representation of movement difficulty or memory load?

OBJECTIVE: To investigate, if increasing ipsilateral cortical activation during sequential finger movements of increasing complexity relates to the difficulty of transitions ('sequence complexity') or to increasing motor memory load ('sequence length'). METHODS: Pre-learned, memorized sequences (MEM) of different complexities (SIMPLE=e.g., 2-2-2-2-2-2-2-2-2-2-2-2-2-2-2-2; SCALE=e.g., 2-5-4-3-2-5-4-3-2-5-4-3-2-5-4-3; and COMPLEX=e.g., 5-3-2-4-3-4-2-5-4-4-2-3-5-2-4-3; 2=index, 5=pinky) were randomly alternated with visually instructed, novel sequences (NOV) of matched complexity. In this design, memory load co-varied with complexity during MEM because of increasing length of the memorized sequences. In NOV, memory load was eliminated because each sequence element was prompted by an instructive visual cue. Cortical activation was measured by spectral power analysis of 28-channel electroencephalogram (EEG) in 15 healthy, right-handed subjects. RESULTS: The increases of ipsilateral sensorimotor activation from SIMPLE over SCALE to COMPLEX in NOV were linearly correlated with the corresponding pattern in MEM (P<0.01). No significant differences were found between MEM and NOV (analysis of variance, n.s.). CONCLUSIONS: The similar dynamics of cortical activation patterns across movement sequences during MEM and NOV indicate that increasing ipsilateral activation primarily reflects processing of increasingly difficult transitions between movements, and not motor memory load. SIGNIFICANCE: Function of ipsilateral sensorimotor areas during complex motor behavior.

Adult↗
PubMed2001

Axonal damage associated with enlargement of ventricles during hydrocephalus: a silver impregnation study.

Motor and cognitive deficits are commonly associated with hydrocephalus. Although the mechanisms responsible for these impairments have not been confirmed, neuronal cell death and axon degeneration may play an important role, and have long lasting consequences on neuronal connectivity. The goal of this study was to determine if neural degeneration occurred during hydrocephalus in structures anatomically related to cognitive motor functioning, namely, the sensorimotor cortex, neostriatum, hippocampus and corpus callosum. Neural damage, as visualized by silver staining, was examined in adult rats 2-10 weeks after obstructive hydrocephalus was induced by kaolin injection into the cisterna magna. In mild or moderate hydrocephalus, mostly occurring 2-6 weeks after kaolin injections, silver-labeled axons were scattered in the white matter of the sensorimotor cortex, corpus callosum, neostriatum, and hippocampus. In severe hydrocephalus, 10 weeks after kaolin injections, axon degeneration was more extensive in these areas, as well as in layers IV through VI of the sensorimotor cortex. Axons in the subiculum and the fimbria were heavily labeled, suggesting damage to hippocampal afferent and efferent fibers. In contrast, neuron cell death was rarely observed at any stage of hydrocephalus. The major pathological change of brain regions involved in motor and learning functions during hydrocephalus is axon degeneration, and this degeneration is correlated with an enlargement of the cerebral ventricles.

Animals↗