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Results for “sensorimotor function”

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PubMed2003

Basic mechanisms of central rhythms reactivity to preparation and execution of a voluntary movement: a stereoelectroencephalographic study.

OBJECTIVE: To localize the sources of mu, beta and gamma rhythms and to explore the functional significance of their reactivity. METHODS: We used the method of quantification of event-related desynchronization (ERD) and synchronization (ERS) to analyze the reactivity of intracerebral rhythms recorded in stereoelectroencephalography within the sensorimotor areas during the preparation and the execution of a simple self-paced hand movement. We recorded 3 epileptic subjects who were explored before a surgical treatment. RESULTS: An ERD of mu and beta rhythms has been recorded before the movement onset in the precentral gyrus, spreading then to the postcentral gyrus and to the frontal medial cortex. The frontal lateral cortex was inconstantly involved during the movement. The movement offset was followed by an important and focused beta ERS which was found within the pre- and post-central gyrus and the frontal medial cortex. Within the beta band, we observed several narrower bands with different reactivities and locations. Focused gamma reactivity was also found in the precentral and postcentral gyri. CONCLUSIONS: The reactivities of mu and beta rhythms are different but their locations overlap. Mu ERD is a diffuse phenomenon that reflects the activation of all the sensorimotor areas during a simple movement. Beta band is likely to be composed of different rhythms with different functional significance. The primary motor area seems to contain two distinct areas with different reactivity to the movement preparation and execution.

Brain Mapping↗

PubMedDate not supplied

Within-subject reproducibility of near-infrared spectroscopy signals in sensorimotor activation after 6 months.

Near-infrared spectroscopy (NIRS) can measure the product of the optical path length and the concentration change in oxygenated hemoglobin (DeltaC'oxy), deoxygenated hemoglobin (DeltaC'deoxy), and their sum (DeltaC'total) in the human cerebral cortex, and it has been used for noninvasive investigation of human brain functions. We evaluate the within-subject reproducibility of the NIRS signals by repeated measurement of the sensorimotor cortex in healthy adults taken over a period of about 6 months using near-infrared (NIR) topography. The maximum signal amplitudes and the location of activation centers are compared between two sessions for each subject. The signal amplitudes vary between sessions and no consistent tendency in the changes is found among subjects. However, the distance between the activation centers identified in two sessions is relatively small, within 20 mm on average across subjects, which is comparable to the smallest distance between measurement positions in the NIR topography (21 mm). Moreover, within-subject comparisons of signal time courses show high correlation coefficients (>0.8) between the two sessions. This result, demonstrating a high within-subject reproducibility of the temporal information in NIRS signals, particularly contributes to the development of a new application of NIRS.

Adult↗

PubMed2006

Two different reorganization patterns after rehabilitative therapy: an exploratory study with fMRI and TMS.

We used two complementary methods to investigate cortical reorganization in chronic stroke patients during treatment with a defined motor rehabilitation program. BOLD ("blood oxygenation level dependent") sensitive functional magnetic resonance imaging (fMRI) and intracortical inhibition (ICI) and facilitation (ICF) measured with transcranial magnetic stimulation (TMS) via paired pulse stimulation were used to investigate cortical reorganization before and after "constraint-induced movement therapy" (CI). The motor hand function improved in all subjects after CI. BOLD signal intensity changes within affected primary sensorimotor cortex (SMC) before and after CI showed a close correlation with ICI (r = 0.93) and ICF (r = 0.76) difference before and after therapy. Difference in number of voxels and ICI difference before and after CI also showed a close correlation (r = 0.92) in the affected SMC over the time period of training. A single subject analysis revealed that patients with intact hand area of M1 ("the hand knob") and its descending motor fibers (these patients revealed normal motor evoked potentials [MEP] from the affected hand) showed decreasing ipsilesional SMC activation which was paralleled by an increase in intracortical excitability. This pattern putatively reflects increasing synaptic efficiency. When M1 or its descending pyramidal tract was lesioned (MEP from the affected hand was pathologic) ipsilesional SMC activation increased, accompanied by decreased intracortical excitability. We suggest that an increase in synaptic efficiency is not possible here, which leads to reorganization with extension, shift and recruitment of additional cortical areas of the sensorimotor network. The inverse dynamic process between both complementary methods (activation in fMRI and intracortical excitability determined by TMS) over the time period of CI illustrates the value of combining methods for understanding brain reorganization.

Aged↗

PubMedDate not supplied

Synaptic interactions mediating synchrony and oscillations in primate sensorimotor cortex.

The appearance of oscillatory modes of 'gamma' activity in many cortical areas of different species has generated interest in understanding their underlying mechanisms and possible functions. This paper reviews evidence from studies on primate motor cortex showing that oscillatory activity entrains many neurons during periods of exploratory manipulative behavior. These oscillatory episodes synchronize widely spread neurons in sensorimotor cortex bilaterally, including descending corticospinal neurons, as evidenced by correlated modulations in EMG activity. The resulting neural synchronization involves task-related and -unrelated neurons similarly, suggesting that it is more likely to play some global role in attention than mediating any obvious interactions involved in coordinating movements. Intracellular recordings have elucidated the strength and types of synaptic interactions between motor cortical neurons that are involved in both normal and oscillatory activity. Spike-triggered averages (STAs) of intracellular membrane potentials have revealed serial connections in the form of unitary excitatory and inhibitory post-synaptic potentials (EPSPs and IPSPs). More commonly, STAs showed large synchronous excitatory or inhibitory potentials (ASEPs and ASIPs) beginning before the trigger spike and composed of multiple unitary events. ASEPs involved synchronous activity in a larger and more widespread group of presynaptic neurons than ASIPs. During oscillatory episodes synchronized excitatory and inhibitory synaptic potentials occurred in varying proportions. EPSPs evoked by stimulating neighboring cortical sites during the depolarizing phase of spontaneous oscillations showed evidence of transient potentiation. These observations are consistent with several functional hypotheses, but fit best with a possible role in attention or arousal.

Animals↗

PubMed1984

Role of basal ganglia in limb movements.

Recent anatomic and physiologic studies have shed new light on the functional organization of the basal ganglia and their role in movement. The basal ganglia receive topographically organized input from the entire neocortex. Influences from sensorimotor and "association" cortices appear to remain segregated in the basal ganglia. The concept of segregated parallel subcortical loops subserving "motor" and "complex" functions is discussed. Recent neurophysiologic studies in behaving primates suggest that basal ganglia output plays a role in controlling the direction and amplitude of movement but is not primarily involved in the initiation of limb movement or selection of specific muscles. These studies are generally consistent with data from patients with Parkinson's disease, which likewise indicates a deficit in the programming of movement amplitude in step-tracking tasks, with little or no change in reaction-time or pattern of muscular activity.

Animals↗

PubMed2003

Hippocampal modulation of sensorimotor processes.

While the hippocampus makes unique contributions to memory, it has also long been associated with sensorimotor processes, i.e. innate processes involving control of motor responses to sensory stimuli. Moreover, hippocampal dysfunction has been implicated in neuropsychiatric diseases, such as schizophrenia and anxiety disorders, primarily characterized by non-mnemonic deficits in the processing of and responding to sensory information. This review is concerned with the hippocampal modulation of three sensorimotor processes in rats-locomotor activity, prepulse inhibition (PPI) of the startle reflex, and the startle reflex itself-whose alterations are related to human psychosis or anxiety disorders. Its main purpose is to present and discuss the picture emerging from studies examining the effects of pharmacological manipulations of the dorsal and ventral hippocampus by local drug microinfusions. While a role of the hippocampus in regulating locomotor activity, PPI, and startle reactivity has also been suggested based on the effects of hippocampal lesions, the microinfusion studies have revealed additional important details of this role and suggest modifications of notions based on lesion studies. In summary, the microinfusion studies corroborate that hippocampal mechanisms can directly influence locomotor activity, PPI, and startle reactivity, and that aberrant hippocampal function may contribute to neuropsychiatric diseases, in particular psychosis. The relation between different sensorimotor processes and hippocampal neurotransmission, the role of ventral and dorsal hippocampus, and the extrahippocampal mechanisms mediating the hippocampal modulation of different sensorimotor processes can partly be dissociated. Thus, the hippocampal modulation of these sensorimotor processes appears to reflect multiple operations, rather than one unitary operation.

Animals↗

PubMed2001

Effects of daily dermal application of DEET and epermethrin, alone and in combination, on sensorimotor performance, blood-brain barrier, and blood-testis barrier in rats.

DEET and permethrin were implicated in the development of illnesses in some veterans of the Persian Gulf War. This study was designed to investigate the effects of daily dermal application of these chemicals, alone or in combination, on the permeability of the blood-brain barrier (BBB) and blood-testes barrier (BTB) and on sensorimotor performance in male Sprague-Dawley rats. Groups of five rats were treated with a dermal daily dose of 4, 40, or 400 mg/kg DEET in ethanol or 0.013, 0.13, or 1.3 mg/kg permethrin in ethanol for 60 d. A group of 10 rats received a daily dermal dose of ethanol and served as controls. BBB permeability was assessed by injection of an iv dose of the quaternary ammonium compound [3H]hexamethonium iodide. While permethrin produced no effect on BBB permeability, DEET alone caused a decrease in BBB permeability in brainstem. A combination of DEET and permethrin significantly decreased the BBB permeability in the cortex. BTB permeability was decreased by treatment with DEET alone and in combination with permethrin. The same animals underwent a battery of functional behavior tests 30, 45, and 60 d after exposure to evaluate their sensorimotor abilities. All treatments caused a significant decline in sensorimotor performance in a dose- and time-dependent manner. These results show that daily dermal exposure to DEET, alone or in combination with permethrin, decreased BBB permeability in certain brain regions, and impaired sensorimotor performance.

Administration, Topical↗

PubMed1996

The subthalamic nucleus and the external pallidum: two tightly interconnected structures that control the output of the basal ganglia in the monkey.

The aim of the present study was to elucidate the organization of the interconnections between the subthalamic nucleus and the two segments of the globus pallidus in squirrel monkeys. By making small deposits of tracers in the two segments of the globus pallidus, we demonstrate that interconnected neurons of the subthalamic nucleus and the external pallidum innervate, via axon collaterals, the same population of neurons in the internal pallidum. Furthermore, this organizational principle holds true for different functional regions of the pallidum and the subthalamic nucleus. Injections of biotinylated dextran amine were made in the dorsal (associative), ventrolateral (sensorimotor) and rostromedial (limbic) regions of the internal pallidum. Following these injections, there were rich clusters of labelled terminals in register with retrogradely labelled perikarya in related functional regions of the subthalamic nucleus and the external pallidum. At the electron microscopic level, the majority of labelled terminals in the external pallidum displayed the ultrastructural features of boutons from the subthalamic nucleus and were non-immunoreactive for GABA, whereas those in the subthalamic nucleus resembled terminals from the external pallidum and displayed GABA immunoreactivity. In both cases, the synaptic targets of the labelled terminals included labelled neurons. These observations suggest that the biotinylated dextran amine injected in the internal globus pallidus was transported retrogradely to perikarya in the external pallidum and the subthalamic nucleus and then anterogradely, via axon collaterals, to the subthalamic nucleus and the external pallidum respectively. This suggestion was supported by injections of biotinylated dextran amine or Phaseolus vulgaris-leucoagglutinin in regions of the external pallidum that corresponded to those containing retrogradely labelled cells following injections in the internal pallidum. The clusters of labelled cells and varicosities that resulted from these injections were found in regions of the subthalamic nucleus similar to those labelled following injections in the internal globus pallidus. Furthermore, terminals from the external pallidum and the subthalamic nucleus converged on the same regions in the internal globus pallidus. The results of the present tracing study define the basic network underlying the interconnections between the external segment of the globus pallidus and the subthalamic nucleus, and their connections with the output neurons of the basal ganglia in primates.

Animals↗

PubMed2006

Facilitated beam-walking recovery during acute phase by kynurenic acid treatment in a rat model of photochemically induced thrombosis causing focal cerebral ischemia.

We previously demonstrated the presence of activated areas in the non-injured contralateral sensorimotor cortex in addition to the ipsilateral sensorimotor cortex of the area surrounding a brain infarction, using a rat model of focal photochemically induced thrombosis (PIT) and functional magnetic resonance imaging. Using this model, we next applied gene expression profiling to screen key molecules upregulated in the activated area. RNA was extracted from the ipsilateral and contralateral sensorimotor cortex to the focal brain infarction and from the sham controlled cortex, and hybridized to gene-expression profiling arrays containing 1,322 neurology-related genes. Results showed that glycine receptors were upregulated in both the ipsilateral and contralateral cortex to the focal ischemic lesion. To prove the preclinical significance of upregulated glycine receptors, kynurenic acid, an endogenous antagonist to glycine receptors on neuronal cells, was administered intrathecally. As a result, the kynurenic acid significantly improved behavioral recovery within 10 days from paralysis induced by the focal PIT (p < 0.0001), as evaluated with beam walking. These results suggest that intrathecal administration of a glycine receptor antagonist may facilitate behavioral recovery during the acute phase after brain infarction.

Animals↗

PubMed2003

Cortical electrical stimulation combined with rehabilitative training: enhanced functional recovery and dendritic plasticity following focal cortical ischemia in rats.

This study assessed the behavioral and dendritic structural effects of combining subdural motor cortical electrical stimulation with motor skills training following unilateral sensorimotor cortex lesions in adult male rats. Rats were pre-operatively trained on a skilled forelimb reaching task, the Montoya staircase test, and then received endothelin-1 induced ischemic lesions of the sensorimotor cortex. Ten to 14 days later, electrodes were implanted over the peri-lesion cortical surface. Rats subsequently began 10 days of rehabilitative training on the reaching task in 1 of 3 conditions: 1. 50 Hz stimulation during training, 2. 250 Hz stimulation during training or 3. no stimulation. No significant difference in performance was found between the 250 Hz and no stimulation groups. The 50 Hz stimulation group had significantly greater rates of improvement with the impaired forelimb in comparison to 250 Hz and no stimulation groups combined. Fifty Hz stimulated animals also had a significant increase in the surface density of dendritic processes immunoreactive for the cytoskeletal protein, microtubule-associated protein 2, in the peri-lesion cortex compared to the other groups. These results support the efficacy of combining rehabilitative training with cortical electrical stimulation to improve functional outcome and cortical neuronal structural plasticity following sensorimotor cortical damage.

Analysis of Variance↗

PubMed1999

Decreased BOLD functional MR activation of the motor and sensory cortices adjacent to a glioblastoma multiforme: implications for image-guided neurosurgery.

A patient with a glioblastoma multiforme and mild sensorimotor deficits had significantly less activation of the motor and sensory cortices on the side with the tumor than on the contralateral side on blood oxygen level-dependent (BOLD) functional MR images. This difference, which may be due to pressure effects or loss of vascular autoregulation, should be considered in preoperative planning in which BOLD functional MR imaging is used to identify eloquent cortices to be avoided during brain tumor surgery.

Adult↗

PubMed2004

Loss-of-function phenotype of hereditary neuropathy with liability to pressure palsies.

Hereditary neuropathy with liability to pressure palsies (HNPP) provides a human model to investigate the role of PMP22 in myelinated peripheral nerve, since the disease is caused by a deletion of one of the two PMP22 alleles. To systematically characterize the phenotype of HNPP, we prospectively evaluated the clinical features and electrophysiological findings in 17 genetically confirmed patients, 7 men and 10 women, ranging in age from 9 to 66 years (mean, 41 +/- 13). Fifteen symptomatic patients presented with episodes of transient focal weakness or sensory loss that were usually related to particular activities causing nerve compression, including stretching or minor repetitive focal trauma. No patient sought medical attention for symptoms of a symmetric polyneuropathy. Neurological examinations were either normal or mildly abnormal. Neither focal slowing of nerve conduction studies, nor reduction in compound muscle action potential (CMAP) or sensory nerve action potential (SNAP) amplitudes consistently predicted the site of symptoms. We conclude that the majority of patients with HNPP present with transient, recurrent, focal symptoms of weakness or sensory loss in the distribution of individual nerves or plexus, and that a diffuse symmetric sensorimotor polyneuropathy is an unusual presentation of HNPP. These studies suggest that the function of PMP22, at least in part, is to stabilize myelin so that it will be protected from injuries resulting from repetitive, minor trauma.

Adolescent↗

PubMed1978

Language and sensorimotor development during the early period of referential speech.

The relation between sensorimotor attainments and linguistic development in children using referential speech at the single- and two-word utterance levels was examined. When age was controlled, the sensorimotor task performance of normal children who produced two-word utterances was highly similar to that of normal children limited to single-work utterances. Identical findings were observed for language-disordered children functioning at the single- and two-word utterance levels. In addition, several children's performances on the sensorimotor tasks were below the level previously thought necessary for the emergence of referential speech. The position is taken that the relationship between sensorimotor development and linguistic development is not as close as has been presumed.

Child Development↗

PubMed2006

Salvianolic acid B improves motor function after cerebral ischemia in rats.

In a previous short-term study, salvianolic acid B was reported to have a protective effect on cerebral ischemia. Here, we investigated whether salvianolic acid B improves the recovery of motor function after cerebral ischemia in a 14-day investigation. Cerebral ischemia was induced by middle cerebral artery occlusion in rats. Motor function was evaluated with beam-walking performance. Neural cell injury in both the sensorimotor cortex and CA1 of the hippocampus ipsilateral to ischemia was studied by Nissl stain with methylene blue. The integrity of cerebral microvessels was monitored by immunoglobulin extravasations. Neurogenesis in the subgranular zone in the dentate gyrus of the hippocampus was detected with 5'-bromo-2'-deoxyuridine incorporation. Animals receiving salvianolic acid B at a dose of 10 mg/kg had a more rapid recovery of beam-walking performance than vehicle-treated ischemia animals, and the improvement became significant at 10 and 14 days after ischemia (P<0.05). Treatment with salvianolic acid B at a dose of 10 mg/kg also significantly prevented neural cell loss in CA1 of the hippocampus. Neural cells in the sensorimotor cortex were also preserved in animals that received salvianolic acid B at a high dose of 10 mg/kg. Salvianolic acid B (10 mg/kg) also improved the integrity of microvessels after ischemia. We observed a slight increase in 5'-bromo-2'-deoxyuridine-positive cells in the subgranular zone of the hippocampus in the animals treated with salvianolic acid B at a dose of 10 mg/kg. These data indicate that salvianolic acid B could improve the recovery of motor function after cerebral ischemia in rats.

Animals↗

PubMed1999

The functional neuroanatomy of voluntary swallowing.

Swallowing is a complex physiological process involving voluntary and reflexive motor activity, sensorimotor integration, salivation, and visceral regulation. Despite the numerous processes required for normal deglutition, traditional models of the central control of swallowing only emphasize the involvement of the brainstem and the inferior precentral gyrus (IPCG). However a number of neurological disorders involving other brain regions also cause dysphagia. To determine the brain regions participating in voluntary swallowing, we assayed regional cerebral blood flow (rCBF) with positron emission tomography (PET) while healthy human subjects swallowed, performed lateral tongue movements, or rested with their eyes closed. Voluntary swallowing produced strong rCBF increases within the IPCG bilaterally, the right anterior insula/claustrum, and the left cerebellum. The maxima in these regions differed from those induced by lateral tongue movements. Swallowing also produced rCBF increases in the putamen, thalamus, and several additional cortical areas, but these foci were not as clearly distinguishable from activity arising during tongue movements. These findings indicate that swallowing involves the recruitment of a large-scale distributed neural network that includes the anterior insula and cerebellum. The distributed nature of this network helps to explain why so many neurological conditions produce dysphagia.

Adult↗

PubMed2005

Silent event-related fMRI reveals deficient motor and enhanced somatosensory activation in orofacial dystonia.

Previous studies showed cortical dysfunction and impaired sensorimotor integration in primary generalized and focal hand dystonia. We used a whistling task and silent event-related fMRI to investigate functional changes in patients with blepharospasm and patients with a combination of blepharospasm and oromandibular dystonia (Meige's syndrome). Whistling served as a model for a skilful orofacial movement with a high demand on sensorimotor integration. It allowed us to study the oromandibular motor system that is clinically affected in Meige's syndrome but not in isolated blepharospasm. In Meige's syndrome, functional MRI revealed deficient activation of the primary motor and ventral premotor cortex within the mouth representation area during whistling. Compared with healthy controls, both forms of orofacial dystonia had increased activation of bilateral somatosensory areas and the caudal supplementary motor area (SMA) in common. While overactivity of somatosensory areas and caudal SMA in Meige patients was partly reversed by botulinum toxin treatment, impaired motor activation was not. We conclude that impaired motor activation appears to be specific for the clinically affected oromandibular motor system in Meige's syndrome while enhanced somatosensory activation is a common abnormality in both forms of orofacial dystonia independent of the affected motor system. Somatosensory overactivity indicates an altered somatosensory representation in orofacial dystonia while impaired motor activation may be a functional correlate of reduced cortical inhibition during oromandibular motor execution in Meige's syndrome.

Aged↗

PubMed1998

The organization of the cortical motor system: new concepts.

A series of recent anatomical and functional data has radically changed our view on the organization of the motor cortex in primates. In the present article we present this view and discuss its fundamental principles. The basic principles are the following: (a) the motor cortex, defined as the agranular frontal cortex, is formed by a mosaic of separate areas, each of which contains an independent body movement representation, (b) each motor area plays a specific role in motor control, based on the specificity of its cortical afferents and descending projections, (c) in analogy to the motor cortex, the posterior parietal cortex is formed by a multiplicity of areas, each of which is involved in the analysis of particular aspects of sensory information. There are no such things as multipurpose areas for space or body schema and (d) the parieto-frontal connections form a series of segregated anatomical circuits devoted to specific sensorimotor transformations. These circuits transform sensory information into action. They represent the basic functional units of the motor system. Although these conclusions mostly derive from monkey experiments, anatomical and brain-imaging evidence suggest that the organization of human motor cortex is based on the same principles. Possible homologies between the motor cortices of humans and non-human primates are discussed.

Animals↗

PubMedDate not supplied

Functional anatomy of pointing and grasping in humans.

The functional anatomy of reaching and grasping simple objects was determined in nine healthy subjects with positron emission tomography imaging of regional cerebral blood flow (rCBF). In a prehension (grasping) task, subjects reached and grasped illuminated cylindrical objects with their right hand. In a pointing task, subjects reached and pointed over the same targets. In a control condition subjects looked at the targets. Both movement tasks increased activity in a distributed set of cortical and subcortical sites: contralateral motor, premotor, ventral supplementary motor area (SMA), cingulate, superior parietal, and dorsal occipital cortex. Cortical areas including cuneate and dorsal occipital cortex were more extensively activated than ventral occipital or temporal pathways. The left parietal operculum (putative SII) was recruited during grasping but not pointing. Blood flow changes were individually localized with respect to local cortical anatomy using sulcal landmarks. Consistent anatomic landmarks from MRI scans could be identified to locate sensorimotor, ventral SMA, and SII blood flow increases. The time required to complete individual movements and the amount of movement made during imaging correlated positively with the magnitude of rCBF increases during grasping in the contralateral inferior sensorimotor, cingulate, and ipsilateral inferior temporal cortex, and bilateral anterior cerebellum. This functional-anatomic study defines a cortical system for "pragmatic' manipulation of simple neutral objects.

Adult↗