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Motor Network (motor + network)

Distribution by Scientific Domains
Medical Sciences66%
Life Sciences33%

Selected Abstracts

Neuroplastic Changes in the Brain: A Case of Two Successive Adaptive Changes Within the Motor Cortex

JOURNAL OF NEUROIMAGING, Issue 3 2010
Eytan Raz MD
ABSTRACT We describe a case of neuroplasticity associated with both arteriovenous malformation (AVM) and stroke, which occurred in two successive events in the same patient. Functional magnetic resonance imaging (fMRI) during right-hand movement in a young man with a left rolandic AVM detected activation of a region corresponding to the left premotor cortex. The AVM was embolized. A few hours after the last embolization session, the patient sustained an ischemic complication in the left subcortical white matter. A second fMRI detected a lower degree of left premotor cortex activation and strong activation of the contralesional right primary motor cortex and bilateral supplementary motor areas. One month later, in association with clinical recovery, the fMRI activation returned to that observed in the first fMRI, ie, selective activation of the ipsilesional left premotor cortex. This is, to our knowledge, the first description of two distinct functional cortical changes determined by an AVM and a stroke within the motor network. [source]

Levodopa affects functional brain networks in parkinsonian resting tremor,

MOVEMENT DISORDERS, Issue 1 2009
Bettina Pollok PhD
Abstract Resting tremor in idiopathic Parkinson's disease (PD) is associated with an oscillatory network comprising cortical as well as subcortical brain areas. To shed light on the effect of levodopa on these network interactions, we investigated 10 patients with tremor-dominant PD and reanalyzed data in 11 healthy volunteers mimicking PD resting tremor. To this end, we recorded surface electromyograms of forearm muscles and neuromagnetic activity using a 122-channel whole-head magnetometer (MEG). Measurements were performed after overnight withdrawal of levodopa (OFF) and 30 min after oral application of fast-acting levodopa (ON). During OFF, patients showed the typical antagonistic resting tremor. Using the analysis tool Dynamic Imaging of Coherent Sources, we identified the oscillatory network associated with tremor comprising contralateral primary sensorimotor cortex (S1/M1), supplementary motor area (SMA), contralateral premotor cortex (PMC), thalamus, secondary somatosensory cortex (S2), posterior parietal cortex (PPC), and ipsilateral cerebellum oscillating at 8 to 10 Hz. After intake of levodopa, we found a significant decrease of cerebro-cerebral coupling between thalamus and motor cortical areas. Similarly, in healthy controls mimicking resting tremor, we found a significant decrease of functional interaction within a thalamus,premotor,motor network during rest. However, in patients with PD, decrease of functional interaction between thalamus and PMC was significantly stronger when compared with healthy controls. These data support the hypothesis that (1) in patients with PD the basal ganglia and motor cortical structures become more closely entrained and (2) levodopa is associated with normalization of the functional interaction between thalamus and motor cortical areas. © 2008 Movement Disorder Society [source]

Motor imagery after stroke: Relating outcome to motor network connectivity,

ANNALS OF NEUROLOGY, Issue 5 2009
Nikhil Sharma PhD
Objective Neuroplasticity is essential for recovery after stroke and is the target for new stroke therapies. During recovery from subcortical motor stroke, brain activations associated with movement may appear normal despite residual functional impairment. This raises an important question: how far does recovery of motor performance depend on the processes that precede movement execution involving the premotor and prefrontal cortex, rather than recovery of the corticospinal system alone? Methods We examined stroke patients with functional magnetic resonance imaging while they either imagined or executed a finger-thumb opposition sequence. In addition to classical analyses of regional activations, we studied neuroplasticity in terms of differential network connectivity using structural equation modeling. The study included 8 right-handed patients who had suffered a left-hemisphere subcortical ischemic stroke with paresis, and 13 age-matched healthy controls. Results With good functional recovery, the regional activations had returned to normal in patients. However, connectivity within the extended motor network remained abnormal. These abnormalities were seen predominantly during motor imagery and correlated with motor performance. Interpretation Our results indicate that neuroplasticity can manifest itself as differences in connectivity among cortical areas remote from the infarct, rather than in the degree of regional activation. Connection strengths between nodes of the cortical motor network correlate with motor outcome. The altered organization of connectivity of the prefrontal areas may reflect the role of the prefrontal cortex in higher order planning of movement. Our results are relevant to the assessment and understanding of emerging physical and neurophysiological therapies for stroke rehabilitation. Ann Neurol 2009;66:604,616 [source]

Altered sensorimotor development in a transgenic mouse model of amyotrophic lateral sclerosis

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2004
Julien Amendola
Abstract Most neurodegenerative diseases become manifest at an adult age but abnormalities or pathological symptoms appear earlier. It is important to identify the initial mechanisms underlying such progressive neurodegenerative disease in both humans and animals. Transgenic mice expressing the familial amyotrophic lateral sclerosis (ALS)-linked mutation (G85R) in the enzyme superoxide dismutase 1 (SOD1) develop motor neuron disease at 8,10 months of age. We address the question of whether the mutation has an early impact on spinal motor networks in postnatal mutant mice. Behavioural tests showed a significant delay in righting and hind-paw grasping responses in mutant SOD1G85R mice during the first postnatal week, suggesting a transient motor deficit compared to wild-type mice. In addition, extracellular recordings from spinal ventral roots in an in vitro brainstem,spinal cord preparation demonstrated different pharmacologically induced motor activities between the two strains. Rhythmic motor activity was difficult to evoke with N -methyl- dl -aspartate and serotonin at the lumbar levels in SOD1G85R mice. In contrast to lumbar segments, rhythmic activity was similar in the sacral roots from the two strains. These results strongly support the fact that the G85R mutation may have altered lumbar spinal motor systems much earlier than previously recognized. [source]

D2 receptors receive paracrine neurotransmission and are consistently targeted to a subset of synaptic structures in an identified neuron of the crustacean stomatogastric nervous system

THE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 3 2010
Max F. Oginsky
Dopamine (DA) modulates motor systems in phyla as diverse as nematodes and arthropods up through chordates. A comparison of dopaminergic systems across a broad phylogenetic range should reveal shared organizing principles. The pyloric network, located in the stomatogastric ganglion (STG), is an important model for neuromodulation of motor networks. The effects of DA on this network have been well characterized at the circuit and cellular levels in the spiny lobster, Panulirus interruptus. Here we provide the first data about the physical organization of the DA signaling system in the STG and the function of D2 receptors in pyloric neurons. Previous studies showed that DA altered intrinsic firing properties and synaptic output in the pyloric dilator (PD) neuron, in part by reducing calcium currents and increasing outward potassium currents. We performed single cell reverse transcriptase-polymerase chain reaction (RT-PCR) experiments to show that PD neurons exclusively expressed a type 2 (D2,Pan) DA receptor. This was confirmed by using confocal microscopy in conjunction with immunohistochemistry (IHC) on STG wholemount preparations containing dye-filled PD neurons. Immunogold electron microscopy showed that surface receptors were concentrated in fine neurites/terminal swellings and vesicle-laden varicosities in the synaptic neuropil. Double-label IHC experiments with tyrosine hydroxylase antiserum suggested that the D2,Pan receptors received volume neurotransmissions. Receptors were further mapped onto three-dimensional models of PD neurons built from Neurolucida tracings of confocal stacks from the IHC experiments. The data showed that D2,Pan receptors were selectively targeted to approximately 40% of synaptic structures in any given PD neuron, and were nonuniformly distributed among neurites. J. Comp. Neurol. 518:255,276, 2010. © 2009 Wiley-Liss, Inc. [source]

The location of white matter lesions and gait,A voxel-based study

ANNALS OF NEUROLOGY, Issue 2 2010
Velandai Srikanth PhD
Little is known about the influence of cerebral white matter lesion (WML) location on gait. We applied partial least squares regression in brain magnetic resonance imaging scans (n = 385) to evaluate which WML voxel systems were independently associated with a composite gait score and identified affected tracts using a diffusion tensor imaging template. Bilateral frontal and periventricular WML-affected voxels corresponding to major anterior projection fibers (thalamic radiations, corticofugal motor tracts) and adjacent association fibers (corpus callosum, superior fronto-occipital fasciculus, short association fibers) showed the greatest covariance with poorer gait. WMLs probably contribute to age-related gait decline by disconnecting motor networks served by these tracts. ANN NEUROL 2010;67:265,269 [source]