DAVID VAILLANCOURT

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..The findings are the first to demonstrate that STN DBS and medication increase strength and movement velocity at the ankle joint...

..Visual angle is the critical informational variable for the visuomotor system during the control of isometric force...

..In contrast, movements that require the internal regulation of the rate of change of force are associated with increased metabolic demand from the subthalamic nucleus and internal segment of the globus pallidus...

..These findings suggest that anterior basal ganglia nuclei are involved in selecting the amplitude of force contractions and posterior basal ganglia nuclei regulate basic aspects of dynamic force pulse production...

..These findings suggest a link between basal ganglia function in scaling both the amplitude and temporal parameters of the input to the motor neuron pool...

..Deep brain stimulation (DBS) of the ventral intermediate (VIM) nucleus of the thalamus successfully reduces tremor rating scores. It is unknown how VIM DBS alters the pathophysiologic characteristics of ET...

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..In contrast, a localized network in the prefrontal cortex retrieves force output from memory during internally guided actions...

..Neurobiol Aging 23: 1-11, 2002)...

..It is proposed that the increased force decay in PD does not result from sensory reflex deficits but from higher order sensory-motor memory processes...

..It is postulated that the observed increase or decrease in complexity with aging and disease is dependent on the nature of both the intrinsic dynamics of the system and the short-term change required to realize a local task demand...

..These findings demonstrate that the frequency of visual information reduces motor error and differentially modulates the neural activation related to visuomotor processing in the cerebellum, parietal cortex, and premotor cortex...

..It is concluded that the 0.5- to 1.5-s time period represents a limit on the temporal capacity that precise visuomotor information is held in short-term memory...

..The aim of this study was to examine the influence of visual and motor processes on the deterministic and stochastic structure of force output and motor unit discharge variability...

..The findings showed that a shift in the relative contribution of approximately 40 Hz to approximately 10 Hz neural activity is related to the reduced capacity of older adults to maintain optimal force control...

..Our findings also provide the first evidence from neuroimaging that hyperactivation in the contralateral primary motor cortex is not a compensatory response but is directly related to upper limb rigidity...

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..Also, the data are consistent with the hypothesis that the GPe has a high level of information convergence from other BG nuclei, which is preserved across different sensory feedback modalities...

..Our findings provide direct evidence that GPi and STN regulate the amplitude of force output. These findings emphasize the heterogeneous role of individual nuclei of the basal ganglia in regulating specific parameters of motor output...

..Furthermore, it is proposed that aging humans lose the adaptive capability to coordinate the excitatory and inhibitory activity of multiple neural oscillators...

..Further, the results provide additional support for the planning and parameterization model of the basal ganglia by demonstrating that specific anterior nuclei of the basal ganglia are involved in planning grip force...

..Use of a mask drawn in standardized space is a valid and time saving method of identifying PSC in the small nuclei of the BG...

..Moreover, this study demonstrates that the DLPFC is not only involved in slow and precisely controlled force generation, but has greater involvement in regulating slow and precisely controlled muscle relaxation...

..This study demonstrates that the frequency of visual feedback drives where in the brain visual gain mediated reductions in force error are regulated...

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..The results suggest better use of visual information in the control of elbow force than ankle force and this improved control may be related to the changes in the pattern of agonist and antagonist activation...

..The current findings suggest that 5 years of chronic STN DBS can have beneficial effects on the motor system over the long term in discrete motor tasks in which maximal effort and maximal neural output is required...

..Instead, specific regions of the visuomotor system selectively change in activity related to large changes in force error and large changes in the spatial amplitude of visual feedback...

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..As such, it is reasonable to evaluate the effect of DBS after 90 min of stimulation in clinical trials and research studies...

..The findings suggest that neural activity in the STN is an important modulator of the neural network(s) responsible for both resting and postural tremor genesis in Parkinson's disease...

..The modulation of the motor neuronal pool is adaptive and depends on the relative contribution of feedback and feedforward control processes, which are driven by the task demands...

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..HMAT is available through e-mail from the corresponding author...

..These findings demonstrate that STN DBS still suppresses tremor in the presence of a cognitive task. Furthermore, a secondary motor task of the opposite limb suppresses tremor to levels comparable to STN DBS...

..We suggest that modulation of output of the internal segment of the globus pallidus by STN DBS may drive the effect of STN DBS on memory guided force control...

..Our results suggest that STN DBS may be more effective in alleviating rigidity in the upper limb of PD patients than medications administered at presurgery dosage level...

..The force fluctuations in precision grip revealed a continuum for the degree of inter-digit individuation in which task constraints, aging, and Parkinson's disease alter the coupling between the digits in controlling grip force...

..These measures provide objective quantification of the severity of motor impairment that can be used to investigate the efficacy of different interventions in individuals with PD...

..These findings will have further implications for better understanding the visuomotor control deficits associated with aging, and diseased persons with Parkinson's disease, ataxia, and cerebellar deficits. ..

..This is the first step toward our long-term goal of using patient-specific visual feedback displays during neurological rehabilitation to facilitate brain activation and maximize recovery of function. ..

..This is the first step toward our long-term goal of using patient-specific visual feedback displays during neurological rehabilitation to facilitate brain activation and maximize recovery of function. ..

..As such, the proposal will have direct application to understanding the motor deficits of millions of Americans who suffer from basal ganglia dysfunction such as Parkinson's disease, stroke, dystonia, and Huntingdon's disease. ..

..Since very little is known regarding the brain function of Parkinson's disease prior to taking medication, we will perform our studies before patients begin a drug treatment program for the disease. ..