1997 |
Nelson, Randall Jay |
U19Activity Code Description: To support a research program of multiple projects directed toward a specific major objective, basic theme or program goal, requiring a broadly based, multidisciplinary and often long-term approach. A cooperative agreement research program generally involves the organized efforts of large groups, members of which are conducting research projects designed to elucidate the various aspects of a specific objective. Substantial Federal programmatic staff involvement is intended to assist investigators during performance of the research activities, as defined in the terms and conditions of award. The investigators have primary authorities and responsibilities to define research objectives and approaches, and to plan, conduct, analyze, and publish results, interpretations and conclusions of their studies. Each research project is usually under the leadership of an established investigator in an area representing his/her special interest and competencies. Each project supported through this mechanism should contribute to or be directly related to the common theme of the total research effort. The award can provide support for certain basic shared resources, including clinical components, which facilitate the total research effort. These scientifically meritorious projects should demonstrate an essential element of unity and interdependence. |
Striatal Activity in Behaving Primates @ University of Tennessee Health Sci Ctr
The precise role of the basal ganglia in motor control is still unclear. Profound deficits in both movement initiation and execution occur in Parkinson's disease patients and experimental animals, especially during ballistic movements and when behavioral requirements and outcome are unpredictable. Both patients and experimental animals also have deficits in proprioceptive control. Current hypotheses suggest that the basal ganglia play a role in movement initiation by "releasing" direct thalamocortical motor pathways thus "disinhibiting" cortex so that prepared movements can be initiated and new motor plans made. These hypotheses also suggest that indirect pathways suppress unwanted movements by suppressing other regions of cortex not directly associated with the motor behavior. Facilitation and suppression of the cortex during movement initiation and executive may alter the responsiveness of sensory neurons in cortical areas that provide input to the basal ganglia. Single-unit electrophysiological techniques will be used to record from striatal neurons from behaving monkeys while they perform hand movement tasks which result in changes in cortical neuronal responsiveness. The specific goals of proposed studies are 1) to understand the influence of unpredictable behavioral requirements upon striatal activity, 2) to understand the role that striatal neurons play in controlling the initiation and execution of proprioceptively guided movements and 3) to determine if a striatal neuron's activation history influences the time of onset and magnitude of stimulus and movement related activity. The results of the proposed experiments will be compared with those of ongoing studies in which sensorimotor cortical neurons are recorded under the same behavioral conditions. This comparison will determine if changes in striatal activity occur before those in cortex, thus suggesting the striatum may influence cortical responsiveness. The long-term goal of this work is to better understand the role the basal ganglia play in motor control during stimulus detection and classification, response programming and selection (initiation) and response production (execution). It is hoped that it will provide additional evidence to support the view that the basal ganglia influences motor control by regulating proprioceptive information processing in sensorimotor centers. Insights from these experiments will be crucial in understanding the cause and extent of motor deficits that accompany basal ganglia dysfunction.
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0.988 |
1999 — 2000 |
Nelson, Randall Jay |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Modulation of Somatosensory Cortical Responses @ University of Tennessee Health Sci Ctr
DESCRIPTION (Adapted from the Investigator's Abstract): The long-term goal of this research is to understand how somatosensory information is processed dynamically during purposeful hand movements. The experiments are designed to demonstrate when, and under what behavioral conditions, the responsiveness of primate sensorimotor cortical neurons is altered. This work is also designed to determine what behavioral consequences result from these alterations. Through neurophysiological experiments, we will determine how sensory responses and movement-related activity is altered during three types of behaviors that mimic those used everyday. The first is designed to show how sensory responsiveness changes immediately following an unpredictable outcome of a previous movement. The second will show how responsiveness changes when somatosensory inputs are needed to guide movements as compared with guidance by explicit visual cues. The third will determine if somatosensory signals can be detected at times before movements when sensory gating is thought to occur, and if this detection depends on the modality of stimuli previously used to trigger movements. Each experiment will determine the conditions under which the activity of sensorimotor cortical neurons is more tightly coupled to sensory stimuli and movement kinematics. The hypotheses to be tested are: (1) That the responsiveness of sensorimotor cortical neurons is attenuated when behavioral conditions are predictable. (2) That facilitation and suppression of responsiveness occur when peripheral and central inputs are crucial for the initiation and execution of movements, and that these modulations are regionally-specific. (3) That overly-trained movements can be altered only up to a certain point before their onset, and that this phenomenon reflects transient sensory gating which can be seen in the activity of sensorimotor cortical neurons. The underlying hypothesis is that external sensory information is utilized more when there has been a mismatch between actual and predicted behavioral outcome. These hypotheses will be tested, using single electrodes and multi-electrode arrays to record extracellular activity in the primary somatosensory, parietal (area 5), primary motor and premotor (PMd) cortices of awake, behaving monkeys trained to perform wrist movement tasks. Coupling of activity to sensory stimuli will be assessed by mean vector analyses. Movement kinematics will be correlated with neuronal activity using multiple regression analyses. The three behaviors to be studied are similar to those used during retraining when sensory disorders occur following stroke, traumatic head injury, peripheral neuropathy and movement disorders. By understanding how and where somatosensory responsiveness is modified during behavior, deficits can be more readily assessed and localized.
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0.988 |
2001 — 2011 |
Nelson, Randall Jay |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Modulation of Primate Somatosensory Cortical Responses @ University of Tennessee Health Sci Ctr
Through neurophysiological experiments, we will determine how sensory responses and movement-related activity is dynamically altered during three types of purposeful hand movements. Specific Aim number 1 is to determine if somatosensory signals can be detected at times before movements when sensory gating is thought to occur, and if this detection depends on the modality of stimuli previously used to trigger movements. Specific Aim number 2 is designed to test changes in responsiveness gain before, during and after changes in visual feedback gain. Specific Aim number 3 is designed to test the modulation of sensory responsiveness with changes in the type of prior information about the task. Each experiment will determine when sensorimotor cortical neuronal activity is more tightly coupled to sensory stimuli and movement kinematics. Three hypotheses will be tested: that (1) Sensory stimuli requesting behavioral changes are less effective in altering movements if presented near movement onset or if other somatosensory stimuli have been presented previously, that (2) Sensory responses are better entrained to vibratory stimuli and movement-related activity is more tightly coupled to movement kinematics when the gain of visual feedback for movement to targets is abruptly changed, and that (3) Knowing where, but not in which direction, tracking-target deviations occur results, in suppression of most peripheral inputs that are time-locked to predicted tracking- target deviation onset, while knowing in which direction but not where (and thus when) a tracking-target deviation will occur results in a gradual increase the suppression of certain peripheral inputs. The under-lying central hypothesis is that external sensory information is utilized as needed to guide behavior and suppressed when redundant or competitive. These hypotheses will be tested, using single electrodes and possibly multi-electrode arrays to record extracellular activity in the primary somatosensory, parietal (area 5 and 7b), primary motor and premotor (PMd) cortices of awake, behaving monkeys trained to perform wrist movement tasks. Coupling of activity to sensory stimuli will be assessed by mean vector analyses. Movement kinematics will be correlated with neuronal activity using multiple regression analyses. The three behaviors to be studied could be used during retraining when sensory disorders occur following stroke, traumatic head injury, peripheral neuropathy and movement disorders. By understanding how and where somatosensory responsiveness is modified during behavior, deficits can be more readily assessed and localized.
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0.988 |