The Experts below are selected from a list of 192 Experts worldwide ranked by ideXlab platform
J K Chapin - One of the best experts on this subject based on the ideXlab platform.
-
distinct temporal activity patterns in the rat m1 and Red Nucleus during skilled versus unskilled limb movement
Behavioural Brain Research, 2004Co-Authors: Linda Hermervazquez, K A Moxon, K-h Kuo, V Viau, Y Zhan, Raymond Hermervazquez, J K ChapinAbstract:The mammalian motor system contains multiple interconnected supraspinal networks, but little is known about their relative roles in producing different movements and behaviors, particularly given their apparently fused activity in primates. We tested whether the task context, as well as using a phylogenetically older mammal, rats, could distinguish the separate contributions of these networks. We obtained simultaneous multi-single neuron recordings from the forelimb motor cortex and Magnocellular Red Nucleus as rats performed two contextually different, but kinematically similar, forelimb reach-like tasks: highly learned, skilled reaching for food through a narrow slot [Behav. Brain Res. 41 (1990) 49], a task requiring extensive training, versus the swing phases of treadmill locomotion. In both the M1 and the mRN, large subpopulations of neurons peaked in their spike firing rates near the onset and the end of the swing phase during treadmill locomotion. In contrast, neural subgroups in the two areas displayed different temporal sequences of activity during the skilled reaching task. In the mRN, the majority of task-modulated neurons peaked in their firing rate in the middle of the reach when the rat was preparing to project the arm through the slot, whereas large subgroups of M1 neurons displayed elevated firing rates during the initial and terminal phases of the reach. These results suggest that motor-behavioral context can alter the degree of overlapping activity in different supraspinal sensorimotor networks. Moreover, results for the skilled reaching task in rats may have highlighted a distinct processing role of the rubral complex: adapting natural muscle synergies across joints and limbs to novel task demands, in concert with cortically based learning. © 2003 Elsevier B.V. All rights reserved.
-
Distinct temporal activity patterns in the rat M1 and Red Nucleus during skilled versus unskilled limb movement.
Behavioural Brain Research, 2004Co-Authors: Linda Hermer-vazquez, Raymond Hermer-vazquez, K A Moxon, K-h Kuo, V Viau, Y Zhan, J K ChapinAbstract:The mammalian motor system contains multiple interconnected supraspinal networks, but little is known about their relative roles in producing different movements and behaviors, particularly given their apparently fused activity in primates. We tested whether the task context, as well as using a phylogenetically older mammal, rats, could distinguish the separate contributions of these networks. We obtained simultaneous multi-single neuron recordings from the forelimb motor cortex and Magnocellular Red Nucleus as rats performed two contextually different, but kinematically similar, forelimb reach-like tasks: highly learned, skilled reaching for food through a narrow slot, a task requiring extensive training, versus the swing phases of treadmill locomotion. In both the M1 and the mRN, large subpopulations of neurons peaked in their spike firing rates near the onset and the end of the swing phase during treadmill locomotion. In contrast, neural subgroups in the two areas displayed different temporal sequences of activity during the skilled reaching task. In the mRN, the majority of task-modulated neurons peaked in their firing rate in the middle of the reach when the rat was preparing to project the arm through the slot, whereas large subgroups of M1 neurons displayed elevated firing rates during the initial and terminal phases of the reach. These results suggest that motor-behavioral context can alter the degree of overlapping activity in different supraspinal sensorimotor networks. Moreover, results for the skilled reaching task in rats may have highlighted a distinct processing role of the rubral complex: adapting natural muscle synergies across joints and limbs to novel task demands, in concert with cortically based learning.
Jason B Carmel - One of the best experts on this subject based on the ideXlab platform.
-
Motor cortex electrical stimulation augments sprouting of the corticospinal tract and promotes recovery of motor function
Frontiers in Integrative Neuroscience, 2014Co-Authors: Jason B Carmel, John H MartinAbstract:The corticospinal system-with its direct spinal pathway, the corticospinal tract (CST) - is the primary system for controlling voluntary movement. Our approach to CST repair after injury in mature animals was informed by our finding that activity drives establishment of connections with spinal cord circuits during postnatal development. After incomplete injury in maturity, spaRed CST circuits sprout, and partially restore lost function. Our approach harnesses activity to augment this injury-dependent CST sprouting and to promote function. Lesion of the medullary pyramid unilaterally eliminates all CST axons from one hemisphere and allows examination of CST sprouting from the unaffected hemisphere. We discoveRed that 10 days of electrical stimulation of either the spaRed CST or motor cortex induces CST axon sprouting that partially reconstructs the lost CST. Stimulation also leads to sprouting of the cortical projection to the Magnocellular Red Nucleus, where the rubrospinal tract originates. Coordinated outgrowth of the CST and cortical projections to the Red Nucleus could support partial re-establishment of motor systems connections to the denervated spinal motor circuits. Stimulation restores skilled motor function in our animal model. Lesioned animals have a persistent forelimb deficit contralateral to pyramidotomy in the horizontal ladder task. Rats that received motor cortex stimulation either after acute or chronic injury showed a significant functional improvement that brought error rate to pre-lesion control levels. Reversible inactivation of the stimulated motor cortex reinstated the impairment demonstrating the importance of the stimulated system to recovery. Motor cortex electrical stimulation is an effective approach to promote spouting of spaRed CST axons. By optimizing activity-dependent sprouting in animals, we could have an approach that can be translated to the human for evaluation with minimal delay.
-
Motor cortex electrical stimulation augments sprouting of the corticospinal tract and promotes recovery of motor function
Frontiers Media S.A., 2014Co-Authors: Jason B Carmel, John EmartinAbstract:The corticospinal system—with its direct spinal pathway, the corticospinal tract (CST)—is the primary system for controlling voluntary movement. Our approach to CST repair after injury in mature animals was informed by our finding that activity drives establishment of connections with spinal cord circuits during postnatal development. After incomplete injury in maturity, spaRed CST circuits sprout and partially restore lost function. Our approach harnesses activity to augment this injury-dependent CST sprouting and to promote function. Lesion of the medullary pyramid unilaterally eliminates all CST axons from one hemisphere and allows examination of CST sprouting from the unaffected hemisphere. We discoveRed that ten days of electrical stimulation of either the spaRed CST or motor cortex induces CST axon sprouting that partially reconstructs the lost CST. Stimulation also leads to sprouting of the cortical projection to the Magnocellular Red Nucleus, where the rubrospinal tract originates. Coordinated outgrowth of the CST and cortical projections to the Red Nucleus could support partial re-establishment of motor systems connections to the denervated spinal motor circuits. Stimulation restores skilled motor function in our animal model. Lesioned animals have a persistent forelimb deficit contralateral to pyramidotomy in the horizontal ladder task. Rats that received motor cortex stimulation either after acute or chronic injury showed a significant functional improvement that brought error rate to pre-lesion control levels. Reversible inactivation of the stimulated motor cortex reinstated the impairment demonstrating the importance of the stimulated system to recovery. Motor cortex electrical stimulation is an effective approach to promote spouting of spaRed CST axons. By optimizing activity-dependent sprouting in animals, we could have an approach that can be translated to the human for evaluation with minimal delay
-
motor cortex electrical stimulation promotes axon outgrowth to brain stem and spinal targets that control the forelimb impaiRed by unilateral corticospinal injury
European Journal of Neuroscience, 2013Co-Authors: Jason B Carmel, Hiroki Kimura, Lauren J Berrol, John H MartinAbstract:We previously showed that electrical stimulation of motor cortex (M1) after unilateral pyramidotomy in the rat increased corticospinal tract (CST) axon length, strengthened spinal connections, and restoRed forelimb function. Here, we tested: 1) if M1 stimulation only increases spinal axon length or if it also promotes connections to brain stem forelimb control centers, especially Magnocellular Red Nucleus; and 2) if stimulation-induced increase in axon length depends on whether pyramidotomy denervated the structure. After unilateral pyramidotomy, we electrically stimulated the forelimb area of intact M1, to activate the intact CST and other corticofugal pathways, for 10 days. We anterogradely labeled stimulated M1 and measuRed axon length using stereology. Stimulation increased axon length in both the spinal cord and Magnocellular Red Nucleus, even though the spinal cord is denervated by pyramidotomy and the Red Nucleus is not. Stimulation also promoted outgrowth in the cuneate and parvocellular Red nuclei. In the spinal cord, electrical stimulation caused increased axon length ipsilateral, but not contralateral, to stimulation. Thus, stimulation promoted outgrowth preferentially to the sparsely corticospinal-innervated and impaiRed side. Outgrowth resulted in greater axon density in the ipsilateral dorsal horn and intermediate zone, resembling the contralateral termination pattern. Importantly, as in spinal cord, increase in axon length in brain stem also was preferentially directed towards areas less densely innervated by the stimulated system. Thus, M1 electrical stimulation promotes increases in corticofugal axon length to multiple M1 targets. We propose the axon length change was driven by competition into an adaptive pattern resembling lost connections.
Linda Hermer-vazquez - One of the best experts on this subject based on the ideXlab platform.
-
Tracing ‘driver’ versus ‘modulator’ information flow throughout large-scale, task-related neural circuitry
Journal of Combinatorial Optimization, 2008Co-Authors: Linda Hermer-vazquezAbstract:Primary objective : To determine the relative uses of neural action potential (‘spike’) data versus local field potentials (LFPs) for modeling information flow through complex brain networks. Hypothesis : The common use of LFP data, which are continuous and therefore more mathematically suited for spectral information-flow modeling techniques such as Granger causality analysis, can lead to spurious inferences about whether a given brain area ‘drives’ the spiking in a downstream area. Experiment : We recorded spikes and LFPs from the forelimb motor cortex (M1) and the Magnocellular Red Nucleus (mRN), which receives axon collaterals from M1 projection cells onto its distal dendrites, but not onto its perisomatic regions, as rats performed a skilled reaching task. Results and implications : As pRedicted, Granger causality analysis on the LFPs—which are mainly composed of vector-summed dendritic currents—produced results that if conventionally interpreted would suggest that the M1 cells drove spike firing in the mRN, whereas analyses of spiking in the two recorded regions revealed no significant correlations. These results suggest that mathematical models of information flow should treat the sampled dendritic activity as more likely to reflect intrinsic dendritic and input-related processing in neural networks, whereas spikes are more likely to provide information about the output of neural network processing.
-
Beta- and gamma-frequency coupling between olfactory and motor brain regions prior to skilled, olfactory-driven reaching
Experimental Brain Research, 2007Co-Authors: Raymond Hermer-vazquez, Linda Hermer-vazquez, Sridhar SrinivasanAbstract:A major question in neuroscience concerns how widely separated brain regions coordinate their activity to produce unitary cognitive states or motor actions. To investigate this question, we employed multisite, multielectrode recording in rats to study how olfactory and motor circuits are coupled prior to the execution of an olfactory-driven, GO/NO-GO variant of a skilled, rapidly executed (∼350–600 ms) reaching task. During task performance, we recorded multi-single units and local field potentials (LFPs) simultaneously from the rats’ olfactory cortex (specifically, the posterior piriform cortex) and from cortical and subcortical motor sites (the caudal forepaw M1, and the Magnocellular Red Nucleus, respectively). Analyses on multi-single units across areas revealed an increase in beta-frequency spiking (12–30 Hz) during a ∼100 ms window surrounding the Final Sniff of the GO cue before lifting the arm (the “Sniff-GO window”) that was seldom seen when animals sniffed the NO-GO cue. Also during the Sniff-GO window, LFPs displayed a striking increase in beta, low-gamma, and high-gamma energy (12–30, 30–50, and 50–100 Hz, respectively), and oscillations in the high gamma band appeaRed to be coherent across the recorded sites. These results indicate that transient, multispectral coherence across cortical and subcortical brain sites is part of the coordination process prior to sensory-guided movement initiation.
-
Distinct temporal activity patterns in the rat M1 and Red Nucleus during skilled versus unskilled limb movement.
Behavioural Brain Research, 2004Co-Authors: Linda Hermer-vazquez, Raymond Hermer-vazquez, K A Moxon, K-h Kuo, V Viau, Y Zhan, J K ChapinAbstract:The mammalian motor system contains multiple interconnected supraspinal networks, but little is known about their relative roles in producing different movements and behaviors, particularly given their apparently fused activity in primates. We tested whether the task context, as well as using a phylogenetically older mammal, rats, could distinguish the separate contributions of these networks. We obtained simultaneous multi-single neuron recordings from the forelimb motor cortex and Magnocellular Red Nucleus as rats performed two contextually different, but kinematically similar, forelimb reach-like tasks: highly learned, skilled reaching for food through a narrow slot, a task requiring extensive training, versus the swing phases of treadmill locomotion. In both the M1 and the mRN, large subpopulations of neurons peaked in their spike firing rates near the onset and the end of the swing phase during treadmill locomotion. In contrast, neural subgroups in the two areas displayed different temporal sequences of activity during the skilled reaching task. In the mRN, the majority of task-modulated neurons peaked in their firing rate in the middle of the reach when the rat was preparing to project the arm through the slot, whereas large subgroups of M1 neurons displayed elevated firing rates during the initial and terminal phases of the reach. These results suggest that motor-behavioral context can alter the degree of overlapping activity in different supraspinal sensorimotor networks. Moreover, results for the skilled reaching task in rats may have highlighted a distinct processing role of the rubral complex: adapting natural muscle synergies across joints and limbs to novel task demands, in concert with cortically based learning.
-
Methods for studying the neural basis of voluntary movement, part 1: correlations among behavior, multiunit activity and local field potential fluctuations
Proceedings of the 25th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (IEEE Cat. No.03CH37439), 1Co-Authors: Linda Hermer-vazquez, Raymond Hermer-vazquezAbstract:In this paper and the one that follows, we describe our approach to studying aspects of the neural basis of the decision-making, planning and execution of a voluntary, skilled, olfactory- driven movement - self-initiated reaching for food in rats. Our ultimate goal was to shed light on the combination of somatic and synaptic events in neural networks processing sensory, motivational, autonomic and motor information underlying the initiation of the motor sequence. We designed our task to combine putatively conscious decision-making with execution of a well-learned, stereotypic movement, to retain a voluntary component to the task while minimizing trial-to-trial variance. In an attempt to study the motivational and autonomic processing underlying voluntary decisions to act in addition to the relevant sensory and motor processing, we recorded from the posterior piriform cortex in addition to the origins of two descending motor tracts, M1 and the Magnocellular Red Nucleus. To gain insight into the subthreshold membrane dynamics leading to synaptic change and ultimately to changes in postsynaptic cell spiking, we recorded local field potentials in addition to action potentials. After carefully segmenting task events associated with significant neural modulation at the spike and LFP levels, we performed discriminant analyses to examine how robustly those neural correlates pRedicted the rats' behavior on single trials. We found high pRedictability through a combination of spike rate and LFP amplitude modulation measures. The robustness of these phenomena allowed us to apply the continuous wavelet transform to prototypical single-trial LFP data to visualize the distinctive 2-D topology of energy at different frequencies across task-time associated with initiating and performing this motor sequence. We found that these task- and phase-specific spectral properties, combined with co-modulation of firing rate and LFP amplitude, led to the most robust pRediction of the rats' behavior on single trials.
John H Martin - One of the best experts on this subject based on the ideXlab platform.
-
Motor cortex electrical stimulation augments sprouting of the corticospinal tract and promotes recovery of motor function
Frontiers in Integrative Neuroscience, 2014Co-Authors: Jason B Carmel, John H MartinAbstract:The corticospinal system-with its direct spinal pathway, the corticospinal tract (CST) - is the primary system for controlling voluntary movement. Our approach to CST repair after injury in mature animals was informed by our finding that activity drives establishment of connections with spinal cord circuits during postnatal development. After incomplete injury in maturity, spaRed CST circuits sprout, and partially restore lost function. Our approach harnesses activity to augment this injury-dependent CST sprouting and to promote function. Lesion of the medullary pyramid unilaterally eliminates all CST axons from one hemisphere and allows examination of CST sprouting from the unaffected hemisphere. We discoveRed that 10 days of electrical stimulation of either the spaRed CST or motor cortex induces CST axon sprouting that partially reconstructs the lost CST. Stimulation also leads to sprouting of the cortical projection to the Magnocellular Red Nucleus, where the rubrospinal tract originates. Coordinated outgrowth of the CST and cortical projections to the Red Nucleus could support partial re-establishment of motor systems connections to the denervated spinal motor circuits. Stimulation restores skilled motor function in our animal model. Lesioned animals have a persistent forelimb deficit contralateral to pyramidotomy in the horizontal ladder task. Rats that received motor cortex stimulation either after acute or chronic injury showed a significant functional improvement that brought error rate to pre-lesion control levels. Reversible inactivation of the stimulated motor cortex reinstated the impairment demonstrating the importance of the stimulated system to recovery. Motor cortex electrical stimulation is an effective approach to promote spouting of spaRed CST axons. By optimizing activity-dependent sprouting in animals, we could have an approach that can be translated to the human for evaluation with minimal delay.
-
motor cortex electrical stimulation promotes axon outgrowth to brain stem and spinal targets that control the forelimb impaiRed by unilateral corticospinal injury
European Journal of Neuroscience, 2013Co-Authors: Jason B Carmel, Hiroki Kimura, Lauren J Berrol, John H MartinAbstract:We previously showed that electrical stimulation of motor cortex (M1) after unilateral pyramidotomy in the rat increased corticospinal tract (CST) axon length, strengthened spinal connections, and restoRed forelimb function. Here, we tested: 1) if M1 stimulation only increases spinal axon length or if it also promotes connections to brain stem forelimb control centers, especially Magnocellular Red Nucleus; and 2) if stimulation-induced increase in axon length depends on whether pyramidotomy denervated the structure. After unilateral pyramidotomy, we electrically stimulated the forelimb area of intact M1, to activate the intact CST and other corticofugal pathways, for 10 days. We anterogradely labeled stimulated M1 and measuRed axon length using stereology. Stimulation increased axon length in both the spinal cord and Magnocellular Red Nucleus, even though the spinal cord is denervated by pyramidotomy and the Red Nucleus is not. Stimulation also promoted outgrowth in the cuneate and parvocellular Red nuclei. In the spinal cord, electrical stimulation caused increased axon length ipsilateral, but not contralateral, to stimulation. Thus, stimulation promoted outgrowth preferentially to the sparsely corticospinal-innervated and impaiRed side. Outgrowth resulted in greater axon density in the ipsilateral dorsal horn and intermediate zone, resembling the contralateral termination pattern. Importantly, as in spinal cord, increase in axon length in brain stem also was preferentially directed towards areas less densely innervated by the stimulated system. Thus, M1 electrical stimulation promotes increases in corticofugal axon length to multiple M1 targets. We propose the axon length change was driven by competition into an adaptive pattern resembling lost connections.
Martha L Mccurdy - One of the best experts on this subject based on the ideXlab platform.
-
Neuronal Correlates of Functional Coupling between Reach- and Grasp-Related Components of Muscle Activity.
Frontiers in Neural Circuits, 2017Co-Authors: Shashwati Geed, Martha L Mccurdy, Peter L E Van KanAbstract:Coordinated reach-to-grasp movements require precise spatiotemporal synchrony between proximal forelimb muscles (shoulder, elbow) that transport the hand towards a target during reach, and distal muscles (wrist, digit) that simultaneously preshape and orient the hand for grasp. The precise mechanisms through which the Redundant neuromuscular circuitry coordinates reach with grasp, however, remain unclear. Recently, we demonstrated, using exploratory factor analysis (EFA), that limited numbers of global, template-like transport/preshape- and grasp-related muscle components underlie the complexity and variability of intramuscular electromyograms (EMGs) of up to 21 distal and proximal muscles recorded while monkeys performed reach-to-grasp tasks. Importantly, transport/preshape- and grasp-related muscle components showed invariant spatiotemporal coupling, which provides a potential mechanism for coordinating forelimb muscles during reach-to-grasp movements. In the present study, we tested whether ensemble discharges of forelimb neurons in the cerebellar Nucleus interpositus (NI) and its target, the Magnocellular Red Nucleus (RNm), a source of rubrospinal fibers, function as neuronal correlates of the transport/preshape- and grasp-related muscle components we identified. EFA applied to single-unit discharges of populations of NI and RNm neurons recorded while the same monkeys that were used previously performed the same reach-to-grasp tasks, revealed neuronal components in the ensemble discharges of both NI and RNm neuronal populations with characteristics broadly similar to muscle components. Subsets of NI and RNm neuronal components were strongly and significantly cross-correlated with subsets of muscle components, suggesting that similar functional units of reach-to-grasp behavior are expressed by NI and RNm neuronal populations and forelimb muscles. Importantly, like transport/preshape- and grasp-related muscle components, their NI and RNm neuronal correlates showed invariant spatiotemporal coupling. Clinical and lesion studies have reported disruption of coupling between reach and grasp following cerebellar damage; the present results expand on those studies by identifying a neuronal mechanism that may underlie cerebellar contributions to spatiotemporal coordination of distal and proximal limb muscles during reaching to grasp. We conclude that finding similar functional units of behavior expressed at multiple levels of information processing along interposito-rubrospinal pathways and forelimb muscles supports the hypothesis that functionally related populations of NI and RNm neurons act synergistically in the control of complex coordinated motor behaviors.
-
contribution of primate Magnocellular Red Nucleus to timing of hand preshaping during reaching to grasp
Journal of Neurophysiology, 2002Co-Authors: Peter L E Van Kan, Martha L MccurdyAbstract:Magnocellular Red Nucleus (RNm) is involved in controlling goal-directed limb movements such as reaching to grasp. We tested two hypotheses related to RNm's role in controlling reach-to-grasp movements. One hypothesis is that forelimb RNm neurons are grasp specific, and the other is that they specify the timing of metacarpi-phalangeal (MCP) extension to preshape the hand during the appropriate phase of the reach. We recorded single-unit discharge while monkeys performed two behavioral tasks that elicited similar reaches but diffeRed in grasp. One task consisted of a reach with a precision grasp that elicited independent use of thumb and forefinger; the other included a whole-hand grasp that elicited concerted use of the four fingers. Most RNm neurons tested were engaged strongly during both the whole-hand and precision tasks, and the magnitude of discharge modulation did not differ between tasks. Thus most RNm neurons are not grasp specific but, instead, may contribute to behavioral features common to the two tasks. Two methods were used to investigate relations between single-unit discharge and kinematic data from the same individual trials of the whole-hand and precision tasks for a subset of forelimb RNm neurons. One method focused on correlations between parameters of RNm discharge and the duration, amplitude, and velocity of rotation of forelimb joints for each of the tasks. The second method compaRed between-task differences in times of peak neuronal discharge to between-task differences in times of rotations of forelimb joints. Parameters of reach-related RNm discharge were more frequently correlated with parameters of MCP extension than with parameters of rotation of wrist, elbow, and shoulder joints. Analyses of temporal relations between discharge and kinematic data during both the whole-hand and precision tasks indicate that discharge was time locked most frequently to MCP extension and, to a lesser extent, elbow extension during both tasks. We conclude that RNm may command muscle synergies that provide a basic preshape of the hand at the appropriate phase of limb transport. In addition, the timing of RNm's contribution to hand preshaping varies with the behavioral requirements of the task.
-
discharge of primate Magnocellular Red Nucleus neurons during reaching to grasp in different spatial locations
Experimental Brain Research, 2002Co-Authors: Peter L E Van Kan, Martha L MccurdyAbstract:Reaching to grasp is of fundamental importance to primate motor behavior. One descending motor pathway that contributes to the control of this behavior is the rubrospinal tract. An important source of origin of the rubrospinal tract is the Magnocellular Red Nucleus (RNm). Forelimb RNm neurons discharge vigorously during reach-to-grasp movements. RNm discharge is important for hand use, as coordinated whole-limb movements without hand use are not associated with strong discharge. Because RNm is functionally linked to muscles of the entire forelimb, RNm discharge may also contribute to use of the proximal limb that accompanies hand use. If RNm contributes to proximal limb use, we pRedict discharge to differ for reaches that differ in proximal limb involvement but require the same grasp. We tested this pRediction by measuring discharge of individual RNm neurons while monkeys reached to grasp objects in four spatial locations in front of them. The animals reached from the waist to locations to the left, right, above, and below the shoulder of the "reaching" limb. RNm neurons of our sample were activated strongly during reach-to-grasp, and discharge of a third of the neurons tested depended on the spatial location of the object grasped. Discharge of RNm neurons and EMG activity of many of the distal and proximal forelimb muscles we tested were larger for reaching to grasp in the upper and/or right than lower and left target locations. Based on comparisons of each individual neuron's discharge patterns during reaches with and without preshaping the hand, we conclude that target location-dependent modulations in discharge rate of the majority of RNm neurons whose discharge diffeRed for reaching to grasp in the four target locations contributed to aspects of hand preshaping that covaried with reach direction.
-
role of primate Magnocellular Red Nucleus neurons in controlling hand preshaping during reaching to grasp
Journal of Neurophysiology, 2001Co-Authors: Peter L E Van Kan, Martha L MccurdyAbstract:Reaching to grasp is of fundamental importance to primate motor behavior and requires coordinating hand preshaping with limb transport and grasping. We aimed to clarify the role of cerebellar output via the Magnocellular Red Nucleus (RNm) to the control of reaching to grasp. Rubrospinal fibers originating from RNm constitute one pathway by which cerebellar output influences spinal circuitry directly. We recorded discharge from individual forelimb RNm neurons while monkeys performed a reach-to-grasp task and two tasks that were similar to the reach-to-grasp task in trajectory, amplitude, and direction but did not include a grasp. One of these, the device task, elicited reaches while holding a handle, and the other, the free-reach task, elicited reaches that did not require any specific hand use for task performance. The results demonstrate that coordinated whole-limb reaching movements are associated with large discharge modulations of RNm neurons pRedominantly when hand use is included. Therefore RNm neurons can at best only make a minor contribution to the control of reaching movements that lack hand use. We evaluated relations between the discharge of individual RNm neurons and electromyographic (EMG) activity of forelimb muscles during the reach-to-grasp task by comparing times of peak RNm discharge to times of peak EMG activity. The results are consistent with the view that RNm discharge may contribute to EMG activity of both distal and proximal muscles during reaching to grasp especially digit extensor and limb elevation muscles. Relations between the discharge of individual RNm neurons and movements of the metacarpi-phalangeal (MCP), wrist, elbow, and shoulder joints during individual trials of task performance were quantified by parametric correlation analyses on a subset of neurons studied during the reach-to-grasp and free-reach tasks. The results indicate that MCP extensions were consistently preceded by bursts of RNm discharge, and strong correlations were observed between parameters of discharge and the duration, velocity, and amplitude of corresponding MCP extensions. In contrast, relations between discharge and movements of proximal joints were poorly represented, and RNm discharge was not related to the speed of limb transport. Based on our data and those of others, we hypothesize that cerebellar output via RNm is specialized for controlling hand use and conclude that RNm may contribute to the control of hand preshaping during reaching to grasp by activating muscle synergies that produce the appropriate MCP extension at the appropriate phase of limb transport.