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James C. Houk - One of the best experts on this subject based on the ideXlab platform.
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Somatosensory and movement-related properties of Red Nucleus: a single unit study in the turtle
Experimental Brain Research, 1996Co-Authors: Ramin Sarrafizadeh, Joyce Keifer, James C. HoukAbstract:Extracellular recordings were performed from turtle Red Nucleus neurons to examine their responsiveness to peripheral somatic stimulation and to study differences between rubral sensory and movement-related responses. In pentobarbital sodium-anesthetized or decerebrate turtles, Red Nucleus neurons could be divided into two categories based on their response characteristics. The first group, which included 87% of neurons studied, had low spontaneous rates of activity and responded with excitation to electrical stimulation of the spinal cord or the cerebellum, or during active movement of the contralateral limbs. Neurons in this category were likely to be rubrospinal cells. The remaining 13% of cells studied had higher rates of spontaneous discharge and were inhibited by electrical stimulation or during active movement. These cells might be rubral GABAergic interneurons. Single Red Nucleus neurons responded with excitation and/or inhibition to somatosensory stimulation. Unlike the motor fields, which were restricted to a single contralateral limb, Red Nucleus sensory receptive fields were wide and often bilaterally distributed. Rubral responsiveness to sensory stimulation was found to be significantly diminished during active limb movements, thereby suggesting that sensory inputs to the Red Nucleus are not used for the on-line modification of motor commands. Inactivation of the cerebellar cortex enhanced the sensory responsiveness of rubral neurons and expanded the size of Red Nucleus receptive fields. These results suggest that the Red Nucleus receives substantial sensory input, and that the cerebellar cortex can modify the flow of sensory information to the Red Nucleus.
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Intrinsic and synaptic properties of turtle Red Nucleus neurons in vitro
Brain Research, 1993Co-Authors: Joyce Keifer, James C. HoukAbstract:Abstract Burst discharges in the Red Nucleus are correlated with discrete limb movements. Intracellular recordings from Red Nucleus neurons in the in vitro turtle brainstem-cerebellum was performed to elucidate mechanisms underlying these bursts. Depolarizing intracellular current injection failed to demonstrate endogenous membrane currents that might produce burst discharges, and neurons did not exhibit significant spike frequency adaptation, which is a characteristic of synaptically driven bursts. Responses of Red Nucleus neurons to synaptic input demonstrated a late slow depolarizing synaptic potential (slow EPSP) having a latency of 9–12 ms, and a maximal duration of 600 ms. it is concluded that neither intrinsic membrane responses, nor the duration of the slow EPSP, can fully account for the behavior of Red Nucleus neurons during burst discharge. We hypothesize that activity in the Red Nucleus is driven by a gradual recruitment of NMDA receptors, and 1 pr by polysynaptic excitatory pathways.
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Evidence for GABAergic interneurons in the Red Nucleus of the painted turtle.
Synapse, 1992Co-Authors: Joyce Keifer, James C. Houk, Devhuti Vyas, Albert S. Berrebi, Enrico MugnainiAbstract:Immunocytochemical and electrophysiological evidence supporting the presence of GABAergic interneurons in the turtle Red Nucleus is presented. Injections of HRP into the spinal cord produced labeling of large neurons in the contralateral Red Nucleus. The peroxidase-antiperoxidase (PAP) method revealed smaller cells immunoreactive to an antibody against glutamate decarboxylase (GAD), the synthetic enzyme for the inhibitory neurotransmitter GABA, that were interspersed among larger immunonegative neurons. Similar small neurons were densely immunostained by antibodies to GABA-glutaraldehyde conjugates obtained from different sources and applied according to pre-embedding and postembedding protocols. Rubrospinal neurons retrogradely labeled with HRP measuRed 16 and 27 μm in mean minor and major cell body diameters, while GABA-like immunopositive neurons situated within the Red Nucleus measuRed 7 and 13 μm. There was very little overlap in soma size between the two cell populations. Therefore, we suggest that the GAD- and GABA-positive neurons may be local inhibitory interneurons. This nition is further supported by observations of pre-embedding immunostaining for GAD and postembedding immunostaining for GABA showing that the turtle Red Nucleus is amply innervated by immunoreactive axon terminals. These puncta are closely apposed to cell bodies and dendrites of both immunonegative large neurons and immunopositive small neurons. Moreover, immunogold staining at the electron microscopic level demonstrated that GABA-like immunoreactive axon terminals with pleomorphic synaptic vesicles formed symmetric synapses with cell bodies and dendrites of the two types of Red Nucleus cells. These ultrastructural features are commonly assumed to indicate inhibitory synapses. A moderately labeled bouton with round vesicles and asymmetric synapses was also observed. In addition, the two types of Red Nucleus neurons received asymmetric axosomatic and axodendritic synapses with GABA-negative boutons provided with round vesicles, features usually associated with excitatory functions. To obtain electrophysiological evidence for inhibition, intracellular recordings from Red Nucleus neurons were conducted using an in vitro brainstem-cerebellum preparation from the turtle. Small, spontaneous IPSPs were recorded from 7 out of 14 Red Nucleus cells studied. These morphological and physiological results provide strong support for concluding that the turtle Red Nucleus, like its mammalian counterpart, contains GABAergic inhibitory interneurons. While we have not indentified the main source of input to these interneurons, in view of the scarce development of the reptilian cerebral cortex, this input is unlikely to come from the motor cortex as it does in mammals. Current concepts of the role of these interneurons in motor control must take into account the presence of this interneuronal system that phylogenetically precedes the emergence of the sensorimotor cortex. © Wiley-Liss, Inc.
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Red Nucleus: role in motor control
Current Opinion in Neurobiology, 1991Co-Authors: James C. HoukAbstract:Experimental reports in the past year have provided a better understanding of the motor functions of excitatory and inhibitory neurotransmitters in the Red Nucleus, and of the sensorimotor properties of single rubral neurons. These data fit well within the framework of a neural network model of the rubrocerebellar system.
Joyce Keifer - One of the best experts on this subject based on the ideXlab platform.
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A hypothalamic projection to the turtle Red Nucleus: an anterograde and retrograde tracing study.
Experimental Brain Research, 1997Co-Authors: James L. Herrick, Joyce KeiferAbstract:It is well known that the reptilian Red Nucleus lacks a descending motor cortical input to the Red Nucleus, but has a well-developed cerebellar input. The present study was undertaken to determine whether there is a descending rubral input that originates from the hypothalamus. Using an in vitro preparation from the turtle, injections of neurobiotin into the Red Nucleus resulted in retrograde labeling of neurons in the suprapeduncular Nucleus of the hypothalamus. Injections of either neurobiotin or fluorescein dextran into the suprapenduncular Nucleus resulted in anterograde labeling of axons and terminal boutons in the Red Nucleus. The majority of these terminations appeaRed to lie in the medial part of the Red Nucleus. These data have implications for the potential control of the somatic motor system of reptiles by limbic system inputs.
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Effects of Red Nucleus inactivation on burst discharge in turtle cerebellum in vitro: evidence for positive feedback
Journal of Neurophysiology, 1996Co-Authors: Joyce KeiferAbstract:1. In behaving animals the Red Nucleus produces sustained action potential discharge during movements of the limbs. These bursts are thought to encode parameters of movement and thereby represent motor commands. Similar bursts can be recorded in the in vitro brain stem-cerebellum from the turtle. In this preparation, sustained discharge of Red Nucleus neurons was postulated to be generated by N-methyl-D-aspartate-mediated cellular mechanisms acting in combination with positive feedback in a recurrent cerebellorubral network. The present study was designed to test this positive feedback hypothesis. During recording of sustained discharge in the deep cerebellar nuclei and cortex, the Red Nucleus was reversibly inactivated by microinjection. The positive feedback hypothesis would be supported if activity in the cerebellum was attenuated by inactivation of the Red Nucleus. A nonrecurrent source of excitation would have to be postulated if cerebellar activity was unaffected. 2. Extracellular single-unit recordings were made from neurons in the deep cerebellar nuclei, cerebellar cortex, and vestibular nuclei. Burst discharges were evoked by brief electrical stimuli applied to the spinal cord that activated sensory structures. During inactivation of the Red Nucleus, sensory projections to the cerebellum that may evoke burst discharge were unaffected. Pressure microinjections of cobalt, lidocaine, gamma-aminobutyric acid (GABA), or 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) were used to reversibly inactivate the Red Nucleus. Saline injections were also tested. 3. Sustained discharge of all neurons recorded in the lateral cerebellar Nucleus was greatly attenuated or blocked completely by injection of the pharmacological agents into the Red Nucleus. These effects were reversible. Of the recordings in the cerebellar cortex, 63% of these were blocked. All four compounds tested were effective blockers of the bursts, although the effects of GABA were less potent than the others. Saline injections into the Red Nucleus showed no effect. Burst discharges of single units recorded in either the medial cerebellar Nucleus or the vestibular complex, which do not receive input from the Red Nucleus, showed no effect of Red Nucleus inactivation. 4. The results showed that sustained discharge in the cerebellum was significantly attenuated by inactivation of the Red Nucleus even though sensory input that may trigger the bursts was intact. These data support the hypothesis that sustained discharge in the cerebellorubral circuit is generated by a distributed neuronal network that uses positive feedback. The results have implications for mechanisms underlying normal brain function and some motor disorders.
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Somatosensory and movement-related properties of Red Nucleus: a single unit study in the turtle
Experimental Brain Research, 1996Co-Authors: Ramin Sarrafizadeh, Joyce Keifer, James C. HoukAbstract:Extracellular recordings were performed from turtle Red Nucleus neurons to examine their responsiveness to peripheral somatic stimulation and to study differences between rubral sensory and movement-related responses. In pentobarbital sodium-anesthetized or decerebrate turtles, Red Nucleus neurons could be divided into two categories based on their response characteristics. The first group, which included 87% of neurons studied, had low spontaneous rates of activity and responded with excitation to electrical stimulation of the spinal cord or the cerebellum, or during active movement of the contralateral limbs. Neurons in this category were likely to be rubrospinal cells. The remaining 13% of cells studied had higher rates of spontaneous discharge and were inhibited by electrical stimulation or during active movement. These cells might be rubral GABAergic interneurons. Single Red Nucleus neurons responded with excitation and/or inhibition to somatosensory stimulation. Unlike the motor fields, which were restricted to a single contralateral limb, Red Nucleus sensory receptive fields were wide and often bilaterally distributed. Rubral responsiveness to sensory stimulation was found to be significantly diminished during active limb movements, thereby suggesting that sensory inputs to the Red Nucleus are not used for the on-line modification of motor commands. Inactivation of the cerebellar cortex enhanced the sensory responsiveness of rubral neurons and expanded the size of Red Nucleus receptive fields. These results suggest that the Red Nucleus receives substantial sensory input, and that the cerebellar cortex can modify the flow of sensory information to the Red Nucleus.
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Intrinsic and synaptic properties of turtle Red Nucleus neurons in vitro
Brain Research, 1993Co-Authors: Joyce Keifer, James C. HoukAbstract:Abstract Burst discharges in the Red Nucleus are correlated with discrete limb movements. Intracellular recordings from Red Nucleus neurons in the in vitro turtle brainstem-cerebellum was performed to elucidate mechanisms underlying these bursts. Depolarizing intracellular current injection failed to demonstrate endogenous membrane currents that might produce burst discharges, and neurons did not exhibit significant spike frequency adaptation, which is a characteristic of synaptically driven bursts. Responses of Red Nucleus neurons to synaptic input demonstrated a late slow depolarizing synaptic potential (slow EPSP) having a latency of 9–12 ms, and a maximal duration of 600 ms. it is concluded that neither intrinsic membrane responses, nor the duration of the slow EPSP, can fully account for the behavior of Red Nucleus neurons during burst discharge. We hypothesize that activity in the Red Nucleus is driven by a gradual recruitment of NMDA receptors, and 1 pr by polysynaptic excitatory pathways.
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Evidence for GABAergic interneurons in the Red Nucleus of the painted turtle.
Synapse, 1992Co-Authors: Joyce Keifer, James C. Houk, Devhuti Vyas, Albert S. Berrebi, Enrico MugnainiAbstract:Immunocytochemical and electrophysiological evidence supporting the presence of GABAergic interneurons in the turtle Red Nucleus is presented. Injections of HRP into the spinal cord produced labeling of large neurons in the contralateral Red Nucleus. The peroxidase-antiperoxidase (PAP) method revealed smaller cells immunoreactive to an antibody against glutamate decarboxylase (GAD), the synthetic enzyme for the inhibitory neurotransmitter GABA, that were interspersed among larger immunonegative neurons. Similar small neurons were densely immunostained by antibodies to GABA-glutaraldehyde conjugates obtained from different sources and applied according to pre-embedding and postembedding protocols. Rubrospinal neurons retrogradely labeled with HRP measuRed 16 and 27 μm in mean minor and major cell body diameters, while GABA-like immunopositive neurons situated within the Red Nucleus measuRed 7 and 13 μm. There was very little overlap in soma size between the two cell populations. Therefore, we suggest that the GAD- and GABA-positive neurons may be local inhibitory interneurons. This nition is further supported by observations of pre-embedding immunostaining for GAD and postembedding immunostaining for GABA showing that the turtle Red Nucleus is amply innervated by immunoreactive axon terminals. These puncta are closely apposed to cell bodies and dendrites of both immunonegative large neurons and immunopositive small neurons. Moreover, immunogold staining at the electron microscopic level demonstrated that GABA-like immunoreactive axon terminals with pleomorphic synaptic vesicles formed symmetric synapses with cell bodies and dendrites of the two types of Red Nucleus cells. These ultrastructural features are commonly assumed to indicate inhibitory synapses. A moderately labeled bouton with round vesicles and asymmetric synapses was also observed. In addition, the two types of Red Nucleus neurons received asymmetric axosomatic and axodendritic synapses with GABA-negative boutons provided with round vesicles, features usually associated with excitatory functions. To obtain electrophysiological evidence for inhibition, intracellular recordings from Red Nucleus neurons were conducted using an in vitro brainstem-cerebellum preparation from the turtle. Small, spontaneous IPSPs were recorded from 7 out of 14 Red Nucleus cells studied. These morphological and physiological results provide strong support for concluding that the turtle Red Nucleus, like its mammalian counterpart, contains GABAergic inhibitory interneurons. While we have not indentified the main source of input to these interneurons, in view of the scarce development of the reptilian cerebral cortex, this input is unlikely to come from the motor cortex as it does in mammals. Current concepts of the role of these interneurons in motor control must take into account the presence of this interneuronal system that phylogenetically precedes the emergence of the sensorimotor cortex. © Wiley-Liss, Inc.
Ramin Sarrafizadeh - One of the best experts on this subject based on the ideXlab platform.
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Somatosensory and movement-related properties of Red Nucleus: a single unit study in the turtle
Experimental Brain Research, 1996Co-Authors: Ramin Sarrafizadeh, Joyce Keifer, James C. HoukAbstract:Extracellular recordings were performed from turtle Red Nucleus neurons to examine their responsiveness to peripheral somatic stimulation and to study differences between rubral sensory and movement-related responses. In pentobarbital sodium-anesthetized or decerebrate turtles, Red Nucleus neurons could be divided into two categories based on their response characteristics. The first group, which included 87% of neurons studied, had low spontaneous rates of activity and responded with excitation to electrical stimulation of the spinal cord or the cerebellum, or during active movement of the contralateral limbs. Neurons in this category were likely to be rubrospinal cells. The remaining 13% of cells studied had higher rates of spontaneous discharge and were inhibited by electrical stimulation or during active movement. These cells might be rubral GABAergic interneurons. Single Red Nucleus neurons responded with excitation and/or inhibition to somatosensory stimulation. Unlike the motor fields, which were restricted to a single contralateral limb, Red Nucleus sensory receptive fields were wide and often bilaterally distributed. Rubral responsiveness to sensory stimulation was found to be significantly diminished during active limb movements, thereby suggesting that sensory inputs to the Red Nucleus are not used for the on-line modification of motor commands. Inactivation of the cerebellar cortex enhanced the sensory responsiveness of rubral neurons and expanded the size of Red Nucleus receptive fields. These results suggest that the Red Nucleus receives substantial sensory input, and that the cerebellar cortex can modify the flow of sensory information to the Red Nucleus.
Ian Q. Whishaw - One of the best experts on this subject based on the ideXlab platform.
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The differential contributions of the parvocellular and the magnocellular subdivisions of the Red Nucleus to skilled reaching in the rat.
Neuroscience, 2015Co-Authors: Renée Morris, K.k. Vallester, S.s. Newton, A.p. Kearsley, Ian Q. WhishawAbstract:During the execution of the skilled reaching task, naive rats bring their elbow to the midline of their body to aim at the food target, perform the arpeggio movement to grasp it and supinate the paw to bring the food to their mouth. Red Nucleus lesions in the rat interfere with each of these three movement elements of reaching. On the other hand, lesions to the rubrospinal tract, which originate from the magnocellular subdivision of the Red Nucleus, only interfere with the arpeggio movement. This latter evidence strongly suggests that impairment in aiming and supinating could be under the control of the parvocellular subdivision of the Red Nucleus. In order to test this hypothesis, rats were trained on the skilled reaching task and then received either complete lesions of the Red Nucleus or lesions restricted to its parvo- or magnocellular subdivision. In line with previous data, complete excitotoxic lesions of the Red Nucleus compromised limb aiming, arpeggio and supination. Lesions restricted to the parvocellular division of the Red Nucleus abolish supination and interfere with aiming, although the latter result did not reach significance. The results are discussed in terms of the distinct connectivity and functional significance of these two architectonic subdivisions of the Red Nucleus.
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Red Nucleus lesions impair overground locomotion in rats: a kinetic analysis.
European Journal of Neuroscience, 2000Co-Authors: Gillian D. Muir, Ian Q. WhishawAbstract:The Red Nucleus is a prominent brainstem Nucleus in mammals which is thought to be involved in production of skilled limb movements. The presence of the Red Nucleus and associated rubrospinal tract in animals that do not produce skilled limb movements, however, suggests that these structures might also be involved in control of more general limb actions, such as those occurring during locomotion. The present study investigates this question by measuring the three-dimensional ground reaction forces produced by locomoting rats with unilateral excitotoxic lesions of the Red Nucleus. Twenty-four to 48 h after the lesion, rats moved with an asymmetric gait during which abnormal braking and propulsive forces were produced during the dual contact time of the forelimb contralateral to the lesion and the ipsilateral hindlimb. Rats did not recover normal symmetrical locomotion within the 55-day duration of the study. The persistent asymmetry produced by Red Nucleus ablation provides the first unequivocal demonstration that the Red Nucleus plays a role in ongoing overground locomotion in the rat. Species differences in phylogeny and connectivity of the Red Nucleus are discussed, as well as the possibility that there is a general compensatory response to unilateral CNS injury in the rat.
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A behavioral study of the contributions of cells and fibers of passage in the Red Nucleus of the rat to postural righting, skilled movements, and learning.
Behavioural Brain Research, 1992Co-Authors: Ian Q. Whishaw, Sergio M. Pellis, Vivien C. PellisAbstract:Although the Red Nucleus consists of cells of origin for the rubro-spinal and rubro-olivary tracts, fibers of passage, including those of the superior cerebellar peduncle, which project from the cerebellum to the ventrolateral thalamus, pass through it. This study examined the relative effect of cell vs. fiber damage in the Red Nucleus on a number of behaviors thought to involve the Red Nucleus, including a skilled movement of reaching for food with a forelimb, postural righting on a surface and in the air, and learning a place response in a swimming pool test. Rats received unilateral or bilateral Red Nucleus lesions, using either the relatively cell-specific neurotoxins, ibotenic and quinolinic acid, or non-specific electrolytic anodal lesions. Both neurotoxic lesions effectively eliminated all Red Nucleus cell bodies, and in some animals they produced small cavities in the Red Nucleus and/or loss of cells in adjacent structures. Electrolytic lesions destroyed both cells and fibers, leaving a large cavity. The severity of the behavioral deficits were not related to the loss of Red Nucleus cells and there was a close relation between fiber damage and behavioral impairments on all of the tasks. The results suggest that for a number of behaviors, which have been thought to involve the Red Nucleus, impairments are more closely associated with fiber damage or damage to structures outside the Red Nucleus than they are to damage to cells of the Red Nucleus.
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Red Nucleus lesions do not affect limb preference or use but exacerbate the effects of motor cortex lesions on grasping in the rat
Behavioural Brain Research, 1990Co-Authors: Ian Q. Whishaw, Joanne Tomie, Ricki L LadowskyAbstract:The corticospinal and rubrospinal systems are thought to collaborate in the production of skilled forelimb movements in primates. This study examined whether this relation holds in rodents. Limb preference and limb skill were assessed in a reaching-for-food task in rats with ibotenic acid lesions of the Red Nucleus or combined Red Nucleus lesions and aspirative motor cortex lesions. Major findings were: (1) Unilateral Red Nucleus lesions did not influence subsequent development of limb preference in naive rats. (2) Unilateral Red Nucleus lesions in pretrained rats failed to affect the incidence of reaching (total reaches) and reaching success (hit percent) by either the contralateral or ipsilateral limb. (3) Whereas motor cortex lesions impaiRed subsequent use of the contralateral limb, additional Red Nucleus lesions did not change total reaches or hit percent, but did produce moderate qualitative changes in limb accuracy and paw opening during grasping. The results demonstrate that in the rat, the Red Nucleus is not essential for the ballistic component of reaching but may contribute to fine motor control.
Ricki L Ladowsky - One of the best experts on this subject based on the ideXlab platform.
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Red Nucleus lesions do not affect limb preference or use but exacerbate the effects of motor cortex lesions on grasping in the rat
Behavioural Brain Research, 1990Co-Authors: Ian Q. Whishaw, Joanne Tomie, Ricki L LadowskyAbstract:The corticospinal and rubrospinal systems are thought to collaborate in the production of skilled forelimb movements in primates. This study examined whether this relation holds in rodents. Limb preference and limb skill were assessed in a reaching-for-food task in rats with ibotenic acid lesions of the Red Nucleus or combined Red Nucleus lesions and aspirative motor cortex lesions. Major findings were: (1) Unilateral Red Nucleus lesions did not influence subsequent development of limb preference in naive rats. (2) Unilateral Red Nucleus lesions in pretrained rats failed to affect the incidence of reaching (total reaches) and reaching success (hit percent) by either the contralateral or ipsilateral limb. (3) Whereas motor cortex lesions impaiRed subsequent use of the contralateral limb, additional Red Nucleus lesions did not change total reaches or hit percent, but did produce moderate qualitative changes in limb accuracy and paw opening during grasping. The results demonstrate that in the rat, the Red Nucleus is not essential for the ballistic component of reaching but may contribute to fine motor control.
