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Background: Closed-loop neuromodulation systems have received increased attention in recent years as potential therapeutic approaches for treating neurological injury and disease. Objective: The purpose of this study was to assess the... more
Background: Closed-loop neuromodulation systems have received increased attention in recent years as potential therapeutic approaches for treating neurological injury and disease. Objective: The purpose of this study was to assess the ability of intraspinal microstimulation (ISMS), triggered by action potentials (spikes) recorded in motor cortex, to alter synaptic efficacy in descending motor pathways in an anesthetized rat model of spinal cord injury (SCI). Methods: Experiments were carried out in adult, male, Sprague Dawley rats with a moderate contusion injury at T8. For activity-dependent stimulation (ADS) sessions, a recording microelectrode was used to detect neuronal spikes in motor cortex that triggered ISMS in the spinal cord grey matter. SCI rats were randomly assigned to one of four experimental groups differing by: a) cortical spike-ISMS stimulus delay (10 or 25 ms) and b) number of ISMS pulses (1 or 3). Four weeks after SCI, ADS sessions were conducted in three consecut...
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Objective. The purpose of this study was to determine the effects of spinal cord injury (SCI) on spike activity evoked in the hindlimb spinal cord of the rat from cortical electrical stimulation. Approach. Adult, male, Sprague Dawley rats... more
Objective. The purpose of this study was to determine the effects of spinal cord injury (SCI) on spike activity evoked in the hindlimb spinal cord of the rat from cortical electrical stimulation. Approach. Adult, male, Sprague Dawley rats were randomly assigned to a Healthy or SCI group. SCI rats were given a 175 kDyn dorsal midline contusion injury at the level of the T8 vertebrae. At 4 weeks post-SCI, intracortical microstimulation (ICMS) was delivered at several sites in the hindlimb motor cortex of anesthetized rats, and evoked neural activity was recorded from corresponding sites throughout the dorsoventral depths of the spinal cord and EMG activity from hindlimb muscles. Main results. In healthy rats, post-ICMS spike histograms showed reliable, evoked spike activity during a short-latency epoch 10–12 ms after the initiation of the ICMS pulse train (short). Longer latency spikes occurred between ∼20 and 60 ms, generally following a Gaussian distribution, rising above baseline a...
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The purpose of this study was to determine if spike-triggered intraspinal microstimulation (ISMS) results in improved motor performance in an ambulatory rat model of spinal cord injury (SCI). Experiments were carried out in adult male... more
The purpose of this study was to determine if spike-triggered intraspinal microstimulation (ISMS) results in improved motor performance in an ambulatory rat model of spinal cord injury (SCI). Experiments were carried out in adult male Sprague Dawley rats with 175 kdyn moderate T8 contusion injury. Rats were randomly assigned to one of two groups: Control or Activity Dependent Stimulation (ADS) therapy. Four weeks post-SCI, all rats were implanted with a recording electrode in the left hindlimb motor cortex and a fine-wire, custom-made stimulating electrode in the contralateral lumbar spinal cord. Intracortical and intraspinal microstimulation were used to find sites of similar hip representation areas, which were paired together for ADS therapy. In the ADS therapy group, spike-stimulus conditioning was administered for 4 hours/day, 4 days/week, for 4 weeks via a tethered cable in a testing chamber. During therapy sessions, single-unit spikes were discriminated in real time in the hi...
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ObjectiveThe purpose of this study was to determine the effects of spinal cord injury (SCI) on spike activity evoked in the hindlimb spinal cord of the rat from cortical electrical stimulation.ApproachAdult, male, Sprague Dawley rats were... more
ObjectiveThe purpose of this study was to determine the effects of spinal cord injury (SCI) on spike activity evoked in the hindlimb spinal cord of the rat from cortical electrical stimulation.ApproachAdult, male, Sprague Dawley rats were randomly assigned to a Healthy or SCI group. SCI rats were given a 175 kDyn dorsal midline contusion injury at the level of the T8 vertebrae. At four weeks post-SCI, intracortical microstimulation (ICMS) was delivered at several sites in the hindlimb motor cortex of anesthetized rats, and evoked neural activity was recorded from corresponding sites throughout the dorsoventral depths of the spinal cord and EMG activity from hindlimb muscles.Main resultsIn healthy rats, post-ICMS spike histograms showed reliable, evoked spike activity during a short-latency epoch 10-12 ms after the initiation of the ICMS pulse train (short). Longer latency spikes occurred between ~20-60 ms, generally following a Gaussian distribution, rising above baseline at time LO...
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The purpose of this study was to assess the ability of intraspinal microstimulation (ISMS), triggered by action potentials (spikes) recorded in motor cortex, to alter synaptic efficacy in descending motor pathways in an anesthetized rat... more
The purpose of this study was to assess the ability of intraspinal microstimulation (ISMS), triggered by action potentials (spikes) recorded in motor cortex, to alter synaptic efficacy in descending motor pathways in an anesthetized rat model of spinal cord injury (SCI). Experiments were carried out in adult, male, Sprague Dawley rats with a moderate contusion injury at T8. For activity-dependent stimulation (ADS) sessions, a recording microelectrode was used to detect neuronal spikes in motor cortex that triggered ISMS in the spinal cord grey matter. SCI rats were randomly assigned to one of four experimental groups differing by: a) cortical spike-ISMS stimulus delay (10 or 25 ms) and b) number of ISMS pulses (1 or 3). Four weeks after SCI, ADS sessions were conducted in three consecutive 1-hour conditioning bouts for a total of 3 hours. At the end of each conditioning bout, changes in synaptic efficacy were assessed using intracortical microstimulation (ICMS) to examine the number...
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Spinal cord injury (SCI) is a devastating neurological trauma with a prevalence of about 282 000 people living with an SCI in the United States in 2016. Advances in neuromodulatory devices hold promise for restoring function by... more
Spinal cord injury (SCI) is a devastating neurological trauma with a prevalence of about 282 000 people living with an SCI in the United States in 2016. Advances in neuromodulatory devices hold promise for restoring function by incorporating the delivery of electrical current directly into the spinal cord grey matter via intraspinal microstimulation (ISMS). In such designs, detailed topographic maps of spinal cord outputs are needed to determine ISMS locations for eliciting hindlimb movements. The primary goal of the present study was to derive a topographic map of functional motor outputs in the lumbar spinal cord to hindlimb skeletal muscles as defined by ISMS in a rat model. Experiments were carried out in nine healthy, adult, male, Sprague Dawley rats. After a laminectomy of the T13-L1 vertebrae and removal of the dura mater, a four-shank, 16-channel microelectrode array was inserted along a 3D (200 µm) stimulation grid. Trains of three biphasic current pulses were used to deter...
Research Interests: Biomedical Engineering, Spinal Cord Injury, Medicine, Functional Electrical Stimulation, Neural Engineering, and 15 moreAnatomy, Movement, Animals, Spinal Cord, Male, Electromyography, Clinical Sciences, Rats, Spinal Cord Stimulation, Muscle contraction, Action Potentials, Ankle, Neurosciences, lumbar vertebrae, and lumbar
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Cortical stimulation (CS) combined with rehabilitative training (RT) has proven effective for enhancing poststroke functional recovery in rats, but human clinical trials have had mixed outcomes. To assess the efficacy of CS/RT versus RT... more
Cortical stimulation (CS) combined with rehabilitative training (RT) has proven effective for enhancing poststroke functional recovery in rats, but human clinical trials have had mixed outcomes. To assess the efficacy of CS/RT versus RT in a nonhuman primate model of cortical ischemic stroke. Squirrel monkeys learned a pellet retrieval task, then received an infarct to the distal forelimb (DFL) representation of primary motor cortex. A subdural monopolar electrode was implanted over the spared DFL representation in dorsal premotor cortex (PMD). Seven weeks postinfarct, monkeys underwent 4 to 6 weeks of RT (n = 8) or CS/RT (n = 7; 100 Hz, cathodal current) therapy. Behavioral performance was assessed before and after infarct, prior to therapy, and 1 and 12 weeks posttherapy (follow-up). The primary outcome measure was motor performance at 1 week posttherapy. Secondary outcomes included follow-up performance at 12 weeks and treatment-related changes in neurophysiological maps of spare...
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Approximately 6 million people in the United States are currently living with paralysis in which 23% of the cases are related to spinal cord injury (SCI). Miniaturized closed-loop neural interfaces have the potential for restoring... more
Approximately 6 million people in the United States are currently living with paralysis in which 23% of the cases are related to spinal cord injury (SCI). Miniaturized closed-loop neural interfaces have the potential for restoring function and mobility lost to debilitating neural injuries such as SCI by leveraging recent advancements in bioelectronics and a better understanding of the processes that underlie functional and anatomical reorganization in an injured nervous system. This paper describes our current progress toward developing a miniaturized brain-machine-spinal cord interface (BMSI) that converts in real time the neural command signals recorded from the cortical motor regions to electrical stimuli delivered to the spinal cord below the injury level. Using a combination of custom integrated circuit (IC) technology for corticospinal interfacing and field-programmable gate array (FPGA)-based technology for embedded signal processing, we demonstrate proof-of-concept of distinct muscle pattern activation via intraspinal microstimulation (ISMS) controlled in real time by intracortical neural spikes in an anesthetized laboratory rat.
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New insights into the brain's ability to reorganize after injury are beginning to suggest novel restorative therapy targets. Potential therapies include pharmacological agents designed to promote axonal growth. The purpose of this... more
New insights into the brain's ability to reorganize after injury are beginning to suggest novel restorative therapy targets. Potential therapies include pharmacological agents designed to promote axonal growth. The purpose of this study was to test the efficacy of one such drug, GSK249320, a monoclonal antibody that blocks the axon outgrowth inhibition molecule, myelin-associated glycoprotein, to facilitate recovery of motor skills in a nonhuman primate model of ischemic cortical damage. Using a between-groups repeated-measures design, squirrel monkeys were randomized to 1 of 2 groups: an experimental group received intravenous GSK249320 beginning 24 hours after an ischemic infarct in motor cortex with repeated dosages given at 1-week intervals for 6 weeks and a control group received only the vehicle at matched time periods. The primary end point was a motor performance index based on a distal forelimb reach-and-retrieval task. Neurophysiological mapping techniques were used to...
Research Interests: Neuroscience, Neurophysiology, Medicine, Human, Antibodies, and 14 moreStroke, Animals, Neuronal Plasticity, Motor Cortex, Clinical Sciences, Squirrel Monkey, Axons, Neurosciences, Monoclonal, Motor Skills, Recovery of Function, Haplorhini, Cardiovascular medicine and haematology, and myelin associated glycoprotein
Both dl-α-difluoromethylornithine (DFMO) and ethanol have been reported to inhibit the growth of fibroblasts in cell culture. The objectives of the present study were to determine whether these compounds could be used to inhibit the... more
Both dl-α-difluoromethylornithine (DFMO) and ethanol have been reported to inhibit the growth of fibroblasts in cell culture. The objectives of the present study were to determine whether these compounds could be used to inhibit the growth of fibroblasts in vivo, with a bleomycin-induced mouse model of pulmonary fibrosis. DBA2J mice were given a single endotracheal injection of bleomycin, 10 nmol. In addition to bleomycin (BLM), groups of animals received 2% DFMO in drinking water for 4 days prior to BLM and 18 days after (BLM DFMO), 6% ethanol in drinking water for 7 days prior to BLM and 21 days after (BLM E7), 6% ethanol in drinking water for 21 days initiated on the day of BLM intubation (BLM E), or DFMO, E7, and BLM in combination (BLM DFMO E7). Animals died or were killed 21 days after bleomycin treatment and lungs were evaluated by histopathologic criteria. DFMO failed to alter the incidence or severity of fibrotic lesions, increased the severity of epithelial metaplasia (p < 0.05), and reduced the lung disease index (from 56.3 to 42.1%, p < 0.05) and mortality from 83.3 to 41.7% (p < 0.025). In contrast to the unsatisfactory response to DFMO, pretreatment with ethanol (BLM E7) reduced the incidence of interstitial fibrosis from 91.3 to 71.4% (p < 0.05) and confluent fibrosis from 73.9 to 20.0% (p < 0.005). The severity of lesions was also reduced by ethanol, resulting in an 18.5% decrease in interstitial fibrosis, a 25.9% decrease in epithelial metaplasia, and a 55.4% reduction in the lung disease index (all p < 0.01). However, when ethanol and DFMO were administered in combination, the beneficial effects of ethanol alone were not observed, and only the lung disease index was decreased.
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ABSTRACT
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All mammals, including the egg-laying mono-tremes, possess an auditory cortex—that is, an auditory area in their cerebral neocortex. In contrast, no reptile or bird possesses even neocortex itself let alone an auditory area within it.... more
All mammals, including the egg-laying mono-tremes, possess an auditory cortex—that is, an auditory area in their cerebral neocortex. In contrast, no reptile or bird possesses even neocortex itself let alone an auditory area within it. Therefore, the question of the evolutionary origin of auditory cortex is entangled in the larger question of the origin of mammalian neocortex. Because there are no animals now extant that serve as an unarguable witness to the transition from the reptilian to the mammalian form of cerebral cortex the question of the origin of mammalian cortex is an old and persistent one. We now have but two snapshots of the forebrain through geological time—a reptilian stage without neocortex and a later mammalian stage with a relatively large amount of neocortex and an auditory area already within it.
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Nearly 6 million people in the United States are currently living with paralysis in which 23% of the cases are related to spinal cord injury (SCI). Miniaturized closed-loop neural interfaces have the potential for restoring function and... more
Nearly 6 million people in the United States are currently living with paralysis in which 23% of the cases are related to spinal cord injury (SCI). Miniaturized closed-loop neural interfaces have the potential for restoring function and mobility lost to debilitating neural injuries such as SCI by leveraging recent advancements in bioelectronics and a better understanding of the processes that underlie functional and anatomical reorganization in an injured nervous system. This paper describes our current progress towards developing a miniaturized brain-machine-spinal cord interface (BMSI) that is envisioned to convert in real time the neural command signals recorded from the brain to electrical stimuli delivered to the spinal cord below the injury level. Specifically, the paper reports on a corticospinal interface integrated circuit (IC) as a core building block for such a BMSI that is capable of low-noise recording of extracellular neural spikes from the cerebral cortex as well as muscle activation using intraspinal microstimulation (ISMS) in a rat with contusion injury to the thoracic spinal cord. The paper further presents results from a neurobiological study conducted in both normal and SCI rats to investigate the effect of various ISMS parameters on movement thresholds in the rat hindlimb. Coupled with proper signal-processing algorithms in the future for the transformation between the cortically recorded data and ISMS parameters, such a BMSI has the potential to facilitate functional recovery after an SCI by re-establishing corticospinal communication channels lost due to the injury.
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Background. There is growing interest in the use of d-amphetamine (d-AMPH) as a pharmacological treatment to supplement rehabilitative therapy following stroke. Based on the success of earlier animal models, several clinical studies have... more
Background. There is growing interest in the use of d-amphetamine (d-AMPH) as a pharmacological treatment to supplement rehabilitative therapy following stroke. Based on the success of earlier animal models, several clinical studies have demonstrated beneficial effects of applying physical rehabilitation while stroke patients are under the influence of d-AMPH. To begin to understand the neural mechanisms underlying this promising adjuvant therapy, the authors examined the effects of a single pairing of d-AMPH and rehabilitative training on motor performance after cortical infarct in squirrel monkeys. Methods. Microelectrode stimulation techniques were used to delineate hand movement areas in the primary motor cortex prior to delivering a unilateral infarct to the complete hand representation. Postinfarct recovery was assessed for 3 groups of monkeys: d-AMPH + training, saline + training, and spontaneous recovery (SR). Postinfarct training groups received 14 consecutive days of motor...
Research Interests: Neuroscience, Psychology, Cognitive Science, Medicine, Female, and 15 moreAnimals, Male, Neural Repair, Amphetamine, Motor Cortex, Brain Ischemia, Clinical Sciences, Hand, Neurosciences, Dextroamphetamine, Cerebral Infarction, Recovery of Function, Central nervous system stimulants, Electric stimulation, and cerebral arteries
Background. Small lesions to rostral versus caudal portions of the hand representation in the primary motor cortex (M1) produce different behavioral deficits. The goal of the present study was to determine if rehabilitative training has... more
Background. Small lesions to rostral versus caudal portions of the hand representation in the primary motor cortex (M1) produce different behavioral deficits. The goal of the present study was to determine if rehabilitative training has similar effects on functional topography of the spared M1 after rostral versus previously reported caudal M1 lesions. Methods. Following a lesion to the rostral M1 hand area, monkeys were trained for 1 h/day for 30 days to retrieve food pellets from small wells using their impaired hand. Electrophysiological maps of the M1 were derived in anesthetized monkeys before infarct and after rehabilitative training using intracortical microstimulation. Results. After a lesion to the rostral M1 and rehabilitative training, the size of the spared hand representation decreased 1.2%. This change is not statistically different from the 9% increase seen after caudal M1 lesion and rehabilitative training ( P > 0.2). Conclusion. Postlesion training spares peri-in...
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Research Interests: Neuroscience, Animal Behavior, Medicine, Applied Animal Behavior, Neuroplasticity, and 15 moreFeasibility Study, Brain Mapping, Female, Animals, Feasibility Studies, Male, Neuronal Plasticity, Motor Cortex, Electromyography, Brain Ischemia, Cortical Plasticity, Clinical Sciences, Neurological, Neurosciences, and Cerebral Infarction
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Object The purpose of the present study was to determine the feasibility of using a common laboratory rat strain for reliably locating cortical motor representations of the hindlimb. Methods Intracortical microstimulation techniques were... more
Object The purpose of the present study was to determine the feasibility of using a common laboratory rat strain for reliably locating cortical motor representations of the hindlimb. Methods Intracortical microstimulation techniques were used to derive detailed maps of the hindlimb motor representations in 6 adult Fischer-344 rats. Results The organization of the hindlimb movement representation, while variable across individual rats in topographic detail, displayed several commonalities. The hindlimb representation was positioned posterior to the forelimb motor representation and posterolateral to the motor trunk representation. The areal extent of the hindlimb representation across the cortical surface averaged 2.00 ± 0.50 mm2. Superimposing individual maps revealed an overlapping area measuring 0.35 mm2, indicating that the location of the hindlimb representation can be predicted reliably based on stereotactic coordinates. Across the sample of rats, the hindlimb representation wa...
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After a cortical lesion, cortical areas distant from the site of injury are known to undergo physiological and anatomical changes. However, the mechanisms through which reorganization of distant cortical areas is initiated are poorly... more
After a cortical lesion, cortical areas distant from the site of injury are known to undergo physiological and anatomical changes. However, the mechanisms through which reorganization of distant cortical areas is initiated are poorly understood. In a previous publication, we showed that the ventral premotor cortex (PMv) undergoes physiological reorganization after a lesion destroying the majority of the primary motor cortex (M1) distal forelimb representation (DFL). After large lesions destroying >50% of the M1 DFL, the PMv DFL invariably increased in size, and the amount of the increase was positively correlated with the size of lesion. To determine whether lesions destroying <50% of the M1 DFL followed a similar trajectory, we documented PMv reorganization using intracortical microstimulation techniques after small, ischemic lesions targeting subregions within the M1 DFL. In contrast to earlier results, lesions resulted in a reduction of the PMv DFL regardless of their locat...
Research Interests: Neuroscience, Electrophysiology, Neurophysiology, Medicine, Brain Mapping, and 13 moreAnimals, Motor Cortex, Brain Ischemia, Microelectrodes, Premotor cortex, Lesion, Neural pathways, Primary Motor Cortex, Cerebral Infarction, Functional Laterality, Psychology and Cognitive Sciences, Medical and Health Sciences, and Electric stimulation
Primary motor cortex (M1) has traditionally been considered a motor structure. Although neurophysiologic studies have demonstrated that M1 is also influenced by somatosensory inputs (cutaneous and proprioceptive), the behavioral... more
Primary motor cortex (M1) has traditionally been considered a motor structure. Although neurophysiologic studies have demonstrated that M1 is also influenced by somatosensory inputs (cutaneous and proprioceptive), the behavioral significance of these inputs has yet to be fully defined in primates. The present study describes differential sensory-related deficits after small ischemic lesions in either the rostral or caudal subregion of the M1 hand area in a nonhuman primate. Squirrel monkeys retrieved food pellets out of different sized wells drilled into a Plexiglas board. Before the lesion, monkeys retrieved pellets by directing the hand to the well, inserting fingers directly into it, and extracting the pellet. After a lesion to the rostral portion of M1, monkeys frequently failed to direct the hand accurately to the well. Instead, fingers contacted the surface of the board outside the well before entering the well. These aiming errors are consistent with both the large amount of ...
Research Interests: Neuroscience, Animal Behavior, Neurophysiology, Medicine, Brain Mapping, and 15 moreMovement, Female, Animals, Male, Motor Cortex, Mental Disorders, Brain Ischemia, Operant Conditioning, Hand, Lesion, Neural pathways, Cerebral Infarction, Motor Skills, Medical and Health Sciences, and Electric stimulation
Neuroimaging studies in stroke survivors have suggested that adaptive plasticity occurs following stroke. However, the complex temporal dynamics of neural reorganization after injury make the interpretation of functional imaging studies... more
Neuroimaging studies in stroke survivors have suggested that adaptive plasticity occurs following stroke. However, the complex temporal dynamics of neural reorganization after injury make the interpretation of functional imaging studies equivocal. In the present study in adult squirrel monkeys, intracortical microstimulation (ICMS) techniques were used to monitor changes in representational maps of the distal forelimb in the supplementary motor area (SMA) after a unilateral ischemic infarct of primary motor (M1) and premotor distal forelimb representations (DFLs). In each animal, ICMS maps were derived at early (3 wk) and late (13 wk) postinfarct stages. Lesions resulted in severe deficits in motor abilities on a reach and retrieval task. Limited behavioral recovery occurred and plateaued at 3 wk postinfarct. At both early and late postinfarct stages, distal forelimb movements could still be evoked by ICMS in SMA at low current levels. However, the size of the SMA DFL changed after ...
Research Interests: Neuroscience, Psychology, Animal Behavior, Neurophysiology, Medicine, and 15 moreApplied Animal Behavior, Brain Mapping, Movement, Animals, Motor Cortex, Brain Ischemia, Supplementary Motor Area, Sma, Squirrel Monkey, Functional Laterality, Psychomotor Performance, Brain injuries, Psychology and Cognitive Sciences, Medical and Health Sciences, and Electric stimulation
Although recent neurological research has shed light on the brain's mechanisms of self-repair after stroke, the role that intact tissue plays in recovery is still obscure. To explore these mechanisms further, we used microelectrode... more
Although recent neurological research has shed light on the brain's mechanisms of self-repair after stroke, the role that intact tissue plays in recovery is still obscure. To explore these mechanisms further, we used microelectrode stimulation techniques to examine functional remodeling in cerebral cortex after an ischemic infarct in the hand representation of primary motor cortex in five adult squirrel monkeys. Hand preference and the motor skill of both hands were assessed periodically on a pellet retrieval task for 3 mo postinfarct. Initial postinfarct motor impairment of the contralateral hand was evident in each animal, followed by a gradual improvement in performance over 1–3 mo. Intracortical microstimulation mapping at 12 wk after infarct revealed substantial enlargements of the hand representation in a remote cortical area, the ventral premotor cortex. Increases ranged from 7.2 to 53.8% relative to the preinfarct ventral premotor hand area, with a mean increase of 36.0 ...
Research Interests: Neuroscience, Psychology, Electrophysiology, Neurophysiology, Medicine, and 14 moreNeuroplasticity, Brain Mapping, Cerebral Cortex, Animals, Motor Cortex, Brain Ischemia, Two Stroke Engine, Brain injury, Premotor cortex, Hand, Primary Motor Cortex, Motor activity, Psychology and Cognitive Sciences, and Medical and Health Sciences
To examine the potential early stages in the evolution of sensorimotor cortex, electrophysiological studies were conducted in the primitive South American marsupial opossum, Monodelphis domestica. Somatosensory maps derived from multiunit... more
To examine the potential early stages in the evolution of sensorimotor cortex, electrophysiological studies were conducted in the primitive South American marsupial opossum, Monodelphis domestica. Somatosensory maps derived from multiunit microelectrode recordings revealed a complete somatosensory representation of the contralateral body surface within a large region of midrostral cortex (primary somatosensory cortex, or S1). A large proportion ( approximately 51%) of S1 was devoted to representation of the glaborous snout, mystacial vibrissae, lower jaw, and oral cavity (the rostrum). A second representation, the second somatosensory area (or S2), was found adjacent and caudolateral to S1 as a mirror image reversed along the representation of the glabrous snout. A reversal of somatotopic order and an enlargement of receptive fields marked the transition from S1 to S2. Mapping of excitable cortex was conducted by using intracortical microstimulation (ICMS) techniques, as well as low-impedance depth stimulation and bipolar surface stimulation. In all three procedures, electrical stimulation resulted in movements confined strictly to the face. Specifically, at virtually all sites from which movements could be evoked, stimulation resulted in only vibrissae movement. ICMS-evoked vibrissae movements typically occurred at sites within S1 with receptive fields of the mystacial vibrissae, lower jaw, and glaborous snout. Results were similar using low-impedance depth stimulation and bipolar surface stimulation techniques except that the motor response maps were generally larger in area. There was no evidence of a motor representation rostral to S1. Examination of the cytoarchitecture in this cortical region (reminiscent of typical mammalian somatosensory cortex) and the high levels of stimulation needed for vibrissae movement suggest that the parietal neocortex of Monodelphis is representative of a primitive sensorimotor condition. It possesses a complete S1 representation with an incomplete motor component overlapping the S1 representation of the face. It contains no primary motor representation. Completion of the motor representations within S1 (trunk, limbs, tail) as well as the emergence of a primary motor cortex rostral to S1 may have occurred relatively late in mammalian phylogeny.
Research Interests: Neuroscience, Electrophysiology, Biology, Medicine, Brain Mapping, and 15 moreAnatomy, Cerebral Cortex, Female, Animals, Male, Motor Cortex, Microelectrodes, Medical Physiology, Biological evolution, Somatosensory Cortex, Opossum, Comparative Neurology, Opossums, Neurosciences, and Electric stimulation
Research Interests: Neuroscience, Biology, Immunohistochemistry, Medicine, Brain Mapping, and 15 moreAnatomy, Animals, New World, Motor Cortex, The, Microelectrodes, Medical Physiology, Premotor cortex, Supplementary Motor Area, Hand, Comparative Neurology, Neurosciences, Functional Laterality, Somatosensory system, and Electric stimulation
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Telencephalic projections from the medial geniculate nucleus (MG) in opossum were traced with tritiated leucine autoradiography and by horseradish peroxidase and fluorescent dye retrograde labeling techniques. The results show that the... more
Telencephalic projections from the medial geniculate nucleus (MG) in opossum were traced with tritiated leucine autoradiography and by horseradish peroxidase and fluorescent dye retrograde labeling techniques. The results show that the opossum&#39;s MG contains two separate populations of neurons-one in the anterior two-thirds of MG projecting to auditory neocortex, the other occupying the entire caudal one-third of MG and projecting mostly to lateral amygdala and putamen. Because the subcortical projection of the MG in opossum is larger than that seen in any other mammal to date, it is reminiscent of the subcortical projections of the MG in reptiles and birds. Furthermore, when the subcortical projections of the MG in reptiles and opossums are compared with similar subcortical projections of the MG in rats, cats, and monkeys, the proportion of the MG neurons projecting to subcortical structures is seen to be inversely related to the recency of each animal&#39;s common ancestry with primates. The possibility that the subcortical projection of the MG in mammals is homologous with that seen in reptiles or birds implies that it might be a dwindling vestige of the projection present in the common ancestry of reptiles and mammals.
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Vascular endothelial growth factor (VEGF) is thought to contribute to both neuroprotection and angiogenesis after stroke. While increased expression of VEGF has been demonstrated in animal models after experimental ischemia, these studies... more
Vascular endothelial growth factor (VEGF) is thought to contribute to both neuroprotection and angiogenesis after stroke. While increased expression of VEGF has been demonstrated in animal models after experimental ischemia, these studies have focused almost exclusively on the infarct and peri-infarct regions. The present study investigated the association of VEGF to neurons in remote cortical areas at three days after an infarct in primary motor cortex (M1). Although these remote areas are outside of the direct influence of the ischemic injury, remote plasticity has been implicated in recovery of function. For this study, intracortical microstimulation techniques identified primary and premotor cortical areas in a non-human primate. A focal ischemic infarct was induced in the M1 hand representation, and neurons and VEGF protein were identified using immunohistochemical procedures. Stereological techniques quantitatively assessed neuronal-VEGF association in the infarct and peri-inf...
Research Interests: Neuroscience, Neurology, Motor Control, Medicine, Angiogenesis, and 15 moreNeuroprotection, Neuroplasticity, Brain Mapping, Brain Circulation, Animals, Animal Model, Motor Cortex, Microelectrodes, Neurons, Clinical Sciences, Cerebral, Neurosciences, Cell count, Cardiovascular medicine and haematology, and Electric stimulation
Clinical and experimental data support a role for the intact cortex in recovery of function after stroke, particularly ipsilesional areas interconnected to the infarct. There is, however, little understanding of molecular events in the... more
Clinical and experimental data support a role for the intact cortex in recovery of function after stroke, particularly ipsilesional areas interconnected to the infarct. There is, however, little understanding of molecular events in the intact cortex, as most studies focus on the infarct and peri-infarct regions. This study investigated neuronal immunoreactivity for hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF) receptor-2 (VEGFR-2) in remote cortical areas 3 days after a focal ischemic infarct, as both HIF-1α and VEGFR-2 have been implicated in peri-infarct neuroprotection. For this study, intracortical microstimulation techniques defined primary motor (M1) and premotor areas in squirrel monkeys (genus Saimiri). An infarct was induced in the M1 hand representation, and immunohistochemical techniques identified neurons, HIF-1α and VEGFR-2. Stereologic techniques quantified the total neuronal populations and the neurons immunoreactive for HIF-1α or ...
Research Interests: Neuroscience, Neurology, Biology, Hypoxia, Medicine, and 15 moreNeuroprotection, Stroke, Neurovascular, Cerebral Cortex, Brain Circulation, Animals, Neurons, Clinical Sciences, Cerebral, Brain Chemistry, Experimental Data, Neurosciences, Recovery of Function, Hypoxia inducible factor, and Cardiovascular medicine and haematology
Research Interests: Neuroscience, Psychology, Neurophysiology, Medicine, Biological Sciences, and 15 moreProtein Structure and Function, Brain Mapping, Humans, Cerebral Cortex, Female, Animals, Brain Plasticity, Male, Neuronal Plasticity, Motor Cortex, Brain Ischemia, Primate, Motor activity, Craniotomy, and Maintenance cost
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Research Interests: Neuroscience, Psychology, Motor Learning, Medicine, Neuroplasticity, and 15 moreBrain Mapping, Cerebral Cortex, Ischemia, Movement, Animals, Male, Motor Cortex, Cortical Plasticity, Analysis of Variance, Primary Motor Cortex, Cerebral Infarction, Motor Skills, Recovery of Function, Psychology and Cognitive Sciences, and Medical and Health Sciences
In eutherians, patterns of plasma protein levels in blood change during the acute phase response to trauma and inflammation. Until now, such an acute phase response has not been characterised in a noneutherian species. Here we describe... more
In eutherians, patterns of plasma protein levels in blood change during the acute phase response to trauma and inflammation. Until now, such an acute phase response has not been characterised in a noneutherian species. Here we describe the acute phase response in a marsupial species, the South American polyprotodont marsupial Monodelphis domestica, after brain surgery or injection of lipopolysaccharide. Several days after brain surgery, transthyretin was not detected in plasma. For 48 hr following injection of lipopolysaccharide, the concentration of haptoglobin in plasma increased, that of transthyretin decreased, and the concentration of albumin in plasma did not change significantly. The American polyprotodont marsupials are probably more closely related to the common ancestor marsupial than the Australian marsupials are. It is most likely that the transthyretin gene was not expressed in the liver of this common ancestor. As the transthyretin gene is expressed in the liver of M. domestica, it seems that as soon as transthyretin is synthesised by the liver, it is under negative acute phase control.