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Stuart N Baker - One of the best experts on this subject based on the ideXlab platform.
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Ipsilateral Motor Evoked Potentials as a Measure of the Reticulospinal Tract in Age-Related Strength Changes.
Frontiers in aging neuroscience, 2021Co-Authors: Stuart Maitland, Stuart N BakerAbstract:Background: The Reticulospinal Tract (RST) is essential for balance, posture, and strength, all functions which falter with age. We hypothesized that age-related strength reductions might relate to differential changes in corticospinal and Reticulospinal connectivity. Methods: We divided 83 participants (age 20-84) into age groups
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evidence for subcortical plasticity after paired stimulation from a wearable device
The Journal of Neuroscience, 2021Co-Authors: Maria Germann, Stuart N BakerAbstract:Existing non-invasive stimulation protocols can generate plasticity in the motor cortex and its corticospinal projections; techniques for inducing plasticity in sub-cortical circuits and alternative descending pathways such as the Reticulospinal Tract are less well developed. One possible approach developed by this laboratory pairs electrical muscle stimulation with auditory clicks, using a wearable device to deliver stimuli during normal daily activities. In this study, we applied a variety of electrophysiological assessments to male and female healthy human volunteers during a morning and evening laboratory visit. In the intervening time (∼6 hours), subjects wore the stimulation device, receiving three different protocols, in which clicks and stimulation of the biceps muscle were paired at either low or high rate, or delivered at random. Paired stimulation: 1) increased the extent of reaction time shortening by a loud sound (the StartReact effect); 2) decreased the suppression of responses to transcranial magnetic brain stimulation (TMS) following a loud sound; 3) enhanced muscle responses elicited by a TMS coil oriented to induce anterior-posterior (AP) current, but not posterior-anterior (PA) current in the brain. These measurements have all been suggested to be sensitive to sub-cortical, possibly Reticulospinal, activity. Changes were similar for either of the two paired stimulus rates tested, but absent after unpaired (control) stimulation. Taken together, these results suggest that pairing clicks and muscle stimulation for long periods does indeed induce plasticity in sub-cortical systems such as the Reticulospinal Tract. SIGNIFICANCE STATEMENT: Sub-cortical systems such as the Reticulospinal Tract are important motor pathways, which can make a significant contribution to functional recovery after cortical damage such as stroke. Here, we measure changes produced after a novel non-invasive stimulation protocol, which uses a wearable device to stimulate for extended periods. We observed changes in electrophysiological measurements consistent with the induction of sub-cortical plasticity. This protocol may prove an important tool for enhancing motor rehabilitation, in situations where insufficient cortical tissue survives to be a plausible substrate for recovery of function.
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ipsilateral motor evoked potentials as a measure of the Reticulospinal Tract in age related strength changes
Frontiers in Aging Neuroscience, 2021Co-Authors: Stuart Maitland, Stuart N BakerAbstract:Background: The Reticulospinal Tract (RST) is essential for balance, posture, and strength, all functions which falter with age. We hypothesized that age-related strength reductions might relate to differential changes in corticospinal and Reticulospinal connectivity. Methods: We divided 83 participants (age 20-84) into age groups <50 (n = 29) and ≥50 (n = 54) years; five of which had probable sarcopenia. Transcranial Magnetic Stimulation (TMS) was applied to the left cortex, inducing motor evoked potentials (MEPs) in the biceps muscles bilaterally. Contralateral (right, cMEPs) and ipsilateral (left, iMEPs) MEPs are carried by mainly corticospinal and Reticulospinal pathways respectively; the iMEP/cMEP amplitude ratio (ICAR) therefore measured the relative importance of the two descending Tracts. Grip strength was measured with a dynamometer and normalized for age and sex. Results: We found valid iMEPs in 74 individuals (n = 44 aged ≥50, n = 29 < 50). Younger adults had a significant negative correlation between normalized grip strength and ICAR (r = -0.37, p = 0.045); surprisingly, in older adults, the correlation was also significant, but positive (r = 0.43, p = 0.0037). Discussion: Older individuals who maintain or strengthen their RST are stronger than their peers. We speculate that reduced RST connectivity could predict those at risk of age-related muscle weakness; interventions that reinforce the RST could be a candidate for treatment or prevention of sarcopenia.
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The Relationship Between Enhanced Reticulospinal Outflow and Upper Limb Function in Chronic Stroke Patients.
Neurorehabilitation and neural repair, 2019Co-Authors: Supriyo Choudhury, A. Shobhana, Ravi Singh, Dwaipayan Sen, Sidharth Shankar Anand, Shantanu Shubham, Mark R. Baker, Hrishikesh Kumar, Stuart N BakerAbstract:Background. Recent evidence from both monkey and human studies suggests that the Reticulospinal Tract may contribute to recovery of arm and hand function after stroke. In this study, we evaluated a...
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Reticulospinal contributions to gross hand function after human spinal cord injury
The Journal of Neuroscience, 2017Co-Authors: Stuart N Baker, Monica A. PerezAbstract:Multiple descending motor pathways likely contribute to the recovery of hand motor function following spinal cord injury (SCI). Reticulospinal neurons project to spinal motor neurons controlling hand muscles and extensively sprout into gray matter structures after SCI; therefore, it has been proposed that the Reticulospinal Tract is one of the descending motor pathways involved in recovery of hand function after injury. To test this hypothesis, we examined the StartReact response, an involuntary release of a planned movement via a startling stimulus that engages the Reticulospinal Tract, by measuring reaction times from electromyographic activity in an intrinsic finger muscle during three motor tasks requiring different degrees of hand dexterity: index finger abduction, a precision grip, and a power grip. Males and females with and without incomplete chronic cervical SCI were tested. We found that although SCI participants voluntarily responded to all tasks, reaction times were shorter during a startle cue while performing a power grip but not index finger abduction or precision grip. Control subjects had similarly shorter reaction times during a startle cue in all motor tasks. These results provide the first evidence for a contribution of the Reticulospinal Tract to hand control in humans with SCI during gross finger manipulations and suggest that this contribution is less pronounced during fine dexterous finger movements. SIGNIFICANCE STATEMENT It has been long proposed that brainstem pathways contribute to the recovery of hand function in humans with spinal cord injury (SCI). Here, we show that individuals with anatomically incomplete chronic cervical SCI responded to a startle stimulus, a test that engages the Reticulospinal Tract, while performing a power grip but not during index finger abduction or precision grip. Control subjects responded to a startle stimulus similarly across tasks. These observations suggest that Reticulospinal outputs after SCI contribute to hand motor tasks involving gross finger movements. Interestingly, this contribution is less pronounced during fine dexterous finger movements.
Zachary A Smith - One of the best experts on this subject based on the ideXlab platform.
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Tract-Specific Volume Loss on 3T MRI in Patients With Cervical Spondylotic Myelopathy.
Spine, 2018Co-Authors: Benjamin Hopkins, Kenneth A Weber, Michael Cloney, Monica Paliwal, Todd B Parrish, Zachary A SmithAbstract:Case-control. The aim of this study was to understand the role of high-resolution magnetic resonance (MR) in identifying regional cord volume loss in cervical spondylotic myelopathy (CSM). Preliminary studies suggest that compression of the ventral region of the cord may contribute disproportionately to CSM symptomology; however, Tract-specific data are lacking in the CSM population. The current study is the first to use 3T MR imaging (MRI) images of CSM patients to determine specific volume loss at the level of detail of individual descending white matter Tracts. Twelve patients with CSM and 14 age-matched were enrolled prospectively and underwent 3-Tesla MRI of the cervical spine. Using the high-resolution images of the spinal cord, straightening and alignment with a template was performed and specific spinal cord Tract volumes were measured using Spinal Cord Tool-box version 3.0.7. Modified Japanese orthopedic association (mJOA) and Nurick disability scores were collected in a prospective manner and were analyzed in relation to descending spinal Tract volumes. Having CSM was predicted by anterior/posterior diameter, eccentricity of the cord [odds ratio (OR) 0.000000621, P = 0.004], ventral Reticulospinal Tract volume (OR 1.167, P = 0.063), lateral corticospinal Tract volume (OR 1.034, P = 0.046), rubrospinal Tract volume (OR 1.072, P = 0.011), and ventrolateral Reticulospinal Tract volume (OR 1.474, P = 0.005) on single variable logistic regression. Single variable linear regression showed decreases in anterior/posterior spinal cord diameter (P = 0.022), ventral Reticulospinal Tract volumes (P = 0.007), and ventrolateral Reticulospinal Tract volumes (P = 0.017) to significantly predict worsening mJOA scores. Similarly, decreases in ventral Reticulospinal Tract volumes significantly predicted increasing Nurick scores (P = 0.039). High-resolution 3T MRI can detect Tract-specific volume loss in descending spinal cord Tracts in CSM patients. Anterior/posterior spinal cord diameter, ventral Reticulospinal Tract, ventrolateral Reticulospinal Tract, lateral corticospinal Tract, and rubrospinal Tract volume loss are associated with CSM symptoms. 2.
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Tract specific volume loss on 3t mri in patients with cervical spondylotic myelopathy
Spine, 2018Co-Authors: Benjamin S Hopkins, Kenneth A Weber, Michael Cloney, Monica Paliwal, Todd B Parrish, Zachary A SmithAbstract:Study design Case-control. Objective The aim of this study was to understand the role of high-resolution magnetic resonance (MR) in identifying regional cord volume loss in cervical spondylotic myelopathy (CSM). Summary of background data Preliminary studies suggest that compression of the ventral region of the cord may contribute disproportionately to CSM symptomology; however, Tract-specific data are lacking in the CSM population. The current study is the first to use 3T MR imaging (MRI) images of CSM patients to determine specific volume loss at the level of detail of individual descending white matter Tracts. Methods Twelve patients with CSM and 14 age-matched were enrolled prospectively and underwent 3-Tesla MRI of the cervical spine. Using the high-resolution images of the spinal cord, straightening and alignment with a template was performed and specific spinal cord Tract volumes were measured using Spinal Cord Tool-box version 3.0.7. Modified Japanese orthopedic association (mJOA) and Nurick disability scores were collected in a prospective manner and were analyzed in relation to descending spinal Tract volumes. Results Having CSM was predicted by anterior/posterior diameter, eccentricity of the cord [odds ratio (OR) 0.000000621, P = 0.004], ventral Reticulospinal Tract volume (OR 1.167, P = 0.063), lateral corticospinal Tract volume (OR 1.034, P = 0.046), rubrospinal Tract volume (OR 1.072, P = 0.011), and ventrolateral Reticulospinal Tract volume (OR 1.474, P = 0.005) on single variable logistic regression. Single variable linear regression showed decreases in anterior/posterior spinal cord diameter (P = 0.022), ventral Reticulospinal Tract volumes (P = 0.007), and ventrolateral Reticulospinal Tract volumes (P = 0.017) to significantly predict worsening mJOA scores. Similarly, decreases in ventral Reticulospinal Tract volumes significantly predicted increasing Nurick scores (P = 0.039). Conclusion High-resolution 3T MRI can detect Tract-specific volume loss in descending spinal cord Tracts in CSM patients. Anterior/posterior spinal cord diameter, ventral Reticulospinal Tract, ventrolateral Reticulospinal Tract, lateral corticospinal Tract, and rubrospinal Tract volume loss are associated with CSM symptoms. Level of evidence 2.
Julian Scott Yeomans - One of the best experts on this subject based on the ideXlab platform.
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Contributions of the vestibular nucleus and vestibulospinal Tract to the startle reflex.
Neuroscience, 2001Co-Authors: Liang Li, Stephan Steidl, Julian Scott YeomansAbstract:AbsTract The startle reflex is elicited by strong and sudden acoustic, vestibular or trigeminal stimuli. The caudal pontine reticular nucleus, which mediates acoustic startle via the Reticulospinal Tract, receives further anatomical connections from vestibular and trigeminal nuclei, and can be activated by vestibular and tactile stimuli, suggesting that this pontine reticular structure could mediate vestibular and trigeminal startle. The vestibular nucleus, however, also projects to the spinal cord directly via the vestibulospinal Tracts, and therefore may mediate vestibular startle via additional faster routes without a synaptic relay in the hindbrain. In the present study, the timing properties of the vestibular efferent pathways mediating startle-like responses were examined in rats using electrical stimulation techniques. Transient single- or twin-pulse electrical stimulation of the vestibular nucleus evoked bilateral, startle-like responses with short refractory periods. In chloral hydrate-anesthetized rats, hindlimb electromyogram latencies recorded from the anterior biceps femoris muscle were shorter than those for stimulation of the trigeminal nucleus, and similar to those for stimulation of the caudal pontine reticular nucleus or ventromedial medulla. In awake rats, combining vestibular nucleus stimulation with either acoustic stimulation or trigeminal nucleus stimulation enhanced the whole-body startle-like responses and led to strong cross-modal summation without collision effects. In both chloral hydrate-anesthetized and awake rats, combining vestibular nucleus stimulation with ventromedial medulla stimulation produced a symmetrical collision effect, i.e. a loss of summation at the same positive and negative stimulus intervals, indicating a continuous connection between the vestibular nucleus and ventromedial medulla in mediating vestibular startle. By contrast, combining trigeminal nucleus stimulation with ventromedial medulla stimulation resulted in an asymmetric collision effect when the trigeminal nucleus stimulation preceded ventromedial medulla stimulation by 0.5 ms, suggesting that a monosynaptic connection between the trigeminal nucleus and ventromedial medulla mediates trigeminal startle. We propose that the vestibulospinal Tracts participate strongly in mediating startle produced by activation of the vestibular nucleus. The convergence of the vestibulospinal Tracts with the Reticulospinal Tract within the spinal cord therefore provides the neural basis of cross-modal summation of startling stimuli.
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The acoustic startle reflex: neurons and connections
Brain Research Reviews, 1995Co-Authors: Julian Scott Yeomans, Paul W. FranklandAbstract:The startle reflex protects animals from blows or predatory attacks by quickly stiffening the limbs, body wall and dorsal neck in the brief time period before directed evasive or defensive action can be performed. The acoustic startle reflex in rats and cats is mediated primarily by a small cluster of giant neurons in the ventrocaudal part of the nucleus reticularis pontis caudalis (RPC) of the reticular formation. Activation of these RPC neurons occurs 3-8 ms after the acoustic stimulus reaches the ear. Undetermined neurons of the cochlear nuclei activate RPC via weak monosynaptic and strong disynaptic connections. The strong disynaptic input occurs via neurons of the contralateral ventrolateral pons, including large neurons of the ventrolateral tegmental nucleus that integrate auditory, tactile and vestibular information. RPC giant neurons, in turn, activate hundreds of motoneurons in the brain stem and the length of the spinal cord via large Reticulospinal axons near the medial longitudinal fasciculus. To hindlimb motoneurons, monosynaptic connections from the Reticulospinal Tract are weak, but disynaptic connections via spinal cord interneurons are stronger and show temporal facilitation, like the startle response itself. © 1996.
Paul W. Frankland - One of the best experts on this subject based on the ideXlab platform.
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tactile acoustic and vestibular systems sum to elicit the startle reflex
Neuroscience & Biobehavioral Reviews, 2002Co-Authors: John S. Yeomans, Brian W Scott, Paul W. FranklandAbstract:The startle reflex is elicited by intense tactile, acoustic or vestibular stimuli. Fast mechanoreceptors in each modality can respond to skin or head displacement. In each modality, stimulation of cranial nerves or primary sensory nuclei evokes startle-like responses. The most sensitive sites in rats are found in the ventral spinal trigeminal pathway, corresponding to inputs from the dorsal face. Cross-modal summation is stronger than intramodal temporal summation, suggesting that the convergence of acoustic, vestibular and tactile information is important for eliciting startle. This summation declines sharply if the cross-modal stimuli are not synchronous. Head impact stimuli activate trigeminal, acoustic and vestibular systems together, suggesting that the startle response protects the body from impact stimuli. In each primary sensory nucleus, large, second-order neurons project to pontine reticular formation giant neurons critical for the acoustic startle reflex. In vestibular nucleus sites, startle-like responses appear to be mediated mainly via the vestibulospinal Tract, not the Reticulospinal Tract. Summation between vestibulospinal and Reticulospinal pathways mediating startle is proposed to occur in the ventral spinal cord.
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The acoustic startle reflex: neurons and connections
Brain Research Reviews, 1995Co-Authors: Julian Scott Yeomans, Paul W. FranklandAbstract:The startle reflex protects animals from blows or predatory attacks by quickly stiffening the limbs, body wall and dorsal neck in the brief time period before directed evasive or defensive action can be performed. The acoustic startle reflex in rats and cats is mediated primarily by a small cluster of giant neurons in the ventrocaudal part of the nucleus reticularis pontis caudalis (RPC) of the reticular formation. Activation of these RPC neurons occurs 3-8 ms after the acoustic stimulus reaches the ear. Undetermined neurons of the cochlear nuclei activate RPC via weak monosynaptic and strong disynaptic connections. The strong disynaptic input occurs via neurons of the contralateral ventrolateral pons, including large neurons of the ventrolateral tegmental nucleus that integrate auditory, tactile and vestibular information. RPC giant neurons, in turn, activate hundreds of motoneurons in the brain stem and the length of the spinal cord via large Reticulospinal axons near the medial longitudinal fasciculus. To hindlimb motoneurons, monosynaptic connections from the Reticulospinal Tract are weak, but disynaptic connections via spinal cord interneurons are stronger and show temporal facilitation, like the startle response itself. © 1996.
Kenneth A Weber - One of the best experts on this subject based on the ideXlab platform.
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Tract-Specific Volume Loss on 3T MRI in Patients With Cervical Spondylotic Myelopathy.
Spine, 2018Co-Authors: Benjamin Hopkins, Kenneth A Weber, Michael Cloney, Monica Paliwal, Todd B Parrish, Zachary A SmithAbstract:Case-control. The aim of this study was to understand the role of high-resolution magnetic resonance (MR) in identifying regional cord volume loss in cervical spondylotic myelopathy (CSM). Preliminary studies suggest that compression of the ventral region of the cord may contribute disproportionately to CSM symptomology; however, Tract-specific data are lacking in the CSM population. The current study is the first to use 3T MR imaging (MRI) images of CSM patients to determine specific volume loss at the level of detail of individual descending white matter Tracts. Twelve patients with CSM and 14 age-matched were enrolled prospectively and underwent 3-Tesla MRI of the cervical spine. Using the high-resolution images of the spinal cord, straightening and alignment with a template was performed and specific spinal cord Tract volumes were measured using Spinal Cord Tool-box version 3.0.7. Modified Japanese orthopedic association (mJOA) and Nurick disability scores were collected in a prospective manner and were analyzed in relation to descending spinal Tract volumes. Having CSM was predicted by anterior/posterior diameter, eccentricity of the cord [odds ratio (OR) 0.000000621, P = 0.004], ventral Reticulospinal Tract volume (OR 1.167, P = 0.063), lateral corticospinal Tract volume (OR 1.034, P = 0.046), rubrospinal Tract volume (OR 1.072, P = 0.011), and ventrolateral Reticulospinal Tract volume (OR 1.474, P = 0.005) on single variable logistic regression. Single variable linear regression showed decreases in anterior/posterior spinal cord diameter (P = 0.022), ventral Reticulospinal Tract volumes (P = 0.007), and ventrolateral Reticulospinal Tract volumes (P = 0.017) to significantly predict worsening mJOA scores. Similarly, decreases in ventral Reticulospinal Tract volumes significantly predicted increasing Nurick scores (P = 0.039). High-resolution 3T MRI can detect Tract-specific volume loss in descending spinal cord Tracts in CSM patients. Anterior/posterior spinal cord diameter, ventral Reticulospinal Tract, ventrolateral Reticulospinal Tract, lateral corticospinal Tract, and rubrospinal Tract volume loss are associated with CSM symptoms. 2.
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Tract specific volume loss on 3t mri in patients with cervical spondylotic myelopathy
Spine, 2018Co-Authors: Benjamin S Hopkins, Kenneth A Weber, Michael Cloney, Monica Paliwal, Todd B Parrish, Zachary A SmithAbstract:Study design Case-control. Objective The aim of this study was to understand the role of high-resolution magnetic resonance (MR) in identifying regional cord volume loss in cervical spondylotic myelopathy (CSM). Summary of background data Preliminary studies suggest that compression of the ventral region of the cord may contribute disproportionately to CSM symptomology; however, Tract-specific data are lacking in the CSM population. The current study is the first to use 3T MR imaging (MRI) images of CSM patients to determine specific volume loss at the level of detail of individual descending white matter Tracts. Methods Twelve patients with CSM and 14 age-matched were enrolled prospectively and underwent 3-Tesla MRI of the cervical spine. Using the high-resolution images of the spinal cord, straightening and alignment with a template was performed and specific spinal cord Tract volumes were measured using Spinal Cord Tool-box version 3.0.7. Modified Japanese orthopedic association (mJOA) and Nurick disability scores were collected in a prospective manner and were analyzed in relation to descending spinal Tract volumes. Results Having CSM was predicted by anterior/posterior diameter, eccentricity of the cord [odds ratio (OR) 0.000000621, P = 0.004], ventral Reticulospinal Tract volume (OR 1.167, P = 0.063), lateral corticospinal Tract volume (OR 1.034, P = 0.046), rubrospinal Tract volume (OR 1.072, P = 0.011), and ventrolateral Reticulospinal Tract volume (OR 1.474, P = 0.005) on single variable logistic regression. Single variable linear regression showed decreases in anterior/posterior spinal cord diameter (P = 0.022), ventral Reticulospinal Tract volumes (P = 0.007), and ventrolateral Reticulospinal Tract volumes (P = 0.017) to significantly predict worsening mJOA scores. Similarly, decreases in ventral Reticulospinal Tract volumes significantly predicted increasing Nurick scores (P = 0.039). Conclusion High-resolution 3T MRI can detect Tract-specific volume loss in descending spinal cord Tracts in CSM patients. Anterior/posterior spinal cord diameter, ventral Reticulospinal Tract, ventrolateral Reticulospinal Tract, lateral corticospinal Tract, and rubrospinal Tract volume loss are associated with CSM symptoms. Level of evidence 2.