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1. Effect of spinal cord injury on neural encoding of spontaneous postural perturbations in the hindlimb sensorimotor cortex

   Jaimie B Dougherty ( January 2021 , Journal of neurophysiology)

   Capers, Miriam (Ed.)

   Supraspinal signals play a significant role in compensatory responses to postural perturbations after spinal cord injury (SCI). SCI disrupts descending motor control signals as well as ascending somatosensory information to and from below the lesion. In intact animals, While cortical signals are not necessary for basic postural tasks, but neurons in the motor cortex have been shown to respond to periodic postural perturbations in intact animals. However, the role of the cortex in postural control after spinal cord injury in response to unexpected postural perturbations has not been studied. To better understand how spinal lesions impact cortical encoding of information about unexpected postural perturbations, the activity of single neurons in the rat hindlimb sensorimotor cortex (HLSMC) were recorded during unexpected tilts before and after a complete midthoracic spinal transection. In a subset of animals, limb ground reaction forces were collected as well. Results show that responses in the HLSMC were modulated with changes in tilt severity (i.e. tilt velocity). As initial velocity of the tilt increased, more information was conveyed by the HLSMC neurons about the perturbation due to increases in both the number of recruited neurons and the magnitude of their response. After SCI hindlimb ground reaction forces were both attenuated and delayed, and the neural responses were delayed and less likely to respond to slower tilts. This resulted in a moderate decrease inan attenuation of the information conveyed by cortical neurons about the tilts, requiring more cells to convey the same amount of information as before the transection. Given that reorganization of the hindlimb sensorimotor cortex in response to therapy after complete mid-thoracic SCI is necessary for behavioral recovery, this sustained encoding of information after SCI could be a substrate for the reorganization that uses sensory information from above the lesion to control trunk muscles that permit weight-supported stepping and postural control. 

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2. Cell-Type Specific Connectivity of Whisker-Related Sensory and Motor Cortical Input to Dorsal Striatum

   https://doi.org/10.1523/ENEURO.0503-23.2023  

   Sanabria, Branden D. ; Baskar, Sindhuja S. ; Yonk, Alex J. ; Linares-Garcia, Iván ; Abraira, Victoria E. ; Lee, Christian R. ; Margolis, David J. ( December 2023 , eneuro)

   The anterior dorsolateral striatum (DLS) is heavily innervated by convergent excitatory projections from the primary motor (M1) and sensory cortex (S1) and considered an important site of sensorimotor integration. M1 and S1 corticostriatal synapses have functional differences in their connection strength with striatal spiny projection neurons (SPNs) and fast-spiking interneurons (FSIs) in the DLS and, as a result, exert distinct influences on sensory-guided behaviors. In the present study, we tested whether M1 and S1 inputs exhibit differences in the subcellular anatomical distribution of striatal neurons. We injected adeno-associated viral vectors encoding spaghetti monster fluorescent proteins (sm.FPs) into M1 and S1 in male and female mice and used confocal microscopy to generate 3D reconstructions of corticostriatal inputs to single identified SPNs and FSIs obtained through ex vivo patch clamp electrophysiology. We found that M1 and S1 dually innervate SPNs and FSIs; however, there is a consistent bias towards the M1 input in SPNs that is not found in FSIs. In addition, M1 and S1 inputs were distributed similarly across the proximal, medial, and distal regions of SPN and FSI dendrites. Notably, closely localized M1 and S1 clusters of inputs were more prevalent in SPNs than FSIs, suggesting that cortical inputs are integrated through cell-type specific mechanisms. Our results suggest that the stronger functional connectivity from M1 to SPNs compared to S1, as previously observed, is due to a higher quantity of synaptic inputs. Our results have implications for how sensorimotor integration is performed in the striatum through cell-specific differences in corticostriatal connections.

    

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3. Postural mechanisms in moderate-to-severe cerebral palsy

   https://doi.org/10.1152/jn.00549.2020  

   Goodworth, Adam ; Saavedra, Sandra ( May 2021 , Journal of Neurophysiology)

   null (Ed.)

   People with moderate-to-severe cerebral palsy (CP) have the greatest need for postural control research yet are usually excluded from research due to deficits in sitting ability. We use a support system that allows us to quantify and model postural mechanisms in nonambulatory children with CP. A continuous external bench tilt stimulus was used to evoke trunk postural responses in seven sitting children with CP (ages 2.5 to 13 yr) in several test sessions. Eight healthy adults were also included. Postural sway was analyzed with root mean square (RMS) sway and RMS sway velocity, along with frequency response functions (FRF, gain and phase) and coherence functions across two different stimulus amplitudes. A feedback model (including sensorimotor noise, passive, reflexive, and sensory integration mechanisms) was developed to hypothesize how postural control mechanisms are organized and function. Experimental results showed large RMS sway, FRF gains, and variability compared with adults. Modeling suggested that many subjects with CP adopted “simple” control with major contributions from a passive and reflexive mechanism and only a small contribution from active sensory integration. In contrast, mature trunk postural control includes major contributions from sensory integration and sensory reweighting. Relative to their body size, subjects with CP showed significantly lower damping, three to five times larger corrective torque, and much higher sensorimotor noise compared with the healthy mature system. Results are the first characterization of trunk postural responses and the first attempt at system identification in moderate-to-severe CP, an important step toward developing and evaluating more targeted interventions. NEW & NOTEWORTHY Cerebral palsy (CP) is the most common cause of motor disability in children. People with moderate-to-severe CP are typically nonambulatory and have major impairments in trunk postural control. We present the first systems identification study to investigate postural responses to external stimulus in this population and hypothesize at how the atypical postural control system functions with use of a feedback model. People with moderate-to-severe CP may use a simple control system with significant sensorimotor noise. 

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4. P-023 Optimizing radial force of stent retrievers to minimize vessel wall injury: mechanical bench testing of radial force generated by a novel braided stent retriever compared to laser-cut stent retrievers in the M1 and m2 vessels

   Katz, Jeffrey M ; Chebl, Alex A ; Janardhan, Vikram ; Janardhan, Vallabh ( July 2018 , Journal of neurointerventional surgery)

   Purpose: Recent reports have raised various concerns about the risk of vessel wall injury while withdrawing current laser-cut stent retrievers during active strut apposition to the vessel walls. The development of braided thrombectomy assist devices in conjunction with aspiration systems may be gentler on the fragile brain vessels and more optimized with regard to the radial force (RF) for vessel diameters of proximal (M1) and distal (M2) large vessel occlusions (LVOs). Methods: Mechanical bench testing of the RF was performed using a radial compression station mounted on a tensile testing machine. The total RF in newtons (N) generated in vessels with diameters ranging from 2.25 to 3 mm as seen in proximal LVOs (∼M1), and in vessel diameters ranging from 1.5 to 2.24 mm as seen in distal LVOs (∼M2), was measured. The outer diameter of each stent was recorded, and an RF ≤1 N was grouped as “low,” while an RF > 1 N was grouped as “high” for this analysis. Results: The total RFs of all laser-cut stent retrievers were all higher in the simulated M2 vessels (> 1 N) than in the M1 vessels (< 1 N), whereas the total RFs of the braided thrombectomy assist devices were uniformly low in both the simulated M1 and the simulated M2 vessels. Conclusions: Novel braided thrombectomy assist devices in conjunction with aspiration systems have lower RFs than existing laser-cut stent retrievers in M1 and M2 vessel diameters. Further in vivo studies are needed to delineate the impact of lowering the RF on vessel wall integrity. Funding Source: This study was funded in part by a research grant (NSF Award: 1819491; PI: Vallabh Janardhan, MD) from the National Science Foundation (NSF). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. Conference Proceeding: This paper was presented in part at the 15th Annual Meeting of the Society of Neuro-Interventional Surgery (SNIS), July 23-26, 2018 in San Francisco, CA. 

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5. Incorporation of a smart sock with the virtual immersive test for postural stability

   Burch, RF ; Chander, H ; Saucier, D ; Ball, J ( January 2023 , The American Journal of the Medical Sciences 2023 Southern Regional Meeting)

   Purpose of Study Assessment of an individual's postural stability serves as an indirect measure for both physiological and biomechanical stresses placed on an individual. More recently, some individuals after COVID-19 (SARS-CoV-2) infection have been identified with neurological complaints (Post-Acute Sequelae of Covid - PASC). These individuals can also be predisposed to decreased postural stability and an increased risk for falls. The purpose of the project was to incorporate two different wearable technology (virtual reality (VR) based virtual immersive sensorimotor test - VIST and pressure senor-based smart sock) to assess postural stability among healthy and individuals with PASC to quantify the overall status of the postural control system. Methods Used All methods were conducted based on the University's Institutional Review Board (IRB# 21-296) with informed consent. A total of 12 males and females (six healthy and six with self-reported complaints of PASC) have completed the study so far. All participants were tested using the VIST, while standing on a force platform and wearing the smart sock simultaneously. The (VIST uses a VR headset and proprietary software to test an individual's integrated sensory, motor, and cognitive processes through eight unique tests (smooth pursuits, saccades, convergence, peripheral vision, object discrimination, gaze stability, head-eye coordination, cervical neuromotor control). Center of pressure (COP) data from force platform and pressure sensor data from the smart socks were used to calculate anterior-posterior and medial-lateral postural sway variables. These postural sway variables were analyzed using an independent samples t-test between the healthy and PASC groups at an alpha set at 0.05. Summary of 

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