scholarly journals “Characteristics and stability of sensorimotor activity driven by isolated-muscle group activation in a human with tetraplegia”

2020 ◽  
Author(s):  
Robert W. Nickl ◽  
Manuel A. Anaya ◽  
Tessy M. Thomas ◽  
Matthew S. Fifer ◽  
David P McMullen ◽  
...  
Keyword(s):  
Sensorimotor Cortex ◽  
Firing Pattern ◽  
Muscle Group ◽  
Full Time ◽  
Spatial Stability ◽  
Firing Rates ◽  
Body Regions ◽  
Cord Injury ◽  
The Stability ◽  
Sensorimotor Map

ABSTRACTThe topography and temporal stability of movement representations in sensorimotor cortex underlie the quality and durability of neural decoders for brain machine interface (BMI) technology. While single- and multi-unit activity (SUA and MUA) in sensorimotor cortex has been used to characterize the layout of the sensorimotor map, quantifying its stability has not been done outside of injury or targeted interventions. Here we aimed to characterize 1) the bilateral sensorimotor body map associated to isolated muscle group contractions and 2) the stability of multiunit firing responses for a single muscle (the extensor carpi radialis, ECR) over short (minutes) and long (days) time intervals. We concurrently recorded surface electromyograms (EMG) and MUA in a participant with incomplete high-spinal-cord injury as he executed (or attempted to execute) different metronome-paced, isolated muscle group contractions. Furthermore, for 8 recording sessions over 2 months, we characterized the sensorimotor map associated to ECR motions both within and across sessions. For each measurement period, we compared the stability of somatotopy (defined by the number of the channels on which a response was consistently detected) and firing pattern stability for each responsive channel. Stability was calculated for each channel in peri-EMG or peri-cue windows using both mean MUA firing rates and the full time-varying responses (i.e., MUA “shape”). First, we found that cortical representations of isolated group muscle contractions overlapped, even for muscles from disparate body regions such as facial and distal leg muscles; this was the case for both intact and de-efferented muscles, in both motor and sensory channels. Second, the spatial stability of somatotopy significantly changed over the course of both minutes and days, with the consistency between sessions decreasing across longer bouts of time. Firing pattern stabilities showed distinct profiles; mean MUA firing rates became less stable over time whereas MUA shape remained consistent. Interestingly, sensory channels were overall more consistent than motor channels in terms of spatial stability, mean MUA firing rates, and MUA shape. Our findings suggest that the encoding of muscle-driven specific activity in sensorimotor cortex at the level of MUA is redundant and widespread with complex spatial and temporal characteristics. These findings extend our understanding of how sensorimotor cortex represents movements, which could be leveraged for the design of non-traditional BMI approaches.

scholarly journals Inviscid spatial stability of a compressible mixing layer. Part 3. Effect of thermodynamics

1991 ◽  
Vol 224 ◽  
pp. 159-175 ◽  
Author(s):  
T. L. Jackson ◽  
C. E. Grosch
Keyword(s):  
Prandtl Number ◽  
Mixing Layer ◽  
Mean Flow ◽  
Temperature Relation ◽  
Compressible Mixing Layer ◽  
Spatial Stability ◽  
Mean Temperature ◽  
The Mean ◽  
The Difference ◽  
The Stability

We report the results of a comprehensive comparative study of the inviscid spatial stability of a parallel compressible mixing layer using various models for the mean flow. The models are (i) the hyperbolic tangent profile for the mean speed and the Crocco relation for the mean temperature, with the Chapman viscosity–temperature relation and a Prandtl number of one; (ii) the Lock profile for the mean speed and the Crocco relation for the mean temperature, with the Chapman viscosity-temperature relation and a Prandtl number of one; and (iii) the similarity solution for the coupled velocity and temperature equations using the Sutherland viscosity–temperature relation and arbitrary but constant Prandtl number. The purpose of this study was to determine the sensitivity of the stability characteristics of the compressible mixing layer to the assumed thermodynamic properties of the fluid. It is shown that the qualitative features of the stability characteristics are quite similar for all models but that there are quantitative differences resulting from the difference in the thermodynamic models. In particular, we show that the stability characteristics are sensitive to the value of the Prandtl number and to a particular value of the temperature ratio across the mixing layer.

scholarly journals Regional, not global, functional connectivity contributes to isolated focal dystonia

Neurology ◽  
2020 ◽  
Vol 95 (16) ◽  
pp. e2246-e2258 ◽  
Author(s):  
Scott A. Norris ◽  
Aimee E. Morris ◽  
Meghan C. Campbell ◽  
Morvarid Karimi ◽  
Babatunde Adeyemo ◽  
...  
Keyword(s):  
Quality Control ◽  
Functional Connectivity ◽  
Sensorimotor Cortex ◽  
Large Scale ◽  
Focal Dystonia ◽  
Whole Brain ◽  
Correlation Matrices ◽  
Body Regions ◽  
And Control ◽  
Rigorous Quality Control

ObjectiveTo test the hypothesis that there is shared regional or global functional connectivity dysfunction in a large cohort of patients with isolated focal dystonia affecting different body regions compared to control participants. In this case-control study, we obtained resting-state MRI scans (three or four 7.3-minute runs) with eyes closed in participants with focal dystonia (cranial [17], cervical [13], laryngeal [18], or limb [10]) and age- and sex-matched controls.MethodsRigorous preprocessing for all analyses was performed to minimize effect of head motion during scan acquisition (dystonia n = 58, control n = 47 analyzed). We assessed regional functional connectivity by computing a seed-correlation map between putamen, pallidum, and sensorimotor cortex and all brain voxels. We assessed significant group differences on a cluster-wise basis. In a separate analysis, we applied 300 seed regions across the cortex, cerebellum, basal ganglia, and thalamus to comprehensively sample the whole brain. We obtained participant whole-brain correlation matrices by computing the correlation between seed average time courses for each seed pair. Weighted object-oriented data analysis assessed group-level whole-brain differences.ResultsParticipants with focal dystonia had decreased functional connectivity at the regional level, within the striatum and between lateral primary sensorimotor cortex and ventral intraparietal area, whereas whole-brain correlation matrices did not differ between focal dystonia and control groups. Rigorous quality control measures eliminated spurious large-scale functional connectivity differences between groups.ConclusionRegional functional connectivity differences, not global network level dysfunction, contributes to common pathophysiologic mechanisms in isolated focal dystonia. Rigorous quality control eliminated spurious large-scale network differences between patients with focal dystonia and control participants.

scholarly journals Dynamics of Strongly Coupled Spiking Neurons

2000 ◽  
Vol 12 (1) ◽  
pp. 91-129 ◽  
Author(s):  
Paul C. Bressloff ◽  
S. Coombes
Keyword(s):  
Dynamical Theory ◽  
Fundamental Result ◽  
Periodic Pattern ◽  
Strong Coupling Regime ◽  
Synaptic Coupling ◽  
Strongly Coupled ◽  
Firing Rates ◽  
Dimensional Network ◽  
Spatially Periodic ◽  
The Stability

We present a dynamical theory of integrate-and-fire neurons with strong synaptic coupling. We show how phase-locked states that are stable in the weak coupling regime can destabilize as the coupling is increased, leading to states characterized by spatiotemporal variations in the interspike intervals (ISIs). The dynamics is compared with that of a corresponding network of analog neurons in which the outputs of the neurons are taken to be mean firing rates. A fundamental result is that for slow interactions, there is good agreement between the two models (on an appropriately defined timescale). Various examples of desynchronization in the strong coupling regime are presented. First, a globally coupled network of identical neurons with strong inhibitory coupling is shown to exhibit oscillator death in which some of the neurons suppress the activity of others. However, the stability of the synchronous state persists for very large networks and fast synapses. Second, an asymmetric network with a mixture of excitation and inhibition is shown to exhibit periodic bursting patterns. Finally, a one-dimensional network of neurons with long-range interactions is shown to desynchronize to a state with a spatially periodic pattern of mean firing rates across the network. This is modulated by deterministic fluctuations of the instantaneous firing rate whose size is an increasing function of the speed of synaptic response.

scholarly journals Single pellet grasping following cervical spinal cord injury in adult rat using an automated full-time training robot

2016 ◽  
Vol 299 ◽  
pp. 59-71 ◽  
Author(s):  
Keith K. Fenrich ◽  
Zacincte May ◽  
Abel Torres-Espín ◽  
Juan Forero ◽  
David J. Bennett ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Cervical Spinal Cord ◽  
Cervical Spinal Cord Injury ◽  
Full Time ◽  
Adult Rat ◽  
Single Pellet ◽  
Cord Injury

scholarly journals Meaningful measurements of maneuvers: People with incomplete spinal cord injury ‘step up’ to the challenges of altered stability requirements

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Wendy L. Ochs ◽  
Jane Woodward ◽  
Tara Cornwell ◽  
Keith E. Gordon
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Force Field ◽  
Force Fields ◽  
Center Of Mass ◽  
Lateral Force ◽  
Step Width ◽  
Incomplete Spinal Cord Injury ◽  
Cord Injury ◽  
The Stability

Abstract Background Many people with incomplete spinal cord injury (iSCI) have the ability to maneuver while walking. However, neuromuscular impairments create challenges to maintain stability. How people with iSCI maintain stability during walking maneuvers is poorly understood. Thus, this study compares maneuver performance in varying external conditions between persons with and without iSCI to better understand maneuver stabilization strategies in people with iSCI. Methods Participants with and without iSCI walked on a wide treadmill and were prompted to perform lateral maneuvers between bouts of straight walking. Lateral force fields applied to the participants’ center of mass amplified or attenuated the participants’ movements, thereby increasing the capability of the study to capture behavior at varied levels of challenge to stability. Results By examining metrics of stability, step width, and center of mass dynamics, distinct strategies emerged following iSCI. The minimum margin of stability (MOSmin) on each step during maneuvers indicated persons with iSCI generally adapted to amplified and attenuated force fields with increased stability compared to persons without iSCI, particularly using increased step width and reduced center of mass excursion on maneuver initiation. In the amplified field, however, persons with iSCI had a reduced MOSmin when terminating a maneuver, likely due to the challenge of the force field opposing the necessary lateral braking. Persons without iSCI were more likely to rely on or oppose the force field when appropriate for movement execution. Compared to persons with iSCI, they reduced their MOSmin to initiate maneuvers in the attenuated and amplified fields and increased their MOSmin to arrest maneuvers in the amplified field. Conclusions The different force fields were successful in identifying relatively subtle strategy differences between persons with and without iSCI. Specifically, persons with iSCI adopted increased step width and reduction in center of mass excursion to increase maneuver stability in the amplified field. The amplified field may provoke practice of stable and efficient initiation and arrest of walking maneuvers. Overall, this work allows better framing of the stability mechanisms used following iSCI to perform walking maneuvers.

Linear Spatial Stability of Developing Flow in a Parallel Plate Channel

1981 ◽  
Vol 48 (1) ◽  
pp. 192-194 ◽  
Author(s):  
S. C. Gupta ◽  
V. K. Garg
Keyword(s):  
Reynolds Number ◽  
Velocity Profile ◽  
Parallel Plate ◽  
Critical Reynolds Number ◽  
Two Dimensional ◽  
Spatial Stability ◽  
Percent Change ◽  
Developing Flow ◽  
The Stability ◽  
Plate Channel

It is found that even a 5 percent change in the velocity profile produces a 100 percent change in the critical Reynolds number for the stability of developing flow very close to the entrance of a two-dimensional channel.

scholarly journals Russian University Students about Distance Learning: Assessments and Opportunities

2020 ◽  
Vol 29 (10) ◽  
pp. 86-100 ◽  
Author(s):  
I. A. Aleshkovskiy ◽  
A. T. Gasparishvili ◽  
O. V. Krukhmaleva ◽  
N. P. Narbut ◽  
N. E. Savina
Keyword(s):  
Distance Learning ◽  
University Students ◽  
Educational Institution ◽  
Educational Systems ◽  
Full Time ◽  
Higher Education System ◽  
Learning Assessments ◽  
Distant Learning ◽  
The Stability ◽  
Russian Universities

The forced shift to remote learning in universities in March 2020 raised the complex issues of organizing lifelong learning for students, conducting academic assessments and maintaining the stability of the educational institution in general for educational systems of all countries of the world. This paper examines peculiarities and general problems of distance learning in the higher education system. It is based on the materials of the sociological survey “Opinions of Russian universities’ students on the forced distance learning”, conducted in May-June 2020. 31,423 university students in all federal subjects of Russia were interviewed. Analysis of research data covers the following areas: organizational problems of transition to distance learning; resources used, organization of lectures and seminars, assessment of the positive and negative aspects of distance learning; perspectives, limitations and trajectories of distance learning implementation in Russian universities.The article also provides comparative data on the analysis of the issues of distant learning of Russian and foreign researchers. The authors propose future-oriented measures for organizing distance learning in universities in the case of the introduction of quarantine restrictions, consider possible forms of combining distance and full-time education, the prospects for the introduction of digital technologies in the organization of training in universities.

scholarly journals Finger somatotopy is preserved after tetraplegia but deteriorates over time

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Sanne Kikkert ◽  
Dario Pfyffer ◽  
Michaela Verling ◽  
Patrick Freund ◽  
Nicole Wenderoth
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Observational Study ◽  
Sensorimotor Cortex ◽  
Structural Mri ◽  
Finger Movement ◽  
Functional Connections ◽  
Cord Injury ◽  
Primary Sensorimotor Cortex ◽  
Over Time

Previous studies showed reorganised and/or altered activity in the primary sensorimotor cortex after a spinal cord injury (SCI), suggested to reflect abnormal processing. However, little is known about whether somatotopically-specific representations can be activated despite reduced or absent afferent hand inputs. In this observational study we used functional MRI and an (attempted) finger movement task in tetraplegic patients to characterise the somatotopic hand layout in primary somatosensory cortex. We further used structural MRI to assess spared spinal tissue bridges. We found that somatotopic hand representations can be activated through attempted finger movements in absence of sensory and motor hand functioning, and no spared spinal tissue bridges. Such preserved hand somatotopy could be exploited by rehabilitation approaches that aim to establish new hand-brain functional connections after SCI (e.g., neuroprosthetics). However, over years since SCI the hand representation somatotopy deteriorated, suggesting that somatotopic hand representations are more easily targeted within the first years after SCI.

scholarly journals Lateral entorhinal cortex suppresses drift in cortical memory representations.

2021 ◽  
Author(s):  
Maryna Pilkiw ◽  
Justin Jarovi ◽  
Kaori Takehara-Nishiuchi
Keyword(s):  
Entorhinal Cortex ◽  
Memory Retrieval ◽  
Firing Pattern ◽  
Memory Trace ◽  
Male Rats ◽  
Memory Representations ◽  
Familiar Environment ◽  
Functional Relevance ◽  
The Stability ◽  
Cortical Representations

Memory retrieval is thought to depend on the reinstatement of cortical memory representations guided by pattern completion processes in the hippocampus. The lateral entorhinal cortex (LEC) is one of the intermediary regions supporting hippocampal-cortical interactions and houses neurons that prospectively signal past events in a familiar environment. To investigate the functional relevance of the LEC's activity for cortical reinstatement, we pharmacologically inhibited the LEC and examined its impact on the stability of ensemble firing patterns in one of the LEC's efferent targets, the medial prefrontal cortex (mPFC). When male rats underwent multiple epochs of identical stimulus sequences in the same environment, the mPFC maintained a stable ensemble firing pattern across repetitions, particularly when the sequence included pairings of neutral and aversive stimuli. With LEC inhibition, the mPFC still formed an ensemble pattern that accurately captured stimuli and their associations within each epoch. However, LEC inhibition markedly disrupted its consistency across the epochs by decreasing the proportion of mPFC neurons that stably maintained firing selectivity for stimulus associations. Thus, the LEC stabilizes cortical representations of learned stimulus associations, thereby facilitating the recovery of the original memory trace without generating a new, redundant trace for familiar experiences. Failure of this process might underlie retrieval deficits in conditions associated with degeneration of the LEC, such as normal aging and Alzheimer's disease.

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