scholarly journals Dissociation of muscle and cortical response scaling to balance perturbation acceleration

2019 ◽  
Vol 121 (3) ◽  
pp. 867-880 ◽  
Author(s):  
Aiden M. Payne ◽  
Greg Hajcak ◽  
Lena H. Ting
Keyword(s):  
Brain Stem ◽  
Cortical Response ◽  
Postural Response ◽  
Single Trial ◽  
Motor Responses ◽  
Initial Burst ◽  
Sensory Inputs ◽  
Automatic Postural Response ◽  
Cortical Responses ◽  
Muscle Responses

The role of cortical activity in standing balance is unclear. Here we tested whether perturbation-evoked cortical responses share sensory input with simultaneous balance-correcting muscle responses. We hypothesized that the acceleration-dependent somatosensory signals that drive the initial burst of the muscle automatic postural response also drive the simultaneous perturbation-evoked cortical N1 response. We measured in healthy young adults ( n = 16) the initial burst of the muscle automatic postural response (100–200 ms), startle-related muscle responses (100–200 ms), and the perturbation-evoked cortical N1 potential, i.e., a negative peak in cortical EEG activity (100–200 ms) over the supplementary motor area. Forward and backward translational support-surface balance perturbations were applied at four levels of acceleration and were unpredictable in timing, direction, and acceleration. Our results from averaged and single-trial analyses suggest that although cortical and muscle responses are evoked by the same perturbation stimulus, their amplitudes are independently modulated. Although both muscle and cortical responses increase with acceleration, correlations between single-trial muscle and cortical responses were very weak. Furthermore, across subjects, the scaling of muscle responses to acceleration did not correspond to scaling of cortical responses to acceleration. Moreover, we observed a reduction in cortical response amplitude across trials that was related to a reduction in startle-related—but not balance-correcting—muscle activity. Therefore, cortical response attenuation may be related to a reduction in perceived threat rather than motor adaptation or changes in sensory inflow. We conclude that the cortical N1 reflects integrated sensory inputs simultaneously related to brain stem-mediated balance-correcting muscle responses and startle reflexes. NEW & NOTEWORTHY Reactive balance recovery requires sensory inputs to be transformed into appropriate balance-correcting motor responses via brain stem circuits; these are accompanied by simultaneous and poorly understood cortical responses. We used single-trial analyses to dissociate muscle and cortical response modulation with perturbation acceleration. Although muscle and cortical responses share sensory inputs, they have independent scaling mechanisms. Attenuation of cortical responses with experience reflected attenuation of brain stem-mediated startle responses rather than the amplitude of balance-correcting motor responses.

scholarly journals Effects of Vestibular Training on Postural Control of Healthy Adults

CommonHealth ◽  
2020 ◽  
Vol 1 (1) ◽  
pp. 31-36
Author(s):  
Kwadwo Osei Appiah-Kubi ◽  
Anne Galgon ◽  
Ryan Tierney ◽  
Richard Lauer ◽  
W. Geoffrey Wright
Keyword(s):  
Postural Control ◽  
Postural Stability ◽  
Medial Gastrocnemius ◽  
Postural Response ◽  
Sensory Reweighting ◽  
Vestibular Loss ◽  
Motor Responses ◽  
Automatic Postural Response ◽  
Weight Shift ◽  
Sensory Weighting

Background: Postural stability depends on the integration of multisensory inputs to drive motor outputs. When visual and somatosensory input is available and reliable, this reduces the postural control system’s reliance on the vestibular system. Despite this, vestibular loss can still cause severe postural dysfunction (1,2). Training one or more of the three sensory systems can alter sensory weighting and change postural behavior. Vestibular activation exercises, including horizontal and vertical headshaking, influence vestibular-ocular and -motor responses and have been showed to be effective in vestibular rehabilitation (3–8).   Purpose/Hypothesis: To assess sensory reweighting of postural control processing and vestibular-ocular and -motor responses after concurrent vestibular activation with postural training. It was hypothesized that the effect of this training would significantly alter the pattern of sensory weighting by changing the ratio of visual, somatosensory and vestibular dependence needed to maintain postural stability, and significantly decrease vestibular responses. Methods: Forty-two young healthy individuals (22 females; 23.0+3.9 years; 1.6+0.1 meters) were randomly assigned into four groups: 1) visual feedback weight shift training (WST) coupled with an active horizontal headshake (HHS), 2) same WST with vertical headshake (VHS), 3) WST with no headshake (NHS) and 4) no training/headshake control (CTL) groups. The headshake groups performed an intensive body WST together with horizontal or vertical rhythmic headshake at 80 to 120 beats/minute. The NHS group performed the WST with no headshake while the controls did not perform any training. Five 15-minute training sessions were performed on consecutive days for one week with the weight shift exercises involving upright limits of stability activities on a flat surface, foam or rocker board (Fig. 1). All groups performed baseline- and post-assessments including sensory organization test (SOT) and force platform ramp perturbations, coupled with electromyographic (EMG) recordings. A video head impulse test was also used to record horizontal vestibulo-ocular reflex (VOR) gain. A between- and within-group repeated measures ANOVA was used to analyze five COP sway variables, the equilibrium and composite scores and sensory ratios of the SOT as well as EMG signals and horizontal VOR gain. Similarly, COP variables, EMG, as well as vestibular reflex data (vertical VOR, vestibulo-collic reflex [VCR] and vestibulo-spinal [VSR] gains) during ramp perturbations were analyzed. Alpha level was set at p<.05. Results: The training showed a significant somatosensory downweighting (p=.050) in the headshake groups compared to the other groups. Training also showed significant decreased horizontal VOR gain (p=.040), faster automatic postural response (p=.003) (Figs. 2-4) with improved flexibility (p=.010) in the headshake groups. Muscle activation pattern in medial gastrocnemius (p=.033) was significantly decreased in the headshake. Conclusion: The concurrent vestibular activation and weight shift training modifies vestibular-dependent responses after the training intervention as evidenced in somatosensory downweighting, decreased VOR gain, better postural flexibility and faster automatic postural response. Findings suggest this is predominantly due to vestibular adaptation and habituation of VOR, VCR and VSR which induced sensory reweighting. Clinical relevance: Findings may be used to guide the development of a vestibular-postural rehabilitation intervention in impaired neurological populations, such as with vestibular disorders or sensory integration problems.

scholarly journals Neurofeedback training of auditory selective attention enhances speech-in-noise perception

2020 ◽  
Author(s):  
Subong Kim ◽  
Caroline Emory ◽  
Inyong Choi
Keyword(s):  
Selective Attention ◽  
Attention Training ◽  
Neurofeedback Training ◽  
Auditory Selective Attention ◽  
Auditory Evoked Responses ◽  
Sensory Inputs ◽  
Speech In Noise ◽  
Cortical Responses ◽  
Improved Performance ◽  
Online Feedback

AbstractSelective attention enhances cortical responses to attended sensory inputs while suppressing others, which can be an effective strategy for speech-in-noise (SiN) understanding. Here, we introduce a training paradigm designed to reinforce attentional modulation of auditory evoked responses. Subjects attended one of two speech streams while our EEG-based attention decoder provided online feedback. After four weeks of this neurofeedback training, subjects exhibited enhanced cortical response to target speech and improved performance during a SiN task. Such training effects were not found in the Placebo group that underwent attention training without neurofeedback. These results suggest an effective rehabilitation for SiN deficits.

Evaluation of experimental spinal cord injury using cortical evoked potentials

1973 ◽  
Vol 39 (1) ◽  
pp. 75-81 ◽  
Author(s):  
Stephen H. Martin ◽  
James R. Bloedel
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Cortical Response ◽  
Neurological Deficits ◽  
Cystic Degeneration ◽  
Post Injury ◽  
Content Type ◽  
Cord Injury ◽  
Cortical Responses ◽  
Control Response

✓ Experiments were performed to determine if changes in cortical evoked responses could be used to predict the extent of the neurological deficits following spinal cord injury by sudden inflation of a Fogarty balloon in the epidural space cephalad to a laminectomy. The cortical responses to stimulation of the posterior tibial nerve were recorded over the sigmoid gyrus at various times following the lesion and compared with the control response. Severe, irreversible neurological deficits occurred in cats in which the cortical response either could not be evoked immediately after injury or disappeared rapidly during this period. At the end of at least 6 weeks following injury, all of these animals were paraplegic and showed severe cystic degeneration of the spinal cord. In animals in which the post-injury cortical response did not completely disappear, only mild changes were observed in a spinal cord 6 weeks following injury. This technique may be helpful in ascertaining the severity and irreversibility of a traumatic spinal cord lesion; because the technique is simple, the method may prove helpful in the clinical management of patients with spinal cord injury.

scholarly journals Molecular Layer Inhibitory Interneurons Provide Feedforward and Lateral Inhibition in the Dorsal Cochlear Nucleus

2010 ◽  
Vol 104 (5) ◽  
pp. 2462-2473 ◽  
Author(s):  
Michael T. Roberts ◽  
Laurence O. Trussell
Keyword(s):  
Brain Stem ◽  
Lateral Inhibition ◽  
Cochlear Nucleus ◽  
Molecular Layer ◽  
Dorsal Cochlear Nucleus ◽  
Inhibitory Input ◽  
Auditory Information ◽  
Parallel Fibers ◽  
Sensory Inputs ◽  
Cartwheel Cells

In the outer layers of the dorsal cochlear nucleus, a cerebellum-like structure in the auditory brain stem, multimodal sensory inputs drive parallel fibers to excite both principal (fusiform) cells and inhibitory cartwheel cells. Cartwheel cells, in turn, inhibit fusiform cells and other cartwheel cells. At the microcircuit level, it is unknown how these circuit components interact to modulate the activity of fusiform cells and thereby shape the processing of auditory information. Using a variety of approaches in mouse brain stem slices, we investigated the synaptic connectivity and synaptic strength among parallel fibers, cartwheel cells, and fusiform cells. In paired recordings of spontaneous and evoked activity, we found little overlap in parallel fiber input to neighboring neurons, and activation of multiple parallel fibers was required to evoke or alter action potential firing in cartwheel and fusiform cells. Thus neighboring neurons likely respond best to distinct subsets of sensory inputs. In contrast, there was significant overlap in inhibitory input to neighboring neurons. In recordings from synaptically coupled pairs, cartwheel cells had a high probability of synapsing onto nearby fusiform cells or other nearby cartwheel cells. Moreover, single cartwheel cells strongly inhibited spontaneous firing in single fusiform cells. These synaptic relationships suggest that the set of parallel fibers activated by a particular sensory stimulus determines whether cartwheel cells provide feedforward or lateral inhibition to their postsynaptic targets.

Influence of instruction, prediction, and afferent sensory information on the postural organization of step initiation

1996 ◽  
Vol 75 (4) ◽  
pp. 1619-1628 ◽  
Author(s):  
A. Burleigh ◽  
F. Horak
Keyword(s):  
Anticipatory Postural Adjustments ◽  
Postural Response ◽  
Postural Adjustments ◽  
Automatic Postural Response ◽  
Step Initiation ◽  
Postural Responses ◽  
Automatic Response ◽  
Perturbation Velocity ◽  
Velocity Information ◽  
Automatic Postural Responses

1. Our previous study showed that two distinct postural modifications occurred when subjects were instructed to step, rather than maintain stance, in response to a backward surface translation: 1) the automatic postural responses to the surfaces perturbation were reduced in magnitude and 2) the anticipatory postural adjustments promoting foot-off were shortened in duration. This study investigates the extent to which task instruction, prediction of perturbation velocity, and afferent sensory information related to perturbation velocity are responsible for these postural modification. 2. Eleven human subjects were instructed in advance, to either maintain stance or step forward in response to a backward surface translation. Four different velocities of translation were used to perturb equilibrium. To assess the influence of predicted versus actual velocity information, the surface translations were presented in both a blocked order of increasing perturbation velocity (predictable) and a random order (unpredictable). Lower-extremity electromyographs (EMGs), ground reaction forces, and movement kinematics were quantified for both the automatic postural responses to perturbation and the anticipatory postural adjustments for step initiation. 3. The instruction to step was not solely responsible for the suppression of the automatic postural response. Prediction of perturbation velocity was required for significant suppression of the early automatic postural response when subjects stepped in response to the perturbation. When compared with the stance condition, the magnitude of the initial 50 ms of the automatic response in bilateral soleus and the left limb gastrocnemius (initial stance limb) was significantly reduced only when the perturbation velocities were presented in a blocked order. The magnitude of the automatic response was not reduced in the gastrocnemius of the right limb, which was always the initial swing limb and recruited for heel-off in the step conditions. This asymmetrical reduction of the gastrocnemius suggests that modification of the response was specific to the instruction, rather than a general decrease in the extensor muscle excitability. 4. The suppression of the early automatic postural response involved a change in the bias of the response. Despite the reduced magnitude during the predictable velocity step condition, the slope (i.e., gain) of the response with increasing velocities was not different from that of the stance condition. Thus the excitability of the automatic response was reduced by a relatively constant amount for each velocity when the perturbation velocity was predictable. 5. In contrast to the importance of velocity prediction for modification of the automatic postural response, actual velocity information was used for modification of the anticipatory postural adjustments when step was initiated in response to the surface perturbation. Regardless of whether the perturbation velocities were presented in a blocked or random order, the anticipatory postural adjustments were rapidly initiated and the duration of the postural adjustments for step initiation was shortened as the velocity of perturbation increased. 6. We conclude that the CNS uses prediction of perturbation velocity to modify the excitability of early automatic postural responses when the postural goal changes. In contrast, actual afferent velocity information can be used to modify the duration of the anticipatory postural adjustments for a voluntary step in response to perturbation. Thus the CNS utilizes feed-forward prediction to modify peripherally triggered postural responses, and utilizes immediate afferent information to modify the centrally initiated postural adjustments associated with voluntary movement.

scholarly journals Task-dependent coordination of rapid bimanual motor responses

2012 ◽  
Vol 107 (3) ◽  
pp. 890-901 ◽  
Author(s):  
Michael Dimitriou ◽  
David W. Franklin ◽  
Daniel M. Wolpert
Keyword(s):  
Sensory Information ◽  
Optimal Feedback Control ◽  
Single Trial ◽  
Mechanical Perturbation ◽  
Contralateral Limb ◽  
Motor Responses ◽  
Bimanual Task ◽  
Rapid Responses ◽  
Long Latency ◽  
Long Latency Reflex

Optimal feedback control postulates that feedback responses depend on the task relevance of any perturbations. We test this prediction in a bimanual task, conceptually similar to balancing a laden tray, in which each hand could be perturbed up or down. Single-limb mechanical perturbations produced long-latency reflex responses (“rapid motor responses”) in the contralateral limb of appropriate direction and magnitude to maintain the tray horizontal. During bimanual perturbations, rapid motor responses modulated appropriately depending on the extent to which perturbations affected tray orientation. Specifically, despite receiving the same mechanical perturbation causing muscle stretch, the strongest responses were produced when the contralateral arm was perturbed in the opposite direction (large tray tilt) rather than in the same direction or not perturbed at all. Rapid responses from shortening extensors depended on a nonlinear summation of the sensory information from the arms, with the response to a bimanual same-direction perturbation (orientation maintained) being less than the sum of the component unimanual perturbations (task relevant). We conclude that task-dependent tuning of reflexes can be modulated online within a single trial based on a complex interaction across the arms.

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