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Hodgson DD, King JA, Darici O, Dalton BH, Cleworth TW, Cluff T, Peters RM. Visual feedback-dependent modulation of arousal, postural control, and muscle stretch reflexes assessed in real and virtual environments. Front Hum Neurosci 2023; 17:1128548. [PMID: 37082148 PMCID: PMC10110857 DOI: 10.3389/fnhum.2023.1128548] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Accepted: 03/14/2023] [Indexed: 04/07/2023] Open
Abstract
IntroductionThe mechanisms regulating neuromuscular control of standing balance can be influenced by visual sensory feedback and arousal. Virtual reality (VR) is a cutting-edge tool for probing the neural control of balance and its dependence on visual feedback, but whether VR induces neuromodulation akin to that seen in real environments (eyes open vs. closed or ground level vs. height platform) remains unclear.MethodsHere we monitored 20 healthy young adults (mean age 23.3 ± 3.2 years; 10 females) during four conditions of quiet standing. Two real world conditions (eyes open and eyes closed; REO and REC) preceded two eyes-open virtual ‘low’ (ground level; VRL) and ‘high’ (14 m height platform; VRH) conditions. We measured arousal via electrodermal activity and psychosocial questionnaires rating perceived fear and anxiety. We recorded surface electromyography over the right soleus, medial gastrocnemius, and tibialis anterior, and performed force plate posturography. As a proxy for modulations in neural control, we assessed lower limb reflexive muscle responses evoked by tendon vibration and electrical stimulation.ResultsPhysiological and perceptual indicators of fear and anxiety increased in the VRH condition. Background soleus muscle activation was not different across conditions; however, significant increases in muscle activity were observed for medial gastrocnemius and tibialis anterior in VRH relative to REO. The mean power frequency of postural sway also increased in the VRH condition relative to REO. Finally, with a fixed stimulus level across conditions, mechanically evoked reflexes remained constant, while H-reflex amplitudes decreased in strength within virtual reality.DiscussionNotably, H-reflexes were lower in the VRL condition than REO, suggesting that these ostensibly similar visual environments produce different states of reflexive balance control. In summary, we provide novel evidence that VR can be used to modulate upright postural control, but caution that standing balance in analogous real and virtual environments may involve different neural control states.
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Affiliation(s)
| | - Jordan A. King
- Biomedical Engineering, University of Calgary, Calgary, AB, Canada
| | - Osman Darici
- Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada
| | - Brian H. Dalton
- School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, BC, Canada
| | | | - Tyler Cluff
- Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada
| | - Ryan M. Peters
- Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada
- Biomedical Engineering, University of Calgary, Calgary, AB, Canada
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada
- *Correspondence: Ryan M. Peters,
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Modulation of tendon tap reflex activation of soleus motor neurons with reduced stability tandem stance. Hum Mov Sci 2019; 64:274-282. [DOI: 10.1016/j.humov.2019.02.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Revised: 02/06/2019] [Accepted: 02/19/2019] [Indexed: 11/22/2022]
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Song S, Geyer H. Evaluation of a Neuromechanical Walking Control Model Using Disturbance Experiments. Front Comput Neurosci 2017; 11:15. [PMID: 28381996 PMCID: PMC5361655 DOI: 10.3389/fncom.2017.00015] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Accepted: 02/28/2017] [Indexed: 01/01/2023] Open
Abstract
Neuromechanical simulations have been used to study the spinal control of human locomotion which involves complex mechanical dynamics. So far, most neuromechanical simulation studies have focused on demonstrating the capability of a proposed control model in generating normal walking. As many of these models with competing control hypotheses can generate human-like normal walking behaviors, a more in-depth evaluation is required. Here, we conduct the more in-depth evaluation on a spinal-reflex-based control model using five representative gait disturbances, ranging from electrical stimulation to mechanical perturbation at individual leg joints and at the whole body. The immediate changes in muscle activations of the model are compared to those of humans across different gait phases and disturbance magnitudes. Remarkably similar response trends for the majority of investigated muscles and experimental conditions reinforce the plausibility of the reflex circuits of the model. However, the model's responses lack in amplitude for two experiments with whole body disturbances suggesting that in these cases the proposed reflex circuits need to be amplified by additional control structures such as location-specific cutaneous reflexes. A model that captures these selective amplifications would be able to explain both steady and reactive spinal control of human locomotion. Neuromechanical simulations that investigate hypothesized control models are complementary to gait experiments in better understanding the control of human locomotion.
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Affiliation(s)
- Seungmoon Song
- Robotics Institute, Carnegie Mellon University Pittsburgh, PA, USA
| | - Hartmut Geyer
- Robotics Institute, Carnegie Mellon University Pittsburgh, PA, USA
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Mildren RL, Peters RM, Hill AJ, Blouin JS, Carpenter MG, Inglis JT. Frequency characteristics of human muscle and cortical responses evoked by noisy Achilles tendon vibration. J Appl Physiol (1985) 2017; 122:1134-1144. [PMID: 28209741 DOI: 10.1152/japplphysiol.00908.2016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Revised: 01/17/2017] [Accepted: 02/11/2017] [Indexed: 11/22/2022] Open
Abstract
Noisy stimuli, along with linear systems analysis, have proven to be effective for mapping functional neural connections. We explored the use of noisy (10-115 Hz) Achilles tendon vibration to examine somatosensory reflexes in the triceps surae muscles in standing healthy young adults (n = 8). We also examined the association between noisy vibration and electrical activity recorded over the sensorimotor cortex using electroencephalography. We applied 2 min of vibration and recorded ongoing muscle activity of the soleus and gastrocnemii using surface electromyography (EMG). Vibration amplitude was varied to characterize reflex scaling and to examine how different stimulus levels affected postural sway. Muscle activity from the soleus and gastrocnemii was significantly correlated with the tendon vibration across a broad frequency range (~10-80 Hz), with a peak located at ~40 Hz. Vibration-EMG coherence positively scaled with stimulus amplitude in all three muscles, with soleus displaying the strongest coupling and steepest scaling. EMG responses lagged the vibration by ~38 ms, a delay that paralleled observed response latencies to tendon taps. Vibration-evoked cortical oscillations were observed at frequencies ~40-70 Hz (peak ~54 Hz) in most subjects, a finding in line with previous reports of sensory-evoked γ-band oscillations. Further examination of the method revealed 1) accurate reflex estimates could be obtained with <60 s of low-level (root mean square = 10 m/s2) vibration; 2) responses did not habituate over 2 min of exposure; and importantly, 3) noisy vibration had a minimal influence on standing balance. Our findings suggest noisy tendon vibration is an effective novel approach to characterize somatosensory reflexes during standing.NEW & NOTEWORTHY We applied noisy (10-115 Hz) vibration to the Achilles tendon to examine the frequency characteristics of lower limb somatosensory reflexes during standing. Ongoing muscle activity was coherent with the noisy vibration (peak coherence ~40 Hz), and coherence positively scaled with increases in stimulus amplitude. Our findings suggest that noisy tendon vibration, along with linear systems analysis, is an effective novel approach to study somatosensory reflex actions in active muscles.
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Affiliation(s)
- Robyn L Mildren
- School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada;
| | - Ryan M Peters
- School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Aimee J Hill
- School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Jean-Sébastien Blouin
- School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada.,Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, British Columbia, Canada.,Institute for Computing, Information and Cognitive Systems, University of British Columbia, Vancouver, British Columbia, Canada
| | - Mark G Carpenter
- School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada.,Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, British Columbia, Canada.,International Collaboration on Repair Discoveries, Vancouver, British Columbia, Canada; and
| | - J Timothy Inglis
- School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada.,Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, British Columbia, Canada.,International Collaboration on Repair Discoveries, Vancouver, British Columbia, Canada; and
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