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Debenham MIB, Bruce CB, McNeil CJ, Dalton BH. The effects of four hours of normobaric hypoxia on the vestibular control of balance. Exp Brain Res 2024:10.1007/s00221-024-06905-9. [PMID: 39147911 DOI: 10.1007/s00221-024-06905-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Accepted: 07/30/2024] [Indexed: 08/17/2024]
Abstract
Whole-body vestibular-evoked balance responses decrease following ~ 55 min of normobaric hypoxia. It is unclear how longer durations of hypoxia affect the vestibular control of balance at the muscle and whole-body levels. This study examined how four hours of normobaric hypoxia influenced the vestibular control of balance. Fifteen participants (4 females; 11 males) stood on a force plate with vision occluded and head rotated rightward while subjected to three blocks of binaural, bipolar stochastic electrical vestibular stimulation (EVS; 0-25 Hz, root mean square amplitude = 1.1 mA) consisting of two, 90-s trials. The relationship between EVS and anteroposterior (AP) forces or medial gastrocnemius (MG) electromyography (EMG) was estimated in the time and frequency domains at baseline (BL; 0.21 fraction of inspired oxygen-FIO2) and following two (H2) and four (H4) hours of normobaric hypoxia (0.11 FIO2). The EVS-MG EMG short-latency peak and peak-to-peak amplitudes were smaller than BL at H2 and H4, but the medium-latency peak amplitude was only lower at H4. The EVS-AP force medium-latency peak amplitude was lower than BL at H4, but the short-latency peak and peak-to-amplitudes were unchanged. The EVS-MG EMG coherence and gain were reduced compared to BL at H2 and H4 across multiple frequencies ≥ 7 Hz, whereas EVS-AP force coherence was blunted at H4 (≤ 4 Hz), but gain was unaffected. Overall, the central nervous system's response to vestibular-driven signals during quiet standing was decreased for up to four hours of normobaric hypoxia, and vestibular-evoked responses recorded within postural muscles may be more sensitive than the whole-body response.
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Affiliation(s)
- M I B Debenham
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, Faculty of Health and Social Development, The University of British Columbia, Okanagan Campus, 1147 Research Road, Kelowna, BC, V1V 1V7, Canada
| | - C B Bruce
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, Faculty of Health and Social Development, The University of British Columbia, Okanagan Campus, 1147 Research Road, Kelowna, BC, V1V 1V7, Canada
| | - C J McNeil
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, Faculty of Health and Social Development, The University of British Columbia, Okanagan Campus, 1147 Research Road, Kelowna, BC, V1V 1V7, Canada
| | - B H Dalton
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, Faculty of Health and Social Development, The University of British Columbia, Okanagan Campus, 1147 Research Road, Kelowna, BC, V1V 1V7, Canada.
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Gallina A, Abboud J, Blouin JS. Vestibular control of deep and superficial lumbar muscles. J Neurophysiol 2024; 131:516-528. [PMID: 38230879 DOI: 10.1152/jn.00171.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Revised: 11/20/2023] [Accepted: 12/26/2023] [Indexed: 01/18/2024] Open
Abstract
The active control of the lumbar musculature provides a stable platform critical for postures and goal-directed movements. Voluntary and perturbation-evoked motor commands can recruit individual lumbar muscles in a task-specific manner according to their presumed biomechanics. Here, we investigated the vestibular control of the deep and superficial lumbar musculature. Ten healthy participants were exposed to noisy electrical vestibular stimulation while balancing upright with their head facing forward, left, or right to characterize the differential modulation in the vestibular-evoked lumbar extensor responses in generating multidirectional whole body motion. We quantified the activation of the lumbar muscles on the right side using indwelling [deep multifidus, superficial multifidus, caudal longissimus (L4), and cranial longissimus (L1)] and high-density surface recordings. We characterized the vestibular-evoked responses using coherence and peak-to-peak cross-covariance amplitude between the vestibular and electromyographic signals. Participants exhibited responses in all lumbar muscles. The vestibular control of the lumbar musculature exhibited muscle-specific modulations: responses were larger in the longissimus (combined cranio-caudal) compared with the multifidus (combined deep-superficial) when participants faced forward (P < 0.001) and right (P = 0.011) but not when they faced left. The high-density surface recordings partly supported this observation: the location of the responses was more lateral when facing right compared with left (P < 0.001). The vestibular control of muscle subregions within the longissimus or the multifidus was similar. Our results demonstrate muscle-specific vestibular control of the lumbar muscles in response to perturbations of vestibular origin. The lack of differential activation of lumbar muscle subregions suggests the vestibular control of these subregions is co-regulated for standing balance.NEW & NOTEWORTHY We investigated the vestibular control of the deep and superficial lumbar extensor muscles using electrical vestibular stimuli. Vestibular stimuli elicited preferential activation of the longissimus muscle over the multifidus muscle. We did not observe clear regional activation of lumbar muscle subregions in response to the vestibular stimuli. Our findings show that the central nervous system can finely tune the vestibular control of individual lumbar muscles and suggest minimal regional variations in the activation of lumbar muscle subregions.
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Affiliation(s)
- Alessio Gallina
- School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, United Kingdom
- Centre of Precision Rehabilitation for Spinal Pain, School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Jacques Abboud
- Département des Sciences de l'Activité Physique, Université du Québec à Trois-Rivières, Trois-Rivières, Quebec, 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
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Houben MMJ, Stuldreher IV, Forbes PA, Groen EL. Using Galvanic Vestibular Stimulation to Induce Post-Roll Illusion in a Fixed-Base Flight Simulator. Aerosp Med Hum Perform 2024; 95:84-92. [PMID: 38263100 DOI: 10.3357/amhp.6325.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2024]
Abstract
INTRODUCTION: The illusions of head motion induced by galvanic vestibular stimulation (GVS) can be used to compromise flight performance of pilots in fixed-base simulators. However, the stimuli used in the majority of studies fail to mimic disorientation in realistic flight because they are independent from the simulated aircraft motion. This study investigated the potential of bilateral-bipolar GVS coupled to aircraft roll in a fixed-base simulator to mimic vestibular spatial disorientation illusions, specifically the "post-roll illusion" observed during flight.METHODS: There were 14 nonpilot subjects exposed to roll stimuli in a flight simulator operating in a fixed-base mode. GVS was delivered via carbon rubber electrodes on the mastoid processes. The electrical stimulus was driven by the high-pass filtered aircraft roll rate to mimic the semicircular canals' physiological response. The post-roll test scenarios excluded outside visual cues or instruments and required subjects to actively maintain a constant bank angle after an abrupt stop following a passive prolonged roll maneuver. The anticipated outcome was an overshot in roll elicited by the GVS signal.RESULTS: The responses across subjects showed large variability, with less than a third aligning with the post-roll illusion. Subjective ratings suggest that the high-pass filtered GVS stimuli were mild and did not induce a clear sense of roll direction. However, uncontrolled head movements during stimulation might have obscured the intended effects of GVS-evoked illusory head movements.CONCLUSION: The mild and transient GVS stimuli used in this study, together with the uncontrolled head movements, did not convincingly mimic the post-roll illusion.Houben MMJ, Stuldreher IV, Forbes PA, Groen EL. Using galvanic vestibular stimulation to induce post-roll illusion in a fixed-base flight simulator. Aerosp Med Hum Perform. 2024; 95(2):84-92.
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Abstract
PURPOSE OF REVIEW Electrical stimulation of the peripheral and central vestibular system using noninvasive (galvanic vestibular stimulation, GVS) or invasive (intracranial electrical brain stimulation, iEBS) approaches have a long history of use in studying self-motion perception and balance control. The aim of this review is to summarize recent electrophysiological studies of the effects of GVS, and functional mapping of the central vestibular system using iEBS in awake patients. RECENT FINDINGS The use of GVS has become increasingly common in the assessment and treatment of a wide range of clinical disorders including vestibulopathy and Parkinson's disease. The results of recent single unit recording studies have provided new insight into the neural mechanisms underlying GVS-evoked improvements in perceptual and motor responses. Furthermore, the application of iEBS in patients with epilepsy or during awake brain surgery has provided causal evidence of vestibular information processing in mostly the middle cingulate cortex, posterior insula, inferior parietal lobule, amygdala, precuneus, and superior temporal gyrus. SUMMARY Recent studies have established that GVS evokes robust and parallel activation of both canal and otolith afferents that is significantly different from that evoked by natural head motion stimulation. Furthermore, there is evidence that GVS can induce beneficial neural plasticity in the central pathways of patients with vestibular loss. In addition, iEBS studies highlighted an underestimated contribution of areas in the medial part of the cerebral hemispheres to the cortical vestibular network.
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Affiliation(s)
- Christophe Lopez
- Aix Marseille Univ, CNRS, Laboratory of Cognitive Neuroscience (LNC), FR3C, Marseille, France
| | - Kathleen E. Cullen
- Department of Biomedical Engineering, Johns Hopkins University
- Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins University
- Department of Neuroscience, Johns Hopkins University
- Kavli Neuroscience Discovery Institute, Johns Hopkins University, Baltimore 21205 MD, USA
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Foulger LH, Charlton JM, Blouin JS. Real-world characterization of vestibular contributions during locomotion. Front Hum Neurosci 2024; 17:1329097. [PMID: 38259335 PMCID: PMC10800732 DOI: 10.3389/fnhum.2023.1329097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2023] [Accepted: 12/06/2023] [Indexed: 01/24/2024] Open
Abstract
Introduction The vestibular system, which encodes our head movement in space, plays an important role in maintaining our balance as we navigate the environment. While in-laboratory research demonstrates that the vestibular system exerts a context-dependent influence on the control of balance during locomotion, differences in whole-body and head kinematics between indoor treadmill and real-world locomotion challenge the generalizability of these findings. Thus, the goal of this study was to characterize vestibular-evoked balance responses in the real world using a fully portable system. Methods While experiencing stochastic electrical vestibular stimulation (0-20 Hz, amplitude peak ± 4.5 mA, root mean square 1.25 mA) and wearing inertial measurement units (IMUs) on the head, low back, and ankles, 10 participants walked outside at 52 steps/minute (∼0.4 m/s) and 78 steps/minute (∼0.8 m/s). We calculated time-dependent coherence (a measure of correlation in the frequency domain) between the applied stimulus and the mediolateral back, right ankle, and left ankle linear accelerations to infer the vestibular control of balance during locomotion. Results In all participants, we observed vestibular-evoked balance responses. These responses exhibited phasic modulation across the stride cycle, peaking during the middle of the single-leg stance in the back and during the stance phase for the ankles. Coherence decreased with increasing locomotor cadence and speed, as observed in both bootstrapped coherence differences (p < 0.01) and peak coherence (low back: 0.23 ± 0.07 vs. 0.16 ± 0.14, p = 0.021; right ankle: 0.38 ± 0.12 vs. 0.25 ± 0.10, p < 0.001; left ankle: 0.33 ± 0.09 vs. 0.21 ± 0.09, p < 0.001). Discussion These results replicate previous in-laboratory studies, thus providing further insight into the vestibular control of balance during naturalistic movements and validating the use of this portable system as a method to characterize real-world vestibular responses. This study will help support future work that seeks to better understand how the vestibular system contributes to balance in variable real-world environments.
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Affiliation(s)
- Liam H. Foulger
- School of Kinesiology, University of British Columbia, Vancouver, BC, Canada
| | - Jesse M. Charlton
- School of Kinesiology, University of British Columbia, Vancouver, BC, Canada
- School of Biomedical Engineering, University of British Columbia, Vancouver, BC, Canada
| | - Jean-Sébastien Blouin
- School of Kinesiology, University of British Columbia, Vancouver, BC, Canada
- Institute for Computing, Information and Cognitive Systems, University of British Columbia, Vancouver, BC, Canada
- Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada
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6
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Forbes PA, Kwan A, Mitchell DE, Blouin JS, Cullen KE. The Neural Basis for Biased Behavioral Responses Evoked by Galvanic Vestibular Stimulation in Primates. J Neurosci 2023; 43:1905-1919. [PMID: 36732070 PMCID: PMC10027042 DOI: 10.1523/jneurosci.0987-22.2023] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Revised: 01/25/2023] [Accepted: 01/30/2023] [Indexed: 02/04/2023] Open
Abstract
Noninvasive electrical stimulation of the vestibular system in humans has become an increasingly popular tool with a broad range of research and clinical applications. However, common assumptions regarding the neural mechanisms that underlie the activation of central vestibular pathways through such stimulation, known as galvanic vestibular stimulation (GVS), have not been directly tested. Here, we show that GVS is encoded by VIIIth nerve vestibular afferents with nonlinear dynamics that differ markedly from those predicted by current models. GVS produced asymmetric activation of both semicircular canal and otolith afferents to the onset versus offset and cathode versus anode of applied current, that in turn produced asymmetric eye movement responses in three awake-behaving male monkeys. Additionally, using computational methods, we demonstrate that the experimentally observed nonlinear neural response dynamics lead to an unexpected directional bias in the net population response when the information from both vestibular nerves is centrally integrated. Together our findings reveal the neural basis by which GVS activates the vestibular system, establish that neural response dynamics differ markedly from current predictions, and advance our mechanistic understanding of how asymmetric activation of the peripheral vestibular system alters vestibular function. We suggest that such nonlinear encoding is a general feature of neural processing that will be common across different noninvasive electrical stimulation approaches.SIGNIFICANCE STATEMENT Here, we show that the application of noninvasive electrical currents to the vestibular system (GVS) induces more complex responses than commonly assumed. We recorded vestibular afferent activity in macaque monkeys exposed to GVS using a setup analogous to human studies. GVS evoked notable asymmetries in irregular afferent responses to cathodal versus anodal currents. We developed a nonlinear model explaining these GVS-evoked afferent responses. Our model predicts that GVS induces directional biases in centrally integrated head motion signals and establishes electrical stimuli that recreate physiologically plausible sensations of motion. Altogether, our findings provide new insights into how GVS activates the vestibular system, which will be vital to advancing new clinical and biomedical applications.
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Affiliation(s)
- Patrick A Forbes
- Department of Neuroscience, Erasmus MC, University Medical Center Rotterdam, 3000 CA Rotterdam, The Netherlands
| | | | | | - Jean-Sébastien Blouin
- School of Kinesiology, University of British Columbia, Vancouver, British Colombia V6T 1Z1, Canada
| | - Kathleen E Cullen
- Physiology, McGill University, Montréal, Québec H3G 1Y6, Canada
- Departments of Biomedical Engineering
- Otolaryngology-Head and Neck Surgery
- Neuroscience, Johns Hopkins University, Baltimore, Maryland 21205
- Kavli Neuroscience Discovery Institute, Johns Hopkins University, Baltimore, Maryland 21205
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Debenham MIB, Kang HJ, Cheung SS, Dalton BH. The influence of reduced foot dorsum cutaneous sensitivity on the vestibular control of balance. Eur J Appl Physiol 2023; 123:65-79. [PMID: 36169737 DOI: 10.1007/s00421-022-05043-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 09/03/2022] [Indexed: 01/07/2023]
Abstract
PURPOSE Foot sole cooling increases vestibular-evoked balance responses, but less is known about foot dorsum temperature alterations. The purpose was to determine whether decreasing cutaneous receptor sensitivity via foot dorsum cooling modulates the vestibular control of balance. METHODS Eighteen participants (9 males; 9 females) stood quietly on a force plate with feet together, eyes closed, and head rotated leftward during 4, 90-s trials (2 control; 2 cooled) of continuous electrical vestibular stimulation (EVS). Icepacks placed on the dorsum of both feet for 15 min induced cooling and remained throughout the EVS trials. Monofilament testing was performed at multiple locations before and after cooling to determine tactile detection thresholds. T-type thermocouples monitored skin temperature over the tibialis anterior, soleus, foot dorsum and arch of the right leg. Vestibular-evoked balance responses were characterized using time (cumulant density) and frequency (coherence and gain) domain analyses to determine the relationship between the EVS input and motor output (anteroposterior force-AP force; right medial gastrocnemius electromyography-MG EMG). RESULTS Skin temperature of the foot dorsum and arch decreased ~ 70 and 15%, respectively during cooling (p < 0.05), but was unaltered at other locations (p ≥ 0.10). Detection thresholds for the foot dorsum increased following cooling (p < 0.05). Surprisingly, cooling reduced EVS-AP force and EVS-MG EMG coherence and gain at multiple frequencies, and peak-to-peak amplitude compared to control (p < 0.05). CONCLUSION Our results indicate that vestibular-driven balance responses are reduced following foot dorsum cooling, likely owing to alterations in cutaneous mechanoreceptor sensitivity and subsequent alterations in the transformation of vestibular cues for balance control.
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Affiliation(s)
- Mathew I B Debenham
- Sensorimotor Physiology and Integrative Neuromechanics Lab, Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, Faculty of Health and Social Development, University of British Columbia Okanagan, Kelowna, BC, Canada
| | - Hogun J Kang
- Sensorimotor Physiology and Integrative Neuromechanics Lab, Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, Faculty of Health and Social Development, University of British Columbia Okanagan, Kelowna, BC, Canada
| | - Stephen S Cheung
- Department of Kinesiology, Brock University, St. Catharines, ON, Canada
| | - Brian H Dalton
- Sensorimotor Physiology and Integrative Neuromechanics Lab, Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, Faculty of Health and Social Development, University of British Columbia Okanagan, Kelowna, BC, Canada.
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Debenham MIB, Grantham TDA, Smirl JD, Foster GE, Dalton BH. The effects of acute normobaric hypoxia on vestibular-evoked balance responses in humans. J Vestib Res 2023; 33:31-49. [PMID: 36530112 DOI: 10.3233/ves-220075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
BACKGROUND Hypoxia influences standing balance and vestibular function. OBJECTIVE The purpose here was to investigate the effect of hypoxia on the vestibular control of balance. METHODS Twenty participants (10 males; 10 females) were tested over two days (normobaric hypoxia and normoxia). Participants stood on a force plate (head rotated leftward) and experienced random, continuous electrical vestibular stimulation (EVS) during trials of eyes open (EO) and closed (EC) at baseline (BL), after 5 (H1), 30 (H2) and 55-min (H3) of hypoxia, and 10-min into normoxic recovery (NR). Vestibular-evoked balance responses were quantified using cumulant density, coherence, and gain functions between EVS and anteroposterior forces. RESULTS Oxyhemoglobin saturation, end-tidal oxygen and carbon dioxide decreased for H1-3 compared to BL; however, end-tidal carbon dioxide remained reduced at NR with EC (p≤0.003). EVS-AP force peak-to-peak amplitude was lower at H3 and NR than at BL (p≤0.01). At multiple frequencies, EVS-AP force coherence and gain estimates were lower at H3 and NR than BL for females; however, this was only observed for coherence for males. CONCLUSIONS Overall, vestibular-evoked balance responses are blunted following normobaric hypoxia >30 min, which persists into NR and may contribute to the reported increases in postural sway.
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Affiliation(s)
- M I B Debenham
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, The University of British Columbia, Kelowna, British Columbia, Canada
| | - T D A Grantham
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, The University of British Columbia, Kelowna, British Columbia, Canada
| | - J D Smirl
- Faculty of Kinesiology, University of Calgary, Calgary, Canada
| | - G E Foster
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, The University of British Columbia, Kelowna, British Columbia, Canada
| | - B H Dalton
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, The University of British Columbia, Kelowna, British Columbia, Canada
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Chen A, Kuo C, Blouin JS. A portable and low-cost solution for real-time manipulation of the vestibular sense. J Neurosci Methods 2022; 382:109709. [PMID: 36116537 DOI: 10.1016/j.jneumeth.2022.109709] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Revised: 09/02/2022] [Accepted: 09/06/2022] [Indexed: 01/05/2023]
Abstract
BACKGROUND The vestibular system encodes head motion in space which is naturally accompanied by other sensory cues. Electrical stimuli, applied across the mastoid processes, selectively activate primary vestibular afferents which has spurred clinical and biomedical applications of electrical vestibular stimulation (EVS). When properly matched to head motion, EVS may also manipulate the closed-loop relationship between actions and vestibular feedback to reveal the mechanisms of sensorimotor recalibration and learning. NEW METHOD We designed a portable, low-cost real-time EVS system using an Arduino microcontroller programmed through Simulink that provides electrical currents based on head angular motion. We used well-characterized vestibular afferent physiological responses to head angular velocity and electrical current to compute head-motion equivalent of real-time modulatory EVS currents. We also examined if our system induced recalibration of the vestibular system during human balance control. RESULTS Our system operated at 199.997 Hz ( ± 0.005 Hz) and delivered head-motion-equivalent electrical currents with ∼10 ms delay. The output driving the current stimulator matched the implemented linear model for physiological vestibular afferent dynamics with minimal background noise (<0.2% of ± 10 V range). Participants recalibrated to the modulated closed-loop vestibular feedback using visual cues during standing balance, replicating earlier findings. COMPARISON WITH EXISTING METHODS EVS is typically used to impose external perturbations that are independent of one's own movement. We provided a solution using open-source hardware to implement a real-time, physiology based, and task-relevant vestibular modulations using EVS. CONCLUSIONS Our portable, low-cost vestibular modulation system will make physiological closed-loop vestibular manipulations more accessible thus encouraging novel investigations and biomedical applications of EVS.
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Affiliation(s)
- Anthony Chen
- School of Kinesiology, University of British Columbia, Vancouver, Canada.
| | - Calvin Kuo
- School of Biomedical Engineering, University of British Columbia, Vancouver, Canada.
| | - Jean-Sébastien Blouin
- School of Kinesiology, University of British Columbia, Vancouver, Canada; Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, Canada; Institute for Computing, Information and Cognitive Systems, University of British Columbia, Vancouver, Canada.
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Laurens J. The otolith vermis: A systems neuroscience theory of the Nodulus and Uvula. Front Syst Neurosci 2022; 16:886284. [PMID: 36185824 PMCID: PMC9520001 DOI: 10.3389/fnsys.2022.886284] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Accepted: 08/22/2022] [Indexed: 12/04/2022] Open
Abstract
The Nodulus and Uvula (NU) (lobules X and IX of the cerebellar vermis) form a prominent center of vestibular information processing. Over decades, fundamental and clinical research on the NU has uncovered many aspects of its function. Those include the resolution of a sensory ambiguity inherent to inertial sensors in the inner ear, the otolith organs; the use of gravity signals to sense head rotations; and the differential processing of self-generated and externally imposed head motion. Here, I review these works in the context of a theoretical framework of information processing called the internal model hypothesis. I propose that the NU implements a forward internal model to predict the activation of the otoliths, and outputs sensory predictions errors to correct internal estimates of self-motion or to drive learning. I show that a Kalman filter based on this framework accounts for various functions of the NU, neurophysiological findings, as well as the clinical consequences of NU lesions. This highlights the role of the NU in processing information from the otoliths and supports its denomination as the "otolith" vermis.
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Affiliation(s)
- Jean Laurens
- Ernst Strüngmann Institute (ESI) for Neuroscience in Cooperation with Max Planck Society, Frankfurt, Germany
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11
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Tisserand R, Rasman BG, Omerovic N, Peters RM, Forbes PA, Blouin JS. Unperceived motor actions of the balance system interfere with the causal attribution of self-motion. PNAS NEXUS 2022; 1:pgac174. [PMID: 36714829 PMCID: PMC9802180 DOI: 10.1093/pnasnexus/pgac174] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Accepted: 08/25/2022] [Indexed: 02/01/2023]
Abstract
The instability of human bipedalism demands that the brain accurately senses balancing self-motion and determines whether movements originate from self-generated actions or external disturbances. Here, we challenge the longstanding notion that this process relies on a single representation of the body and world to accurately perceive postural orientation and organize motor responses to control balance self-motion. Instead, we find that the conscious sense of balance can be distorted by the corrective control of upright standing. Using psychophysics, we quantified thresholds to imposed perturbations and balance responses evoking cues of self-motion that are (in)distinguishable from corrective balance actions. When standing immobile, participants clearly perceived imposed perturbations. Conversely, when freely balancing, participants often misattributed their own corrective responses as imposed motion because their balance system had detected, integrated, and responded to the perturbation in the absence of conscious perception. Importantly, this only occurred for perturbations encoded ambiguously with balance-correcting responses and that remained below the natural variability of ongoing balancing oscillations. These findings reveal that our balance system operates on its own sensorimotor principles that can interfere with causal attribution of our actions, and that our conscious sense of balance depends critically on the source and statistics of induced and self-generated motion cues.
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Affiliation(s)
- Romain Tisserand
- School of Kinesiology, University of British Columbia, Vancouver, BC V6T 1Z1, Canada,Institut PPRIME (UPR3346), Université de Poitiers ENSMA, CNRS, 86360 Chasseneuil-du-Poitou, France,Centre de Recherches sur la Cognition et l'Apprentissage (UMR 7295), Université de Poitiers, Université de Tours, CNRS, 86073 Poitiers, France
| | - Brandon G Rasman
- Department of Neuroscience, Erasmus MC, University Medical Center Rotterdam, Rotterdam 3015 GD, The Netherlands,School of Physical Education, Sport, and Exercise Sciences, University of Otago, Dunedin 9054, New Zealand
| | - Nina Omerovic
- Department of Neuroscience, Erasmus MC, University Medical Center Rotterdam, Rotterdam 3015 GD, The Netherlands
| | - Ryan M Peters
- School of Kinesiology, University of British Columbia, Vancouver, BC V6T 1Z1, Canada,Faculty of Kinesiology, University of Calgary, Calgary, AB T2N 1N4, Canada
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Banman CJ, Schneider KJ, Cluff T, Peters RM. Altered Vestibular Balance Function in Combat Sport Athletes. J Neurotrauma 2021; 38:2291-2300. [PMID: 33752455 DOI: 10.1089/neu.2020.7432] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Combat sports pose a risk for accumulative injuries to the nervous system, yet fighters have remained an understudied population. Here, our purpose was to determine whether repetitive blows to the head have an effect on vestibular balance reflexes in combat sports athletes. We compared lower-limb muscle responses evoked with electrical vestibular stimuluation (EVS) between fighters (boxing/muay thai) and non-fighter controls. Each participant received stochastic vestibular stimulation (0-25 Hz, ±3 mA) over their mastoid processes while they stood relaxed with their head to the left or right. Surface electromyography was recorded from the medial gastrocnemius and soleus muscles bilaterally. Short and medium latency response (SLR/MLR) peaks were significantly delayed in the fighter group compared to controls. SLR and MLR peak amplitudes were also significantly lower in fighters. Fighter-estimated cumulative repetitive head impact (RHI) events demonstrated strong positive correlations with the timing of SLR and MLR peaks. Cumulative RHI events also negatively correlated with peak MLR amplitude and response gain at frequencies above 5 Hz. Our results provide evidence of a progressive vestibular impairment in combat sports athletes, potentially resulting from blows to the head accumulated in sparring practice and competitive bouts throughout their careers. Taken together, EVS-based vestibular assessments may provide a valuable clinical diagnostic tool and help better inform "return-to-play" and career-length decisions for not only combat sports athletes, but potentially other populations at risk of RHIs.
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Affiliation(s)
- Christopher J Banman
- Faculty of Kinesiology, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
| | - Kathryn J Schneider
- Faculty of Kinesiology, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
- Hotchkiss Brain Institute, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
- Sport Injury Prevention Research Centre, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
- Alberta Children's Hospital Research Institute for Child and Maternal Health, Cumming School of Medicine, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
- Sport Medicine Centre, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
- Evidence Sport and Spinal Therapy, Calgary, Alberta, Canada
| | - Tyler Cluff
- Faculty of Kinesiology, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
- Hotchkiss Brain Institute, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
| | - Ryan M Peters
- Faculty of Kinesiology, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
- Hotchkiss Brain Institute, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada
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13
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Rasman BG, Forbes PA, Peters RM, Ortiz O, Franks I, Inglis JT, Chua R, Blouin JS. Learning to stand with unexpected sensorimotor delays. eLife 2021; 10:65085. [PMID: 34374648 PMCID: PMC8480973 DOI: 10.7554/elife.65085] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2020] [Accepted: 08/04/2021] [Indexed: 11/23/2022] Open
Abstract
Human standing balance relies on self-motion estimates that are used by the nervous system to detect unexpected movements and enable corrective responses and adaptations in control. These estimates must accommodate for inherent delays in sensory and motor pathways. Here, we used a robotic system to simulate human standing about the ankles in the anteroposterior direction and impose sensorimotor delays into the control of balance. Imposed delays destabilized standing, but through training, participants adapted and re-learned to balance with the delays. Before training, imposed delays attenuated vestibular contributions to balance and triggered perceptions of unexpected standing motion, suggesting increased uncertainty in the internal self-motion estimates. After training, vestibular contributions partially returned to baseline levels and larger delays were needed to evoke perceptions of unexpected standing motion. Through learning, the nervous system accommodates balance sensorimotor delays by causally linking whole-body sensory feedback (initially interpreted as imposed motion) to self-generated balance motor commands. When standing, neurons in the brain send signals to skeletal muscles so we can adjust our movements to stay upright based on the requirements from the surrounding environment. The long nerves needed to connect our brain, muscles and sensors lead to considerable time delays (up to 160 milliseconds) between sensing the environment and the generation of balance-correcting motor signals. Such delays must be accounted for by the brain so it can adjust how it regulates balance and compensates for unexpected movements. Aging and neurological disorders can lead to lengthened neural delays, which may result in poorer balance. Computer modeling suggests that we cannot maintain upright balance if delays are longer than 300-340 milliseconds. Directly assessing the destabilizing effects of increased delays in human volunteers can reveal how capable the brain is at adapting to this neurological change. Using a custom-designed robotic balance simulator, Rasman et al. tested whether healthy volunteers could learn to balance with delays longer than the predicted 300-340 millisecond limit. In a series of experiments, 46 healthy participants stood on the balance simulator which recreates the physical sensations and neural signals for balancing upright based on a computer-driven virtual reality. This unique device enabled Rasman et al. to artificially impose delays by increasing the time between the generation of motor signals and resulting whole-body motion. The experiments showed that lengthening the delay between motor signals and whole-body motion destabilized upright standing, decreased sensory contributions to balance and led to perceptions of unexpected movements. Over five days of training on the robotic balance simulator, participants regained their ability to balance, which was accompanied by recovered sensory contributions and perceptions of expected standing, despite the imposed delays. When a subset of participants was tested three months later, they were still able to compensate for the increased delay. The experiments show that the human brain can learn to overcome delays up to 560 milliseconds in the control of balance. This discovery may have important implications for people who develop balance problems because of older age or neurologic diseases like multiple sclerosis. It is possible that robot-assisted training therapies, like the one in this study, could help people overcome their balance impairments.
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Affiliation(s)
- Brandon G Rasman
- School of Physical Education, Sport, and Exercise Sciences, University of Otago, Dunedin, New Zealand
| | - Patrick A Forbes
- Department of Neuroscience, Erasmus University Medical Centre, Rotterdam, Netherlands
| | - Ryan M Peters
- Faculty of Kinesiology, University of Calgary, Calgary, Canada
| | - Oscar Ortiz
- Faculty of Kinesiology, University of New Brunswick, Fredericton, Canada
| | - Ian Franks
- School of Kinesiology, University of British Columbia, Vancouver, Canada
| | - J Timothy Inglis
- School of Kinesiology, University of British Columbia, Vancouver, Canada
| | - Romeo Chua
- School of Kinesiology, University of British Columbia, Vancouver, Canada
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14
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Magnani RM, Bruijn SM, van Dieën JH, Forbes PA. Stabilization demands of walking modulate the vestibular contributions to gait. Sci Rep 2021; 11:13736. [PMID: 34215780 PMCID: PMC8253745 DOI: 10.1038/s41598-021-93037-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Accepted: 06/04/2021] [Indexed: 12/26/2022] Open
Abstract
Stable walking relies critically on motor responses to signals of head motion provided by the vestibular system, which are phase-dependent and modulated differently within each muscle. It is unclear, however, whether these vestibular contributions also vary according to the stability of the walking task. Here we investigate how vestibular signals influence muscles relevant for gait stability (medial gastrocnemius, gluteus medius and erector spinae)-as well as their net effect on ground reaction forces-while humans walked normally, with mediolateral stabilization, wide and narrow steps. We estimated local dynamic stability of trunk kinematics together with coherence of electrical vestibular stimulation (EVS) with muscle activity and mediolateral ground reaction forces. Walking with external stabilization increased local dynamic stability and decreased coherence between EVS and all muscles/forces compared to normal walking. Wide-base walking also decreased vestibulomotor coherence, though local dynamic stability did not differ. Conversely, narrow-base walking increased local dynamic stability, but produced muscle-specific increases and decreases in coherence that resulted in a net increase in vestibulomotor coherence with ground reaction forces. Overall, our results show that while vestibular contributions may vary with gait stability, they more critically depend on the stabilization demands (i.e. control effort) needed to maintain a stable walking pattern.
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Affiliation(s)
- Rina M Magnani
- Department of Physiotherapy, School of Physical Education and Physical Therapy, State University of Goiás, Goiânia, GO, Brazil
| | - Sjoerd M Bruijn
- Department of Human Movement Sciences, Faculty of Behavioral and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam, The Netherlands.,Institute Brain and Behavior Amsterdam, Amsterdam, The Netherlands
| | - Jaap H van Dieën
- Department of Human Movement Sciences, Faculty of Behavioral and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam, The Netherlands
| | - Patrick A Forbes
- Department of Neuroscience, Erasmus MC, University Medical Center Rotterdam, P.O. Box 2040, 3000 CA, Rotterdam, The Netherlands.
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15
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Hannan KB, Todd MK, Pearson NJ, Forbes PA, Dakin CJ. Vestibular attenuation to random-waveform galvanic vestibular stimulation during standing and treadmill walking. Sci Rep 2021; 11:8127. [PMID: 33854124 PMCID: PMC8046779 DOI: 10.1038/s41598-021-87485-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Accepted: 03/24/2021] [Indexed: 11/09/2022] Open
Abstract
The ability to move and maintain posture is critically dependent on motion and orientation information provided by the vestibular system. When this system delivers noisy or erred information it can, in some cases, be attenuated through habituation. Here we investigate whether multiple mechanisms of attenuation act to decrease vestibular gain due to noise added using supra-threshold random-waveform galvanic vestibular stimulation (GVS). Forty-five participants completed one of three conditions. Each condition consisted of two 4-min standing periods with stimulation surrounding a 1-h period of either walking with stimulation, walking without stimulation, or sitting quietly. An instrumented treadmill recorded horizontal forces at the feet during standing and walking. We quantified response attenuation to GVS by comparing vestibular stimulus-horizontal force gain between conditions. First stimulus exposure caused an 18% decrease in gain during the first 40 s of standing. Attenuation recommenced only when subjects walked with stimulation, resulting in a 38% decrease in gain over 60 min that did not transfer to standing following walking. The disparity in attenuation dynamics and absent carry over between standing and walking suggests that two mechanisms of attenuation, one associated with first exposure to the stimulus and another that is task specific, may act to decrease vestibulomotor gain.
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Affiliation(s)
- Kelci B Hannan
- Department of Kinesiology and Health Science, Utah State University, Logan, UT, USA
| | - Makina K Todd
- Department of Kinesiology and Health Science, Utah State University, Logan, UT, USA
| | - Nicole J Pearson
- Department of Kinesiology and Health Science, Utah State University, Logan, UT, USA
| | - Patrick A Forbes
- Department of Neuroscience, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Christopher J Dakin
- Department of Kinesiology and Health Science, Utah State University, Logan, UT, USA.
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16
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Hannan KB, Todd MK, Pearson NJ, Forbes PA, Dakin CJ. Absence of Nonlinear Coupling Between Electric Vestibular Stimulation and Evoked Forces During Standing Balance. Front Hum Neurosci 2021; 15:631782. [PMID: 33867958 PMCID: PMC8046432 DOI: 10.3389/fnhum.2021.631782] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Accepted: 03/03/2021] [Indexed: 11/13/2022] Open
Abstract
The vestibular system encodes motion and orientation of the head in space and is essential for negotiating in and interacting with the world. Recently, random waveform electric vestibular stimulation has become an increasingly common means of probing the vestibular system. However, many of the methods used to analyze the behavioral response to this type of stimulation assume a linear relationship between frequencies in the stimulus and its associated response. Here we examine this stimulus-response frequency linearity to determine the validity of this assumption. Forty-five university-aged subjects stood on a force-plate for 4 min while receiving vestibular stimulation. To determine the linearity of the stimulus-response relationship we calculated the cross-frequency power coupling between a 0 and 25 Hz bandwidth limited white noise stimulus and induced postural responses, as measured using the horizontal forces acting at the feet. Ultimately, we found that, on average, the postural response to a random stimulus is linear across stimulation frequencies. This result supports the use of analysis methods that depend on the assumption of stimulus-response frequency linearity, such as coherence and gain, which are commonly used to analyze the body’s response to random waveform electric stimuli.
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Affiliation(s)
- Kelci B Hannan
- Department of Kinesiology and Health Sciences, Utah State University, Logan, UT, United States
| | - Makina K Todd
- Department of Kinesiology and Health Sciences, Utah State University, Logan, UT, United States
| | - Nicole J Pearson
- Department of Kinesiology and Health Sciences, Utah State University, Logan, UT, United States
| | - Patrick A Forbes
- Department of Neuroscience, Erasmus MC, University Medical Center, Rotterdam, Netherlands
| | - Christopher J Dakin
- Department of Kinesiology and Health Sciences, Utah State University, Logan, UT, United States
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17
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Piccolo C, Bakkum A, Marigold DS. Subthreshold stochastic vestibular stimulation affects balance-challenged standing and walking. PLoS One 2020; 15:e0231334. [PMID: 32275736 PMCID: PMC7147773 DOI: 10.1371/journal.pone.0231334] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Accepted: 03/20/2020] [Indexed: 11/19/2022] Open
Abstract
Subthreshold stochastic vestibular stimulation (SVS) is thought to enhance vestibular sensitivity and improve balance. However, it is unclear how SVS affects standing and walking when balance is challenged, particularly when the eyes are open. It is also unclear how different methods to determine stimulation intensity influence the effects. We aimed to determine (1) whether SVS affects stability when balance is challenged during eyes-open standing and overground walking tasks, and (2) how the effects differ based on whether optimal stimulation amplitude is derived from sinusoidal or cutaneous threshold techniques. Thirteen healthy adults performed balance-unchallenged and balance-challenged standing and walking tasks with SVS (0–30 Hz zero-mean, white noise electrical stimulus) or sham stimulation. For the balance-challenged condition, participants had inflatable rubber hemispheres attached to the bottom of their shoes to reduce the control provided by moving the center of pressure under their base of support. In different blocks of trials, we set SVS intensity to either 50% of participants’ sinusoidal (motion) threshold or 80% of participants’ cutaneous threshold. SVS reduced medial-lateral trunk velocity root mean square in the balance-challenged (p < 0.05) but not in the balance-unchallenged condition during standing. Regardless of condition, SVS decreased step-width variability and marginally increased gait speed when walking with the eyes open (p < 0.05). SVS intensity had minimal effect on the standing and walking measures. Taken together, our results provide insight into the effectiveness of SVS at improving balance-challenged, eyes-open standing and walking performance in healthy adults.
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Affiliation(s)
- Chiara Piccolo
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Amanda Bakkum
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Daniel S. Marigold
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
- * E-mail:
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18
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Neural Mechanisms Underlying High-Frequency Vestibulocollic Reflexes In Humans And Monkeys. J Neurosci 2020; 40:1874-1887. [PMID: 31959700 DOI: 10.1523/jneurosci.1463-19.2020] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Revised: 12/30/2019] [Accepted: 01/07/2020] [Indexed: 01/16/2023] Open
Abstract
The vestibulocollic reflex is a compensatory response that stabilizes the head in space. During everyday activities, this stabilizing response is evoked by head movements that typically span frequencies from 0 to 30 Hz. Transient head impacts, however, can elicit head movements with frequency content up to 300-400 Hz, raising the question whether vestibular pathways contribute to head stabilization at such high frequencies. Here, we first established that electrical vestibular stimulation modulates human neck motor unit (MU) activity at sinusoidal frequencies up to 300 Hz, but that sensitivity increases with frequency up to a low-pass cutoff of ∼70-80 Hz. To examine the neural substrates underlying the low-pass dynamics of vestibulocollic reflexes, we then recorded vestibular afferent responses to the same electrical stimuli in monkeys. Vestibular afferents also responded to electrical stimuli up to 300 Hz, but in contrast to MUs their sensitivity increased with frequency up to the afferent resting firing rate (∼100-150 Hz) and at higher frequencies afferents tended to phase-lock to the vestibular stimulus. This latter nonlinearity, however, was not transmitted to neck motoneurons, which instead showed minimal phase-locking that decreased at frequencies >75 Hz. Similar to human data, we validated that monkey muscle activity also exhibited low-pass filtered vestibulocollic reflex dynamics. Together, our results show that neck MUs are activated by high-frequency signals encoded by primary vestibular afferents, but undergo low-pass filtering at intermediate stages in the vestibulocollic reflex. These high-frequency contributions to vestibular-evoked neck muscle responses could stabilize the head during unexpected head transients.SIGNIFICANCE STATEMENT Vestibular-evoked neck muscle responses rely on accurate encoding and transmission of head movement information to stabilize the head in space. Unexpected transient events, such as head impacts, are likely to push the limits of these neural pathways since their high-frequency features (0-300 Hz) extend beyond the frequency bandwidth of head movements experienced during everyday activities (0-30 Hz). Here, we demonstrate that vestibular primary afferents encode high-frequency stimuli through frequency-dependent increases in sensitivity and phase-locking. When transmitted to neck motoneurons, these signals undergo low-pass filtering that limits neck motoneuron phase-locking in response to stimuli >75 Hz. This study provides insight into the neural dynamics producing vestibulocollic reflexes, which may respond to high-frequency transient events to stabilize the head.
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19
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Woo EJ, Siegmund GP, Reilly CW, Blouin JS. Asymmetric Unilateral Vestibular Perception in Adolescents With Idiopathic Scoliosis. Front Neurol 2019; 10:1270. [PMID: 31849828 PMCID: PMC6903771 DOI: 10.3389/fneur.2019.01270] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Accepted: 11/18/2019] [Indexed: 11/13/2022] Open
Abstract
The cause of Adolescent Idiopathic Scoliosis (AIS) remains unclear, but one proposed cause of AIS is asymmetric vestibular function and the related descending drive to the spine musculature. The objective of this study was to determine if asymmetric vestibular function is present in individuals with AIS. Ten individuals with AIS (8F, 2M) and 10 healthy age- and sex-matched controls were exposed to 10s-long virtual rotations induced by monaural or binaural electrical vestibular stimulation (EVS), and 10s-long real rotations delivered by a rotating chair. Using a forced-choice paradigm, participants indicated their perceived rotation direction (right or left) to stimuli of varying intensity. A Bayesian adaptive algorithm adjusted the stimulus intensity and direction to identify a stimulus level, which we called the direction recognition threshold, at which participants correctly identified the rotation direction 69% of the time. For unilateral vestibular stimuli (monaural EVS), the direction recognition thresholds were more asymmetric in all participants with AIS compared to control participants [(0.22-1.00 mA) vs. (0.01-0.21 mA); p < 0.001]. For bilateral vestibular stimuli, however, the direction recognition thresholds did not differ between groups for either the real or virtual rotations (multiple p > 0.05). Previous reports of semicircular canal orientation asymmetry in individuals with AIS could not explain the magnitude of the vestibular function asymmetry we observed, suggesting a functional cause to the observed vestibular asymmetry. Thus, the present results suggest that a unilateral vestibular dysfunction is linked to AIS, potentially revealing a new path for the screening and monitoring of scoliosis in adolescents.
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Affiliation(s)
- Emma J Woo
- School of Kinesiology, University of British Columbia, Vancouver, BC, Canada
| | - Gunter P Siegmund
- School of Kinesiology, University of British Columbia, Vancouver, BC, Canada.,MEA Forensic Engineers & Scientists, Richmond, BC, Canada
| | - Christopher W Reilly
- British Columbia Children's Hospital, Vancouver, BC, Canada.,Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
| | - Jean-Sébastien Blouin
- School of Kinesiology, University of British Columbia, Vancouver, BC, Canada.,Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, Canada.,Institute for Computing, Information, and Cognitive System, University of British Columbia, Vancouver, BC, Canada
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20
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Chen A, Khosravi-Hashemi N, Kuo C, Kramer JK, Blouin JS. Development of a conversion model between mechanical and electrical vestibular stimuli. J Neurophysiol 2019; 123:548-559. [PMID: 31851563 DOI: 10.1152/jn.00276.2019] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The vestibular end-organs encode for linear and angular head accelerations in space contributing to our internal representation of self-motion. Activation of the vestibular system with transmastoid electrical current has recently grown in popularity; however, a direct relationship between electrically evoked and mechanically evoked vestibular responses remains elusive in humans. We have developed and tested a mechanical-to-electrical vestibular stimulus conversion model incorporating physiological activation of primary vestibular afferents identified in nonhuman primates. We compared ocular torsional responses between mechanical (chair rotation) and model-derived electrical (binaural-bipolar) stimuli in separate experiments for an angular velocity step change (±10 deg/s over 1 s, ±4-mA peak amplitude; n = 10) and multisine angular velocities (±10 deg/s, 9.7 mA peak to peak, 0.05-1 Hz; n = 5), respectively. Perception of whole body rotation (n = 18) to our step-change stimuli was also evaluated. Ocular torsional slow-phase velocity responses between stimulation types were similar (paired two one-sided tests of equivalence: multiple P < 0.002; one-sample t test: P = 0.178) and correlated (Pearson's coefficient: multiple P < 0.001). Bootstrap analysis of perceived angular velocity likewise showed similarity in perceptual decay dynamics. These data suggest that central processing between stimuli was similar, and our vestibular stimulus conversion model with a conversion factor of ∼0.4 mA per deg/s for an angular velocity step change can generate electrical stimuli that replicates dynamic vestibular activation elicited by mechanical whole body rotations. This proposed vestibular conversion model represents an initial framework for using electrical stimuli to generate mechanically equivalent activation of primary vestibular afferents for use in biomedical applications and immersive reality technologies.NEW & NOTEWORTHY With the growing popularity of electrical vestibular stimulation in biomedical and immersive reality applications, a direct conversion model between electrical and mechanical vestibular stimuli is needed. We developed a model to generate electrical stimuli mimicking the physiological activation of vestibular afferents evoked by mechanical rotations. Ocular and perceptual responses evoked by mechanical and model-derived electrical stimuli were similar, thus providing a critical first step toward generation of electrically induced vestibular responses that have a realistic mechanical equivalent.
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Affiliation(s)
- A Chen
- School of Kinesiology, University of British Columbia, Vancouver, BC, Canada
| | - N Khosravi-Hashemi
- School of Kinesiology, University of British Columbia, Vancouver, BC, Canada.,International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, BC, Canada
| | - C Kuo
- School of Kinesiology, University of British Columbia, Vancouver, BC, Canada.,Department of Computer Science, University of British Columbia, Vancouver, BC, Canada
| | - J K Kramer
- International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, BC, Canada
| | - J-S Blouin
- School of Kinesiology, University of British Columbia, Vancouver, BC, Canada
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