Modulation of cortical activity in response to visually induced postural perturbation: Combined VR and EEG study

doi:10.1016/j.neulet.2013.05.001

Neuroscience Letters

Volume 547, 28 June 2013, Pages 6-9

https://doi.org/10.1016/j.neulet.2013.05.001 Get rights and content

Highlights

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Virtual reality (VR) and EEG were used to investigate the effect of visual perturbation on standing posture.
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Whole body postural responses were not different between predictable and unpredictable conditions.
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Unpredictable timing and direction of perturbation.

Abstract

There is evidence from EEG studies that unexpected perturbations to standing posture induce a differential modulation of cortical activity compared to self-initiated and/or predictable conditions. However, the neural correlates of whole body postural response to visually induced perturbations on standing posture have not been examined. Here we employ a novel experimental paradigm via combined virtual reality (VR) and EEG measures to examine the effects of visually induced perturbations on the dynamics of postural responses. Twelve Penn State student-athletes without prior history of neurologic disorders and/or orthopaedic injuries participated in this study. There were no differences in response/reaction time measures between both spatially and temporally unpredictable and fully predictable conditions (p > .05). However, significantly stronger modulation of frontal–central EEG theta activity was present prior to onset of unpredictable postural perturbations (p < .05). It is postulated that enhanced EEG theta in unpredictable conditions reflects increased effort to recruit additional brain resources to meet the demands of the postural tasks.

Section snippets

Acknowledgements

This research was supported by National Institutes of Health Grant RO1NS056226 0 01A2 “Identification of athletes at risk for traumatic brain injury”. We would like to thank Tracy Brewer for help with data collection, Kai Zhang for Matlab programming, and Elena Slobounov for VR programming.

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Citation Excerpt :
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Participants with AIS showed brain oscillations differences compared to CTL in the sensorimotor cortex while controlling their balance in various sensory conditions.
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However, Figs. 2 and 4 suggest a slight reduction in theta power during the postural tasks, with the exception of Cz. Given that theta oscillations are understood to be important during transient balance perturbations (Slobounov et al., 2009; Sipp et al., 2013; Slobounov et al., 2013; Varghese et al., 2014), a possible explanation for this discrepancy is that there are multiple, opposing event-sensitive changes in theta power that are not reflected in summary measurements of power in “steady-state”, continuous balance. Evidence exists to support this concept.
Cortical involvement in postural control is well recognized, however the role of non-visual afferents remains unclear. Parietal cortical areas are strongly implicated in vestibulo-spatial functions, but topographical localization during balance tasks remains limited. Here, we use electroencephalography (EEG) during continuous balance tasks of increasing difficulty at single electrode positions. Twenty-four healthy, right-handed individuals performed four balance tasks of increasing difficulty (bipedal and unipedal) and a seated control condition with eyes closed. Subjective ratings of task difficulty were obtained. EEG was recorded from 32 electrodes; 5 overlying sensory and motor regions of interest (ROIs) were chosen for further investigation: C3, Cz, C4, P3, P4. Spectral power and coherence during balance tasks were analyzed in theta (4–8 Hz) and alpha (8–12 Hz) bands. Alpha power reduced as task difficulty increased and this reduction correlated with subjective difficulty ratings. Alpha coherence increased with task difficulty between C3–Cz–C4 electrode pairs. Differential changes in power were observed in Cz, suggestive of a distinct role at this electrode location, which captures lower limb cortical representation. Hemispheric asymmetry was observed, as reflected by greater reductions in theta and alpha power in right-sided areas. Our results demonstrate the functional importance of bilateral central and parietal cortices in continuous balance control. The hemispheric asymmetry observed implies that the non-dominant hemisphere is involved with online monitoring of postural control. Although the posterior parietal asymmetry found may relate to vestibular, somatosensory or multisensory feedback processing, we argue that the finding relates to active balance control rather than simple sensory-intake or reflex circuit activation.
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Individuals with autism spectrum disorder (ASD) have been associated with sensorimotor difficulties, commonly presented by poor postural control. Postural control is necessary for all motor behaviors. However, findings concerning the effect of visual motion on postural control and the age progression of postural control in individuals with ASD are inconsistent. The aims of the present study were to examine postural responses to optic flow in children and adults with and without ASD, postural responses to optic flow in the central and peripheral visual fields, and the changes in postural responses between the child and adult groups. Thirty-three children (8–12 years old) and 33 adults (18–50 years old) with and without ASD were assessed on quiet standing for 60 seconds under conditions of varying optic flow illusions, consisting of different combinations of optic flow directions and visual field display. The results showed that postural responses to most optic flow conditions were comparable between children with and without ASD and between adults with and without ASD. However, adults with ASD appeared more responsive to forward-moving optic flow in the peripheral visual field compared with typically developed adults. The findings suggest that children and adults with ASD may not display maladaptive postural responses all the time. In addition, adults in the ASD group may have difficulties prioritizing visual information in the central visual field over visual information in the peripheral visual field when in unfamiliar environments, which may have implications in understanding their motor behaviors in new surroundings.

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View full text

Modulation of cortical activity in response to visually induced postural perturbation: Combined VR and EEG study

Highlights

Abstract

Section snippets

Acknowledgements

Gait Posture

Cogn. Brain Res.

Clin. Neurophysiol.

Biol. Psychol.

Cortical responses associated with predictable and unpredictable compensatory balance reactions

Exp. Brain Res.

On use of a nominal internal model to detect a loss of balance in a maximal forward reach

J. Neurophysiol.

Changes in performance monitoring during sensorimotor adaptation

J. Neurophysiol.

Postural adjustments induced by simulated motion of differently structures environments

Exp. Brain Res.