Biology subjects

Peterka, R. J.

Publications and source records attributed to Peterka, R. J..

4 recordsLinked to original sources

bioRxiv2025

The Relationship Between Visual Motion Detection Thresholds and Visual Sensitivity to Medial/Lateral Balance Control

The ability to differentiate between self-motion and motion in the environment is an important factor for maintaining upright balance control. Visual motion can elicit the sensation of a fall by cueing a false position sense. While there is evidence supporting the role of central vision and fall risk, including measures of contrast sensitivity, depth perception, and size of the visual field, the relationship between motion detection thresholds and balance control remains unknown. The aim of this study is to explore the relationship between thresholds for visual motion detection (VMDTs) of the environment and measures of visual sensitivity to balance disturbances in the environment while walking. Thirty young adults (18-35 years) and thirty older adults (55-79 years) participated in a counter-balanced study where they 1) walked on a self-paced treadmill within a virtual environment that delivered frontal plane multi-sine visual disturbances at three amplitudes (6{degrees}, 10{degrees}, and 15{degrees}), and 2) performed 100 trials of a two-alternative forced choice (2AFC) task in which they discriminated between a counterclockwise ("left") and clockwise ("right") rotation of a visual scene under three conditions (standing, standing with optic flow, and walking). Visual sensitivity was measured using frequency response functions of the center of mass displacement relative to the screen tilt (cm/deg) while VMDTs were measured by fitting a psychometric curve to the responses of the 2AFC task. We found significant positive correlations between measures of visual sensitivity and VMDTs for 7 out of the 9 conditions in young adults, and nonsignificant positive correlations between the two measures in older adults. VMDTs were overall higher in older adults, although not significantly in the standing condition, indicating more motion in the environment is required for older adults to consciously perceive it. VMDTs also tended to increase from standing, standing with optic flow, and walking, although not significantly between the standing and standing with optic flow conditions for both populations. We interpret the positive correlations between the two measures as an indication that individuals with lower motion detection thresholds can more accurately differentiate between self-motion and motion in the environment, resulting in lower responses from visual disturbances in the environment.

neuroscience↗

bioRxiv2024

SENSITIVITY OF MEDIAL/LATERAL BALANCE CONTROL TO VISUAL DISTURBANCES WHILE WALKING IN YOUNG AND OLDER ADULTS

Humans integrate multiple sources of sensory information to estimate body orientation in space. Balance control experiments while standing provide evidence that the contributions of these sensory channels change under different conditions in a process called sensory reweighting. This study aims to address whether there is evidence for sensory reweighting while walking and explores age-related differences in medial/lateral balance control under visually perturbing walking conditions. Thirty young adults (18-35 years) and thirty older adults (55-79 years) walked on a self-paced treadmill within a virtual environment that delivered frontal plane multi-sine visual disturbances at three amplitudes (6{degrees}, 10{degrees}, and 15{degrees}). Frequency response functions were used to quantify visual sensitivity to balance disturbances, while spatiotemporal gait parameters (e.g., step width, step-width variability) were measured to assess balance control. Visual sensitivity decreased in both populations with increasing stimulus amplitude, analogous to the sensory reweighting hypothesis in balance control while standing. Despite the decrease in visual sensitivity, the compensatory upweighting of other sensory systems was not observed through measurements of remnant sway. Older adults exhibited higher visual sensitivity at all amplitudes compared to young adults, indicating a more sensitive response to visual disturbances to balance control. Both groups showed increases in step width and step width variability with higher visual amplitudes, with older adults demonstrating more pronounced effects. Weak correlations existed between changes in visual sensitivity and changes in step width and step width variability suggesting a limited interaction between sensory reweighting and gait stability.

neuroscience↗

bioRxiv2024

Is it me or the train moving? Humans resolve sensory conflicts with a nonlinear feedback mechanism in balance control

Humans use multiple sensory systems to estimate body orientation in space. Sensory contributions change depending on context. A predominant concept for the underlying multisensory integration (MSI) is the linear summation of weighted inputs from individual sensory systems. Changes of sensory contributions are typically attributed to some mechanism explicitly adjusting weighting factors. We provide evidence for a conceptually different mechanism that performs a multisensory correction if the reference of a sensory input moves in space without the need to explicitly change sensory weights. The correction is based on a reconstruction of the sensory reference frame motion (RFM) and automatically corrects erroneous inputs, e.g., when looking at a moving train. The proposed RFM estimator contains a nonlinear dead-zone that blocks corrections at slow velocities. We first demonstrate that this mechanism accounts for the apparent changes in sensory contributions. Secondly, using a balance control model, we show predictions of specific distortions in body sway responses to perturbations caused by this nonlinearity. Experiments measuring sway responses of 24 subjects (13 female, 11 male) to visual scene movements confirmed these predictions. The findings indicate that the central nervous system resolves sensory conflicts by an internal reconstruction of the cause of the conflict. Thus, the mechanism links the concept of causal inference to shifts in sensory contributions, providing a cohesive picture of MSI for the estimation of body orientation in space. Significance StatementHow the central nervous system (CNS) constructs body orientation in space from multiple sensory inputs is a fundamental question in neuroscience. It is a prerequisite to maintain balance, navigate and interact with the world. To estimate body orientation, the CNS dynamically changes the contribution of individual sensory inputs depending on context and reliability of the cues. However, it is not clear how the CNS achieves these dynamic changes. The findings in our study resolve major aspects of this question. Importantly, the proposed solution using nonlinear multisensory feedback contrasts with traditional approaches assuming context-dependent gain-scaling of individual inputs. Thus, our findings demonstrate how complex, intelligent, and unintuitive behavior can emerge from a comparably simple nonlinear feedback mechanism.

neuroscience↗

bioRxiv2019

Head Stabilization During Standing in People with Persisting Symptoms after Mild Traumatic Brain Injury

Increased postural sway is often observed in people with mild traumatic brain injury (mTBI), but our understanding of how individuals with mTBI control their head during stance is limited. The purpose of this study was to determine if people with mTBI exhibit increased sway at the head compared with healthy controls. People with persisting symptoms after mTBI (n = 59, 41 women) and control participants (n = 63, 38 women) stood quietly for one minute in four conditions: eyes open on a firm surface (EO-firm), eyes closed on a firm surface (EC-firm), eyes open on a foam pad (EO-foam), and eyes closed on foam (EC-foam). Inertial sensors at the head, sternum, and lumbar region collected tri-axial accelerations. Root-mean-square (RMS) accelerations in anteroposterior (AP) and mediolateral (ML) directions. Sway ratios between the head and sternum, head and lumbar, and sternum and lumbar region, were compared between groups. Temporal coupling of anti-phase motion between the upper and lower body angular accelerations was assessed with magnitude squared coherence and cross-spectral phase angles. People with mTBI demonstrated greater sway than controls across conditions and directions. During foam-surface conditions, the control group, but not the mTBI group, reduced ML sway at their head and trunk relative to their lumbar by increasing the expression of an anti-phase hip strategy within the frontal plane. These results are consistent with suggestions of inflexible or inappropriate postural control in people with mTBI.

neuroscience↗