Biology subjects

Raffegeau, T. E.

Publications and source records attributed to Raffegeau, T. E..

3 recordsLinked to original sources

bioRxiv2024

Behavioral risk models explain locomotor and balance changes when walking at virtual heights

Walking in daily life requires humans to adapt to environments that can influence ones fear of falling and anxiety about a potential fall. In such environments, individuals may adopt compensatory locomotor and balance changes to maintain a constant expected risk function equal to the product of the probability of some event (e.g., a fall) and the cost of that event (e.g., injury or death). Here, we tested whether locomotor behaviors broadly align with this risk model in two experiments with height-related threats in immersive virtual reality. In Experiment 1, we examined how individuals change their locomotor trajectory while walking along a straight high-elevation walkway. In Experiment 2, we examined how individuals change trajectory and balance control during curved walking where the location of high elevation threat varied. Participants adopted two behaviors that decreased their probability of falling off the edge and aligned with the risk-based model: participants altered their proximity to perceived threats that pose high costs (e.g., a high-elevation ledge), and decreased mediolateral center of mass velocity when that was not possible. Taken together, our results suggest that individuals alter locomotor behavior to change the probability of falling based on the perceived cost of that fall.

neuroscience↗

bioRxiv2023

Walking (and talking) the plank: Dual-task performance costs in a virtual balance-threatening environment

We evaluated the effects of engaging in extemporaneous speech while walking in virtual environments meant to elicit low or high levels of mobility-related anxiety. We expected that mobility-related anxiety imposed by a simulated balance threat (i.e. virtual high elevation) would impair walking behavior and lead to greater dual-task costs. Altogether, 15 adults (age = 25.6 {+/-} 4.7 yrs, 7 women) walked at their self-selected speed within low (ground) and high elevation (15 meters) VR settings while speaking extemporaneously (dual-task) or not speaking (single-task). Likert-scale ratings of cognitive and somatic anxiety, confidence, and mental effort were evaluated after experiencing each condition, and gait speed, step length, and step width, and the variability of each, was calculated for each trial using the position of trackers attached to participants ankles. Silent speech pauses (>150ms) were determined from audio recordings to infer the cognitive costs of extemporaneous speech planning at low and high virtual elevation. The presence of a balance threat and the inclusion of a concurrent speech task both perturbed gait kinematics, but only the virtual height illusion increased anxiety and mental effort while decreasing confidence. Extemporaneous speech pauses were longer on average when walking, but no effects of virtual elevation were reported. Trends toward interaction effects arose in self-reported responses, participants reported more comfort walking at virtual heights if they engaged in extemporaneous speech. Walking at virtual elevation and walking while talking have independent and significant effects on gait; both effects were robust and did not support an interaction when combined (i.e., walking and talking at virtual heights). Rather than additive cognitive-motor demands, the nature of extemporaneous speech may have distracted participants from the detrimental effects of walking in anxiety-inducing settings.

bioengineering↗

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↗