Attentional cost in additional visual feedback protocols in healthy young subjects

Area of Science:

• Neuroscience
• Biomechanics
• Human Motor Control

Background:

• Additional visual feedback (VFB) improves postural stability in healthy individuals by increasing muscular activity.
• Opposing trends in center-of-gravity (CGv) and center-of-pressure (CP) movements (CP-CGv) suggest a interplay between automatic and voluntary control.
• Understanding the neural circuits underlying these controls is crucial for optimizing VFB applications.

Purpose of the Study:

• To investigate the specific contributions of automatic and voluntary controls in VFB protocols.
• To analyze postural behavior under dual-task conditions combining VFB with a cognitive navigation task.
• To elucidate the neural mechanisms and optimal usage conditions for VFB.

Main Methods:

• A dual-task protocol was implemented, involving three VFB conditions (no VFB, VFB based on body-weight distribution [VFB_BW], VFB based on CP displacements [VFB_CP]) with or without a concurrent cognitive task.
• Postural behaviors were assessed using variances of CP-CGv and CGv movements (mediolateral [ML] and anteroposterior [AP] axes).
• Fractional Brownian motion modeling parameters (transition points, scaling regimes) were used to evaluate deterministic and stochastic activity levels.

Main Results:

• Under VFB_CP with dual-tasking, deterministic activity in CP-CGv movements decreased, reducing variances and altering CGv correction without affecting CGv variances.
• Cognitive load during VFB_BW decreased CP-CGv and CGv movements along ML and AP axes, respectively, highlighting the attentional demands of VFB.
• While VFB generally decreased tonic postural activity (CP-CGv), its effect on CGv movements depended on the type of feedback (BW or CP).

Conclusions:

• Excessive voluntary control can be detrimental to CP-CGv movement magnitudes but beneficial for CGv movements during stance maintenance.
• VFB protocols engage significant attentional resources, influencing both automatic and voluntary postural control mechanisms.
• These findings provide insights into the neural circuits involved in VFB and specify conditions for its effective application.