Modulation of human vestibular reflexes with increased postural threat

Area of Science:

• Neuroscience
• Vestibular System
• Human Balance Control

Background:

• Anxiety and arousal influence vestibulo-ocular reflexes via neural pathways.
• The impact of anxiety and fear on balance-relevant vestibular reflexes remains largely unexplored.

Purpose of the Study:

• To investigate if anxiety and fear modulate the relationship between vestibular signals and balance reflexes during stance.
• To examine the effects of manipulated standing height on vestibular-evoked balance responses.

Main Methods:

• Subjects stood on LOW and HIGH surfaces, experiencing varying degrees of postural threat.
• Stochastic vestibular stimulation (SVS) was applied to evoke ground reaction forces (GRF).
• The SVS-GRF relationship was analyzed for coupling (coherence, cumulant density) and gain in medio-lateral (ML) and antero-posterior (AP) directions.

Main Results:

• Vestibular-evoked balance responses (cumulant density and gain) were significantly increased in the HIGH condition (height-induced postural threat) compared to LOW.
• Coherence between SVS and GRF was statistically greater at specific frequencies in both ML and AP directions in the HIGH condition.
• Gain of the SVS-GRF relationship increased substantially (81% ML, 231% AP) when standing in the HIGH condition.

Conclusions:

• Height-induced postural threat augments vestibular-evoked balance responses.
• Fear or anxiety may alter central processing of vestibular information, thereby affecting balance control.
• These findings provide insights into the neural mechanisms underlying anxiety-related modulations of postural stability.