Assessing head acceleration to identify a motor threshold to galvanic vestibular stimulation

Area of Science:

• Neuroscience
• Biomechanics
• Vestibular System Research

Background:

• Galvanic vestibular stimulation (GVS) is crucial for evaluating vestibular function.
• Response variability in GVS protocols complicates quantitative analysis and comparisons.
• Standardizing GVS intensity is needed for reliable assessment of vestibulospinal responses.

Purpose of the Study:

• To identify an objective motor threshold for GVS intensity using head acceleration.
• To establish a standardized method for assessing standing postural responses with GVS.
• To explore novel approaches for understanding vestibular system changes.

Main Methods:

• Healthy subjects underwent GVS with binaural and bipolar configurations.
• Head acceleration was measured using an accelerometer placed on the vertex.
• Electromyography of the soleus muscle and force platform data were recorded concurrently.

Main Results:

• GVS induced a biphasic head acceleration response at 15 ms latency.
• An objective motor threshold was determined via recruitment curves and the method of limits.
• Objective motor thresholds differed significantly from subjective perceptual thresholds, except for the method of limits approach.

Conclusions:

• An objective motor threshold for GVS, based on head acceleration, was successfully identified in standing participants.
• The development of recruitment curves for GVS response amplitude is feasible.
• These objective measures offer a standardized approach to assess vestibular system function and its changes over time or across conditions.