Cortical Effects of Noisy Galvanic Vestibular Stimulation Using Functional Near-Infrared Spectroscopy

Area of Science:

• Neuroscience
• Vestibular System
• Neuroimaging

Background:

• Noisy galvanic vestibular stimulation (nGVS) enhances motor, sensory, and cognitive functions.
• The neural mechanisms underlying nGVS benefits are not fully understood.
• Functional near-infrared spectroscopy (fNIRS) offers a portable, motion-artifact-resistant method for studying cortical activity.

Purpose of the Study:

• To assess fNIRS's ability to detect cortical hemodynamic changes induced by subthreshold nGVS.
• To investigate how subthreshold nGVS influences fNIRS-derived oxygenated hemoglobin (HbO) and deoxygenated hemoglobin (HbR) responses.
• To explore the utility of fNIRS in understanding nGVS's impact on brain activity during naturalistic behaviors.

Main Methods:

• Twelve healthy participants underwent resting-state fNIRS during both nGVS and sham stimulation.
• Cortical activity was measured by changes in HbO and HbR concentrations.
• Hemodynamic responses were compared between nGVS and sham conditions in specific regions (BA40, BA39) and across the left hemisphere.

Main Results:

• A significant increase in HbR was observed in the left BA40 and across all left hemisphere channels during nGVS compared to sham stimulation (p < 0.05).
• No significant differences in HbO responses were detected between nGVS and sham conditions.
• These findings indicate differential modulation of cerebral blood oxygenation by nGVS.

Conclusions:

• fNIRS can detect task-related hemodynamic changes in cortical regions associated with vestibular processing during nGVS.
• Subthreshold nGVS appears to primarily affect deoxygenated hemoglobin levels, suggesting a specific neural response.
• fNIRS is a promising tool for investigating the neurophysiological underpinnings of nGVS effects on brain function.