Daily artificial gravity partially mitigates vestibular processing changes associated with head-down tilt bedrest

Area of Science:

• Neuroscience
• Space Physiology
• Human Physiology

Background:

• Microgravity significantly impacts vestibular signaling and body loading, leading to sensory reweighting.
• Head-down tilt bedrest (HDT) is a ground-based model simulating unloading effects similar to spaceflight.
• Artificial gravity (AG) is a potential countermeasure for spaceflight-induced physiological declines.

Purpose of the Study:

• To evaluate the efficacy of daily artificial gravity (AG) in counteracting brain and behavioral changes induced by 60 days of head-down tilt bedrest (HDT).
• To investigate the effects of AG on vestibular processing and brain activation patterns during HDT using functional magnetic resonance imaging (fMRI).

Main Methods:

• Two groups received 30 minutes of daily AG via short-arm centrifuge during 60 days of HDT (continuous or intermittent bouts).
• A control group (CTRL) underwent HDT without AG.
• fMRI scans were collected before, during, and after HDT to assess brain activation during vestibular stimulation in regions of interest and the whole brain.

Main Results:

• The AG group exhibited no changes in cerebellar activation during vestibular stimulation, unlike the CTRL group which showed decreased activation.
• Individuals in the AG group with minimal changes in left vestibular cortex activation demonstrated better post-HDT balance.
• Whole-brain analysis revealed that AG maintained pre-HDT activation levels in the right precentral and inferior frontal gyri, while CTRLs showed increased activation.

Conclusions:

• Daily AG can mitigate alterations in vestibular processing and associated brain activation changes induced by HDT.
• AG may preserve neural pathways crucial for vestibular function and balance control during simulated microgravity.
• These findings support AG as a promising countermeasure for maintaining physiological function during spaceflight.