Artificial gravity during a spaceflight analog alters brain sensory connectivity, 2023, McGregor et al.

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Artificial gravity during a spaceflight analog alters brain sensory connectivity
McGregor; Lee; Mulder; De Dios; Beltran; Wood; Bloomberg; Mulavara; Seidler

Spaceflight has numerous untoward effects on human physiology. Various countermeasures are under investigation including artificial gravity (AG). Here, we investigated whether AG alters resting-state brain functional connectivity changes during head-down tilt bed rest (HDBR), a spaceflight analog. Participants underwent 60 days of HDBR. Two groups received daily AG administered either continuously (cAG) or intermittently (iAG). A control group received no AG. We assessed resting-state functional connectivity before, during, and after HDBR. We also measured balance and mobility changes from pre- to post-HDBR. We examined how functional connectivity changes throughout HDBR and whether AG is associated with differential effects.

We found differential connectivity changes by group between posterior parietal cortex and multiple somatosensory regions. The control group exhibited increased functional connectivity between these regions throughout HDBR whereas the cAG group showed decreased functional connectivity. This finding suggests that AG alters somatosensory reweighting during HDBR. We also observed brain-behavioral correlations that differed significantly by group. Control group participants who showed increased connectivity between the putamen and somatosensory cortex exhibited greater mobility declines post-HDBR. For the cAG group, increased connectivity between these regions was associated with little to no mobility declines post-HDBR. This suggests that when somatosensory stimulation is provided via AG, functional connectivity increases between the putamen and somatosensory cortex are compensatory in nature, resulting in reduced mobility declines.

Given these findings, AG may be an effective countermeasure for the reduced somatosensory stimulation that occurs in both microgravity and HDBR.

Link | PDF (NeuroImage)

 

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Participants resided at the:envihab facility throughout this 88 day study. All participants underwent an ambulatory 14-day baseline data collection (BDC) phase prior to commencing a 60-day phase of strict 6° head down tilt bed rest (HDBR). Participants remained in the head down tilt position at all times during the HDBR phase (all activities and hygiene maintenance took place in this position) and were monitored for compliance.

On the first day of HDBR, participants were assigned to one of three groups: i) the continuous AG (cAG, n = 8) group exposed to a continuous 30-minute bout of centrifugation each day of HDBR, ii) the intermittent AG group (iAG, n = 8) exposed to six 5-minute bouts of centrifugation each day of HDBR, or iii) the control group (CTRL, n = 8) that received no centrifugation during HDBR. AG was applied using a short-arm centrifuge such that participants received 1 G at their center of mass, directed axially towards the feet. This resulted in a centrifuge speed of approximately 30 rpm, depending on participant height.

After the 60-day bed rest phase, participants underwent a 14-day recovery phase during which they were reambulated within the bed rest facility.

 

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In Characteristics and Treatment of Exercise Intolerance in Patients With Long COVID (2023) the authors concluded —

Long COVID results, in large part, from deconditioning, which may result from as little as 20 hr of inactivity.

Noting: American, European and Russian space agencies routinely investigate zero-g effects and counter-measures with volunteers in 5-6° head-down tilt full time for 2 months. They have done this since the 1960s. Subjects recover fine and there has never been a report of long-term symptoms.