Brain plasticity and sensorimotor deterioration as a function of 70 days head down tilt bed rest

Koppelmans, Vincent; Bloomberg, Jacob J.; Dios, Y. E. De; Wood, Scott J.; Reuter‐Lorenz, Patricia A.; Kofman, I. S.; Riascos, Roy; Mulavara, Ajitkumar P.; Seidler, Rachael D.

doi:10.1371/journal.pone.0182236

Cited by 76 publications

(65 citation statements)

References 70 publications

(90 reference statements)

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“…Such a reduction in neural efficiency could result from adaptation to the bed rest environment. When participants are in a head‐down tilt supine position for a long period, the extravascular and intravascular fluids are shifted toward the upper body, and the brain shifts into a new position toward the posterior skull, resulting in gray matter volume change (Koppelmans et al, ; Roberts et al, ).…”

Section: Discussionmentioning

confidence: 99%

“…Region: the brain region with peak T value; k: cluster size; peak T: t value at the peak voxel; peak p: p value at the peak voxel; x, y, z: MNI coordinates of the peak voxel. and intravascular fluids are shifted toward the upper body, and the brain shifts into a new position toward the posterior skull, resulting in gray matter volume change (Koppelmans et al, 2017;Roberts et al, 2015).…”

Section: Discussionmentioning

confidence: 99%

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Vestibular brain changes within 70 days of head down bed rest

Peng

Koppelmans

Reuter‐Lorenz

et al. 2018

Human Brain Mapping

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Head-down-tilt bed rest (HDBR) is frequently utilized as a spaceflight analog research environment to study the effects of axial body unloading and fluid shifts that are associated with spaceflight in the absence of gravitational modifications. HDBR has been shown to result in balance changes, presumably due to sensory reweighting and adaptation processes. Here, we examined whether HDBR results in changes in the neural correlates of vestibular processing. Thirteen men participated in a 70-day HDBR intervention; we measured balance, functional mobility, and functional brain activity in response to vestibular stimulation at 7 time points before, during, and after HDBR. Vestibular stimulation was administered by means of skull taps, resulting in activation of the vestibular cortex and deactivation of the cerebellar, motor, and somatosensory cortices. Activation in the bilateral insular cortex, part of the vestibular network, gradually increased across the course of HDBR, suggesting an upregulation of vestibular inputs in response to the reduced somatosensory inputs experienced during bed rest. Furthermore, greater increase of activation in multiple frontal, parietal, and occipital regions in response to vestibular stimulation during HDBR was associated with greater decrements in balance and mobility from before to after HDBR, suggesting reduced neural efficiency. These findings shed light on neuroplastic changes occurring with conditions of altered sensory inputs, and reveal the potential for central vestibular-somatosensory convergence and reweighting with bed rest.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Vestibular brain changes within 70 days of head down bed rest

Peng

Koppelmans

Reuter‐Lorenz

et al. 2018

Human Brain Mapping

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“…The Functional Mobility Test (FMT) is sensitive to the effects of spaceflight (Mulavara et al, 2010) and to the effects of bed rest (Reschke et al, 2009;Koppelmans et al, 2017). The FMT requires subjects to arise from a seated position and walk through a 6-m × 4-m two-part obstacle course consisting of foam hurdles, pylons, and bars.…”

Section: Functional Mobility Test (Fmt)mentioning

confidence: 99%

“…Thus, during HDBR, in the absence of normal somatosensory inputs to the foot, vestibular processing appears to be altered, with vestibular cues weighted more heavily (Mulavara et al, 2018). HDBR also results in reduced functional mobility and decreased postural stability, which are both behaviors that depend upon the vestibular system and multisensory integration (Reschke et al, 2009;Mulder et al, 2014;Koppelmans et al, 2015Koppelmans et al, , 2017Miller et al, 2018;Mulavara et al, 2018). Thus, taken together, HDBR provides an effective environment for studying neural vestibular adaptation and has applications for both space travel and for better understanding plasticity of the vestibular system and multisensory integration.…”

Section: Introductionmentioning

confidence: 99%

Neural Correlates of Vestibular Processing During a Spaceflight Analog With Elevated Carbon Dioxide (CO2): A Pilot Study

Hupfeld

Lee

Gadd

et al. 2020

Front. Syst. Neurosci.

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Astronauts return to Earth from spaceflight missions with impaired mobility and balance; recovery can last weeks postflight. This is due in large part to the altered vestibular signaling and sensory reweighting that occurs in microgravity. The neural mechanisms of spaceflight-induced vestibular changes are not well understood. Head-down-tilt bed rest (HDBR) is a common spaceflight analog environment that allows for study of body unloading, fluid shifts, and other consequences of spaceflight. Subjects in this context still show vestibular changes despite being in Earth's gravitational environment, potentially due to sensory reweighting. Previously, we found evidence of sensory reweighting and reduced neural efficiency for vestibular processing in subjects who underwent a 70-day HDBR intervention. Here we extend this work by evaluating the impact of HDBR paired with elevated carbon dioxide (CO 2) to mimic International Space Station conditions on vestibular neural processing. Eleven participants (6 males, 34 ± 8 years) completed 30 days of HDBR combined with 0.5% atmospheric CO 2 (HDBR + CO 2). Participants underwent six functional magnetic resonance imaging (fMRI) sessions pre-, during, and post-HDBR + CO 2 while we measured brain activity in response to pneumatic skull taps (a validated method of vestibular stimulation). We also measured mobility and balance performance several times before and after the intervention. We found support for adaptive neural changes within the vestibular system during bed rest that subsequently recovered in several cortical and cerebellar regions. Further, there were multiple brain regions where greater pre-to postdeactivation was associated with reduced pre-to post-balance declines. That is, increased deactivation of certain brain regions associated with better balance post-HDBR + CO 2. We also found that, compared to HDBR alone (n = 13 males; 29 ± 3 years) HDBR + CO 2 is associated with greater increases in activation of multiple frontal, parietal, and temporal regions during vestibular stimulation. This suggests interactive or additive effects of bed rest and elevated CO 2. Finally, we found stronger correlations between pre-to post-HDBR + CO 2 brain changes and dependence on the visual system during balance for subjects who developed signs of Spaceflight-Associated Neuro-ocular Syndrome

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“…Whether these changes have any functional impacts is not known at present. There are some indications that grey and white matter changes are related to balance disturbances induced by spaceflight, but the clinical significance is unclear at the moment …”

Section: Other Fluid Shift Effectsmentioning

confidence: 99%

Adaptation of the cardiovascular system to weightlessness: Surprises, paradoxes and implications for deep space missions

Norsk

2020

Acta Physiologica

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Weightlessness in space induces a fluid shift from the dependent to the cephalad parts of the body leading to distension of the cardiac chambers and an accumulation of blood in the veins of the head and neck. Surprisingly, central venous pressure (CVP) during the initial hours of spaceflight decreases compared to being horizontal supine on the ground. The explanation is that the thorax is expanded by weightlessness leading to a decrease in inter‐pleural pressure (IPP), which exceeds the measured decrease in CVP. Thus, transmural CVP (TCVP = CVP − IPP) is increased indicating an augmented cardiac preload. Simultaneously, stroke volume and cardiac output (CO) are increased by 18%‐26% within the initial weeks and more so by 35%‐56% during the subsequent months of flight relative to in the upright posture on the ground. Mean arterial pressure (MAP) is decreased indicating a lower systemic vascular resistance (MAP/CO). It is therefore a surprise that sympathetic nerve activity is not suppressed in space and thus cannot be a mechanism for the systemic vasodilation, which still needs to be explored. Recent observations indicate that the fluid shift during long duration (months) flights is associated with increased retinal thickness that sometimes leads to optical disc oedema. Ocular and cerebral structural changes, increases in left atrial size and decreased flows with thrombi formation in the left internal jugular vein have also been observed. This is of concern for future long duration deep space missions because the health implications are unknown.

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Brain plasticity and sensorimotor deterioration as a function of 70 days head down tilt bed rest

Cited by 76 publications

References 70 publications

Vestibular brain changes within 70 days of head down bed rest

Vestibular brain changes within 70 days of head down bed rest

Neural Correlates of Vestibular Processing During a Spaceflight Analog With Elevated Carbon Dioxide (CO2): A Pilot Study

Adaptation of the cardiovascular system to weightlessness: Surprises, paradoxes and implications for deep space missions

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