1. PROJECT AIMS/OBJECTIVES:
Original:
Aim 1: Determine if insole vibration improves adaptation of postural stability during standing balance in simulated Mars gravity and during re-adaptation to Earth (1 g) gravity.
Aim 2: Determine if insole vibration improves adaptation of stability during locomotion in simulated Mars gravity and during re-adaptation to Earth (1 g) gravity.
Aim 3: Determine if adaptation to simulated Mars gravity alters early somatosensory processing of lower limb afferent inputs during upright stance. I will also test if changes in somatosensory cortical processing are associated with changes in balance and locomotion performance during adaptation to partial gravity.
Aim 4: Determine if insole vibration during upright stance augments early cortical processing of lower limb somatosensory inputs.
Update:
Somatosensory evoked potentials (SEPs), collected using electroencephalogram (EEG), were intended to probe changes in early cortical processing of lower limb somatosensory inputs. We have been encountering noise issue with the EEG system in the lab. We can only acquire SEPs if everything in the lab is unplugged. When we plug in the treadmill and/or the tactors embedded in the insoles, the SEPs are just noise and unusable. We have purchased troubleshooting equipment, sought assistance from collaborators and other researchers in the department, reached out the EEG system company, and changed EEG systems. Nothing has been able to resolve the issue. Changing rooms is not feasible as we need at least 13-foot ceilings and exposed i-beams to hold the body weight system. It has not been feasible to collect SEPs in this study.
Instead, I can adapt the study to use a subset of my existing EEG experimental setup (i.e., electrical stimulations applied to foot sensory nerves) and measure changes in subjects' perceptual sensitivity to lower limb sensory inputs. This can be done by gradually increasing the intensity of foot sensory nerve stimulation and having the subject report when they begin to detect stimulation. As indicated in the Main Findings section (b), this method examining perceptual changes to lower limb somatosensory inputs can be used to detect sensory changes associated with adaptation following gravitational transitions.
Aim 1 (unchanged): Determine if insole vibration improves adaptation of postural stability during standing balance in simulated Mars gravity and during re-adaptation to Earth (1 g) gravity.
Aim 2 (unchanged): Determine if insole vibration improves adaptation of stability during locomotion in simulated Mars gravity and during re-adaptation to Earth (1 g) gravity.
Aim 3: Determine if adaptation to simulated Mars gravity alters subjects’ perceptual sensitivity to lower limb afferent inputs during upright stance. I will also test if changes in somatosensory perceptual sensitivity are associated with changes in balance and locomotion performance during adaptation to partial gravity.
2. KEY FINDINGS
We have acquired pilot data from 1 pilot participant who was run through the experimental group protocol. Subsensory insole vibration was applied while the pilot participant adapted their balance and locomotor control to simulated Martian gravity (simulated using a body weight support system), and also while readapting to Earth gravity (i.e., no body weight supported). These preliminary findings are discussed in the Main Findings section. Briefly, we see:
a) Transient impairments in standing balance when reintroduced to Earth gravity after adapting to simulated Mars gravity.
b) Changes in subjects' perceptual sensitivity to sensory stimulation applied to the lower limbs in simulated Mars gravity, and during readaptation to Earth gravity. The pilot subject showed increased sensitivity to somatosensory inputs during the simulated Martian gravity condition. Then, immediately after transitioning back to Earth gravity condition, we see transient reductions in sensitivity followed by gradual increases in sensitivity throughout readaptation.
c) Changes in multi-sensory weighting after adapting to each of the 3 different gravity conditions, with down weighting of both proprioceptive and vestibular inputs and upweighting visual inputs after adaptation to simulated Martian gravity.
3. IMPACT
Additional data from both the experimental and control groups are required to test the study hypotheses, but these preliminary data show promise of balance adaptation, somatosensory perception changes, and multisensory reweighting.
4. PROPOSED RESEARCH PLAN FOR THE COMING YEAR
Progress in year 1:
- I learned to use the body weight support system and inertial measurement units.
- I hired and trained a research assistant, and obtained IRB approval for the study.
- I selected, ordered, and purchased all required equipment and troubleshooting supplies.
- I troubleshooted SEP collections as noted above, and have adapted the study as noted above.
- Institutional Review Board (IRB) amendments are in progress.
- I have collected pilot data and have preliminary data analysis protocols set in place.
Plans for year 2:
- Data collection will begin in August 2022.
- Data collection is anticipated to take approximately 4 months for all 24 participants.
- Following data collection, data analyses will be performed over 2 months.
- Findings of this study will be presented as the 2023 NASA Human Research Program (HRP) Investigators’ Workshop (IWS) meeting, at the Society for Neural Control of Movement (NCM) meeting, and the International Society for Posture and Gait Research (ISPGR) meeting.
- Based on critical feedback from these meetings, I will begin to draft manuscripts for publication.
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