Cerebral cortex plasticity after 90 days of bed rest: data from TMS and fMRI

Aviat Space Environ Med. 2010 Jan;81(1):30-40. doi: 10.3357/asem.2532.2009.

Abstract

Introduction: Microgravity animal models have demonstrated corticospinal plasticity; however, little is understood of its functional significance. In this pilot study, we explored corticospinal plasticity in a bed rest model. We hypothesized that the lack of weight bearing would induce cortical reorganization correlating with performance.

Methods: Four subjects underwent functional MRI (fMRI), transcranial magnetic stimulation (TMS), and functional mobility testing (FMT) before and after 90 d of bed rest. Recruitment curves (RC) were created by measuring motor evoked potentials over a range of TMS intensities with changes in the slope of the RC reflecting changes in corticospinal excitability.

Results: Significant leg RC slope decreases were observed on post-bed rest day 1 (P1) (t(2805) = -4.14, P < 0.0001), P2 (t(2805) = -6.59, P < 0.0001), P3 (t(2805) = -6.15, P < 0.0001), P5 (t(2805) = -7.93, P <0.0001), P8 (t(2805) = -3.30, P = 0.001), and P12 (t(2805)= -3.33, P = 0.0009), suggesting a group decrease in corticospinal excitability in the immediate post-bed rest period with recovery approaching baseline over the following 2 wk. Significant effects were observed for hand RC slopes only for P2 (t(2916) = 1.97, P = 0.049), P3 (t(2916) = -2.12, P = 0.034), and P12 (t(2916) = -2.19, P = 0.029); no significant effects were observed for days P0 (t(2916) = -1.32, ns), P1 (t(2916) = 1.00, ns), P5 (t(2916) = -0.21, ns), or P8 (t(2916) = -0.27, ns). fMRI showed no change in activation for the hand but an increase in activation post-bed rest for the leg. On an individual basis, a more heterogeneous response was found which showed a potential association with performance on FMT.

Discussion: Results of this research include a better understanding of the cortical plasticity associated with leg disuse and may lead to applications in patient and astronaut rehabilitation.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Action Potentials
  • Adaptation, Physiological*
  • Adult
  • Bed Rest / adverse effects*
  • Cerebral Cortex / physiology*
  • Evoked Potentials, Motor
  • Female
  • Humans
  • Leg / physiology*
  • Magnetic Resonance Imaging / instrumentation
  • Male
  • Models, Statistical
  • Neuronal Plasticity*
  • Pilot Projects
  • Time Factors
  • Transcranial Magnetic Stimulation / instrumentation