Macroscopic Model of Hypogravity-Induced Primate Brain Activity via Identification and Analysis of a Neurovisuomotor Performance Pathway

Abstract

Abstract During long-duration spaceflight, astronauts will experience gravity-transitions (G-transitions) between Earth-gravity (1G) and hypogravity (gravity < 1G), as well as prolonged time in hypogravity environments (i.e., interplanar, the Moon and Mars). The neural substrate underlying coordinated, volitional visuomotor movements like reach-to-grasp is tuned to produce proper movement in 1G. During G-transitions and hypogravity, the brain’s visuomotor control network becomes inadvertently configured through its activity states and interconnections to produce erroneous movements. Thus, the need to identify the brain performance pathways underlying mission-critical behaviors like performing visuomotor tasks and understanding their neurophysiological responses during space travel is critical for astronauts’ safety and mission success. This work utilizes a whole-brain, primate connectome to identify a visuomotor subnetwork, using a novel modularity algorithm. The identified visuomotor subnetwork is analyzed using local graph theory measures, suggesting the parietal cortex intraparietal sulcus (PCIP), superior parietal cortex (PCS), and secondary visual cortex (V2) are structurally positioned to play an important role in network activity and function. 1G macroscopic neural network, neural ensemble models are developed and subjected to emulated hypogravity, analyzed using an unsupervised machine learning technique to cluster simulations into hypogravity-affected and -unaffected groups. Qualitative analyses of region-wise frequency distributions and means between groups suggest the cingulate cortex (CCP), PCS, ventrolateral pre-motor cortex (PMCVL), primary visual cortex (V1), and V2 are hypogravity-affected, producing non-normal neural activity in frequency space. Synthesizing the structural and modeling results, this work suggests PCS and V2 may be viable countermeasure targets, ensuring proper visuomotor performance during and after spaceflight.