Artificial gravity results in changes in frontal lobe activity measured by EEG tomography

Mental and perceptual motor performance has been reported to be impaired during hypergravity. Current research has focused on physiological explanations (e.g., deficient proprioceptive feedback) and neglected psycho-physiological effects (e.g., arousal, emotion, cognitive engagement). This study aims at localising changes in brain cortical activity by using a distributed source localisation algorithm (sLORETA) to model the probable neural generators of changes in scalp voltage under hypergravity conditions. Brain cortical activity was measured by EEG before, during and after exposure to three time terrestrial gravity (3G(z)) on ten naive subjects aged 29+/-5 years. Changes in EEG activity were localised using standardised low resolution brain electromagnetic tomography (sLORETA) for alpha-1 [7.5-10 Hz], alpha-2 [10-12.5 Hz], beta-1 [12.5-18 Hz], beta-2 [18-35 Hz] and gamma [35-45 Hz] activities. Individual concentrations of blood cortisol and perceived psychological strain were related to changes in cortical current density. An increase in alpha-1 activity occurred in the right inferior frontal lobe, beta-1 activity was found to be increased in the limbic lobe during 3G(z). Post acceleration alpha-2 and beta-1 activities declined in frontal, temporal and limbic lobes. Changes in blood cortisol concentrations and perceived strain showed a clear relationship to changes in right sided frontal alpha-1 activity. We conclude that frontal activity during hypergravity may serve as a marker of anxiety. This puts a new light on the debate as to whether cognitive and sensorimotor impairments are attributable to primary physiological effects or secondary psychological effects of a hypergravity environment.