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Research Article

The Influence of Body Position on Regional Brain Activation

S.J. Petruzzello, E.E. Hall, & P. Ekkekakis, University of Illinois, Urbana, IL 61801

Psychophysiology has become an important avenue for understanding various affective and cognitive phenomena within the exercise sciences. In particular, the use of EEG as a measure of brain activation has seen increasing use in recent years. Numerous discrepancies exist in the literature regarding outcomes from studies using different measurement protocols, but the extent to which certain factors might influence these outcomes is not known. It has been shown that body positions ranging from -12° head-down tilt to 45° head-up tilt result in a fairly linear decrease in EEG spectral power. The purpose of this study was to examine what the effect of different upright postures would be on EEG spectral power (4-20 Hz). Four, 60-s epochs of EEG were collected from 6 sites (F3, F4, C3, C4, P3, P4; referenced to linked ears) in 15 subjects. Subjects were placed in 3 different body positions (all head-up; 45° seated, 90° seated, standing). Repeated measures ANOVAs revealed that across EEG sites, there was a significant increase (Ps<0.015) in spectral power (8-20 Hz) as subjects went from a seated position to a standing position, with no differences between the two seated positions. Trends in the same direction occurred for slower frequencies (4-7 Hz). Coupled with previous data, it appears that there is a U-shaped relationship between body position and EEG spectral power, such that from head-down tilt to upright sitting, there is a fairly linear decrease in spectral power. As body position goes from upright sitting to standing, spectral power shows a significant increase, particularly in the frequency range from 8-20 Hz. The cause of this increase is unknown, but may be linked with loading of baroreceptors. Such a finding is important for exercise scientists using EEG techniques to examine relevant affective and cognitive variables.

Supported by NIMH RO3 MH55513-01.