External Focus of Attention Influences Cortical Activity Associated With Single Limb Balance Performance.

Abstract

External focus (EF) of attention leads to improved balance performance. Consideration of the neuromodulatory effects of EF may inform its clinical utility in addressing neuroplastic impairments after musculoskeletal injuries. This study aimed to determine whether electrocortical activity and balance performance changed with attentional foci that prioritized differing sensory feedback and whether changes in electrocortical activity and balance were associated. Individuals who were healthy (n = 15) performed a single-limb balance task under 3 conditions: internal focus (IF), somatosensory focus (EF with a baton [EF-baton]), and visual focus (EF with a laser [EF-laser]). Electrocortical activity and postural sway were recorded concurrently using electroencephalography and a triaxial force plate. Electroencephalographic signals were decomposed, localized, and clustered to generate power spectral density in θ and α-2 frequency bands. Postural sway signals were analyzed with center-of-pressure sway metrics (eg, area, distance, velocity) and knee angle. The relationship between percent change in clustered brain activity and task performance metrics was assessed. Both EF conditions resulted in increased cortical activity and improved balance performance compared with IF. EF-laser had the largest effect, demonstrating increased frontal θ power (d = 0.64), decreased central θ power (d = -0.30), and decreased bilateral motor, bilateral parietal, and occipital α-2 power (d = -1.38 to -4.27) as well as a shorter path distance (d = -0.94) and a deeper (d=0.70) and less variable (d = -1.15) knee angle than IF. Weak to moderate associations exist between increases in cortical activity and improved balance performance (ρ = 0.405-0.584). EF resulted in increased cortical activity associated with cognitive, motor, somatosensory, and visual processing. EF-laser, which prioritized visual feedback, had the largest and broadest effects. Changes in cortical activity resulting from EF were independently associated with improved balance performance. This study demonstrates that goal-oriented attention results in functional increases in brain activity compared with internally directed self-focus. These results suggest EF may target neurophysiologic impairments and improve balance in clinical populations.