Functional Balance and Goal-Directed Eye-Hand Coordination After Exogenous or Endogenous Visual-Vestibular Perturbation: Current Findings and Recommendations for Portable or Ambulatory Applications

Orientation and balance can be disrupted by a sensory integration or sensorimotor challenge of exogenous origin, including rhythmic alterations in G-force and direction that occur during turbulent flight or travel by sea, as well as a visual-vestibular-somatosensory rearrangement caused by exposure to a moving vehicle simulator or virtual environments. Balance can also be disrupted by an endogenous challenge associated with an inner-ear disease or a head injury affecting peripheral or central balance systems. We sought to determine whether operationally relevant psychomotor performance (a dynamic simulated shooting task) was sensitive to a functional balance challenge caused by the aftereffect of unusual vestibular stimulation or blast/concussion. Seventy healthy subjects and 30 mild traumatic brain injury (mTBI) patients were evaluated with a shooting simulator used for military training. They performed four new shooting tests designed to quantify marksmanship speed and accuracy during tasks similar to established clinical gait challenges. Our exploratory tasks were assessed for their sensitivity to a temporary exogenous challenge (the aftereffect of spinning healthy subjects in a rotating chair to simulate vestibular vertigo) and their sensitivity to imbalance associated with the lingering effect of mTBI. The task that was the most reliable and most sensitive to an exogenous balance challenge was kneeling while shooting at targets to the left and right of the frontal visual field. This test merits further development. We present recommendations for developing this test further and for making the large testing apparatus portable, robust, and capable of expanded quantification of shooting performance, rifle kinematics, and postural sway.