The time course of attention shifts during the control of rapid balance reactions to perturbations of varied magnitude
This thesis addressed the time course and extent of attentional shifts associated with compensatory balancing reactions using a novel dual-task paradigm. Seated subjects performed a continuous visuomotor tracking task with the hand while the feet balanced an inverted pendulum. The pendulum was perturbed with varied magnitudes of perturbation, evoking balance reactions. It was hypothesized that (1) following a perturbation, a profound deviation in tracking would be observed, (2) the deviation would occur after the onset of the balance response, and (3) the extent of the tracking deviation would be dependent upon the magnitude of the perturbation. The hypotheses were supported. Discrete deviation in visuomotor tracking, typically a pause in tracking, followed the balance reaction. The duration of this pause was stimulus dependent. The findings reveal evidence of dynamic shifts in attention associated with distinct phases of compensatory balance control. The initial phase appears to be triggered automatically, whereas later phases involve varying degrees of attentional resources.