Visual load and variability of muscle activation: Effects on reactive driving of older adults

The functional significance of the increase in motor output variability with increased visual information processing in older adults remains unclear. Here, we test the hypothesis that increased visual information processing increases muscle activation variability in older adults and impairs their ability to react as fast and as precisely as young adults during a simulated reactive driving task.

Fourteen young and sixteen older adults performed a reactive driving simulation task that required responding to unexpected brake lights of the car ahead during a simple reaction time task (low visual information processing condition) and a choice reaction time task with "no go" trials condition (high visual information processing condition). We quantified the following: 1) reactive driving performance - combination of premotor response time, motor response time, and brake force error; 2) motor output variability - brake impulse variability; 3) muscle activation variability - variability in the tibialis anterior (TA) muscle activity.

The increase in information processing exacerbated the impaired reactive driving performance in older adults. The best predictor of this impairment was the increase in brake force error. The impaired reactive driving performance was related to brake impulse variability and variability in the TA activity.

This study provides novel evidence that increased information processing increases muscle activation variability in older adults with detrimental consequences to their ability to perform a simulated reactive driving task.