Effect of Action Selection Demands on the Execution of Goal-Directed Reaches

A well-studied model of cognitive motor function is the process of action selection. It is unclear how the planning demands of a reaching movement interact with the added complexity of s election. Therefore, this thesis investigated the effect of adding selection demands to the performance of skilled reaches in a virtual environment. Thirty young, healthy participants reached ipsilaterally or contralaterally with either their dominant (right hand) or non-dominant (left hand) under two conditions: execute only (EO) and action selection (AS). Selection accuracy was higher for the EO condition than the AS condition for both arms and both directions (left arm: ipsilateral reaches Z = -3.420, p \u3c 0.001, contralateral reaches Z = -2.695, p = 0.007; right arm: ipsilateral reaches Z = -3.123, p = 0.002, contralateral reaches Z = -3.301, p \u3c 0.001). Reaction times for the AS condition were significantly longer than for the EO condition (p \u3c 0.001, η2 = 0.931). The primary measures of reach performance, movement time and endpoint error, did not differ between the EO and AS conditions. However, peak velocity and peak acceleration, measures of movement speed, were lower for AS compared to EO (p \u3c 0.001, η2 \u3e 0.364). In summary, we did not find that the AS condition affected primary reach performance variables significantly but did affect secondary variables (movement speed). These findings can inform therapists on the use of selection tasks to improve the reach performance in aging and stroke populations