The dual role of vision in sequential aiming movements

Common vs. independent limb control in sequential vertical aiming: The cost of potential errors during extensions and reversals

“…For Experiment 1, we observed significant negative between-component correlations for displacement at kinematic landmarks suggesting individuals updated the limb position in the second component based on errors attained in the first component. This is consistent with the interpretation given to previous findings of increased negative relations when presented with vision compared to no vision, thus indicating the greater use of online sensory feedback (Khan et al, 2011). However, here we go one step further by attributing these feedback-based control procedures to the mid-late kinematic landmarks of the first and second components, which become more negatively related as the movement components unfold.…”

“…The use of these z-scores was intended to explore the extent to which participants used online sensory feedback acquired within the first movement component to subsequently update the movement executed in the second component. Typically, strong negative correlations are synonymous with an enhanced use of online sensory feedback, whilst weak, or positive correlations, reflect feedforward limb-control (see Khan, Sarteep, Mottram, Lawrence, & Adam, 2011). For example, if the limb is moved with a higher magnitude of peak acceleration and peak velocity, and thus travels further than the target in the first component, an adjustment should be made to reduce the displacement of the second component in order to reach the second target.…”

The integration of sequential aiming movements: Switching hand and direction at the first target

“…Instead, along the lines of the movement integration hypothesis, it appears that the implementation of the second segment during the execution of first leads to interference and hence the lengthening of movement times. Khan et al ( , 2011 have suggested that in order to ensure an efficient transition between segments, visual feedback is regulated during the first segment in order to time the implementation of the second segment. It is the central processes associated with the timing of the second segment that leads to interference and the one target movement time advantage (also see Ketelaars, Khan, & Franks, 1999).…”

“…That is, in the single hand tasks participants adopt central control strategies that involve both the implementation of the pre-programmed motor commands of movement two (i.e., the movement integration hypothesis) together with applying online control mechanisms to ensure accurate endpoint locations of movement one (i.e., the movement constraint hypothesis) (Khan et al, 2011). The reduced PTs of the two target two hand movements relative to the two target single hand movements, might therefore be due to the removal of the processes associated with constraining the endpoint of the first movement.…”

“…Understanding the factors that influence the nature of the interdependency between segments has been of considerable interest to researchers (Adam et al, 2000;Cullen et al, 2001;Khan, Mottram, Adam, & Buckolz, 2010;Khan, Sarteep, Mottram, Lawrence, & Adam, 2011;Lavrysen, Helsen, Elliott, & Adam, 2002;Lavrysen et al, 2003;Lawrence, Reilly, Khan, Mottram, & Elliott, 2013;Mottram, Khan, Lawrence, Adam, & Buckolz, 2014). The aim of the present study was to differentiate between the processes underlying the integration between movement segments at central cognitive and peripheral neuromuscular levels by examining the interactive effects of switching hands and movement direction at the first target.…”