Dissecting online control in XXXX : a kinematic analysis of double-step reaching.

@entity1 @entity12541 @entity13074 @entity1957 @entity717
In a recent study, @entity1 with @entity717 (or @entity1957 - @entity13074 ) were shown to have difficulties making rapid online corrections when reaching, demonstrated by slower and less accurate movements to double-step targets (Hyde _ Wilson, 2011). These results suggest that @entity1 with @entity13074 have difficulty using predictive estimates of limb position when making rapid adjustments to movement, in-flight. However, chronometric data alone does not provide strong evidence for this hypothesis: it remains unclear whether early (and rapid) control parameters or post-correction stages of the movement trajectory are affected. Thus, the overarching aim of this study was to conduct a kinematic analysis of double-step reaching in order to isolate the different control parameters that might explain the slower and less accurate double-step reaching performance of @entity1 with @entity13074 . @entity1 were a new sample of 13 @entity1 with @entity13074 aged between 8-12 years and 13 age-matched controls. @entity1 were required to reach and touch one of three possible targets presented at the coordinates -20  , 0   and 20   on a 17 in. @entity12541 touch-screen. For most trials (80%) the target remained stationary for the duration of movement (non-jump trials), while for the remainder (20%), the target jumped randomly to one of two peripheral locations at movement onset (jump trials). Consistent with earlier work, @entity1 with @entity13074 were slower to initiate reaching compared to controls and showed longer MT and more errors on jump trials. Kinematic data showed that while the two groups did not differ on time to peak velocity or acceleration, @entity1 with @entity13074 were slower to correct reach trajectory on jump trials. No group differences were observed on late kinematic markers, e.g., post-correction time. The pattern of results support and extend earlier work showing deficits in ROC in @entity13074 . From a computational perspective, delayed corrections to the reach trajectory suggests some difficulty integrating information about the target perturbation with a predictive (or forward) estimate of limb position relative to the initial target. These conclusions are discussed, along with directions for future research.
