Trajectory evolution and changes in the structure of movement amplitude time series.

Trajectory evolution and changes in the structure of movement amplitude time series.
Hum Mov Sci. 2020 Jun;71:102617
Authors: Slifkin AB, Eder JR
Abstract
With increases in the index of difficulty [ID = log2(2A/W)], the time-series structure of movement amplitude values shift from pink to white noise. The appearance of pink noise at low-ID levels may be attributed to the dominance of feedforward control processes, while the appearance of white noise at high-ID levels may be attributed to increased reliance on visuomotor feedback processes needed to guide movement into the target region. Such within-movement corrections may disrupt the pink-noise time-series correlations that exist in the absence of feedback processing. In our prior work, movement amplitude was defined as the distance moved from movement start until its end. In contrast, in the current study we examined the time-series structure of movement amplitude values at each of 10 different percentages of time into the movement trajectory-ranging between 10 and 100% of the movement time (%MT)-at a low (2 bits) and a high (5 bits) ID level. We hypothesized that at both ID levels a pink-noise time-series structure would be seen during the early portions of the movement trajectory when feedforward control should dominate, but during later portions of the trajectory, increased whitening of time-series structure would emerge only under ID 5 as there would be an increased need to ...

Source: Human Movement Science - May 27, 2020 Category: Neurology Authors: Slifkin AB, Eder JR Tags: Hum Mov Sci Source Type: research