Do you feel my vibe? Quantifying iterative visuo-motor feedback-loops in the jerk profiles of manual aiming movements using frequency analyses

Abstract

Contemporary models of visuo-motor control posit that the use of visual information during voluntary movement is likely an iterative process. Stemming from this assumption, it was hypothesized that iterative changes in the kinematics of movements should be present, and visual-motor feedback processing times should be measurable using frequency analysis (Fast Fourier Transform, FFT). To test this hypothesis, we evaluated reaching movements of 10, 20, and 30 cm amplitudes performed with and without visual feedback (V & NV, respectively). Trajectories in both the primary and secondary movement axes were differentiated to attain jerk profiles using a 2-point central difference algorithm and filtered with a 20 Hz low-pass filter at each stage. The power spectral density (PSD) functions were estimated for each trajectory using FFT. Differences between V and NV were quantified in decibels (DB: NV as reference signal) and analyzed across the 7.8–13.7 Hz range (iteration times: 73-128 ms). No significant DB differences were found for the primary movement axis. Conversely, the secondary movement axis showed an increase in the DB of the 11.71 Hz bin relative to the 7.8 and 9.7 Hz bins. This indicated that in the presence of vision, there is greater power in the 11.71 Hz oscillation bin. Therefore, although frequency analysis failed to distinguish between visual conditions in the primary axis, visual control in the secondary axis may occur at a rate of approximately 11.71 Hz (i.e., 85 ms iteration times).

Acknowledgments: Canada Foundation for Innovation; Natural Sciences and Engineering Research Council of Canada