Fractionation of the visuomotor feedback response to directions of movement and perturbation

Abstract

Recent studies have highlighted the modulation and control of feedback gains as support for optimal feedback control. While many experiments contrast feedback gains across different environments, only a few have demonstrated the appropriate modulation of feedback gains from one movement to the next. Here we extend previous work by examining whether different visuomotor feedback gains can be learned for different directions of movement or perturbation directions in the same posture. To do this we measure visuomotor responses (involuntary motor responses to shifts in the visual feedback of the hand) during reaching movements. Previous work has demonstrated that these feedback responses can be modulated depending on the statistical distributions of the environment. Specifically, feedback gains were upregulated for task-relevant environments and downregulated for task-irrelevant environments. Using these two statistical distributions, the first experiment examined whether these feedback responses could be independently modulated for the same limb posture for two directions of movement (same limb posture but on either an inward or outward movement), while the second examined whether the feedback responses could modulate, within a single movement, to perturbations to the left or right of the reach. Both experiments demonstrated that visuomotor feedback responses could be learned independently such that the response was appropriate for the environment. This work demonstrates that feedback gains can be simultaneously tuned (upregulated and downregulated) depending on the state of the body and the environment. The results indicate the degree to which feedback responses can be fractionated in order to adapt to the world.

Error Detection Is Critical for Visual-Motor Corrections

“…The effect of the preceding jump on the reflex response was clear—the reflex response was down-regulated when the jump was further away, while it was up-regulated when the target was displaced toward the start-position. Similar results have been reported by Franklin and colleagues for “visuomotor” reflexes (Franklin, Franklin, & Wolpert, 2014). This indicates that the target displacement, within a short latency of 100 ms, induced direction-dependent modulation of spinal circuits suggesting that this is a somewhat ‘smart’ response, in that it is adapted to the direction of the visual perturbation, relative to the ongoing movement.…”

Visual Feedback Processing of the Limb Involves Two Distinct Phases

“…We then normalized each participant's muscle activity by the mean activity in an initial set of trials where the participant maintained their hand inside a target while resisting a Ϯ1 Nm elbow or shoulder mechanical load and then averaged across trials. For each participant we then binned the ⌬EMG into an early epoch 90 -120 ms and a late epoch 120 -180 ms coinciding with previous reports (Dimitriou et al, 2013;Franklin et al, 2014;Gu et al, 2016).…”

“…A jump of the cursor can generate muscle responses ϳ90 ms after the jump (Brenner and Smeets, 2003;Saunders and Knill, 2004;Franklin and Wolpert, 2008). Kinematic responses scale with the jump size (Veyrat-Masson et al, 2010;Franklin et al, 2016), however, scaling of the muscle response amplitude has only been observed when cursor errors occur frequently and are task relevant (Franklin et al, 2014). Furthermore, few studies have examined whether this muscle response is sensitive to behavioral contexts.…”

Time-to-Target Simplifies Optimal Control of Visuomotor Feedback Responses

“…From intercepting a basketball pass between opponents to catching a vase accidentally knocked off the shelf -visuomotor feedback responses play a familiar role in human motor behaviour. Previous research has extensively analysed these responses in human reaching movements (Day and Lyon (2000); Reichenbach et al (2014); de Brouwer et al (2017de Brouwer et al ( , 2018; Saunders and Knill (2003); Saunders (2004); Saunders and Knill (2005); Sarlegna et al (2003); Knill et al (2011)), and showed an interesting combination of task-dependent variability on the timescale of a single movement (Dimitriou et al (2013); Franklin et al (2014Franklin et al ( , 2017; Cross et al (2019)), as well as sub-voluntary feedback onset times (Prablanc and Martin (1992); Day and Lyon (2000); Franklin and Wolpert (2008); Zhang et al (2018); Oostwoud Wijdenes et al…”