A rapid visuomotor response on the human upper limb is selectively influenced by implicit motor learning

Abstract

How do humans learn to adapt their motor actions to achieve task success? Recent behavioral and patient studies have challenged the classic notion that motor learning arises solely from the errors produced during a task, suggesting instead that explicit cognitive strategies can act in concert with the implicit, error-based, motor learning component. In this study, we show that the earliest wave of directionally tuned neuromuscular activity that begins within ~100 ms of peripheral visual stimulus onset is selectively influenced by the implicit component of motor learning. In contrast, the voluntary neuromuscular activity associated with reach initiation, which evolves ~100–200 ms later, is influenced by both the implicit and explicit components of motor learning. The selective influence of the implicit, but not explicit, component of motor learning on the directional tuning of the earliest cascade of neuromuscular activity supports the notion that these components of motor learning can differentially influence descending motor pathways. NEW & NOTEWORTHY Motor learning can be driven both by an implicit error-based component and an explicit strategic component, but the influence of these components on the descending pathways that contribute to motor control is unknown. In this study, we show that the implicit component selectively influences a reflexive circuit that rapidly generates a visuomotor response on the human upper limb. Our results show that the substrates mediating implicit and explicit motor learning exert distinct influences on descending motor pathways.

Implicit motor learning within three trials

“…In addition, participants who perform no-cursor reaches with minimal instruction or more detailed instruction (to ensure strategy wasn’t used) show similar rates and extents of learning of reach aftereffects (see OSF; https://osf.io/9db8v/ ), which is in line with some previous findings 24 , 36 . If no-cursor reach deviations reflect implicit changes in state estimation, these arise much quicker than previously thought bolstering recent claims that the earliest wave of muscle activity during adaptation is influenced by implicit motor learning 37 .…”

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

“…Moreover, the fact that both stretch reflex and visuomotor feedback systems exhibit similar control policies despite different sensory inputs, perhaps only sharing the final output pathway, suggests that this simple feedback pathway may be an evolutionary old system. Indeed, several studies have suggested that visuomotor feedback is controlled via a pathway through the colliculus (Reynolds and Day (2012); Gu et al (2018); Corneil et al (2004)). Furthermore, it has been suggested that visuomotor feedback responses involve two different phases that are behaviourally different Cross et al (2019).…”

Towards a unified neural mechanism for reactive adaptive behaviour

“…Following the first description in non-human primates, a number of studies have reported the existence of SLRs in humans (12,(21)(22)(23)(24). Such studies have mostly adopted arm reaching tasks, often performed in the presence of a constant force field opposing the reach direction (25), given that a sustained background EMG activity appears to enhance the detectability of SLR (21).…”