Motor training strengthens corticospinal suppression during movement preparation

Abstract

46Motor training improves the efficiency of trained movements and modifies neural activity 47 at rest and during motor execution. Training may also shape preparatory processes but the neural 48 correlates and the potential behavioral relevance of changes at the level of action preparation 49 remain unclear. In humans, transcranial magnetic stimulation (TMS) studies have shown that 50 movement preparation is accompanied by a suppression of corticospinal (CS) excitability relative 51 to a baseline measure; a phenomenon called preparatory suppression. Here, we trained participants 52 to initiate quick movements in an instructed-delay reaction time (RT) task and investigated resting 53 CS excitability as well as preparatory suppression over the practice blocks. We found that training 54 speeds up motor initiation, with no repercussion on error rates. Moreover, training increased 55 baseline CS excitability and deepened preparatory suppression. Importantly, training-related 56 changes in preparatory suppression were correlated to behavioral improvements: the subjects who 57 showed a stronger expansion of preparatory suppression were also those exhibiting larger gains in 58 RTs. Finally, in line with previous data, we observed a trial-by-trial relationship between the 59 amount of preparatory suppression and the subsequent RT: subjects responded faster on trials with 60 more preparatory suppression. Strikingly though, such a dependency of RTs on preparatory 61 suppression was tuned by the amount of training performed: while it was not evident early on, the 62 link emerged during the later practice blocks. Overall, our data indicate that training induces 63 changes in motor preparatory processes that are linked to an enhanced ability to initiate fast 64 movements. 65 66 67 3 Significance statement 68 69 Any movement is preceded by a period of preparation which involves significant changes 70 in the activity of the motor system, including a broad suppression of the corticospinal output 71 pathway, commonly referred to as preparatory suppression in human studies. Whether training can 72 alter such preparatory activity is unknown. Here, we show that motor training leads to a 73 strengthening of preparatory suppression in an instructed-delay reaction time (RT) task, and that 74 such change is related to a shortening of RTs. Moreover, at the single-trial level, we observed a 75 dependency of RTs on preparatory suppression which developed over training: the stronger the 76 preparatory suppression, the faster the RT. These results indicate that motor training can alter 77 motor preparatory activity in a behaviorally-relevant manner. 78 79 80 4 1. Introduction 81 82 Motor training generally improves the speed and/or accuracy at which movements are 83 selected, initiated and executed. A great deal of research has been devoted to unveiling the 84 functional changes at the basis of such improvements (Krakauer et al., 2019). At the neural level, 85 neuroimaging (e.g., Wiestler and Diedrichsen, 2013; Wenger et al., 2017; Yokoi and D...

Neurophysiological modulations in the (pre)motor-motor network underlying age-related increases in reaction time and the role of GABA levels – a bimodal TMS-MRS study

“…Interestingly, an age-related reduction in resting-state intra-cortical inhibition is suggested to predict a reduced capacity to modulate inhibitory processes during a motor task, which relates to motor function declines ( Heise et al, 2013 ). In our experiment, however, we did not probe baseline measures at complete rest, but at the start of each trial to control for the processes related to the task-driven increases in attention ( Kastner et al, 1999 ; Labruna et al, 2011 ; Vassiliadis et al, 2020 ). An interesting hypothesis for future research would be to investigate to what extent our observed relation between motor performance and (dis)inhibitory fronto-motor modulations are driven by the inhibitory state measured at baseline.…”

Selecting and Executing Actions for Rewards

“…An alternative explanation for the lack of effect of reward on RTs may arise, however, if one concedes that this measure not only reflects the speed of action selection but also the rapidity of sensory processing (Haith et al, 2016;Vassiliadis et al, 2020), and that reward could have affected these two processes in opposite ways. Indeed, the task described above puts a considerable demand on sensory processing, as it required participants to discriminate between four target locations and, in some trials, to avoid distractor cues.…”

Rise-to-threshold and dynamical systems views of proactive inhibition

“…This preparatory inhibition may reflect a form of volitional proactive inhibition that prevents premature release of the intended movement; alternatively, it may represent a necessary part of preparing to move. Given that the suppression occurs regardless of proactive inhibition (RDE), it is more likely that CSE suppression at the time of the go cue represents a necessary part of movement preparation (Vassiliadis et al, 2020).…”