Stimulating stopping? Investigating the effects of tDCS over the inferior frontal gyri and visual cortices

Abstract

The ability to cancel an already initiated response is central to flexible behavior. While several different behavioral and neural markers have been suggested to quantify the latency of the stopping process, it remains unclear if they quantify the stopping process itself, or other supporting mechanisms such as visual and/or attentional processing. The present study sought to investigate the contributions of inhibitory and sensory processes to stopping latency markers by combining transcranial direct current stimulation (tDCS), electroencephalography (EEG) and electromyography (EMG) recordings in a within-subject design. Active and sham tDCS were applied over the inferior frontal gyri (IFG) and visual cortices (VC), combined with both online and offline EEG and EMG recordings. We found evidence that neither of the active tDCS condition affected stopping latencies relative to sham stimulation. Our results challenge previous findings suggesting that anodal tDCS over the IFG can reduce stopping latency and demonstrates the necessity of adequate control conditions in tDCS research.Additionally, while the different putative markers of stopping latency showed generally positive correlations with each other, they also showed substantial variation in the estimated latency of inhibition, making it unlikely that they all capture the same construct exclusively.

Temporal cascade of frontal, motor and muscle processes underlying human action-stopping

“…While, one interpretation of this partial EMG activity is that it merely reflects 'weak' Go activation that did not run to completion (De Jong et al, 1990), several lines of evidence strongly suggest it is a muscle manifestation of the stopped response. First, CancelTime was positively correlated with SSRT Beh , similar to recent studies (Huster et al, 2019;Thunberg et al, 2019). Second, the variability of CancelTime was positively correlated with the variability of SSRT estimated from the BEESTS modeling framework.…”

“…Our results have several important implications. First, whereas several earlier studies of action-stopping recorded partial EMG for various purposes (De Jong et al, 1990;Mcgarry et al, 2000;McGarry and Franks, 1997), some more recent ones specifically interpreted the time of the partial EMG as related to stopping (Huster et al, 2019;Nguyen et al, 2019;Raud et al, 2019;Raud and Huster, 2017;Thunberg et al, 2019). Our results strongly affirm that partial EMG can be used to estimate the latency of stopping reflected in the muscle.…”