A TMS study of preparatory suppression in binge drinkers

Abstract

Highlights Normally, action preparation involves a global suppression of motor activity. Such preparatory suppression is deficient in alcohol-dependent patients. Binge drinking may represent a first step toward alcohol-use disorder. Here, we tested whether binge drinkers also display altered preparatory suppression. Our results indicate abnormally high motor preparatory activity in binge drinkers.

Augmented tendency to act and altered impulse control in alcohol use disorders

“…By contrast, because a higher excitatory drive was observed both in HDs and SAUDs, a greater tendency to act might represent a common feature of hazardous drinking. Interestingly, young binge-drinkers, who are also characterized by unhealthy drinking habits ( Lannoy et al, 2019 ), present a pattern of MEP changes remarkably similar to the one reported in HDs ( Grandjean and Duque, 2020 ). As such, they have been found to show a drastically weaker MEP suppression when probed in selected effectors, despite a normal suppression in task-irrelevant muscles ( Grandjean and Duque, 2020 ).…”

“…Hence, while the lack of MEP suppression in SAUDs was initially interpreted as reflecting a lack of inhibitory influences, an alternative explanation might be that the tendency to act was abnormally high in these subjects, causing an excessive excitatory drive in potential responders that was captured in our MEP measures ( Nardone et al, 2019 ). This hypothesis is supported by the recent observation that binge drinkers exhibit similar MEP suppression as healthy controls when probed in task-irrelevant muscles; the abnormality there only involved a weaker MEP suppression in the selected effector, which may thus reflect an abnormally strong tendency to act rather than deficient inhibition ( Grandjean and Duque, 2020 ).…”

“…Note that because finger representations have a large degree of overlap in M1 ( Schieber, 2001 ), TMS pulses applied over the FDI hotspot can also elicit reliable MEPs in other finger muscles. So here, we also recorded MEPs in the abductor pollicis brevis (APB) of both hands, as successfully done in past studies ( Grandjean and Duque, 2020 , Márquez et al, 2018 ). This allowed us to obtain measures of corticospinal excitability in both a task-relevant muscle (FDI, index finder abductor) and a task-irrelevant muscle (APB, thumb abductor).…”

“…Additionally, to assess the presence of preparatory changes in corticospinal excitability in each condition, one-sample t-tests (Bonferroni-corrected) were used to compare these percentage values to a constant value of 100 (i.e., to TMS BASELINE-IN ). Finally, to specifically address our hypotheses regarding the strength of excitatory and inhibitory influences across the three groups, we performed two separate ANOVAs (uncorrected) on MEPs at TMS DELAY in the selected FDI, which best capture the excitatory drive associated with the tendency to act (1), and on MEPs in the APB of the non-selected hand, which best capture the inhibitory drive related to impulse control (2) ( Grandjean and Duque, 2020 , Quoilin et al, 2016 ). Those data were analyzed using BLOCK (1, 2, 3) and MEP-SIDE (MEP ND, MEP D ) as within-subject factors and GROUP (HCs, HDs, SAUDs) as the between-subject factor.…”

Hasty sensorimotor decisions rely on an overlap of broad and selective changes in motor activity

“…Importantly, MEPs in these three muscles were obtained by stimulating a single spot. This hotspot was found for each M1 at the beginning of every single session in each subject; it corresponded to the hotspot of the ADM 107 , which usually provides the most consistent MEPs when these three muscles are considered together (see Figure S1.A). Further, eliciting concurrent MEPs in both hands allowed us to capture excitability changes on the two sides of the motor system at once (in each trial), thus concerning finger representations that are both on the side of the chosen index and on the side of the unchosen finger (e.g., right and left MEPs, respectively, preceding a right index finger choice).…”