Causal computations of supplementary motor area on spatial impulsivity

Abstract

Spatial location of stimuli often leads to impulsive behaviour. How we overcome impulsive tendencies is what determines behaviour to be adaptive. Here, we used virtual reality to investigate whether spatial proximity of stimuli is causally related to the supplementary motor area (SMA) functions. In two experiments, we set out to investigate these processes using a virtual environment that recreates close and distant spaces to test the causal contributions of the SMA in spatial impulsivity. In an online first experiment (N = 93) we validated and measured the influence of distant stimuli using a go/no-go task with close (21 cm) or distant stimuli (360 cm). In experiment 2 (N = 28), we applied transcranial static magnetic stimulation (tSMS) over the SMA (double-blind, crossover, sham-controlled design) to test its computations in controlling impulsive tendencies towards close vs distant stimuli. Close stimuli elicited faster responses compared to distant stimuli but also exhibited higher error rates, specifically in commission errors (experiment 1). SMA stimulation (both real and sham) slowed response latencies (experiment 2), marked by increased decision thresholds in real stimulation compared to sham. Although exploratory, analysis on the effects of real stimulation showed a decrease in commission errors for close stimuli but not for distant stimuli (compared with the effect of sham stimulation). The findings suggest that impulsivity to nearby objects engages hastened actions accompanied by higher error rates. Our study provides a first starting point on the role of the SMA in regulating spatial impulsivity.