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

Abstract

Humans and other animals are able to adjust their speed-accuracy tradeoff (SAT) at will depending on the urge to act, favoring either cautious or hasty decision policies in different contexts. An emerging view is that SAT regulation relies on influences exerting broad changes on the motor system, tuning its activity up globally when hastiness is at premium. The present study aimed to test this hypothesis. Fifty subjects performed a task involving choices between left and right index fingers, in which incorrect choices led either to a high or to a low penalty in two contexts, inciting them to emphasize either cautious or hasty policies. We applied transcranial magnetic stimulation on multiple motor representations, eliciting motor evoked potentials (MEP) in nine finger and leg muscles. MEP amplitudes allowed us to probe activity changes in the corresponding finger and leg representations, while subjects were deliberating about which index to choose. Our data indicate that hastiness entails a broad amplification of motor activity, though this amplification was limited to the chosen side. On top of this effect, we identified a local suppression of motor activity, surrounding the chosen index representation. Hence, a decision policy favoring speed over accuracy appears to rely on overlapping processes producing a broad (but not global) amplification and a surround suppression of motor activity. The latter effect may help increasing the signal-to-noise ratio of the chosen representation, as supported by single-trial correlation analyses indicating a stronger differentiation of activity changes in finger representations in the hasty context.

Movement characteristics impact decision-making and vice versa

“…causing a stronger recency effect. However, more research is needed on this matter, as two other studies reported no change in excitability of unchosen motor representations across urgency contexts (Derosiere et al, 2021;Spieser et al, 2018).…”

“…However, over the course of the past ten years or so, increased interest in the interaction between decisions and movements has generated findings which challenge the view that these processes operate independently. For instance, properties of decisions such as reward expectancy (Klein-Flügge & Bestmann, 2012;Shadmehr et al, 2019), choice preference (Calderon et al, 2018;de Lange et al, 2013;, conflict anticipation (Derosiere et al, 2018;Duque et al, 2016) and time pressure (Derosiere et al, 2021;Kelly et al, 2021;Murphy et al, 2016;Steinemann et al, 2018) systematically change activity in motor areas of the brain, and alter kinematics of movements expressing those decisions (Freeman, 2018;Shadmehr et al, 2019;Spieser et al, 2017;Thura, 2020).…”