Biology subjects

Smeets, J. B. J.

Publications and source records attributed to Smeets, J. B. J..

3 recordsLinked to original sources

bioRxiv2026

Motor effort biases perceptual decisions through later-stage evidence accumulation rather than early sensory-attentional processing

Motor effort has been shown to bias perceptual decisions toward less effortful choices, but it remains unknown whether this bias already takes effect during the early stages of decision formation through preparatory attentional allocation or sensory processing, or during later-stage evidence accumulation preceding response execution. This study investigated when motor effort becomes integrated into decision formation by focusing on the temporal evolution of neural processing during perceptual decision-making. While 64-channel EEG was recorded, twenty-four healthy adults performed an orientation discrimination task in which two Gabor patches appeared simultaneously in the left and right visual hemifield and decisions were reported using two pressure-sensitive response buttons requiring different levels of force. We found that motor effort modulated EEG activity at both the preparatory and later decision stages: pre-stimulus alpha power was reduced over the occipito-parietal cortex contralateral to the low-effort option, and mean centro-parietal positivity (CPP) amplitude preceding response execution was greater over centro-parietal cortex for low-effort choices, while leaving early sensory representations intact as indicated by no differences in P1 or N1 amplitude following stimulus onset. Trial-by-trial CPP amplitude preceding response execution increased with the likelihood of selecting the low-effort option, whereas the pre-stimulus alpha modulation was not associated with behavioral decision bias. These findings suggest that motor effort biases perceptual decisions primarily during later-stage evidence accumulation, thereby providing insight into the neural basis of embodied perceptual decision making.

neuroscience↗

bioRxiv2025

How Prior Motor States Can Shape Perceptual Decision Bias: Insights from Sensorimotor Beta Oscillations

Emerging evidence suggests that decision making is not a purely cognitive process preceding motor output but rather an embodied phenomenon in which the sensorimotor system actively shapes choice selection. Beta oscillations (13-30 Hz) over left and right sensorimotor cortex have been shown to encode motor action and exert inhibitory influence through lateralization of the post-movement rebound, biasing subsequent decisions toward responses with the other hand. This study investigated whether sensorimotor beta oscillations elicited by an isolated choice-unrelated motor action could influence a subsequent perceptual decision. Twenty-nine healthy adults (25 right-handed) completed a two-stage task while 64-channel EEG was recorded. In each trial, participants executed an initial button press with either the left or right thumb to a letter cue ("L" or "R") followed by, after a variable delay (0.5, 1.2 or 3 s), a briefly presented visual grating requiring a decision response on the orientation of the grating via a second button press. We computed the degree of beta power lateralization between left and right (pre-) motor cortical sources that was present during presentation of the grating stimulus and quantified choice bias as the threshold difference between psychometric curves fitted to left-versus right-initial response trials. Participants with stronger beta lateralization during stimulus presentation showed a greater tendency to alternate their decision response from the hand used for the initial button press and exhibited slower decision speeds. However, we failed to detect a significant group-level decision bias induced by the initial motor action, nor were there consistent within-subject correlations between decision bias and beta lateralization across delays. Following the perspective of embodied-decision making, our results partially support the influence of motor cortex activity on the choice process, while also suggesting that beta activity may serve as a trait-like index of individual susceptibility to decision bias.

neuroscience↗

bioRxiv2019

Quantifying exploration in reward-based motor learning

Exploration in reward-based motor learning is observable in experimental data as increased variability. In order to quantify exploration, we compare three methods for estimating other sources of variability: sensorimotor noise. We use a task in which participants could receive stochastic binary reward feedback following a target-directed weight shift. Participants first performed 6 baseline blocks without feedback, and next twenty blocks alternating with and without feedback. Variability was assessed based on trial-to-trial changes in movement endpoint. We estimated sensorimotor noise by the median squared trial-to-trial change in movement endpoint for trials in which no exploration is expected. We identified three types of such trials: trials in baseline blocks, trials in the blocks without feedback, and rewarded trials in the blocks with feedback. We estimated exploration by the median squared trial-to-trial change following non-rewarded trials minus sensorimotor noise. As expected, variability was larger following non-rewarded trials than following rewarded trials. This indicates that our reward-based weight-shifting task successfully induced exploration. Most importantly, our three estimates of sensorimotor noise differed: the estimate based on rewarded trials was significantly lower than the estimates based on the two types of trials without feedback. Consequently, the estimates of exploration also differed. We conclude that the quantification of exploration depends critically on the type of trials used to estimate sensorimotor noise. We recommend the use of variability following rewarded trials.

neuroscience↗