PT - JOURNAL ARTICLE AU - Nima Khalighinejad AU - Aaron Schurger AU - Andrea Desantis AU - Leor Zmigrod AU - Patrick Haggard TI - Human self-initiated action is reliably preceded by a process of noise reduction AID - 10.1101/120105 DP - 2017 Jan 01 TA - bioRxiv PG - 120105 4099 - http://biorxiv.org/content/early/2017/04/05/120105.short 4100 - http://biorxiv.org/content/early/2017/04/05/120105.full AB - A gradual buildup of electrical potential over motor areas precedes self-initiated movements. These “readiness potentials” (RPs) could simply reflect stochastic fluctuations in neural activity. We operationalised self-initiated actions as endogenous ‘skip’ responses while waiting for target stimuli in a perceptual decision task. Across-trial variability of EEG decreased more markedly prior to self-initiated compared to externally-triggered skip actions. This convergence towards a fixed pattern suggests a consistent preparatory process prior to self-initiated action. A leaky stochastic accumulator model could reproduce these features of the data, given the additional assumption of a decrease in noise level at the input to the accumulator prior to self-initiated, but not externally-triggered actions. The assumed reduction in neural noise was supported by analyses of both within-trial EEG variability and of spectral power. We suggest that a process of noise reduction is consistently recruited prior to self-initiated action. This precursor event may underlie the emergence of RP.