Spontaneous EEG fluctuations determine the readiness potential: is preconscious brain activation a preparation process to move?

Abstract

It has been repeatedly shown that specific brain activity related to planning movement develops before the conscious intention to act. This empirical finding strongly challenges the notion of free will. Here, we demonstrate that in the Libet experiment, spontaneous fluctuations of the slow electro-cortical potentials (SCPs) account for a significant fraction of the readiness potential (RP). The individual potential shifts preceding self-initiated movements were classified as showing a negative or positive shift. The negative and positive potential shifts were analyzed in a self-initiated movement condition and in a no-movement condition. Comparing the potential shifts between both conditions, we observed no differences in the early part of the potential. This reveals that the apparently negative RP emerges through an unequal ratio of negative and positive potential shifts. These results suggest that ongoing negative shifts of the SCPs facilitate self-initiated movement but are not related to processes underlying preparation or decision to act.

An issue for Wegner’s theory about the conscious will: the Readiness Potential does not conclusively represent preparation for an action

“…Other experiments corroborate these findings (JO et al, 2013;SCHLEGEL et al, 2013;HERRMANN et al, 2008). For instance, Trevena and Miller (2010) developed a Libet style experiment in which participants heard a random tone after which they should decide to move or not to move (experiment 1).…”

“…Since the activity was observed before action, it became widely accepted that it represented preparation for the action, and Wegner seems to accept this conception. New evidence, however, suggests that the RP cannot be treated as preparation for the movement, and therefore does not reliably show that unconscious brain preparation to move precedes the ESA in the causal production of the action (SCHURGER et al, 2012;JO et al, 2013;SCHLEGEL et al, 2013;TREVENA;MILLER, 2010;HERRMANN et al, 2008).…”

Nowhere and Everywhere: The Causal Origin of Voluntary Action

“…In the short time since the stochastic decision model was first introduced (Schurger et al 2012), other studies have emerged providing evidence that ongoing stochastic variability might play a role in the choice of action (Bengson et al 2014) and might account for the shape of the readiness potential (Jo et al 2013). The model offers a parsimonious explanation of the mechanisms underlying 'when' a pre-specified action is initiated.…”

Noninvasive Electromagnetic Methods for Brain Monitoring: A Technical Review

“…EEG signal can be classified as two types depending on the generation of the bran signals such as Event related potentials (ERPs) [144] and Spontaneous or freerunning EEG [118].…”