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sexta-feira, janeiro 08, 2016

The point of no return in vetoing self-initiated movements

Matthias Schultze-Kraft a,b,c,1,2, Daniel Birman a,d,1, Marco Rusconi a,d, Carsten Allefeld a,d, Kai Görgen a,d, Sven Dähne e, Benjamin Blankertz a,b,c, and John-Dylan Haynes a,c,d,f,g,h,2

aBernstein Center for Computational Neuroscience, Charité–Universitätsmedizin Berlin, 10117 Berlin, Germany;

bNeurotechnology Group, Technische Universität Berlin, 10587 Berlin, Germany;

cBernstein Focus: Neurotechnology, Technische Universität Berlin, 10587 Berlin, Germany;

dBerlin Center for Advanced Neuroimaging, Charité–Universitätsmedizin Berlin, 10117 Berlin, Germany;

eMachine Leaning Group, Technische Universität Berlin, 10587 Berlin, Germany;

fCluster of Excellence NeuroCure, Charité–Universitätsmedizin Berlin, 10117 Berlin, Germany;

gDepartment of Psychology, Humboldt Universität zu Berlin, 12489 Berlin, Germany;

hClinic of Neurology, Charité–Universitätsmedizin Berlin, 10117 Berlin, Germany

Edited by William T. Newsome, Stanford University, Stanford, CA, and approved November 4, 2015 (received for review July 10, 2015)


Many studies have shown that movements are preceded by early brain signals. There has been a debate as to whether subjects can still cancel a movement after onset of these early signals. We tested whether subjects can win a “duel” against a brain–computer interface designed to predict their movements in real time from observations of their EEG activity. Our findings suggest that subjects can exert a “veto” even after onset of this preparatory process. However, the veto has to occur before a point of no return is reached after which participants cannot avoid moving.


In humans, spontaneous movements are often preceded by early brain signals. One such signal is the readiness potential (RP) that gradually arises within the last second preceding a movement. An important question is whether people are able to cancel movements after the elicitation of such RPs, and if so until which point in time. Here, subjects played a game where they tried to press a button to earn points in a challenge with a brain–computer interface (BCI) that had been trained to detect their RPs in real time and to emit stop signals. Our data suggest that subjects can still veto a movement even after the onset of the RP. Cancellation of movements was possible if stop signals occurred earlier than 200 ms before movement onset, thus constituting a point of no return.

free choice readiness potential brain–computer interface point of no return veto


1M.S.-K. and D.B. contributed equally to this work.

2To whom correspondence may be addressed. Email: haynes{at}bccn-berlin.de or schultze-kraft{at}tu-berlin.de.

Author contributions: J.-D.H. conceived the study; M.S.-K., D.B., M.R., B.B., and J.-D.H. designed the experiment; M.S.-K. and D.B. performed research; M.S.-K., D.B., M.R., C.A., K.G., S.D., B.B., and J.-D.H. contributed new analytic tools; M.S.-K. and B.B. adapted the BBCI toolbox for this experiment; M.S.-K. and D.B. analyzed data; M.S.-K., D.B., and J.-D.H. wrote the paper; and M.R. and B.B. contributed to writing the paper.

The authors declare no conflict of interest.

This article is a PNAS Direct Submission.

Data deposition: EEG data have been deposited at bbci.de/supplementary/2015-PNAS-Veto.

This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1513569112/-/DCSupplemental.

Freely available online through the PNAS open access option.