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Clarifying the nature of stochastic fluctuations and accumulation processes in spontaneous movements

Experiments on choice-predictive brain signals have played an important role in the debate on free will. In a seminal study, Benjamin Libet and colleagues found that a negative-going EEG signal, the readiness potential (RP), can be observed over motor-related brain regions even hundreds of ms before...

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Autores principales: Bogler, Carsten, Grujičić, Bojana, Haynes, John-Dylan
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Frontiers Media S.A. 2023
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10602783/
https://www.ncbi.nlm.nih.gov/pubmed/37901069
http://dx.doi.org/10.3389/fpsyg.2023.1271180
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author Bogler, Carsten
Grujičić, Bojana
Haynes, John-Dylan
author_facet Bogler, Carsten
Grujičić, Bojana
Haynes, John-Dylan
author_sort Bogler, Carsten
collection PubMed
description Experiments on choice-predictive brain signals have played an important role in the debate on free will. In a seminal study, Benjamin Libet and colleagues found that a negative-going EEG signal, the readiness potential (RP), can be observed over motor-related brain regions even hundreds of ms before the time of the conscious decision to move. If the early onset of the readiness potential is taken as an indicator of the “brain’s decision to move” this could mean that this decision is made early, by unconscious brain activity, rather than later, at the time when the subject believes to have decided. However, an alternative kind of interpretation, involving ongoing stochastic fluctuations, has recently been brought to light. This stochastic decision model (SDM) takes its inspiration from leaky accumulator models of perceptual decision making. It suggests that the RP originates from an accumulation of ongoing stochastic fluctuations. In this view, the decision happens only at a much later stage when an accumulated noisy signal (plus imperative) reaches a threshold. Here, we clarify a number of confusions regarding both the evidence for the stochastic decision model as well as the interpretation that it offers. We will explore several points that we feel are in need of clarification: (a) the empirical evidence for the role of stochastic fluctuations is so far only indirect; (b) the interpretation of animal studies is unclear; (c) a model that is deterministic during the accumulation stage can explain the data in a similar way; (d) the primary focus in the literature has been on the role of random fluctuations whereas the deterministic aspects of the model have been largely ignored; (e) contrary to the original interpretation, the deterministic component of the model is quantitatively the dominant input into the accumulator; and finally (f) there is confusion regarding the role of “imperative” in the SDM and its link to “evidence” in perceptual decision making. Our aim is not to rehabilitate the role of the RP in the free will debate. Rather we aim to address some confusions regarding the evidence for accumulators playing a role in these preparatory brain processes.
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spelling pubmed-106027832023-10-28 Clarifying the nature of stochastic fluctuations and accumulation processes in spontaneous movements Bogler, Carsten Grujičić, Bojana Haynes, John-Dylan Front Psychol Psychology Experiments on choice-predictive brain signals have played an important role in the debate on free will. In a seminal study, Benjamin Libet and colleagues found that a negative-going EEG signal, the readiness potential (RP), can be observed over motor-related brain regions even hundreds of ms before the time of the conscious decision to move. If the early onset of the readiness potential is taken as an indicator of the “brain’s decision to move” this could mean that this decision is made early, by unconscious brain activity, rather than later, at the time when the subject believes to have decided. However, an alternative kind of interpretation, involving ongoing stochastic fluctuations, has recently been brought to light. This stochastic decision model (SDM) takes its inspiration from leaky accumulator models of perceptual decision making. It suggests that the RP originates from an accumulation of ongoing stochastic fluctuations. In this view, the decision happens only at a much later stage when an accumulated noisy signal (plus imperative) reaches a threshold. Here, we clarify a number of confusions regarding both the evidence for the stochastic decision model as well as the interpretation that it offers. We will explore several points that we feel are in need of clarification: (a) the empirical evidence for the role of stochastic fluctuations is so far only indirect; (b) the interpretation of animal studies is unclear; (c) a model that is deterministic during the accumulation stage can explain the data in a similar way; (d) the primary focus in the literature has been on the role of random fluctuations whereas the deterministic aspects of the model have been largely ignored; (e) contrary to the original interpretation, the deterministic component of the model is quantitatively the dominant input into the accumulator; and finally (f) there is confusion regarding the role of “imperative” in the SDM and its link to “evidence” in perceptual decision making. Our aim is not to rehabilitate the role of the RP in the free will debate. Rather we aim to address some confusions regarding the evidence for accumulators playing a role in these preparatory brain processes. Frontiers Media S.A. 2023-10-12 /pmc/articles/PMC10602783/ /pubmed/37901069 http://dx.doi.org/10.3389/fpsyg.2023.1271180 Text en Copyright © 2023 Bogler, Grujičić and Haynes. https://creativecommons.org/licenses/by/4.0/This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
spellingShingle Psychology
Bogler, Carsten
Grujičić, Bojana
Haynes, John-Dylan
Clarifying the nature of stochastic fluctuations and accumulation processes in spontaneous movements
title Clarifying the nature of stochastic fluctuations and accumulation processes in spontaneous movements
title_full Clarifying the nature of stochastic fluctuations and accumulation processes in spontaneous movements
title_fullStr Clarifying the nature of stochastic fluctuations and accumulation processes in spontaneous movements
title_full_unstemmed Clarifying the nature of stochastic fluctuations and accumulation processes in spontaneous movements
title_short Clarifying the nature of stochastic fluctuations and accumulation processes in spontaneous movements
title_sort clarifying the nature of stochastic fluctuations and accumulation processes in spontaneous movements
topic Psychology
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10602783/
https://www.ncbi.nlm.nih.gov/pubmed/37901069
http://dx.doi.org/10.3389/fpsyg.2023.1271180
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