Reduced readiness potential and post-movement beta synchronization reflect self-disorders in early course schizophrenia

Disturbances of conscious awareness, or self-disorders, are a defining feature of schizophrenia. These include symptoms such as delusions of control, i.e. the belief that one’s actions are controlled by an external agent. Models of self-disorders point at altered neural mechanisms of source monitoring, i.e. the ability of the brain to discriminate self-generated stimuli from those driven by the environment. However, evidence supporting this putative relationship is currently lacking. We performed electroencephalography (EEG) during self-paced, brisk right fist closures in ten (M = 9; F = 1) patients with Early-Course Schizophrenia (ECSCZ) and age and gender-matched healthy volunteers. We measured the Readiness Potential (RP), i.e. an EEG feature preceding self-generated movements, and movement-related EEG spectral changes. Self-disorders in ECSCZ were assessed with the Examination of Anomalous Self-Experience (EASE). Patients showed a markedly reduced RP and altered post-movement Event-Related Synchronization (ERS) in the beta frequency band (14–24 Hz) compared to healthy controls. Importantly, smaller RP and weaker ERS were associated with higher EASE scores in ECSCZ. Our data suggest that disturbances of neural correlates preceding and following self-initiated movements may reflect the severity of self-disorders in patients suffering from ECSCZ. These findings point towards deficits in basic mechanisms of sensorimotor integration as a substrate for self-disorders.

Readiness Potential Prevalence During A Deliberate Decision-making Task

This study investigated the hypothesis that neural markers associated with arbitrary decision-making are present in higher order, deliberate decisions. Furthermore, the study aimed to investigate the effect of higher order decision content on neurophysiological markers such as the readiness potential and the P300 potential. An experiment was designed to measure, evaluate, and compare these electroencephalographic potentials under both arbitrary and deliberate choice conditions. Participants were presented with legal cases and had to convict and acquit criminal offenders. Distinct readiness potentials and P300 potentials were observed for both arbitrary and deliberate decisions across all participants. These findings support the hypothesis that the readiness potential and the P300 potential are present in the neurophysiological data for higher order deliberate decisions. The study also showed initial findings of how the readiness potential may inherently relate to decision content. Increased readiness potential amplitudes were observed for participants with previous exposure to violent crime when they had to acquit or convict criminals accused of violent crimes.

Nós temos livre-arbítrio?

Adotei uma abordagem experimental para essa questão. Atos de vontade livre são precedidos por uma mudança elétrica específica no cérebro (readiness potential, RP)3, que inicia 550 milissegundos antes do ato. As pessoas tomaram consciência da intenção de agir 350-400 milissegundos depois do início do RP e 200 milissegundos antes do ato motor. O processo volitivo é, portanto, iniciado inconscientemente. Mas a função consciente ainda poderia controlar o resultado; pode vetar o ato. O livre-arbítrio não é, portanto, excluído. Essas descobertas impõem restrições às visões de como o livre-arbítrio pode operar; não faria iniciar um ato voluntário, mas poderia controlar a realização. As descobertas também afetam perspectivas de culpa e responsabilidade.

Confusions regarding stochastic fluctuations and accumulators 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 already a few hundred ms before a participant makes a conscious decision to move. If the onset of the readiness potential is taken as an indicator of the "brain's decision to move" this could mean that this decision to move is made early, by unconscious brain activity, rather than later, at the time when the subject believes to be deciding. However, an alternative interpretation has recently been discussed, the stochastic decision model (SDM), that takes its inspiration from models of perceptual decision making. It suggests that the RP originates from an accumulation of stochastic internal fluctuations. In this view the decision happens only at a much later stage when an accumulated noise signal reaches a threshold. Here we address a number of confusions regarding both the evidence for the stochastic decision model as well as its interpretation. We will show: (a) that the evidence for the role of stochastic fluctuations is highly indirect; (b) that there is little direct support for the SDM from animal studies; (c) that deterministic (non-random) processes can explain the data in a similar way; (d) that the relative components of the model have been mischaracterized leading to an over-emphasis on the role of random fluctuations and an under-emphasis of deterministic aspects of the model; (e) that there is confusion regarding the role of "urgency" and "evidence" in the SDM and its link to perceptual decision making; (f) that the question whether the decision happens early or late depends on the nature of the noise fluctuations, specifically, whether they reflect "absolute" or "epistemic" randomness; (g) finally, that the model does not explain the temporal relationship between conscious decision and neural decision. Our aim is not to rehabilitate the role of RPs in the free will debate. Rather we aim to address some confusions and premature conclusions regarding the evidence for accumulators playing a role in these preparatory brain processes.

The limits of the neuroscience of moral responsibility

The findings of the neuroscientist Benjamin Libet are among the most discussed in moral philosophy. They present a clear challenge to the notion of intentional action as a consciously chosen action. According to them, the awareness of the decision to act by the subjects of his studies came only after the moment of preparedness of the action in our brains, called “readiness potential”. Many, including Libet, saw these results as an evidence that we do not have free will nor moral responsibility. The aim of this article is to criticize the claim that moral responsibility would be in danger because of the Libet’s findings. First, the concept of free will as intentional action will be explained in order to understand how the notion of being conscious in deciding when and how to act is relevant. Then, the findings from Libet’s experiments and the argument of how they could be a challenge to the notions of free will and of moral responsibility are presented. At the end, it will be argued that the notion of moral responsibility involves more than psychological capacities, but, foremost, the attribution of social roles in a moral community.

Why the Readiness Potential Does Not Disprove Free Will

Neuroscientist Benjamin Libet has conducted a series of experiments that reveal the existence of certain neural processes in the brain of human subjects, initiating an action prior to the human subject’s intention to act, thus seemingly threatening our idea of free will. The purpose of this paper is to show how these processes do not disprove any idea of free will one might have as one would, if accepting such a thesis, be committing two distinct mereological fallacies and ultimately, would treat the human subject as inhabiting some of its parts as opposed to being the sum of its parts.