Brain preparation before a voluntary action: Evidence against unconscious movement initiation

ArticleinConsciousness and Cognition 19(1):447-456 · March 2010with332 Reads
DOI: 10.1016/j.concog.2009.08.006
Abstract
Benjamin Libet has argued that electrophysiological signs of cortical movement preparation are present before people report having made a conscious decision to move, and that these signs constitute evidence that voluntary movements are initiated unconsciously. This controversial conclusion depends critically on the assumption that the electrophysiological signs recorded by Libet, Gleason, Wright, and Pearl (1983) are associated only with preparation for movement. We tested that assumption by comparing the electrophysiological signs before a decision to move with signs present before a decision not to move. There was no evidence of stronger electrophysiological signs before a decision to move than before a decision not to move, so these signs clearly are not specific to movement preparation. We conclude that Libet’s results do not provide evidence that voluntary movements are initiated unconsciously.

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    • "They argued that the RP is not an intention to move, but only indicates that an attentional process is in place in the brain, since when subjects ''attended to their intention rather than their movement, there was an enhancement of activity in the pre-SMA'' (Lau et al., 2004). In any case, ''there was no evidence of stronger electrophysiological signs before a decision to move than before a decision not to move, so these signs clearly are not specific to movement preparation'', (Trevena and Miller, 2010). Others have noted that the introspective estimates of event timing are disputable or inaccurate, and measures in general are not sufficiently exact (Dennett, 1984aDennett, ,b, 2003). "
    [Show abstract] [Hide abstract] ABSTRACT: The concept of free will is hard to define, but crucial to both individual and social life. For centuries people have wondered how freedom is possible in a world ruled by physical determinism; however, reflections on free will have been confined to philosophy until half a century ago, when the topic was also addressed by neuroscience. The first relevant, and now well-known, strand of research on the brain correlates of free will was that pioneered by Benjamin Libet (Libet et al., 1983), which focused on the allegedly unconscious intentions taking place in decisions regarded as free and voluntary. Libet’s interpretation of the so-called readiness potential (RP) seems to favour a sort of deflation of freedom (Soon et al., 2008). However, recent studies seem to point to a different interpretation of the readiness potential, namely that the apparent build-up of the brain activity preceding subjectively spontaneous voluntary movements may reflect the ebb and flow of the background neuronal noise, which is triggered by many factors (Schurger et al. 2016). This interpretation seems to bridge the gap between the neuroscientific perspective on free will and the intuitive, commonsensical view of it (Roskies, 2010b), but many problems remain to be solved and other theoretical paths can be hypothesised. The paper therefore proposes to start from an operationalizable concept of free will (Lavazza and Inglese, 2015) to find a connection between higher order descriptions (useful for practical life) and neural bases. This new way to conceptualize free will should be linked to the idea of “capacity”: that is, the availability of a repertoire of general skills that can be manifested and used without moment by moment conscious control. The capacity index, which is also able to take into account the differences of time scales in decisions, includes reasons-responsiveness and is related to internal control, understood as the agent’s ownership of the mechanisms that trigger the relevant behaviour. Cognitive abilities, needed for one to have capacity, might be firstly operationalized as a set of neuropsychological tests, which can be used to operationalize and measure specific executive functions, as they are strongly linked to the concept
    Full-text · Article · Jun 2016
    • "Understanding the relationship between cognitive processes and the underlying patterns of brain activity has been a fundamental goal for cognitive neuroscience research (J. Trevena & Miller, 2010) and for applications of neuroscience to work and everyday activities, or neuroergonomics (Ayaz et al., 2013; Mehta & Parasuraman, 2013; Parasuraman, 2011). Unlike the explicit cognitive processes during rest and movement, the cognitive process during transition period between rest and movement, which usually corresponds to the preparation period preceding movement, is implicit (J. A. Trevena & Miller, 2002). "
    [Show abstract] [Hide abstract] ABSTRACT: Our results illustrate the enhanced functional connectivity (FC) between motor-related brain regions and high-level cognitive brain regions during the transition period between rest and hand movements. These results suggest that the sensorimotor network is interacting with prefrontal areas during the transition period to maintain the preparation state. Both actual movement and the transition period without actual movement modulate brain activities. Capturing the detailed relationship of movement intention could be utilized to improve precision and latency of anticipation-based brain-computer interfaces (BCI). Furthermore, consistent with the neuroergonomic approach, this study demonstrates that functional near infrared spectroscopy is a suitable tool for region-specific, task-related, and resting-state FC analysis. Our findings could enhance the development of more intuitive and natural interfaces between human and machine systems in diverse areas. The approach presented here could help create assistive devices that perceive and predict operator's intention of movements. Introduction: Traditional and new generations of neuroimaging techniques allow observing the modulation of brain activities during transition periods between rest and physical movement execution. A thorough understanding of the brain activity and FC changes during these transitions could contribute to increasing the precision and decreasing the latency of anticipation-based brain-computer interfaces, and improving human-system integration in general. Consistent with the neuroergonomic approach, functional near infrared spectroscopy (fNIRS) can monitor the outer cortex during extensive physical movement and in realistic settings using wearable and portable sensors. Methods: In this study, 19 healthy subjects were monitored with fNIRS during rest, a fist opening and closing task, and the transition period preceding the task. FC analysis was used to evaluate how the transition period preceding the task modulated the brain activities. Results: There were several increases in FC during the transition period, especially between the right dorsolateral prefrontal cortex and the contralateral primary somatosensory and primary motor cortices, as well as the FC connecting the contralateral primary somatosensory cortex with the ipsilateral primary somatosensory cortex and the primary motor cortex. Regions located in the sensorimotor networks and right dorsolateral prefrontal cortex were also found to be activated during the transition period. Conclusions: These results demonstrate that the sensorimotor network was interacting with the high-level cognitive brain network during the transition period to maintain the preparation state. Furthermore, fNIRS is an emerging tool well-suited for region specific task-related and resting-state FC analysis. The results and the approach presented here suggests that operators' intention to move can be detected before the actual movement, and that could be employed for development of more intuitive and natural interfaces between human and machine systems.
    Article · Jun 2016
    • "The reasoning was that if RPs reflect the preparation of an impending action, RPs preceding an actual movement should be different than RPs preceding no movement. However, no such difference were detected, thus suggesting RPs do not even code for the decision of moving and do not correspond to motor preparation (J. Trevena & Miller, 2010). However, it can be argued that EEG are crude signals, and that recording of the actual neural activity in SMA and pre-SMA can be used to predict movements, as it could be done in monkeys (Averbeck & Lee, 2003). "
    [Show description] [Hide description] DESCRIPTION: To understand the neurobiological basis of volition, I first reviewed the phenomenology of voluntary actions and the brain circuits involved in each aspects of action generation. In a second part, I focused on a question that has dominated the free-will debate in neuroscience for the last decades: do motor intentions form unconsciously in the brain before we are aware of them? I presented the Libet experiment that first suggested that unconscious neural process are at the origin of conscious motor decisions, I described more recent experiments that arrived at similar conclusions and then detailed the technical and conceptual shortcomings of these experiments. Finally, I reflected on the implications of these findings on the mind-brain problem and reviewed the philosophical and scientific solutions proposed to explain or refute mental causation of actions.
    Full-text · Research · Oct 2015 · Frontiers in Human Neuroscience
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