From Mind to Movement.

Ted Chiang, one of science fiction’s preeminent writers, once imagined an interesting fictional device in his short story, “What’s expected of us”. Without fail, a device called a Predictor flashes a light one second before the user presses the button. But, as Chiang puts it:

If you try to press the button without having seen a flash, the flash immediately appears, and no matter how fast you move, you never push the button until a second has elapsed. If you wait for the flash, intending to keep from pressing the button afterwards, the flash never appears. No matter what you do, the light always precedes the button press. There’s no way to fool a Predictor.1

The Predictor functions by sending a signal back in time, which allows it to anticipate the user’s actions and flash accordingly. If it existed, the Predictor would raise many interesting questions on free will. For instance, by what standard could we consider an individual the decision-maker, given that an event in the past would systematically precede his or her decision? Could it be that the light makes an individual press the button? Although most neuroscientists would be hard-pressed to answer the question of whether or not free will exists, many studies have begun to reveal what goes on in the brain from the initial stage of preparation for a movement and during the action itself2. It is in the preparation stage that the relevance of the fictional Predictor is of greatest interest.

As early as 300 milliseconds before making the conscious decision to move, volunteers in a 1983 study exhibited shifts in brain activity within the supplementary motor area (SMA), a region of our brain involved in movement

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preparation3. This precursor activity in the brain (called readiness potentials) demonstrated that even before humans are aware of their decision to act, processes in the brain are already preparing actions.

A typical readiness potential, brain activities that precede movement, recorded from electrodes located above the motor and premotor cortices.

Image released in the public domain.

Building upon this study, another group conducted an experiment bearing zoloft reviews uncanny resemblance to the events surrounding the fictional Predictor. Participants were asked to press one of two buttons (left or right), deciding for themselves which button to press and when to press it. The precise time at which these conscious decisions were made was determined (see here), and by measuring brain activity using fMRI, the authors arrived at an astonishing finding4. In two brain regions, the frontopolar cortex and parietal cortex, the outcome of the participant’s decision was encoded 7 seconds before they reported making the decision. In other words, the brain http://zoloftonline-generic.com/catalog/Depression/Celexa.htm had already made the decision on which button to press, seconds before participants knew they would make the choice.

Brain activities appear to predict actions, yet precede subjective feelings of intentions. This may seem counterintuitive to our notion that intentions ought to drive behavior. However, the available evidence supports the hypothesis that this notion may not necessarily hold true all the time, with action preparation in the brain taking place before any conscious intent is perceived by the subject. What is the function of conscious intent then, if it emerges after the process of preparing for an action has already begun? This question is rarely asked, and we are far from obtaining an answer. Among the possibilities that I find most fascinating, conscious intent may be cymbalta interactions involved in the process by which we formulate plans that ultimately impact actions that have already been somewhat automatically selected in the brain. Or perhaps intent could take part in a parallel process that allows us to halt such actions, based on factors that were originally computed during the initiation of the action. Intent could also be a component of the brain machinery that translates fictive scenarios – those we form based on our knowledge of the world we live in – into motor programs that are ready to deploy in response to our changing environment.

The view we have of how the brain prepares actions remains incomplete, but studies so far suggest a considerably complex process that can last as many as several seconds preceding a movement. It is neuroscience’s incredible potential to elucidate these processes that makes it such an exciting field of research, with numerous studies driven by the fundamental question of how our behaviors are controlled and how our mind works.

DianaLXie

Today I brought you the text of a brilliant colleague of mine, Diana L. Xie, who has accepted to write this guest post. Diana is a graduate in Biology with does accutane work a concentration in Pharmacology. She is interested in how oxytocin changes the way we interact socially.

References

1. Chiang T. (2005) What’s expected of us. Nature 436.

2. Shenoy V., Sahani M., Churchland, M. (2013) Cortical control of arm movements: A dynamical systems perspective. Annual Review of Neuroscience 36:337-359.

3. Libet B., Gleason C., Wright E., Pearl D. (1983) Time of conscious intention to act in relation to onset of cerebral activity (readiness-potential). The unconscious initiation of a freely voluntary act. Brain 106:623-642.

4. generic cymbalta Soon C., Brass M., Heinze H., Haynes, J. (2008) Unconscious determinants of free decisions in the human brain. Nature Neuroscience 11:543-545.

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