© Family Business / FotoliaResults of a new study challenge the traditional view of decision making.
Choices, it is commonly understood, lead to action - but how does this happen in the brain? Intuitively, we first make a choice between the options. For example, when approaching a yellow traffic light, we need to decide either to hit the breaks or to accelerate the car. Next, the appropriate motor response is selected and carried out, in this case moving the foot to the left or to the right. Traditionally, it is assumed that separate brain regions are responsible for these stages.
Specifically, it is assumed that the motor cortex carries out this final response selection without influencing the choice itself.Two Tübingen Neuroscientists, Anna-Antonia Pape and research group leader Markus Siegel of the Werner Reichardt Centre for Integrative Neuroscience (CIN) and MEG Center, have found evidence that challenges this intuitive division between a 'deciding' and a 'responding' stage in decision making. The results of their study have been published in the latest
Nature Communications.
While recording brain activity using magnetoencephalography (MEG) to monitor activity in motor areas, Pape and Siegel set 20 human subjects the simple task of deciding whether or not a field of dots on a screen was slowly moving together. The subjects could respond "yes" or "no" by pressing a button with either their left or their right hand. The mapping from choice (yes/no) to response (left/right button) changed randomly on each trial, with a short cue telling subjects the current configuration. This ensured the participants' brains could not plan a motor response, i.e. the correct button press, during choice formation. Astonishingly, while the test subjects were able to press the 'correct' button most of the time, subjects still showed a strong tendency towards motor response alternation.
In other words, they often simply pressed the button they had not pressed in the trial just prior to the current one. This tendency was pronounced enough to detract from subjects' overall decision task performance.
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