Did we decide before processing enough data from the outside world? A study carried out by researchers from the Autonomous University of Madrid (UAM) and the National Autonomous University of Mexico maintains that,when making decisions in contexts of great uncertainty, what we choosenot only based on sensory evidence, otherwisealso in internal mechanisms of the brain.
In a work published in the latest issue of the magazinePNAS, Spanish and Mexican neuroscientists provide evidence that contradicts the theory commonly accepted until now to explain the activity that occurs in our brain when we make decisions based on perception. According to this current theory, the arrival of a sensory stimulus increases neuronal activity and the decision is reached when this activity exceeds a certain threshold.
To refute this idea, in a series of experiments the researchers used a tactile vibration as sensory stimulation that was applied to one of the fingers of the subjects studied, without them knowing when the stimulus would occur. Furthermore, the vibration was sometimes extremely weak or even absent. Volunteers were required to indicate whether or not they had perceived a vibration, and were rewarded in cases where their decisions were correct. The results obtained showed that there is an internally generated signal that prompts the individual to categorically affirm that they have perceived a vibration even when it has not been applied.
According to the authors, the conclusion of the results is that decisions made in highly uncertain contexts are, in many cases, defined by brain mechanisms independent of observation. And that the answer is the result ofdeductions or inferencesthat the brain realizes about what happens in the sensory world, sometimes before anything happens.
