French researchers have shed further light on the areas of the brain involved when we make the decision, for example, to cross a street.
- A new study highlights the mechanisms and areas of the brain behind the decision to cross a street when a car is entering.
- The researchers carried out experiments on patients who were awake during open skull surgery and were shown role-playing videos. If the subject begins to want to cross when he does not have time to do so, or on the contrary, if he does not do so even though he has it, this means that the electrically stimulated area is essential for this decision-making.
- They identified “very many areas, very small, fragmented, like a slightly shattered puzzle”, located at the level of the right parietal cortex, which are involved in the decision to cross or not a street.
Although crossing a street may seem perfectly natural to us, this action is nevertheless the result of a complex cerebral process. When we want to cross the road unexpectedly but a vehicle is already on it, our brain faces a dilemma: to cross or not to cross? To answer this, we need to do a brief calculation to determine whether we have enough time to cross it safely: this is called contact time perception.
But how does our brain take everything into account at once – the speed of the car, its distance, the time it will take to reach us, and of course our physical capabilities, knowing that we have no not the same at 70 as at 20, or with heavy cardboard as without? A new study, published in the Journal of Neuroscience Research and relayed by the CNRShighlights the mechanisms and areas of the brain behind this decision-making.
Electrically stimulating the brains of awake patients during surgery
Although similar work has already been carried out in recent years, it was mainly based on MRI scans, which are a fairly indirect measure of brain activity: it is difficult to know if the area stimulated by the task is exactly the area in which the process decision takes place.
To better probe the brain, the team of researchers from Brain and Cognition Research Center (CerCo), a joint unit of the CNRS and Paul Sabatier University in Toulouse, therefore carried out experiments on patients who were awake during their brain tumor removal operation. It’s common: using small, painless electrical pulses, surgeons test whether the area they are about to touch has an essential function. To do this, they ask patients to carry out certain tasks such as counting or recognizing an object.
Highly fragmented brain areas involved in decision-making
In this case, the scientists subjected the subjects to a particular task, with situational videos: we see a street and a car moving forward, either very quickly or very slowly – so that there is no have no possible doubt regarding the perception of contact time. If the subject begins to want to cross even though he has no time to do so, or on the contrary, if he does not do so even though he has time, this means that the area which is being electrically stimulated is essential for this decision-making.
However, researchers have identified an area, or rather “very many areas, very small, fragmented, like a slightly shattered puzzle”located in the right parietal cortex, which are involved in the decision to cross or not a street, explains Professor Robin Baurès, who led the study, at the microphone of France Culture. “It is not one very large unified region“, which means that, “when the surgeon operates [le patient éveillé]the difference between an involved area and an uninvolved area can sometimes be less than 1 centimeter.
After this study which lifts the veil a little more on the cerebral bases of decision-making, the next step will consist, according to the researcher, of adding sound to these videos, of mixing auditory and visual stimuli, to see if the Integration of this multisensory information takes place in the same areas of the brain.
