Thursday, 13 October 2016

"Seek, and you shall find": the functioning of attentional selection in our brain

A CIMeC study published in the Journal of Neuroscience

Versione stampabile

As the old say goes, “seek, and you shall find”: now science makes a step forward and captures what happens in our brain when it comes to attention.

When we are doing complex and attention-demanding activities, like working or driving for example, it is of crucial importance to pick the appropriate information at the right moment. So if we are behind the wheel, it is vital to identify possibly dangerous obstacles as fast as possible. There’s no need to catch each and every aspect of the pedestrian who is crossing the street. What really matters is how fast we are in recognizing it as a potential danger so that we can brake or steer to avoid it.

In general, when we look at the world around us, we constantly separate relevant information from information that we consider less important.

But how does the brain acquire information and operate this selection so quickly and accurately? How does it separate relevant and irrelevant information? Does this occur automatically?
To answer these questions the researchers of the Mind/Brain Center (CIMeC) of the University of Trento have conducted a study whose results were published today in the prestigious Journal of Neuroscience.

The researchers – Daniel Sebastian Kaiser, Nikolaas Oosterhof and Marius Peelen – asked volunteers recruited for the study to watch hundreds of pictures portraying everyday life situations, and to identify in each picture people or cars among a variety of different objects.

The study revealed that brain signals reflected very quickly, within 200ms, what the volunteers were actively looking for (cars, for example), as if they had seen and recognized the object at the same time, out of the context. Surprisingly, on the other hand, when volunteers viewed the same scenes later on, but were now looking for something else (people, for example), the fast neural response to the (now irrelevant) cars was gone, , as if the cars were no longer present in the scene. 

These results demonstrate that the brain dynamically prioritizes information that is relevant in a given moment, and that this process is remarkably fast. In the example of the driver watching out for pedestrians this means that within a fraction of a second after a person steps on the road, the brain already has constructed a clear visual representation of this person, allowing the driver to react appropriately in time to avoid an accident.

The technology used
During the task, the volunteers’ brain activity was measured using magnetoencephalography(MEG), a biomedical functional imaging technique that measures magnetic fields produced by the brain’s electrical activity. With this technique, the researchers were able to track the magnetic fluctuations of brain activity millisecond by millisecond. The great advantage of MEG recordings lies in their precision, allowing for precisely estimating the timing of processes occurring in the volunteers’ brain. 

«When we open our eyes and look at an object in front of us - explained the CIMeC researchers - it takes the brain less than 200 ms, a fraction of a second, to recognize the category of the object, that the object in front of us is a car, for example. However, in most daily life situations — while driving through a city street, crossing a road, or looking at a shopping window — there are many objects present at the same time. We used highly advanced technologies to investigate how the brain processes objects under these circumstances, and we found out that the attitude of the observer determines what he or she sees and what is ignored: it all depends on what you are looking for. This research work opens new perspectives for studies on attention and concentration».