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A team of scientists - finally - has just identified the seat of perception in three dimensions inside the human brain. This exploit, which rests on a succession of particularly complex experiments, opens the way with new research.
Who never questioned himself in front of the exploits of a professional juggler? At the beginning of information in two dimensions transmitted by each eye, its brain must rebuild an image not only three-dimensional, but also four-dimensional because the concept of time and speed is dominating here so that the artist can project the hand in the direction where the object will be when it must seize it. The whole, of an automated gesture and without any possibility of reasoned decision.
Professor Guy Orban, neurobiologist of the catholic university of Leuwen (Belgium) and his colleagues succeeded in locating the processing center of this two visual information (space position, speed and direction) within the brain, on the level of a zone called former cortex intraparietal (anterior intraparietal cortex, or AIP).
Process of identification
The identification of an object with three dimensions rests, in the primates, on the binocular vision. The image perceived by each eye is slightly different, it is what the specialists name the space binocular disparity. In the second place, the form of an objective changes while this one moves.
Very a long time, the way in which our brain manages to integrate these data to provide us a representation of reality remained a mystery. In order to better track this process, the researchers proceeded to two series of experiments not traumatisantes on primates, which utilize the Imagery by Functional Magnetic Resonance (IRMf). This technique makes it possible to visualize the activity sitting in a brain, in three dimensions and real time.
The first experiment consisted in presenting at subjects similar objectives in three dimensions, such as for example of the inter-connected trombones of office. Those were selected to be easily identifiable by the monkeys, in condition however of seeing them as a whole. During the test, masks were laid out so that the object appears only partially in each eye. It was thus a question for the brain of assembling these two complementary images in only one.
During the second experiment, synthesized images in three dimensions generated by computer were subjected to the animals, which had their binocular vision. The complexity of the simulated objects requested in this case a treatment of information in three dimensions starting from a real binocular vision.
The role of the AIP
With the analysis of the results, Orban and its team noted that during the two experiments, information converged towards a single zone of the brain, the AIP.
With the favor of former experiments, it had already been established that the AIP intervened during the visual monitoring of the movements of the hand, inter alia, a practically exclusive type of synchronization to the primates, which were distinguished from this manner of the other animals during the evolution.
The discovery of the neuronal bases of the depth perception starting from the visual movement, by using the Imagery by functional Magnetic Resonance (IRMf), reinforces knowledge of the scientists on the operation of the brain. It could allow, in the near future, to better identify the origin of certain deficiencies or some disturb behavioral associated, and to cure it.
 

About The Researcher:

Guy Orban
Department of Neurosciences and Psychiatry
Contact address :
Afdeling Neurofysiologie
O&N II Herestraat 49 - bus 01021
B-3000 Leuven
tel.:+ 32 16 34 57 44
fax: + 32 16 34 59 93
e-mail: guy.orban@med.kuleuven.be
In The Images:
1.Guy Orban
2.Sagittal cut of a human brain in fMRI. Credit UCL.