Neuroscientists at the California Institute of Technology in Pasadena have identified neurons that are responsible for the perception of visual information and the creation of a visual image. This was achieved through a psychological phenomenon called binocular rivalry. The article of scientists was published in the journal Nature.
Binocular rivalry occurs when the eyes transmit completely different visual information to the brain. Usually, to create a complete visual image, the brain combines signals from both eyes with each other. However, in the event that one eye sees an image that does not in any way correlate with what the other eye sees, a situation arises when a person alternately sees one or the other image. In this case, the "extra" information is simply suppressed without reaching our consciousness.
Scientists turned to this phenomenon to determine which neurons in the cerebral cortex are responsible for switching perception from one picture to another. The experiment involved nine patients with epilepsy, in whose brains electrodes were implanted to record the activity of certain areas of the central nervous system. The volunteers were given a series of images to look at, and the patterns were identified that elicited a response in neurons in the medial surface of the temporal cortex and those that did not. The images were combined into pairs, each of which included drawings of both types.
During the test, a couple of pictures were placed in front of the eyes of the volunteers in such a way as to create binocular rivalry. Patients pressed buttons, noting which of the two images they saw, how long this perception lasted, and when the perception shifted from one picture to another. Each session, during which the participants were shown one pair of drawings, lasted 90-120 seconds, and between the images there were from 21 to 68 transitions.
Scientists were able to identify individual neurons that specifically respond to a particular image. At the same time, the switching on or off of these cells located in the anterior cingulate cortex of the cerebral hemispheres and in the pre-additional motor cortex (pre-SMA) occurred not only at the very moment of the visual transition, but also as much as two seconds before it. In the temporal lobe, the neuronal response preceded the button press by approximately one second.
As the scientists write in the article, the results show that neural networks that cover the temporal and frontal lobes of the cerebral hemispheres and participate in subconscious processes play an important role in the formation of human consciousness. In addition, the researchers were able to identify neurons that occupy a higher position in the hierarchy of visual information processing than nerve cells in the temporal inferior cortex, previously identified in experiments with primates.