The neuroscientists at the California Institute of Technology in Pasadena have identified neurons that are responsible for understanding visual information and creating a visual image. This was achieved with the help of a psychological phenomenon called binocular rivalry. The article of scientists is published in the journal Nature.
Binocular rivalry occurs when the eyes transmit completely different visual information to the brain. Usually, to create a full visual image, the brain combines with each other the signals coming from both eyes. However, in the event that one eye sees an image that does not correspond in any way to what the other eye sees, a situation arises when the 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 perceptions from one picture to another. In the experiment, nine patients with epilepsy participated in which the electrodes were implanted in the brain to record the activity of certain areas of the central nervous system. Volunteers were given a look at a number of images, while pictures were identified that caused an answer in the neurons of the medial surface of the temporal cortex, and those that did not lead to such a reaction. Of the images, pairs were composed, each of which included drawings of both types.
During the test, a couple of pictures were placed in front of the volunteers’ eyes in such a way that a binocular rivalry arose. Patients pressed the buttons, noting which of the two images they see how long this perception lasted and when the perception shifted from one pattern to another. Each session, during which participants demonstrated one pair of drawings, lasted 90-120 seconds, and between images there were from 21 to 68 transitions.
Scientists were able to identify individual neurons, specifically reacting to a particular image. At the same time, the inclusion or deactivation of these cells located in the anterior cingulate cortex of the cerebral hemispheres and in the pre-complementary motor cortex (pre-SMA) occurred not only at the moment of the visual transition, but also for two whole seconds before it. In the temporal lobe, the neuronal response preceded the button pressing for approximately one second.
As the scientists write in the article, the results show that in the formation of human consciousness an important role is played by neural networks that encompass the temporal and frontal lobes of the cerebral hemispheres and participate in subconscious processes. In addition, researchers were able to identify neurons occupying a higher position in the hierarchy of visual information processing than nerve cells in the temporal lower cortex, previously established in experiments with primates.