Tel Aviv-based brain researchers, in collaboration colleagues in Israel and the United States, have carried out brain activity experiments on epilepsy patients that may greatly further our understanding of experience creation.
Dr. Hagar Gelbard-Sagiv of Tel Aviv University’s Sackler Faculty of Medicine and TAU’s School of Neuroscience noted that humans have been looking for answers to these fascinating questions for thousands of years. “Each generation deals with the tools available. We were looking for a new perspective through advanced brain research technologies.”
Gelbard-Sagiv and her colleagues used electrodes implanted in the brains of epilepsy patients. They utilized a unique medical situation to find out what happens within the human brain at the moment of experience creation. Surgeons implanted electrodes in the brains of patients to identify the epicenter of epileptic seizures and then neutralize it using surgery.
“We usually use lab animals that are unable to report their experiences, and we can measure brain activity in an individual only using external and indirect means, such as and electroencephalogram or functional MRI,” she said. But here, when the electrodes are implanted in human brains for medical purposes, a rare research opportunity is also created – to measure and record brain electrical activity, directly and with unprecedented resolution of a single nerve cell. At the same time, since he is conscious, we can get a report from the person about his subjective experiences.”
A new experience is born in the brain every time you taste chocolate, see a smiling child, smell a fragrant flower or listen to music. Such events can be described as “the taste of life.”
But how do our brains process this subjective and qualitative information physiologically? Where is the connection between the external world that the senses absorb and the inner world of experience and consciousness? And how is all this carried out?
In the course of the study, each subject was presented with two images at the same time – a different picture for each eye, such as one of a house to the right eye and the image of a face to the left one. In such a situation, called binocular rivalry, the brain cannot combine the two images, and the subject sees them alternately, without having control over the process of switching between the images. In other words, the external reality does not change – each eye has a fixed image; and the only change that takes place is within the brain itself.
“In this way, we have been able to isolate the crucial moment in which a new experience of awareness is created,” said Prof. Itzhak Fried of UCLA, TAU and TASMC the senior author on the paper. “We can say that this is the golden experiment of the study of consciousness, and here we succeeded in performing it in humans at the level of the single nerve cell.”
The researchers found a change in the brain, or more precisely in the frontal lobe cells, which begins two seconds before the subject reports the change of image it sees. A second before the report, electrical activity is also recorded in the middle temporal lobe, in areas associated with visual activity. These are very long periods of time in terms of brain activity, which is measured in milliseconds. In a control experiment, researches screened a “repeat film” of the spontaneous images to the subjects, who then reacted much quicker the next time.
“The new study brings us one step closer to understanding consciousness and the conscious experience, at the most obvious and real level – the level of electrical activity in the single nerve cell,” concluded Gelbard-Sagiv.
University of California at Los Angeles, Tel Aviv Sourasky Medical Center, TAU and at the California Institute of Technology jointly conducted the study, and which the prestigious journal Nature Communications recently published.