New research sheds light on a difficult idea about consciousness: There is a difference between what the brain takes in and what we are conscious of taking in.
Scientists now believe they have pinpointed the brain region where conscious awareness is controlled.
The team from the Hebrew University of Jerusalem in Israel and the University of California, Berkeley (UC Berkeley), in the US, found sustained brain activity in the occipitotemporal area of visual cortex at the back of the brain.
While this activity dropped to about 10–20 percent of its level about 300 milliseconds after an original visual stimulus, the pattern of activity remained while the stimulus was being viewed.
It was in contrast to other brain areaswhere information disappeared completely within half a second (500 milliseconds).
“This stable representation suggests a neural basis for stable perception over time despite the changing level of activity.” say psychologist Leon Deouell from the Hebrew University of Jerusalem.
In other words, this neural region is where we don’t just notice something, but also notice that we notice it. As the visual stimulus changed – a series of images – the brain activity also changed. Machine learning algorithms then filtered out the noise and spot patterns.
Researchers recruited 10 epilepsy patients for the study, which was already planned to have electrodes fitted inside their skulls. These electrodes allow for a more complete measure of brain activity over time, with less guesswork compared to other brain scanning methods that work externally.
“We’re adding a piece to the puzzle of awareness—how things stay in your mind’s eye so you can act on them.” say psychologist Robert Knight from UC Berkeley.
The researchers cannot say with certainty how their findings relate to consciousness, but they suggest that the persistent activity in the visual cortex could be fed back to the prefrontal cortex, where thoughts and actions are controlled.
There is still a lot of scientific debate about how all this works or doesn’t work. After damage to one hemisphere of the brain after a stroke, for example, some people experience unilateral neglect: They consciously perceive only half a photo or scene, but react emotionally to it in its entirety.
Ultimately, further research and data collection leading to a better understanding of consciousness may help restore the brain when conditions such as unilateral neglect take hold.
“What is required for something not only to be sensed by the brain, but for you to have a subjective experience?” say Deouell.
“Understanding that would ultimately help us understand what’s missing in the cognitive system and in the brain of patients who have this kind of syndrome.”
The research is published in Cell reports.