Researchers have found evidence that awareness or consciousness results from widespread communication across sensory and association areas of the cortex, challenging previous hypotheses that changes in restricted areas of the brain were responsible for producing awareness.
“Identifying the fingerprints of consciousness in humans would be a significant advancement for basic and medical research, let alone its philosophical implications on the underpinnings of the human experience,” said René Marois, professor and chair of psychology at Vanderbilt University and senior author of the study.
“Many of the cognitive deficits observed in various neurological diseases may ultimately stem from changes in how information is communicated throughout the brain.” The researchers used graph theory, a branch of mathematics concerned with explaining the interactive links between members of a complex network, such as social networks or flight routes, to characterize how connections between the various parts of the brain were related to awareness.
In the experiment, participants in a functional magnetic resonance imaging (fMRI) scanner were asked to detect a disk that was briefly flashed on a screen. In each trial, participants responded whether they were able to detect the target disk and how much confidence they had in their answer. Experimenters then compared the results of the high-confidence trials during which the target was detected to the trials when it was missed by participants. These were treated as “aware” and “unaware” trials, respectively.
They found that no one area or network of areas of the brain stood out as particularly more connected during awareness of the target; the whole brain appeared to become functionally more connected following reports of awareness.
“We know there are numerous brain networks that control distinct cognitive functions such as attention, language and control, with each node of a network densely interconnected with other nodes of the same network, but not with other networks,” Marois said. “Consciousness appears to break down the modularity of these networks, as we observed a broad increase in functional connectivity between these networks with awareness.”