What is consciousness? As questions go, that’s quite a whopper, with all sorts of philosophical and neurological implications – but that didn’t stop an international team of researchers from attempting to answer it. Publishing their findings in the Journal of the Royal Society Interface, they suggest that consciousness may be produced by an “ordered chaos” within the brain, with neurons communicating in a spontaneous manner, forming transient patterns that adhere to underlying structures.
It has often been remarked that consciousness is more than just the sum of our sensory perception. Rather, it is a continuous subjective experience, shaped by our senses and assembled in our brains. Exactly how the various input signals are merged in order to form a complete and ongoing state of awareness is extremely complex.
To try and better understand the signals that produce consciousness, the study authors decided to see what happens when consciousness is turned off. They gave volunteers an anesthetic drug called propofol, and used functional magnetic resonance imaging (fMRI) to observe the activity in their brains during wakefulness, sedation, unconsciousness, and recovery.
By focusing on the ways in which signaling patterns differed between the conscious and unconscious brain, the researchers were able to draw conclusions about how neurons communicate during consciousness.
They found that the fully conscious mind operates at what they call a “critical point,” which they describe as “between ordered and disordered.” In this state, neurons communicate with one another in accordance with the underlying anatomical structure of the brain, sending signals that respect the physical boundaries between different brain regions.
Because of this, a large but ultimately limited number of possible pathways exist for any particular signal to take. However, that is where the rigidity ends, with the researchers reporting that neurons do not communicate along the most direct routes, but instead “explore” every possible permutation of connections linking them.
Consciousness may be produced by a "spontaneous" mode of communication, with neurons exploring every available path as they transmit signals around the brain. ktsdesign/Shutterstock
In other words, “spontaneous brain activity can be understood as an ever-transient (or metastable) exploration of the wide repertoire of paths offered by the underlying structural connectivity.”
Under the effects of propofol, however, these spontaneous fluctuations break down, with rather different signaling patterns emerging. The study authors found that, when consciousness is disabled, inter-neuronal communication tends to occur via the most direct route, rather than exploring all possible connections. Furthermore, these routes are not necessarily bound by the anatomical structure of the brain.
They therefore claim that such direct communication is insufficient to generate the experience of consciousness, which instead requires a more spontaneous and chaotic form of signal distribution. While more research is needed to confirm their findings, the researchers conclude that any departure from this critical point of neuronal connectivity – whether as a result of an increase or a decrease in spontaneity – is likely to result in a loss of consciousness.