What Anesthesia Can Tell Us About Consciousness

This piece, by Onno Berkan, was published on 10/08/24. This piece was recently published at NeuroscienceNews.

Our brains are prediction machines, perpetually trying to guesstimate what’s going on around us. This may be the basis for consciousness, and it is the main idea that this new MIT paper revolves around.

Anesthesia blocks this prediction mechanism by disrupting synchronized communication between brain regions, and this is thought to disrupt consciousness. The keyword there is synchronized, as the frequency ranges in which brain waves occur give us an idea about what is currently happening in the brain.

Sensory regions of the brain (described as being towards the back of the head, or caudal) continuously relay external stimuli to the cortex, but usually at low frequencies, called alpha and beta waves. These can be suppressed by the decision-making parts of the brain, which are located towards your forehead.

When the sensory regions detect something of interest (perhaps a threat,) they send out signals at a much higher frequency, called gamma waves. This increase in frequency (or the amount of times these neurons fire per second) allows the signals to spread further and essentially be taken more seriously. Anesthesia disrupts this signaling. 

Under anesthesia, your cortical decision-making regions cannot fully process the input from your sensory regions. When activity cannot be regulated, when communication is blocked, neurons become more disorganized, and the brain’s ability to make predictions plummets. 

This blocks consciousness, suggesting “an important role for prefrontal cortex activation, in addition to sensory cortex activation, for conscious perception”. While we do not know how consciousness works, this is quite revealing of some of the underlying mechanisms.

If this study interests you, be on the lookout for dream or anesthesia experiments, as they are often gateways towards studying consciousness.

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