The researchers tracked brain activity in rats as they recovered from anaesthesia-induced comas and found that consciousness returns through a series of distinct and ordered brain activity patterns rather than directly. Specifically, they discovered that the brain must pass through certain "hub" activity patterns for the recovery of consciousness to proceed in a structured sequence similar to a computer rebooting through a boot sequence. Understanding this process could help improve strategies for bringing people out of long-term comas or monitoring patients under anaesthesia.

1. Booting up the brain after anaesthesia
The way the brain "boots up" from anaesthesia has been detailed in a new paper
that shows the return to consciousness is a staged journey rather than a direct
leap.
The findings, published this week in Proceedings of the National Academy of
Sciences, could have implications for bringing people out of coma, and improve
monitoring of patients under anaesthetic.
Senior author Assistant Professor Alex Proekt, at Weill Cornell Medical College in
New York, likens the return to consciousness to re-booting a computer.
"If the power is turned off, all activity inside the computer ceases," he says. "Yet,
once the power is turned on, the computer is eventually able to restore itself back
to the state in which it was right before the power was turned off without any
instructions from the outside world."
Proekt says the computer is able to do this by following a certain set of instructions
each time it is turned on.
"Without this boot sequence the computer would never work even if it is otherwise
totally intact," he notes.
Tracking consciousness
While Proekt admits the brain is somewhat different to a computer, the ability to
start "ex nihilo" - or from seemingly nothing - is important for the return to
consciousness, he says.
The researchers were able to track the return to consciousness in rats by
monitoring brain activity in rats that were put into a comatose state using
anaesthetic.
Their work shows that as the brain recovers it abruptly switches between several
distinct "spatiotemporal" activity patterns, he says.
However, Proekt says, the transition between these patterns must happen in a set
order.
"If we consider each pattern to be a node and each transition a link that links the
nodes then we can construct a network that mediates recovery of consciousness,"
he says.
Proekt and colleagues from The Rockefeller University and the University of
California, Los Angeles, found that some nodes form hubs that connect groups of
otherwise disconnected nodes.

2. Importantly they discovered the system will not proceed further towards waking up
unless it first passes through these hubs.
"In this sense the recovery of consciousness is akin to a boot sequence - it gives
rise to an ordered set of states (activity patterns)," he says.
Structured approach
This structured approach is important as it answers how the brain is able to find -
given the billions of neurons and brain plasticity at play - the activity patterns
compatible with consciousness.
Proekt says he and colleagues are yet to determine what influences the transition
from one activity pattern to the next, but are currently investigating this area.
The findings could be important for bringing people in long-term comas back to
consciousness as it would make it possible to increase the chances of transition.
However he says the work helps explain how people can recover almost full
cognitive function after years being trapped in a coma.
The new work suggests, brain injury may disrupt the processes, such as the
transitions between activity states, used by the brain to move back to
consciousness.
While the study was undertaken on rats, Proekt believes the findings can be
translated to humans as "the patterns of neuronal activity that occur in humans and
rats when they are deeply anaesthetised are quite similar".
"My suspicion is that we may find the specific features of activity states may be
different between humans and rats, but the overall message that there will be
multiple states with structured transitions will be conserved," he says, although
Proekt stresses this is "just a hunch" at this stage.
The work could help inform better design of anaesthetic monitors.
These could determine what activity pattern the brain is in and the chances of it
reaching consciousness, Proekt says.
He says he and colleagues are now looking at further experimentation on humans
to investigate how to make this system work.
http://www.abc.net.au/science/articles/2014/06/11/4022173.htm