Switch flicked to wake brains
New research has revealed what appears to be a ‘switch’ that controls consciousness in the brain.
A recent experiment that stimulated the brains of anaesthetised macaques found one tiny piece of tissue deep inside the forebrain – the central lateral thalamus – appears to be pivotal in influencing in passing signals from the higher-order sections such as the cortex to deeper structures such as the thalamus. These areas are known to be integral to consciousness.
The study was set up to see how the central lateral thalamus communicates with other areas of the brain during different states of activity.
“We decided to go beyond the classical approach of recording from one area at a time,” says neuroscientist Yuri Saalmann from the University of Wisconsin.
“We recorded from multiple areas at the same time to see how the entire network behaves.”
Macaques used in the study had their brain structures imaged before specially tailored electrodes were inserted.
The electrodes monitored activity while the monkeys were awake, asleep, and under the effects of a strong anaesthetic.
The variations in electrical activity showed that the central lateral thalamus has a role in maintaining consciousness, at least in macaques.
The team then used their highly-sensitive electrodes to stimulate neurons with incredible precision, triggering them while the macaques were knocked out with ketamine.
“We found that when we stimulated this tiny little brain area, we could wake the animals up and reinstate all the neural activity that you'd normally see in the cortex during wakefulness,” Dr Saalmann says.
“They acted just as they would if they were awake.”
As soon as the stimulation stopped, the macaques were back asleep within seconds.
“There are many exciting implications for this work,” says University of Wisconsin psychologist Michelle Redinbaugh.
“It's possible we may be able to use these kinds of deep-brain stimulating electrodes to bring people out of comas. Our findings may also be useful for developing new ways to monitor patients under clinical anaesthesia, to make sure they are safely unconscious.”
This research has been published in the journal Neuron.