An international team of researchers has shown that a specific brain region is responsible for awakening fully anesthetised macaques, providing new insight into consciousness.  

When humans and other animals are awake, brain regions communicate in a coordinated way, much like an orchestra, combining their activity to produce perception, emotion and behaviour.   

To explore how this coordination changes during unconsciousness, a consortium led by the University of Cambridge (UK) and with researchers from France, Germany, Italy and Japan measured brain activity in humans, macaques, marmosets and mice under anaesthesia using functional magnetic resonance imaging (fMRI), a non-invasive imaging technique that measures brain activity through changes in blood flow.  

Across all four studied species, anaesthesia disrupted this orchestra-like coordination, leaving brain regions less able to work together as a unified system. 

To identify what acts as the brain’s orchestra conductor, the researchers delivered deep brain stimulation in macaques by placing a very thin electrode in the central thalamus – the brain region essential for sensory and motor information - to send small, controlled electrical pulses. This stimulation led to brain signals consistent with a return to wakefulness. Using computational tools, the team mapped how brain regions communicate and how genes are activated across the brain, revealing shared biological patterns linked to the loss and recovery of consciousness across species. 

"My long-term goal is to understand the mechanisms that govern consciousness, and how we can use pharmacology or brain stimulation to restore consciousness in patients," said Andrea Luppi from the University of Cambridge andfirst author of the study published in Nature Human Behaviour.  

The findings could help scientists to better understand disorders of consciousness that arise after brain injuries, infections or tumours, including comatose and minimally conscious states.