Research from Newcastle University on how neurotransmitters can control brain states, between sleep and consciousness

As the start of a new year at university approaches, the topic of whether students are getting enough sleep arises. With many late nights and early 9am lectures, getting sufficient sleep when starting a new term is always a challenge. Studies into sleep and the brain are incredibly complex and interesting, with some amazing scientific investigations happening right here within Newcastle University.

The various stages and states of sleep are controlled within the brain by molecules called neurotransmitters. Their job is to send critical information as signals across gaps in neurones called synapses. There are billions of neurones and trillions of synapses in the human brain making the role of these neurotransmitters extremely important in delivering these signals.

Recent research from Newcastle University Neural Circuits Laboratory investigated further how the brain’s chemical messengers control consciousness and sleep. This work was completed in collaboration with the Blue Brain Project (EPFL, Switzerland).

The three neurotransmitters studied in this research were Acetylcholine, Dopamine and Serotonin. Specifically, Acetylcholine is known for its ability to support the transitions between brain states, such as from wake-fullness to sleep or from REM sleep to non-REM sleep.

The study found that the release of Dopamine and Serotonin in the location of the sensory cortices (the parts of the brain which receive and process information from the body’s senses) induced a desynchronisation network by the inhibition of oscillations. Desynchronisation happens when the brain becomes active as cells stop firing information in unison.

 Alongside this finding, the role of dopamine exerting a broad anatomical influence was reestablished. Interestingly, Serotonin was found to induce faster theta oscillations, which reflects different active brain states. This is a previously under appreciated area and therefore of high importance within this study. This recent finding, alongside further research, could provide understanding on how serotonin targeting antidepressants brings out their therapeutic effects.

In terms of acetylcholine, network simulations showed that it suppresses slow oscillations and promotes desynchronisation of cortical networks typically associated with deep sleep. The slow oscillations observed are the large, rhythmic electrical waves which are typically seen in non-REM sleep, the dampening of these waves allows the brain to fully awaken, thus switching the brain state.

The press release describes this specific finding: ‘the team's simulations suggest this effect is better explained by precise, synapse-to-synapse signalling rather than diffuse "volume" release — resolving a long-standing debate in the field.’

Using a combination of computational modelling and experimental measurements, these groups investigated how the neuromodulatory fibres in the rat somatosensory cortex are organised, and how they influence the dynamics of these networks. These neuromodulatory fibres are extremely thin parts of neurones which help to broadcast neurotransmitters across the nervous system to regulate brain states.

So next time you are worrying about the amount of sleep you are getting whilst at university, you can have a think about what is really going on inside your brain, with help from the research carried out by the incredible team at the Newcastle University Neural Circuits Laboratory.