Introducing the brain: the drive system master swutch (Introduction)

by David Turell , Thursday, October 10, 2024, 22:17 (42 days ago) @ David Turell

From mildly alert to anxiety:

https://www.newscientist.com/article/mg26435122-900-take-control-of-your-brains-master-...

"...near a fluid-filled cavity in the root of your brain, lies a small bundle of pigmented cells the colour of lapis lazuli. This is the locus coeruleus – Latin for “blue dot”. It measures just a few millimetres, but its diminutive size belies its power over your thoughts.

"Research has revealed that the structure is instrumental in coordinating our mental processing. Sometimes labelled the brain’s “master switch”, it is perhaps better imagined as a gearbox. “It can set the pace of your brain to suit the specific kind of mental work you are doing,” says neuroscience researcher turned writer Mithu Storoni. When it is in the right gear, we feel pleasantly engaged in the task at hand. Often, however, it can get stuck in the wrong one, leading either to dreamy procrastination or frenzied frustration.

"...The structure, which contains only up to 50,000 neurons, was first identified by Marie Antoinette’s physician Félix Vicq d’Azyr in the late 18th century, after he noted a small blue stain in the brainstem, the mass of neural tissue joining the cerebrum to the spinal cord. Exactly what this little blue dot did, however, remained an unexplored mystery until well into the 20th century, even after Japanese researchers in the 1940s observed in monkeys that damage to this structure results in a loss of consciousness.

"...the power of the locus coeruleus is intimately tied to its distinctive appearance. It is the brain’s primary producer of a neurotransmitter called noradrenaline, or norepinephrine, which it stores in blue-tinged bundles. When a cell within the locus coeruleus becomes active, it releases those bundles along its projections to other neurons within the brain, where the noradrenaline modulates their electrical activity in response to signals from other cells. “It makes it more likely that a cell will ‘spike’ when it gets the next input, and it makes any spike more forceful and impactful,” says James “Mac” Shine at the University of Sydney, Australia. In other words, cells become more reactive, and the result is enhanced communication. “You’re making it much easier for a message to be passed [between brain regions],” he says.

***

"The locus coeruleus is directly connected to changes in the pupils of our eyes: the busier it becomes, the wider they dilate. Tracking these movements while keeping light levels constant therefore offers a window on its activity.

***
"According to this metaphor, Gear 0 is the state of the locus coeruleus when you are asleep. It is almost completely silent at this point, apart from transient bursts of activity that seem to enhance the long-term storage of memories.

***

"This combination of moderate baseline activity and short-lived bursts of neurotransmitter release is characteristic of Gear 2 and allows the brain to process new information more efficiently. If they are large enough, these spikes can trigger a “network reset” – a shift in focus to new and important information – which is essential for flexible thinking.

***

"Problems may arise when the hum turns to a roar. This is what happens in Gear 3. Here, high levels of noradrenaline streaming from the locus coeruleus can activate areas of the brain associated with emotional processing. These tend to have receptors that respond only when concentrations of the neurotransmitter have reached a higher threshold. This can lead to the fight-or-flight response – useful if we are in danger and need to be hyperalert.

***

"...we know that Ritalin raises the levels of dopamine, a neurotransmitter associated with the brain’s reward system. This could increase the sense of reward associated with tasks and, therefore, the attention paid to them.

"But Ritalin also keeps the brain’s noradrenaline at a more constant level, which could then moderate the activity of the locus coeruleus through a feedback loop. “[The structure] is exquisitely sensitive to the amount of free noradrenaline and, like a thermostat, turns down its firing rate if local noradrenaline concentrations get too high,” says Shine.

***

"Given these findings, many neuroscientists now consider moderate locus coeruleus activity – that is, Gear 2 – to be key to optimum cognitive performance, a sweet spot between dreamy and frantic. “It’s when the prefrontal cortex is completely engaged and working at its best,” says Storoni.

***

"Recent research even suggests that Gear 2 underpins the famous “flow state” – the feeling of being so totally engaged in a task that you forget the passing of time. “People find flow rewarding,” says Dimitri van der Linden at Erasmus University Rotterdam in the Netherlands. “They can spend hours on the same activity.'”

Comment: an amazing brain control center. Can't image it just evolved.