The brain's vivid blue cells that tune your sleep
The locus coeruleus is emerging as a major new area of research interest, with many important functions such as regulating our attention and sleep.
Anyone with insomnia knows the impatience and frustration that accompanies sleeplessness, as you struggle to turn out the lights in your head and mute its inner voice. You long for a button or dial that could instantly dampen all that mental activity.
The idea of a mental dimmer switch is not quite as far-fetched as it might seem. Most neuroscientists now agree that our wakefulness exists on a kind of continuum. It is coordinated by a complex network of brain regions, at the heart of which lies a tiny bundle of neurons known as the "locus coeruleus", Latin for "blue dot".
It is a literal description: the neurons in the locus coeruleus are dyed the colour of sapphire from the production of a particular neurotransmitter, called norepinephrine. This is also a clue to the blue dot's function, since norepinephrine controls our physiological and psychological arousal.
For a long time, scientists assumed that the locus coeruleus was dormant during sleep, but it is now becoming clear that it is never completely quiet, with low levels of intermittent activity that may regulate the depths of our slumbers. A better understanding of this process may help to treat the disturbed sleep associated with conditions like anxiety.
The locus coeruleus lies in the brain stem, just above the back of the neck – and contains around 50,000 cells, a tiny portion of the 86 billion neurons in the average central nervous system. Marie Antoinette's physician Félix Vicq d'Azyr was the first to note its existence in the late 18th Century – but for a long time, it failed to attract any further attention.
That began to change in the 20th Century, when it became clear that the locus coeruleus' blue pigment played a key role in brain signalling. Norepinephrine (also known as noradrenaline) raises the chance that a neuron will "spike" with an electric current. When they become active, cells in the locus coeruleus pass bundles of this neurotransmitter along their projections to other regions of the brain – enhancing the communication between the neurons in that area.
There are nuances to this process. Depending on the types of receptors they have, some neurons are more sensitive to smaller amounts of norepinephrine, while others only respond to higher thresholds. This means that, as the locus coeruleus activity rises, it will start to affect some brain areas more than others, which can have dramatic effects on things like our focus, concentration and creativity.
In her book Hyperefficient: Optimize Your Brain to Transform the Way You Work, the neuroscience researcher and writer Mithu Storoni describes the locus coeruleus, and its control over norepinephrine signalling, as the brain's gearbox, with different modes that are best suited to certain kinds of activities.
Gear 1: very gentle activity in the blue dot. The low levels of norepinephrine mean that our attention is diffuse and our mind wanders from thought to thought.
Gear 2: moderate firing in the blue dot, accompanied by occasional spikes in response to the most relevant stimuli. The prefrontal cortex, which is involved in self-control and abstract thinking, is most sensitive to this concentration of norepinephrine. We may find it easier to stay focused on intellectual tasks in this brain state.
Gear 3: constantly high firing in the........
© BBC
