The Nocturnal Brain

Robert is also not wh

Robert

some researchers have suggested that, in REM sleep, signals from the motor cortex, the part of the brain where movements are generated, simply bypass the basal ganglia, the areas involved in Parkinson’s disease that regulate movement in waking life.

The patient, who during the day had been unable to squat down, was very slow of movement and had a quietened voice, had been dreaming of being a police-duck, flying after a pigeon-thief.

A research study has shown that patients with Parkinson’s and RBD are less aggressive during the day than those with Parkinson’s and no RBD, at least suggesting that changes within the brainstem have some role in aggressive tendencies, but certainly this does not give us a full explanation.

But, despite our brains appearing to be so active during REM sleep, our bodies are largely paralysed. All muscles, with the exception of the muscles of the eyes, the diaphragm (the large muscle that is responsible for most breathing movements) and sphincters at the top and bottom of the gastrointestinal tract, develop complete weakness.

Individuals woken from REM sleep often describe dreams with a narrative structure, a story evolving like the plot of a book or a film. In contrast, the dreaming of non-REM sleep often contains only simple visual imagery, like animals, people or inanimate objects.

In fact, in recent years, we have begun to understand that previous notions of REM sleep being the stage of sleep exclusively in which we dream is not correct. It seems that dreaming in non-REM sleep is not unusual at all, although the content of the dreams is different.

During the sleepwalking episode, a deep area of the brain called the posterior cingulate cortex was found to be very active, while another area, the frontoparietal cortex, showed significantly reduced activity compared to wakefulness. Essentially, what they found was that small areas of the brain were awake, while other areas of the brain remained asleep. Those areas with increased activity, the cingulate cortex in particular, are involved in the control of behaviour associated with strong emotions.

We have known for years that certain animals like dolphins, seals and birds can sleep with one half of their brain at a time, allowing them to swim or fly while sleeping, what is termed ‘uni-hemispheric sleep’.