Performance
An Indian neuroscientist introduces sleep stages, waking, dreams, deprivation, biological rhythms, and the neural regulation of REM sleep.
In this account, dreaming sleep begins less by pressing an accelerator than by lifting a brake. Cells that release noradrenaline normally hold the dreaming-sleep cells in check. When those brake cells stop firing, or when other inputs block their signal right at its endpoint, the dreaming-sleep cells are freed and the phase can begin.
Dreaming sleep probably appeared around 140 million years ago, and its origin and purpose still remain mostly hypothetical. Even so, the author argues that accumulating evidence rules out treating it as a useless evolutionary relic. On his view, a feature can be poorly understood and still clearly important.
The author proposes that dreaming sleep serves as the brain's housekeeping, keeping its excitability and its noradrenaline levels within an optimal range. On this view, the phase evolved in higher animals to do that job. When it is lost, noradrenaline builds up, and the author reports that this disrupts nerve-cell excitability, gene activity and thinking.
Dreaming sleep starts and stops through a push-pull between two groups of brainstem nerve cells: one group that fires to turn it on and another that must fall silent to let it happen. The author treats this on-off interaction as the basic scaffold of how this sleep phase is regulated, so the state is defined by some cells speeding up while others go quiet.
Because one shared chemical system is thrown off balance, the author argues that losing dreaming sleep affects most mental, bodily and physiological processes, rather than causing a single isolated deficit. He links deprivation of this phase to a wide range of mind-body disorders. These are the author's research claims, not medical advice.
The dopamine cells that are lost in Parkinson's disease feed into the circuit that switches dreaming sleep on and off. Disturbed dreaming sleep shows up alongside Parkinson's, depression and a disorder in which people act out their dreams. The author points to this overlapping circuitry as a possible reason these conditions and sleep problems travel together, an association rather than a proven cause.