The Nature of Consciousness

Piero Scaruffi

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These are excerpts and elaborations from my book "The Nature of Consciousness"

Dreams are Energetic

Most of the cells in the brain are actually not neurons but astrocytes or astroglia. These cells provide many functions to the nervous system and, in particular, store and release glycogen. Ramon y Cajal had already speculated that sleep might have to do with these cells. The Swedish neurologists Holger Hydén and Paul Lange (“Rhythmic enzyme changes in neurons and glia during sleep and wakefulness”, 1965) discovered that the level of enzyme activity is higher in neurons during sleep and slower during wakefulness, and viceversa in glia. It took three decades but eventually the US biologists Craig Heller and Joel Benington formulated the theory that the main role of sleep is to restore the brain’s energy. Adenosine is a nitrogen-based building block of adenosine triphosphate, or ATP, the energy-rich engine of the cell, stored as glycogen in the brain. During wakefulness ATP is consumed. Whenever the cell needs energy because the ATP reserves are being depleted, adenosine is released by brain cells. In other words, the processes of perception, thought and action use up the glycogen stores in the brain.  Adenosine is an inhibitory neurotransmitter. Eventually adenosine reaches a level that inhibits signal propagation and triggers non-REM sleep. Basically, adenosine triggers a chemical process that signals the depleted cells to enter a state of rest. In this state the brain is less active, consuming much less glycogen and energy can be replenished with new glycogen. Glycogen stores take time to replenish.

This homeostatic process works independently from the circadian clock. The US psychiatrists Dale Edgar and William Dement (“Evidence for Opponent Processes in Sleep/Wake Regulation”, 1992) showed that the circadian clock, in fact, keeps us awake during the day, even when we get tired and technically we should be falling asleep to recharge our energy storage. Other animals don’t have such opposing clocks and sleep whenever they need energy restoration.

 


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