Reverse Brain Firing During Sleep Wipes Out Unimportant Information

A new study in rats conducted by researchers at the National Institutes of Health finds:

"When the mind is at rest, the electrical signals by which brain cells communicate appear to travel in reverse [reverse firing shown in image], wiping out unimportant information in the process, but sensitizing the cells for future sensory learning.

In the current study, the researchers found that these reverse signals weakened circuits formed during waking hours, apparently so that unimportant information could be erased from the brain. But the reverse signals also appeared to prime the brain to relearn at least some of the forgotten information. If the animals encountered the same information upon awakening, the circuits re-formed much more rapidly than when they originally encountered the information.

“The brain doesn’t store all the information it encounters, so there must be a mechanism for discarding what isn’t important,” said senior author R. Douglas Fields, Ph.D. ... "These reverse brain signals appear to be the mechanism by which the brain clears itself of unimportant information.”

The classic understanding of brain cell activity is that electrical signals travel from dendrites — antenna-like projections at one end of the cell — through the cell body. From the cell body, they then travel the length of the axon, a single long projection at the other end of the cell. This electrical signal stimulates the release of chemicals at the end of the axon, which bind to dendrites on adjacent cells, stimulating these recipient cells to fire electrical signals, and so on. When groups of cells repeatedly fire in this way, the electrical signals increase in intensity.

Dr. Bukalo and her team examined electrical signals that traveled in reverse — from the cell’s axon, to the cell body, and out its many dendrites. This reverse firing happens during sleep and at rest, appearing to reset the cell, the researchers found. ... A connection that is reset but never stimulated again may simply fade from use over time, Dr. Bukalo explained. But when a cell is stimulated again, it fires a stronger signal and may be more easily synchronized to the reinforced signals of other brain cells, all of which act in concert over time."

________