Role of Sleep on Brain Rebalancing

Lisa Franchi March 23, 2016

Sleep has long been regarded as one of the most important biological processes that play a role in human development. Without sleep, humans can never survive. During sleep, amazing processes take place particularly in our brain. These include the repair of cells and formation of long-term memories. Scientists call it “memory consolidation”.

A prominent and competing theory, which was first discovered by researchers from Brandeis University is that sleep is important for re-balancing activity in brain networks that have been perturbed during learning while awake. Such "rebalancing" of brain activity involves homeostatic plasticity mechanisms.

In their latest research, the same team found that homeostatic brain rebalancing occurs exclusively when animals are awake, and is suppressed by sleep - a finding which is contrary to the popular view.

The results raise intriguing possibility that different forms of brain plasticity - for example those involved in memory consolidation and those involved in homeostatic rebalancing - must be temporally segregated from each other to prevent interference.

The lab experiments conducted at Brandeis’ revealed that the homeostatic regulation of neuronal activity in the cortex is gated by sleep and wake states. In a surprising and unpredicted twist, the homeostatic recovery of activity occurred almost exclusively during periods of activity and was inhibited during sleep. Prior predictions either assumed no role for behavioural state, or that sleeping would account for homeostasis.

Their findings, which were published in the journal Cell, open the doors onto a new field of understanding the behavioural, environmental, and circadian influences on homeostatic plasticity mechanisms in the brain. Researchers sought to figure out what it is about sleep that precludes the expression of homeostatic plasticity, how it is possible that mechanisms requiring complex patterns of transcription, translation, trafficking, and modification can be modulated on the short timescales of behavioural state-transitions in rodents, and finally, how generalizable their finding is.

Source of this article:

Keith B. Hengen et al. Neuronal Firing Rate Homeostasis Is Inhibited by Sleep and Promoted by Wake, Cell