The latest UCL study in zebrafish has found the impact of intensity of brain activity on sleep. The research team has discovered a gene that responds to brain activity and coordinates the need for sleep.
This research has shown that the intensity of brain activity, notwithstanding the time a person remains awake, determines the need for sleep. The journal “Neuron” has presented the study results.
Increased brain activity and greater need for sleep
Two systems regulate sleep. One is the circadian system, while the other is the homeostatic system. The circadian system is a built-in 24-hour clock in a person’s body. That times the biological rhythms, such as sleep and wake cycle.
On the contrary, there isn’t much understanding of the homeostatic system. This system leads to an increase in the feeling of tiredness after a very long day or a sleepless night. The research team has found that not just the awake time, but also the intensity of brain activity since the last sleep, drives this system.
The team has studied the larvae of zebrafish for looking at the brain processes that drive homeostatic sleep regulation, independent of time of day. Biomedical research has used it due to its similarities with humans.
Like humans, zebrafish also sleep every night. Besides this, they have nearly transparent bodies that can facilitate imaging. The research team has increased the intensity of brain activity in zebrafish by using various stimulants. That can also include coffee.
The results have shown that zebrafish with a drug-induced increase in brain activity have slept for a long time after the drugs had worn off. It has confirmed that increased intensity of brain activity can lead to a greater need for sleep.
The team has also found that one specific area of the brain in zebrafish was dominant in the effect on sleep pressure. In this area, a specific signaling molecule – galanin was active during recover sleep. On the contrary, this molecule didn’t play a big role in regular overnight sleep.
Increase in the activity of galanin
The researchers have further conducted a test to confirm that the drug-induced findings are related to actual sleep deprivation. In this test, they kept the zebrafish awake for all night on a treadmill. Where the team showed moving stripes to the fish, by imitating fast-flowing water.
This method gave the fish the impression that there is a need to keep swimming. The results have indicated that these awake zebrafish slept more the next day. Whereas, an increase in galanin activity was also present in their brain during recovery sleep.
These findings may suggest that galanin neurons track total brain activity. But there is a need for further research to clarify how these neurons detect what’s going on in the whole brain. The research team has said that this finding can explain the reason why people often feel tired after a seizure.
Furthermore, these results may also enlighten how some animals can avoid sleep during starvation. Whereas, the reason may be that their brains are capable of reducing brain activity to limit the need for sleep.
Discovering the gene that plays a key role in homeostatic sleep regulation, can help in understanding sleep disorders and conditions that affect sleep. While identifying a good target for these sleep disorders can lead to the development of therapies that act on galanin.