BRAIN WEEK: Why Does Our Brain “Clean Up” Overnight?
Studying the human brain during sleep reveals a fascinating biological process. While we sleep, the brain actively consolidates the knowledge and experiences gathered throughout the day. A research team from the Institute of Normal and Pathological Physiology of the Centre of Experimental Medicine, Slovak Academy of Sciences, has focused on the relationship between sleep, memory, and the important protein BDNF. Their findings confirm that BDNF acts as a key regulator at night, when our experiences are transformed into long-term memories.
Sleep as the architect of memory
Memory is not a static archive. “When we learn something new, whether it is a list of foreign vocabulary or a new movement in sports, the brain first forms an initial, fragile memory trace. For this information to last a week or even a year, it must undergo a process called consolidation,” explains Rastislav Rovný from the institute.
Sleep plays a crucial role in this process. According to current scientific understanding, memory consolidation occurs in two stages. Information is first stored in a fast, temporary system in a brain region called the hippocampus. During sleep, it is gradually transferred to a slower but more stable storage system in the cerebral cortex. This process requires synaptic plasticity, the ability of connections between neurons to change their strength and structure.
BDNF: a key mediator of synaptic plasticity
These changes require specific molecular “tools.” One of the most important is brain-derived neurotrophic factor, or BDNF. “It is a protein that acts like a kind of ‘fertiliser’ for neurons. It supports their growth, survival, maturation, and above all, their ability to form, modify, and strengthen connections,” the researcher explains.
However, our genetic makeup is not identical. A common variation in the BDNF gene, known as Val66Met, affects how readily the brain releases this protein. In individuals carrying the Met variant, BDNF secretion is somewhat reduced, which may influence memory formation.
We learn similarly, but forget differently
In the study, researchers observed 174 healthy young participants. “We examined how this genetic difference influences memory when learning a list of words. The results showed a distinction between how we acquire information and how we retain it,” says Rovný.
Immediately after learning, there were no differences between participants. Regardless of the BDNF variant, everyone recalled a similar number of words. This suggests that the BDNF gene does not affect our ability to acquire and encode new information. The difference became apparent only after 24 hours. After sleep, carriers of the Met variant recalled fewer words than others.
This finding indicates that BDNF is particularly important for the long-term stabilisation of memory. Its role is crucial during the later phase of consolidation, when the brain transitions from short-term storage to long-term encoding by producing new proteins. This process takes place mainly during sleep. If BDNF release is less efficient, as in Met carriers, this overnight stabilisation may be weaker.
Not all learning is the same
Interestingly, this genetic difference was observed only in episodic memory, the memory of events and their context, and not in motor learning, such as quickly tapping numerical sequences. “Both groups improved in the motor task after sleep, and the Val66Met variant did not play a role here,” the researcher explains. One possible reason is that motor skills involve different brain circuits, such as the basal ganglia or the cerebellum, which may be less dependent on BDNF in the early stages of learning or may show its influence only during longer training.
The importance of the research
“Our genes are not our destiny, but they provide important context for how we function. Understanding the role of BDNF in sleep-related memory consolidation helps explain individual differences in learning,” says Rovný. He adds that Brain Week is a good reminder that every hour of quality sleep is an investment in our brain. “It is the time when our neurons, with the help of factors such as BDNF, strengthen the foundations of our knowledge and help shape who we are.”
Today is also World Sleep Day.
Source: Rastislav Rovný, Institute of Normal and Pathological Physiology, CEM SAS
Prepared by: Andrea Nozdrovická
Photo: canva.com