Sleep is often associated with boosting long-term memory. A new article, published in Trends in Neurosciences, has taken it a step further, suggesting that immunological memory is also strengthened during deep sleep.
Researchers from the University of Tuebingen in Germany hypothesised that deep sleep might be beneficial not just to psychological memory but to that of the immune system as well. Slow-wave sleep (SWS), the technical term for deep sleep, could strengthen memories of past encounters with pathogens in a system similar to psychological memory.
“Why do we have to sleep?” asks professor Jan Born, senior author of the paper. “We need it to form persisting memories in the psychological domain and also the immune domain.”
When psychological memory is formed, the central nervous system (CNS) acts as medium for the responses to psychological events, thereby forming long-term neuronal memory relating to the physical and social environments. The immune system appears to be behaving in a similar manner. Long-lasting memories kept in the specialised cells of the immune system (T- and B-cells) pertaining to key features of antigens are formed in this way to cater for faster and more effective responses when the body meets with the antigen again.
According to the scientists, SWS reinforces the memory formation to allow for the extraction and storage of relevant information of the environment for future use in terms of responses. They say they are probably the first scientists to put forward the concept that sleep and memory might affect all body organs.
But, how does SWS assist the immune system’s memory? When a bacteria or virus is detected by the immune system, it is encoded so that memory T cells can be created. The newly-encoded representation is then turned into a stable and long-term representation (a process known as consolidation) – this is what allegedly happens during SWS. Furthermore, past studies have shown that SWS is linked with the long-term increase in memory T cells after vaccination. The researchers explain that the CNS and the immune system are similar based on the principles of consolidation.
“We consider our approach toward a unifying concept of biological long-term memory foundation, in which sleep plays a critical role, a new development in sleep research and memory research,” says professor Born.