Scientists from the University of Tsukuba and the University of Tokyo have identified a specific group of neurons that is necessary for memory consolidation during REM sleep. Scientists revealed that adult-born neurons (ABNs) in the hippocampus, monitors memory consolidation during REM sleep.
There is little information available on the contribution of ABNs to memory formation during sleep. Hence, scientists decided to study the role of ABNs.
Lead author of the study Associate Professor Masanori Sakaguchi said, “Although ABNs in the dentate gyrus region of the hippocampus are rare and not frequently active, they show heightened plasticity, indicating their potential role in the formation of memories. We wanted to investigate how manipulating ABN activity would affect memory consolidation in freely behaving mice.”
For the study, scientists exposed mice to a context-specific fear memory task. Then, they recorded activity in specific ABNs across the learning, consolidation, and retrieval stages of memory.
They found that young ABNs that were most active during REM sleep after the memory task were most likely to have been active during learning.
When examining the effects of optogenetic silencing on young ABN activity during sleep, scientists observed that the consolidation of contextual fear memories was impaired.
Scientists noted, “The data represent causal evidence that activity in young ABNs during REM sleep is necessary for memory consolidation. This is a significant development as the activity and role of ABNs in memory consolidation during sleep was previously unknown, as was the type of hippocampal neuron responsible for memory consolidation during sleep. “
Professor Sakaguchi said, “During learning, specific ABNs may undergo synaptic changes that enable memory consolidation. Further, these synaptic changes may depend on synchronization between specific ABNs and brain oscillations that take place during REM sleep.”
Clarification of these possibilities may lead to a deeper understanding of how memories are formed, retrieved, and consolidated, and could facilitate the development of new treatments for memory disorders.
Journal Reference:
- Deependra Kumar et al., Sparse Activity of Hippocampal Adult-Born Neurons during REM Sleep Is Necessary for Memory Consolidation. DOI: 10.1016/j.neuron.2020.05.008