A research team has discovered a brain circuit that governs how certain memories are consolidated in the brain during sleep.
Published in the May 26 issue of Science magazine, the study shows how experimentally manipulating the identified neural connection during non-REM sleep (deep sleep) can prevent or enhance memory retention in mice.
The team led by Masanori Murayama studied the long-known phenomenon of memory consolidation during sleep by building off their recent study on tactile perception in which they found that perceiving texture requires signaling within a neural circuit from higher-level motor-related brain regions back to lower-level touch-related sensory areas. They reasoned that the same “top-down” pathway might also consolidate memories of textures.
Explains Murayama, “There is a long standing hypothesis that top-down input is crucial for memory consolidation and that during sleep, neurons in sensory regions activated during the initial experience can “reactivate” by unknown pathways. We found such reactivation of the top-down pathway is critical for mice to encode memories of their tactile experiences.”
The researchers developed a task to assess memory retention that relies on the natural inclination of mice to spend more time investigating new items in their environment. First they allowed mice to explore objects in two rooms with smooth floors, then they changed one of the smooth floors to a textured floor and again allowed the mice to explore. With normal sleep, mice spent more time exploring the room with the textured floor, showing that they remembered the smooth room and were less interested in it. Typically, this behavior was observed as long as the second exploration occurred within two days.
Photo Credit: RIKEN