A perineuronal network (red) in the mouse brain, surrounding a neuron that expresses Arc (green), a protein involved in memory processing. Holes in the perineuronal network may represent memory storage sites that are regulated during sleep. Credit: Pantazopoulos et al., ENeuro 2020
Changes in brain cartilage may explain why sleep helps you learn
Scientists discover a potential mechanism behind sleep-induced memory changes.
The new structure of the brain’s “cartilage cells” can regulate how memories change while you sleep, according to new research in eNeuro.
Sleep allows the body to rest, but not the brain. During sleep, the brain represents a day of learning by strengthening strong memories and weaker weak memories, a process known as memory consolidation. But changing memories requires changing synapses, the connections between neurons. The changes induced by sleep must overcome the perineuronal networks, cartilage sheaths that not only surround and protect neurons, but also prevent changes in synapses.
Pantazopoulos et al. investigated how perineural networks varied during sleep in mice. By documenting whether or not they could tag the networks with a protein that binds to a specific sugar chain, they could observe the changes at the synapses. A decrease in the number of labeled networks would indicate an increase in the number of neurons that allow synaptic changes.
The marking increased during wakefulness and decreased during sleep. Lack of sleep prevented this change. The levels of an enzyme that alters the network expressed by the brain’s immune cells cycle in opposition, suggesting that it may be responsible for the change. The research team also compared the levels of labeled networks in human brain tissue with the time of donor death. Human brains showed similar sleep-focused rhythms in the network structure. Altered structure of the perineuronal networks may be one of the mechanisms behind sleep-induced memory changes.
Reference: “Circadian Rhythms of Net Perineuronal Composition” July 27, 2020, eNeuro.
DOI: 10.1523 / ENEURO.0034-19.2020
