Unveiling the brain mechanism behind memory consolidation in sleep

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Neuroscientists person established successful caller decades nan thought that immoderate of each day's experiences are converted by nan encephalon into imperishable memories during slumber nan aforesaid night. Now, a caller study proposes a system that determines which memories are tagged arsenic important capable to linger successful nan encephalon until slumber makes them permanent.

Led by researchers astatine NYU Grossman School of Medicine, nan caller study revolves astir encephalon cells called neurons that "fire"—bring astir swings successful nan equilibrium of their affirmative and antagonistic charges—to transmit electrical signals that encode memories. Large groups of neurons successful a encephalon region called nan hippocampus occurrence together successful rhythmic cycles, creating sequences of signals wrong milliseconds of each different that tin encode analyzable information.

Called "sharp wave-ripples," these "shouts" to nan remainder of nan encephalon correspond nan near-simultaneous firing of 15 percent of hippocampal neurons, and are named for nan style they return erstwhile their activity is captured by electrodes and recorded connected a graph.

While past studies had linked ripples pinch representation statement during sleep, nan caller study, published online March 28 successful nan diary Science, recovered that daytime events followed instantly by 5 to 20 crisp wave-ripples are replayed much during slumber and truthful consolidated into imperishable memories. Events followed by very fewer aliases nary crisp wave-ripples grounded to shape lasting memories.

Our study finds that crisp wave-ripples are nan physiological system utilized by nan encephalon to 'decide' what to support and what to discard."

György Buzsáki, MD, PhD, elder study author, nan Biggs Professor of Neuroscience successful nan Department of Neuroscience and Physiology astatine NYU Langone Health

Walk and pause

The caller study is based connected a known pattern: humans and different mammals acquisition nan world for a fewer moments, past pause, past acquisition a small more, past region again. After we salary attraction to something, opportunity nan study authors, encephalon computation often switches into an "idle" reassessment mode. Such momentary pauses hap passim nan day, but nan longest idling periods hap during sleep.

Dr. Buzsáki and colleagues had antecedently established that nary crisp wave-ripples hap arsenic we actively research sensory accusation aliases move, but only during nan idle pauses earlier aliases after. The existent study recovered that crisp wave-ripples correspond nan earthy tagging system during specified pauses aft waking experiences, pinch nan tagged neuronal patterns reactivated during post-task sleep.

Importantly, crisp wave-ripples are known to beryllium made up of nan firing of hippocampal "place cells" successful a circumstantial bid that encodes, for instance, each room we participate and each conception of a maze entered by a mouse. For memories that are remembered, those aforesaid cells occurrence astatine precocious speed, arsenic we sleep, "playing backmost nan recorded arena thousands of times per night," arsenic nan study authors put it. The process strengthens nan connections betwixt nan cells involved.

For nan existent study, successive maze runs by study mice were tracked via electrodes by populations of hippocampal cells that perpetually changed complete time, contempt signaling very akin experiences. This revealed for nan first clip nan maze runs during which ripples occurred during waking pauses and past were replayed during sleep.

Sharp wave-ripples were typically recorded erstwhile a rodent paused to bask a sugary dainty aft each maze run. The depletion of nan reward, opportunity nan authors, prepared nan encephalon to move from an exploratory to an idle pattern, truthful that crisp wave-ripples could occur.

Using dual-sided silicon probes, nan investigation squad was capable to grounds up to 500 neurons simultaneously successful nan hippocampi of animals during maze runs. This successful move created a challenge, because information becomes exceedingly analyzable nan much neurons are independently recorded. To summation an intuitive knowing of nan data, visualize neuronal activity, and shape hypotheses, nan squad successfully reduced nan number of dimensions successful nan data, which is successful immoderate ways for illustration converting a 3D into a level one, without losing nan data's integrity.

"We worked to return nan outer world retired of nan equation, and looked astatine nan mechanisms by which nan mammalian encephalon innately and subconsciously tags immoderate memories to go permanent," said first writer Wannan (Winnie) Yang, PhD, a postgraduate student successful nan Buzsáki Lab. "Why specified a strategy evolved is still a mystery, but early investigation whitethorn uncover devices aliases therapies that tin set crisp wave-ripples to amended memory, aliases moreover lessen callback of traumatic events."

Along pinch Dr. Buzsáki and Dr. Yang, study authors from NYU Langone's Neuroscience Institute were Roman Huszár and Thomas Hainmueller. Kirill Kiselev, of NYU's Center for Neural Science, was besides an author, arsenic was Chen Sun of Mila, nan Quebec Artificial Intelligence Institute, successful Montréal. The activity was supported by National Institutes of Health grants R01MH122391 and U19NS107616.

Source:

Journal reference:

Yang, W., et al. (2024) Selection of acquisition for representation by hippocampal crisp activity ripples. Science. doi.org/10.1126/science.adk8261.