Albert Aguayo Lecture: Do You Remember? Let Me Explain You How

Abstract: A general wisdom is that only selected aspects of our experiences are remembered. Extensive work over the past decades has shown that sleep plays a critical role in the consolidation process of memory. We identified a brain pattern, known as sharp wave-ripple (SPW-R), that supports the “replay” of waking experience in compressed snippets (~100 ms) in the hippocampal-neocortical circuits. SPW-Rs evolved in evolution to support body functions, such as regulating glucose levels and hormone release, and we exapted to serve cognitive functions, parallel with the development of the neocortex. SPW-Rs are present in the resting and waking brain, and these compressed information packages repeat fragments of learned information 2000 to 4000 times each night during non-REM sleep. However, brain mechanisms that select experiences for lasting memory are not known. To address the selection (or “credit assignment”) problem, we combined large-scale neural recordings with a novel application of dimensionality-reduction techniques in rodents. When the brain state changed from theta oscillations during maze exploration to SPW-Rs during reward consumption, the spike content of SPW-Rs decoded the trial in which they occurred. In turn, during post-experience sleep, SPW-Rs continued to replay those trial contents that were reactivated most frequently during waking SPW-Rs. These findings demonstrate that the replay content of awake SPW-Rs provides a tagging mechanism to select critical aspects of experience that are consolidated and preserved for future use during sleep. In related experiments, we aborted or prolonged SPW-Rs by closed-loop optogenetic methods and demonstrated impaired and enhanced memory of the previous experience, respectively. Thus, SPW-Rs provide a hippocampal mechanism for prioritizing and tagging aspects of experience and consolidating them during post-learning sleep.

Bio: György Buzsáki is Biggs Professor of Neuroscience at New York University. His main focus is “neural syntax”, i.e., how the numerous brain rhythms organize segmentation of neural information to support cognitive functions. He is among the top 0.1% of most-cited neuroscientists and an elected member of the National Academy of Sciences USA, Academiae Europaeae, and the Hungarian Academy of Sciences. He sits on the editorial boards of several leading neuroscience journals, including Science and Neuron, honoris causa at Université Aix-Marseille, France and University of Kaposvar, Hungary and University of Pécs, Hungary. He is a co-recipient of the 2011 Brain Prize and the recipient of the 2020 Ralph Gerard Award (SFN). (Books: G. Buzsáki, Rhythms of the Brain, Oxford University Press, 2006; The Brain from Inside Out, OUP, 2019)

This annual lecture honours Dr. Albert Aguayo, OC, FRCP, Professor Emeritus founder and former Director of the Centre for the Research in Neuroscience at McGill University.

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