Schedule of Events | Symposia

Ripples facilitate human memory consolidation by driving reactivation of learning-related neurons

Poster Session C - Sunday, March 30, 2025, 5:00 – 7:00 pm EDT, Back Bay Ballroom/Republic Ballroom

Marcel S. Kehl¹, Florian Mormann², Bernhard P. Staresina¹; ¹University of Oxford, ²University Hospital Bonn

Sleep is fundamental for stabilizing newly formed memory traces, yet the neural mechanisms underlying this process remain elusive in humans. In rodents, hippocampal ripples drive consolidation of spatial information through coordinated reactivation of navigation-specific cells (e.g., place cells). However, the processes that support human memory consolidation remain poorly understood, particularly at the cellular level. Are neurons tuned to learned stimuli preferentially recruited in service of memory consolidation? To tackle this question, we recorded activity of more than 1,000 neurons in the human medial temporal lobe (MTL) during an associative learning task and tracked their activity throughout subsequent sleep. We found that MTL neurons exhibit robust reactivation during ripples, with significantly stronger activation during sleep ripples than during awake ripples. Notably, this reactivation was amplified when local ripple events co-occurred with other MTL ripples recorded in the same hemisphere. Importantly, neurons that were tuned to specific stimuli of the learning task coupled more strongly to ripples compared to other neurons. Again, this effect was particularly apparent during sleep ripples compared to awake ripples. Crucially, ripple-mediated reactivation was stronger in neurons whose preferred stimuli were successfully recalled compared to those neurons whose preferred stimuli were not successfully recalled, directly linking ripple-triggered reactivation to human memory performance. Together, these findings uncover a mechanism by which ripples recruit learning-related neurons to support memory consolidation during human sleep.

Topic Area: LONG-TERM MEMORY: Episodic