A Causal Role for the Hippocampus in Gating Rapid Motor Memory Consolidation

How humans learn new skills is a fundamental aspect of behavior. Rapid memory consolidation during brief rests is crucial, but the causal role of the hippocampus remains unclear. Here, we used personalized transcranial ultrasound stimulation (TUS) to non-invasively modulate the hippocampus. We found that hippocampal neuromodulation fundamentally alters how a skill is learned. Compared to sham stimulation, TUS shifted performance gains from rest periods (offline consolidation) to active practice (online learning). Paradoxically, this manipulation not only reshaped the learning process but also boosted overall performance by unmasking a latent and highly efficient online learning pathway, leading to superior skill retention 24 hours later. These findings provide causal evidence that the hippocampus acts as a gating mechanism, governing a key trade-off between online and offline learning pathways. Our work demonstrates that non-invasive deep brain modulation can causally alter the balance between competing memory systems, opening new avenues to optimize human performance.