Attention modulates hippocampal sharp-wave ripples in humans

Hippocampal sharp-wave ripples (SWRs) are high-frequency events critical for memory consolidation, typically studied during sleep and quiet wakefulness. Emerging evidence suggests that SWRs also occur during active behavior, yet their role in awake cognition remains unclear. Here, we demonstrate that changes in sustained attention modulate both the occurrence of SWRs and their temporal alignment to ongoing hippocampal oscillations. Using intracranial EEG recordings from epilepsy patients performing a sustained attention to response task (SART), we first identified attentional states based on behavioral variability and subjective reports. Next, we observed that SWRs were more frequent during high-attention periods, despite the absence of memory demands. Importantly, SWRs during low-attention periods showed higher phase synchrony with low-frequency oscillations (theta to lower beta) indicating increased endogenous coordination of SWRs under low attentional focus. These findings show that SWRs are dynamically regulated by attentional engagement, supporting a broader role for ripples in active cognitive processing.