Exposure to broadband noise during NREM sleep suppresses the hippocampal sharp-wave ripples essential for memory consolidation, and the timing of the noise relative to these neural events determines the severity of the impairment, according to a study published July 8 in Current Biology.
Researchers at the University of Michigan led by Karla Salgado-Puga, Utku Kaya and Gideon Rothschild recorded neural activity from the CA1 region of the hippocampus in rats while delivering broadband noise through a closed-loop system triggered by real-time detection of sharp-wave ripples (SWRs) — the brief, high-frequency bursts of neural activity that are the electrophysiological signature of memory replay during sleep.
What they found. Broadband noise delivered during NREM sleep suppressed ripple power and reduced SWR rates. The suppression was greatest when noise was timed to coincide with SWRs (On-SWR condition) compared with delivery between ripples (Off-SWR condition), and it was accompanied by substantial changes in SWR-associated spiking patterns.
In behavioral tests using a conditioned place preference paradigm, On-SWR noise abolished memory retention at 24 hours after learning, while immediate recall tested right after sleep remained intact. Off-SWR noise weakened memory at both time points. The On-SWR condition produced a significantly larger impairment at 24 hours than Off-SWR, indicating that sounds coinciding with ripples are most damaging to long-term memory.
Why it matters. Environmental noise is pervasive in modern sleep environments, such as traffic, construction and household sounds, and is known to disrupt sleep quality and cognitive function. This study provides a direct mechanistic link: noise during sleep interferes with the hippocampal SWRs that are critical for transferring memories from short-term to long-term storage. The finding that even non-waking sounds can disrupt offline memory processing has implications for sleep hygiene recommendations and for the design of clinical and residential environments.
Limits. The study was conducted in rats using a specific broadband noise stimulus. Human hippocampal SWRs during sleep may respond differently, and real-world noise environments are more complex than controlled laboratory conditions.
Bottom line. Noise during NREM sleep disrupts hippocampal sharp-wave ripples and impairs memory consolidation in a timing-dependent manner, with sounds that coincide with ripples causing the greatest long-term memory deficit.
Source. Salgado-Puga K, Kaya U, Rothschild G. “Exposure to broadband noise during non-REM sleep impairs hippocampal sharp-wave ripples and memory consolidation.” Current Biology. 2026 Jul 8. doi:10.1016/j.cub.2026.06.039. PMID: 42419296.