Brief non-arousing auditory signals (like sounds, music, noises) received at certain sleep phases have shown the potential to enhance specific sleep functions. Huber et al. from University Children’s Hospital of Zurich were investigating the effects of phase-targeted auditory signals on verbal memory.
One important function of sleep is to reactivate our memories and thereby consolidate them, leading to a better retrieval of these memories the next day.
During sleep the brain shows slow electric waves, measurable by electroencephalography (EEG). The strongest of these waves is the so-called K-complex. It is often followed by sleep spindles – a waxing and waning burst of neural activity with smaller wavelengths. The synchronized occurrence of these two neural activities are supposed to be involved in the memory consolidation.
The researchers conducted a test on 14 young healthy adults. They tested them for two nights, in the first applying brief auditory signals (which were played repeatedly the whole night) and in the second without applying any signal. Brain-activity was recorded by high-density EEG during both nights. Before sleeping they had to memorize word-pairs which were then recalled the next morning to test if the sound signal had any effect on their memory.
The results show that the sounds generated brain activities very similar to the K-complex followed by sleep spindles. After the night where they received the signal the probands were significantly better in remembering the word pairs. Thus, the auditory signals correlate with a better memory formation – showing that inducing brain signals similar to the K-complex is sufficient to boost our memory.
Reference:
Leach, S., Krugliakova, E., Sousouri, G. et al. Acoustically evoked K‑complexestogether with sleep spindles boost verbal declarative memory consolidation in healthy adults. Sci Rep 14, 19184, 2024. https://doi.org/10.1038/s41598-024-67701-7
Useful links:
About Reto Huber: https://www.med.uzh.ch/de/UeberdieFakultaet/fakultaetsmitglieder/huberreto.html
Image:
Kinga Howard, Unsplash