Electrophysiological Evidence of Local Sleep During Yoga Nidra Practice.
Level 4 - case-series / case-control
Single-arm pre-post intervention and electrophysiological study without a control group
PubMed 35903117 · doi:10.3389/fneur.2022.910794
What was done
Thirty participants completed five supervised yoga nidra sessions followed by independent practice. Sleep diaries were kept for two weeks before and two weeks during the intervention. Electrophysiological characterization was conducted after two weeks using 19-channel EEG polysomnography to assess pre-practice, during-practice, and post-practice states. Standard sleep-wake staging and power spectral density (PSD) across multiple brain regions (central, frontal, prefrontal, parietal, temporal, occipital) were evaluated alongside pre-post sleep diary metrics.
What was found
Participants were scored as awake throughout the yoga nidra session (n = 26). Compared to pre-practice baseline, PSD showed a significant increase in delta power in the central area (mean difference 1.953 dB; P = 0.033) and a significant decrease in the prefrontal area (mean difference 2.713 dB; P = 0.041) during yoga nidra. Sleep diary metrics showed significant improvements in sleep duration (P = 0.0001), sleep efficiency (P = 0.0005), sleep quality (P = 0.0005), and total wake duration (P = 0.00005).
Why it matters
This study provides electrophysiological evidence that yoga nidra induces localized slow-wave activity (local sleep) in central regions while the individual remains globally awake by conventional criteria.
Limits
The study had a small sample size (30 enrolled, 26 analyzed for EEG) and lacked a randomized or active control group. Sleep outcomes were assessed solely via subjective sleep diaries rather than overnight polysomnography, and baseline participant demographics and health status were not reported in the abstract.