{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,17]],"date-time":"2026-08-17T23:32:45Z","timestamp":1787009565135,"version":"build-2736575974"},"reference-count":58,"publisher":"Oxford University Press (OUP)","issue":"6","funder":[{"DOI":"10.13039\/100000027","name":"National Institute on Alcohol Abuse and Alcoholism","doi-asserted-by":"publisher","award":["Y1AA-3009"],"award-info":[{"award-number":["Y1AA-3009"]}],"id":[{"id":"10.13039\/100000027","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000027","name":"National Institute on Alcohol Abuse and Alcoholism","doi-asserted-by":"publisher","award":["ZIAAA000550"],"award-info":[{"award-number":["ZIAAA000550"]}],"id":[{"id":"10.13039\/100000027","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Intramural Research Program of the National Institutes of Health"},{"DOI":"10.13039\/501100012264","name":"NIH","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100012264","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000016","name":"US Department of Health and Human Services","doi-asserted-by":"publisher","id":[{"id":"10.13039\/100000016","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2026,5,30]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>Sleep profoundly alters large-scale brain dynamics, yet its impact on the cortex's macroscale functional hierarchy remains incompletely understood. We analyzed transitions from wakefulness to nonrapid eye movement (NREM) 1 and NREM2 sleep in a simultaneous electroencephalography\u2013functional MRI (EEG-fMRI) dataset of 33 healthy adults, deriving cortical gradients and local and global functional connectivity density (lFCD, gFCD) from stage-specific fMRI time series. Cortical gradients remained highly correlated across states (R &amp;gt; 0.92), indicating preservation of the overall hierarchical scaffold, yet both principal and secondary gradients showed progressive compression during NREM2, with prominent posterior\/visual involvement. lFCD increased within unimodal regions and closely tracked gradient position, whereas gFCD showed broader, less spatially specific increases, consistent with altered low-frequency synchronization and network integration during early sleep. Complementary analysis of an independent eyes-open\/eyes-closed dataset revealed milder, more localized gradient changes during eyes-closed wakefulness, suggesting that early NREM sleep may involve broader sensory disengagement than eye closure alone. Together, these results indicate that early NREM sleep preserves large-scale cortical topology while reducing differentiation along its principal axes and strengthening local connectivity within sensory systems, marking a shift toward more internally dominated cortical dynamics as the brain transitions away from external input.<\/jats:p>","DOI":"10.1093\/pnasnexus\/pgag221","type":"journal-article","created":{"date-parts":[[2026,6,18]],"date-time":"2026-06-18T08:02:41Z","timestamp":1781769761000},"source":"Crossref","is-referenced-by-count":1,"title":["Compression of functional gradients during early nonrapid eye movement sleep"],"prefix":"10.1093","volume":"5","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-0183-5678","authenticated-orcid":false,"given":"Dardo","family":"Tomasi","sequence":"first","affiliation":[{"name":"National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health , Bethesda, MD 20892-1013 ,","place":["USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nora D","family":"Volkow","sequence":"additional","affiliation":[{"name":"National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health , Bethesda, MD 20892-1013 ,","place":["USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"286","published-online":{"date-parts":[[2026,6,18]]},"reference":[{"key":"2026062614483248000_pgag221-B1","doi-asserted-by":"crossref","first-page":"681","DOI":"10.1152\/physrev.00032.2012","article-title":"About sleep's role in memory","volume":"93","author":"Rasch","year":"2013","journal-title":"Physiol Rev"},{"key":"2026062614483248000_pgag221-B2","doi-asserted-by":"crossref","first-page":"12","DOI":"10.1016\/j.neuron.2013.12.025","article-title":"Sleep and the price of plasticity: from synaptic and cellular homeostasis to memory consolidation and integration","volume":"81","author":"Tononi","year":"2014","journal-title":"Neuron"},{"key":"2026062614483248000_pgag221-B3","doi-asserted-by":"crossref","first-page":"1017","DOI":"10.1016\/S1474-4422(14)70172-3","article-title":"Connections between sleep and cognition in older adults","volume":"13","author":"Yaffe","year":"2014","journal-title":"Lancet Neurol"},{"key":"2026062614483248000_pgag221-B4","doi-asserted-by":"crossref","first-page":"3238","DOI":"10.1038\/s41467-023-38972-x","article-title":"Hierarchical fluctuation shapes a dynamic flow linked to states of consciousness","volume":"14","author":"Li","year":"2023","journal-title":"Nat Commun"},{"key":"2026062614483248000_pgag221-B5","doi-asserted-by":"crossref","first-page":"92","DOI":"10.3389\/fncir.2017.00092","article-title":"The roles of cortical slow waves in synaptic plasticity and memory consolidation","volume":"11","author":"Miyamoto","year":"2017","journal-title":"Front Neural Circuits"},{"key":"2026062614483248000_pgag221-B6","doi-asserted-by":"crossref","first-page":"1589","DOI":"10.1093\/sleep\/33.12.1589","article-title":"Functional neuroimaging insights into the physiology of human sleep","volume":"33","author":"Dang-Vu","year":"2010","journal-title":"Sleep"},{"key":"2026062614483248000_pgag221-B7","doi-asserted-by":"crossref","first-page":"163","DOI":"10.1038\/383163a0","article-title":"Functional neuroanatomy of human rapid-eye-movement sleep and dreaming","volume":"383","author":"Maquet","year":"1996","journal-title":"Nature"},{"key":"2026062614483248000_pgag221-B8","doi-asserted-by":"crossref","first-page":"831","DOI":"10.1038\/77744","article-title":"Experience-dependent changes in cerebral activation during human REM sleep","volume":"3","author":"Maquet","year":"2000","journal-title":"Nat Neurosci"},{"key":"2026062614483248000_pgag221-B9","doi-asserted-by":"crossref","first-page":"101691","DOI":"10.1016\/j.smrv.2022.101691","article-title":"The microbiota-gut-brain axis in sleep disorders","volume":"65","author":"Wang","year":"2022","journal-title":"Sleep Med Rev"},{"key":"2026062614483248000_pgag221-B10","doi-asserted-by":"crossref","first-page":"403","DOI":"10.1007\/s13311-016-0429-3","article-title":"Sleep, sleep disorders, and mild traumatic brain injury. 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