0227 Sleep Deprivation Alters Local Connectivity: Insights into Local Sleep Processes

Abstract Introduction Prolonged wakefulness disrupts the brain’s capacity to maintain uniform arousal, giving rise to “local sleep” events in which cortical regions transiently exhibit sleep-like activity. Resulting unstable wakefulness reflects a breakdown in network stability and has been linked to impaired cognition and reduced vigilance. This study examined regional connectivity across a period of overnight sleep deprivation to determine whether changes in localized hemodynamic signals represent a hallmark of a sleep deprivation. Methods Individuals were recruited from the central Tucson area using fliers and online advertisements (n = 20). Interested participants completed an online screener to select for self-reported healthy sleep patterns and no current neurologic conditions or mental illnesses. Sleep deprivation took place over 39-hours with seven resting-state MRI. Polysomnography was recorded for baseline and recovery sleep-episodes. Functional data were analyzed and preprocessed using the MATLAB toolbox CONN (22.v). Local correlation (LCOR) represents a weighted average of nearby connections (10 mm Gaussian area), computed from the matrix of bivariate correlation coefficients estimated using a singular value decomposition of z-score normalized signals, reflecting local coherence. Results Over sleep deprivation, significant increases in LCOR occurred in large-scale cortical areas, primarily within the somatosensory and visual networks (T = 9.9, p <.01). LCOR cluster maxima were localized within the thalamus (Z = 6.1; p < .01), postcentral gyri (Z = 5.94; p < .01), and superior temporal gyri (Z = 6.0; p < .01). A secondary analysis at 37-hour sleep deprivation revealed a negative association between subsequent N3 (% total sleep time) and LCOR in the brainstem, centered at MNI (–4, –32, –52), extending adjacent to the pontine cistern (β = -0.77; p < .01; R^2 = .56). Conclusion Progressive sleep deprivation was associated with increased LCOR, primarily within the somatosensory and visual networks. Increased LCOR may reflect enhanced slow or infra-slow neuronal oscillatory activity. Prior to recovery sleep, LCOR in a region of the brainstem and pontine cistern was negatively associated with N3 (% total sleep time). Given the proximity to CSF, physiological artifacts related to pulsatile fluid dynamics cannot be excluded. Support (if any) Army Research Office award W911NF2210223.