Shattered Sleep, Fragmented Mind? Impact of Sleep Fragmentation and its Restoration on Cognition

Public defense of drs. Oumaïma Benkirane to obtain the double degree of Doctor of Psychology (VUB) and Docteur en sciences psychologiques (ULB). 

The defense will take place on April 1, 2025 at 3 p.m. in Room R42.5.110 located in the Solvay building D, on the Solbosch campus of the Université libre de Bruxelles (Ixelles).

NB: the defense will be held in French.

For those of you who are not able to attend the seminar in person, it will also be possible to follow the seminar with this Teams link: https://bit.ly/3FoyQjQ

Title: Shattered Sleep, Fragmented Mind ? Impact of Sleep Fragmentation and its restoration on Cognitive  Fatigue & Cognition.

Promotors:

• Prof. Dr. Philippe Peigneux (ULB)
• Prof. Dr. Olivier Mairesse (VUB)

Abstract:  This thesis explores the impact of sleep fragmentation (SF) on cognitive functions, particularly cognitive fatigue (CF), and its neurophysiological underpinnings. SF, common in conditions like obstructive sleep apnea (OSA), impairs executive functions and attention, affecting daily life. The thesis comprises two main studies: an experimental investigation of induced SF in healthy participants and a clinical study on the cognitive and fatigue-related effects of continuous positive airway pressure (CPAP) therapy in OSA patients. In healthy young adults, three nights of SF altered sleep architecture, reducing sleep efficiency, N3 and REM sleep, while increasing sleep stage transitions. Participants reported higher fatigue, and inhibitory control declined post-SF. However, CF evolution remained similar between SF and undisturbed sleep, suggesting compensation. EEG analyses during the CF-inducing TloadDback task showed increased high beta power under high cognitive load after SF, indicating greater effort. Post-task resting EEG revealed increased beta, alpha, and theta power, suggesting a relaxation rebound, while beta activity varied based on cognitive load and sleep condition. These findings confirm that SF disrupts sleep and negatively affects fatigue and cognitive control. In OSA patients, CPAP treatment over three to six months improved cognitive functions—attention, working memory, and executive control—while reducing fatigue. These benefits were more pronounced with longer CPAP use, emphasizing its cumulative effects. After six months, participants reported better sleep quality, enhanced alertness, and improved quality of life, supporting CPAP’s role in mitigating CF and enhancing cognitive resilience. A final study examined CPAP’s impact on verbal memory integration in OSA using a false memory paradigm. After CPAP initiation, patients showed improved recognition of learned words and semantic lures, suggesting enhanced memory processes.  Overall, this thesis provides new insights into the distinct yet interconnected effects of SF and OSA on CF and memory, reinforcing the importance of sleep quality for cognitive resilience.