Default network response to a working memory challenge after withdrawal of continuous positive airway pressure treatment for obstructive sleep apnea.

Lower working memory performance and altered brain activity have been reported in studies of obstructive sleep apnea (OSA) patients. However, little is known about the effect of treatment of OSA on brain function, particularly effects on default network processing. We previously reported increased brain response to a working memory challenge in active regions and decreased response in relatively deactivated a priori regions of interest (ROIs) following withdrawal of continuous positive airway pressure (CPAP) treatment. This follow-up analysis was conducted to examine the effects of CPAP withdrawal on default network processing using empirically defined ROIs analyses (i.e., in ROIs exhibiting significant deactivation in the sample). Ten OSA patients performed a 2-Back working memory task during functional magnetic resonance imaging in two separate conditions, following regular CPAP use, and after two nights of CPAP withdrawal. Eleven clusters of significant 2-Back-related deactivation consistent with the default network were identified and further examined for CPAP withdrawal effects. Significant further deactivation relative to the treatment adherent baseline was observed in the majority of these ROIs during the withdrawal condition. The magnitude of deactivation during withdrawal was significantly associated with better working memory performance in the posterior cingulate and right postcentral gyrus, and greater sleepiness in the left and right medial frontal gyrus. Results suggest that default network functions are further suspended as a result of a shifting of attention towards a more difficult active task in the context of lowered attentional capacity related to sleepiness.