Sleep apnea: Altered brain connectivity underlying a working-memory challenge

Abstract

Obstructive sleep apnea (OSA) is characterized by the frequent presence of neuro-cognitive impairment. Recent studies associate cognitive dysfunction with altered resting-state brain connectivity between key nodes of the executive and default-mode networks, two anti-correlated functional networks whose strength of activation increases or decreases with cognitive activity, respectively. To date no study has investigated a relationship between cognitive impairment in OSA and brain connectivity during an active working-memory challenge. We thus investigated the effect of OSA on working-memory performance and underlying brain connectivity.OSA patients and matched healthy controls underwent functional magnetic resonance imaging (fMRI) scanning while performing a 2-back working-memory task. Standard fMRI analyses highlighted the brain regions activated at increasing levels of working-memory load, which were used as seeds in connectivity analyses. The latter were based on a multiregional Psycho-Physiological-Interaction (PPI) approach, to unveil group differences in effective connectivity underlying working-memory performance.Compared with controls, in OSA patients normal working-memory performance reflected in: a) reduced interhemispheric effective connectivity between the frontal “executive” nodes of the working-memory network, and b) increased right-hemispheric connectivity among regions mediating the “salience-based” switch from the default resting-state mode to the effortful cognitive activity associated with the executive network. The strength of such connections was correlated, at increasing task-demands, with executive (Stroop test) and memory (Digit Span test) performance in neuro-cognitive evaluations.The analysis of effective connectivity changes during a working-memory challenge provides a complementary window, compared with resting-state studies, on the mechanisms supporting preserved performance despite functional and structural brain modifications in OSA.

Gray matter volume and estimated brain age gap are not linked with sleep‐disordered breathing

“…Despite numerous individual studies and meta‐analyses focused on the changes in gray matter in middle‐aged patients with OSA, there are few studies on gray matter changes in older adults with SDB and, to our knowledge, neither have found decreases in thickness or volume in cortical gray matter (Sébastien Celle et al, ; Cross et al, ; Lutsey et al, ). Secondly, it is possible that SDB impairs selective brain functions (Canessa et al, ) or amyloid burden (Yun et al, ) before gray matter volume. Furthermore, differential diagnosis between SDB‐related and age‐related brain atrophy is difficult in single‐point observational studies, particularly in those cases in which groups are matched by age and cognitive status.…”

Aberrant Awake Spontaneous Brain Activity in Obstructive Sleep Apnea: A Review Focused on Resting-State EEG and Resting-State fMRI

“…Most of these brain regions are involved in emotions and goal-directed responses. During the execution of specific cognitive tasks, the above three brain networks always cooperate, and the moderation of the SN between the DMN and CEN may be the physiological mechanism of transition from resting state to cognitive processing state (52).…”

Interhemispheric sleep depth coherence predicts driving safety in sleep apnea

“…In a previous small study, OSA subjects ( n = 15) were found to have a lower central interhemispheric agreement in sleep depth than controls (Saunamaki, Jehkonen, Huupponen, Polo, & Himanen, 2009). Similarly, several studies concerning OSA and its neurocognitive outcomes reported a reduction in interhemispheric coherence, quantified by both EEG (power (Jones et al., 2014), spindle frequency (Schonwald et al., 2012) and sleep depth (Saunamaki et al., 2009)) and fMRI characteristics (Canessa et al., 2018; Santarnecchi et al., 2013). To our knowledge, this is the first time that the agreement in interhemispheric sleep depth has been examined in relation to driving safety.…”

“…There is growing evidence that OSA is associated with regional reductions in sleep electroencephalography (EEG) power (Jones et al., 2014), topography‐specific alterations in spindle frequency (Schonwald, Carvalho, de Santa‐Helena, Lemke, & Gerhardt, 2012), localized cortical thinning in the brain (Joo, Jeon, Kim, Lee, & Hong, 2013), and reduced fMRI‐measured brain connectivity (Canessa et al., 2018; Santarnecchi et al., 2013). Moreover, repetitive periods of obstructive breathing may be associated with reduced functional interhemispheric connectivity (Rial et al., 2013), unlike the normal pattern in humans, in whom sleep generally occurs bihemispherically (Rattenborg, Amlaner, & Lima, 2000).…”