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Functional Connectivity in the Default Mode Network is Reduced in Association with Nocturnal Awakening in Mild
Andrew C McKinnon1,2, Shantel L Duffy1,3, Nathan E Cross1,4
1Healthy Brain Ageing Program, The University of Sydney, Camperdown NSW, Australia.
Background:
Sleep disturbance is prevalent in MCI, and is a risk factor for cognitive deterioration.
Objective:
To identify functional connectivity deficits in the default mode network (DMN) in patients with mild cognitive impairment (MCI) and sleep disturbance, relative to MCIs with intact sleep.
Methods:
Participants comprised 47 adults aged 55 years and over, recruited from the Healthy Brain Ageing Clinic at the Brain and Mind Centre, Sydney, Australia. This sample contained 15 controls and 32 participants meeting criteria for MCI. Participants underwent resting-state fMRI and actigraphy, along with comprehensive neuropsychological, medical and psychiatric assessment. MCIs were split into two groups according to average wake after sleep onset (WASO) per night. WASO equal to or greater than 1 standard deviation (SD) above the control mean was deemed to reflect disturbed sleep. There were 11 patients in the MCI sleep-disturbed group, and 21 in the MCI sleep-intact group.
Results:
Relative to controls, MCIs demonstrated significant connectivity reductions between parietal and temporoparietal regions, and between temporal regions. Relative to MCIs with intact sleep, MCIs with sleep disturbance demonstrated reductions in functional connectivity between temporal and parietal regions, and between temporal and temporoparietal regions.
Conclusions:
MCIs with nocturnal awakenings demonstrate reductions in DMN connectivity. These reductions comprise brain regions that are crucially involved in sleep and memory processes. These results strengthen our previous findings, which found reduced connectivity in MCIs with self-reported sleep disturbances. Future studies may build on these findings through incorporating complementary neuroimaging techniques and experimental manipulations of sleep.
Insights
Sleep disturbance in mild cognitive impairment (MCI) is linked to reduced default mode network (DMN) connectivity. This brain network is crucial for sleep and memory, suggesting a pathway for cognitive decline.
Area of Science:
- Neuroscience
- Cognitive Science
- Sleep Medicine
Background:
- Sleep disturbance is common in mild cognitive impairment (MCI).
- Sleep problems are a risk factor for worsening cognitive function in MCI patients.
Purpose of the Study:
- To investigate functional connectivity differences in the default mode network (DMN).
- To compare DMN connectivity in MCI patients with and without sleep disturbances.
Main Methods:
- Utilized resting-state fMRI and actigraphy in 47 adults (15 controls, 32 MCI).
- Classified MCI patients into sleep-disturbed and sleep-intact groups based on wake after sleep onset (WASO).
Main Results:
- MCI patients showed reduced connectivity between parietal and temporal regions compared to controls.
- MCI patients with sleep disturbance exhibited decreased functional connectivity in the DMN compared to MCI patients with intact sleep.
Conclusions:
- Nocturnal awakenings in MCI are associated with reduced DMN connectivity.
- These DMN alterations involve brain regions critical for sleep and memory, reinforcing the link between sleep disturbance and cognitive decline in MCI.
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