Default Mode Network Connectivity in Stroke Patients

Abstract

The pathophysiology of episodic memory dysfunction after infarction is not completely understood. It has been suggested that infarctions located anywhere in the brain can induce widespread effects causing disruption of functional networks of the cortical regions. The default mode network, which includes the medial temporal lobe, is a functional network that is associated with episodic memory processing. We investigated whether the default mode network activity is reduced in stroke patients compared to healthy control subjects in the resting state condition. We assessed the whole brain network properties during resting state functional MRI in 21 control subjects and 20 ‘first-ever’ stroke patients. Patients were scanned 9–12 weeks after stroke onset. Stroke lesions were located in various parts of the brain. Independent component analyses were conducted to identify the default mode network and to compare the group differences of the default mode network. Furthermore, region-of-interest based analysis was performed to explore the functional connectivity between the regions of the default mode network. Stroke patients performed significantly worse than control subjects on the delayed recall score on California verbal learning test. We found decreased functional connectivity in the left medial temporal lobe, posterior cingulate and medial prefrontal cortical areas within the default mode network and reduced functional connectivity between these regions in stroke patients compared with controls. There were no significant volumetric differences between the groups. These results demonstrate that connectivity within the default mode network is reduced in ‘first-ever’ stroke patients compared to control subjects. This phenomenon might explain the occurrence of post-stroke cognitive dysfunction in stroke patients.

Stroke and the Connectome: How Connectivity Guides Therapeutic Intervention

“…Increasingly, study of this relatively poorly defined form of activity can nonetheless reflect the function and integrity of circuits both in the healthy brain and after disease such as stroke. Resting-state functional connectivity has been assessed in a large number of human stroke patients (Carter et al, 2010a(Carter et al, , 2012Grefkes and Ward, 2014;He et al, 2007;Tuladhar et al, 2013). Brain-wide connections based on resting-state data in humans were used to simulate the effects of a virtual stroke.…”

Feeling, learning from and being aware of inner states: interoceptive dimensions in neurodegeneration and stroke

“…Following previous reports [49][50][51][52], during a 10-min fMRI session, participants were instructed not to think about anything in particular, to keep their eyes closed, and avoid moving and falling asleep. We chose the closed-eyes modality to avoid highly noisy signals coming from the visual cortex [53] and to facilitate attention during interoceptive processing [54,55].…”

“…For each participant, we extracted the BOLD signal time-course from the voxels within each seed region. To obtain a functional connectivity map, we then correlated these data to every voxel in the brain using Pearson's correlation coefficient [52]. We used the SPM multiple regression rstb.royalsocietypublishing.org Phil.…”

Impairment of functional integration of the default mode network correlates with cognitive outcome at three months after stroke

“…The term “deactivate” refers to the fact that there is a decrease of activity in the DMN during cognitive tasks compared to baseline. DMN disruption has been commonly observed by resting-state functional studies in patients with mild cognitive impairment [Wang et al, 2006; Sorg et al, 2007], vascular cognitive impairment with subcortical lesions [Sun et al, 2011], patients with carotid stenosis [Cheng et al, 2012; Lin et al, 2014], and patients with stroke [Tuladhar et al, 2013]. Despite the considerable interest of this network, little is known about its possible alterations in ischemic stroke patients.…”