Implication of the Slow-5 Oscillations in the Disruption of the Default-Mode Network in Healthy Aging and Stroke

• Published in: Brain connectivity Vol. 6; no. 6; pp. 482 - 495
• Main Authors: La, Christian, Nair, Veena A., Mossahebi, Pouria, Young, Brittany M., Chacon, Marcus, Jensen, Matthew, Birn, Rasmus M., Meyerand, Mary E., Prabhakaran, Vivek
• Format: Journal Article
• Language: English
• Published: United States Mary Ann Liebert, Inc 01.07.2016
• Subjects: Adult; Aged; Aging; Brain - physiology; Brain - physiopathology; Brain Ischemia - physiopathology; Brain Mapping; Brain Waves; Female; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Original; Stroke - physiopathology; Young Adult; posterior DMN; rs-fMRI; default-mode network; slow-5; aging; fALFF; stroke
• ISSN: 2158-0014; 2158-0022; 2158-0022
• DOI: 10.1089/brain.2015.0375

The processes of normal aging and aging-related pathologies subject the brain to an active re-organization of its brain networks. Among these, the default-mode network (DMN) is consistently implicated with a demonstrated reduction in functional connectivity within the network. However, no clear stipulation on the underlying mechanisms of the de-synchronization has yet been provided. In this study, we examined the spectral distribution of the intrinsic low-frequency oscillations (LFOs) of the DMN sub-networks in populations of young normals, older subjects, and acute and subacute ischemic stroke patients. The DMN sub-networks were derived using a mid-order group independent component analysis with 117 eyes-closed resting-state functional magnetic resonance imaging (rs-fMRI) sessions from volunteers in those population groups, isolating three robust components of the DMN among other resting-state networks. The posterior component of the DMN presented noticeable differences. Measures of amplitude of low-frequency fluctuation (ALFF) and fractional ALFF (fALFF) of the network component demonstrated a decrease in resting-state cortical oscillation power in the elderly (normal and patient), specifically in the slow-5 (0.01-0.027 Hz) range of oscillations. Furthermore, the contribution of the slow-5 oscillations during the resting state was diminished for a greater influence of the slow-4 (0.027-0.073 Hz) oscillations in the subacute stroke group, not only suggesting a vulnerability of the slow-5 oscillations to disruption but also indicating a change in the distribution of the oscillations within the resting-state frequencies. The reduction of network slow-5 fALFF in the posterior DMN component was found to present a potential association with behavioral measures, suggesting a brain-behavior relationship to those oscillations, with this change in behavior potentially resulting from an altered network integrity induced by a weakening of the slow-5 oscillations during the resting state. The repeated identification of those frequencies in the disruption of DMN stresses a critical role of the slow-5 oscillations in network disruption, and it accentuates the importance of managing those oscillations in the health of the DMN.