Source space connectomics of neurodegeneration : one-metric approach does not fit all

Prado, Pavel and Moguilner, Sebastian and Mejía, Jhony A. and Sainz-Ballesteros, Agustín and Otero, Mónica and Birba, Agustina and Santamaria-Garcia, Hernando and Legaz, Agustina and Fittipaldi, Sol and Cruzat, Josephine and Tagliazucchi, Enzo and Parra, Mario and Herzog, Rubén and Ibáñez, Agustín (2023) Source space connectomics of neurodegeneration : one-metric approach does not fit all. Neurobiology of Disease, 179. 106047. ISSN 0969-9961 (https://doi.org/10.1016/j.nbd.2023.106047)

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Abstract

Brain functional connectivity in dementia has been assessed with dissimilar EEG connectivity metrics and estimation procedures, thereby increasing results’ heterogeneity. In this scenario, joint analyses integrating information from different metrics may allow for a more comprehensive characterization of brain functional interactions in different dementia subtypes. To test this hypothesis, resting-state electroencephalogram (rsEEG) was recorded in individuals with Alzheimer’s Disease (AD), behavioral variant frontotemporal dementia (bvFTD), and healthy controls (HCs). Whole-brain functional connectivity was estimated in the EEG source space using 101 different types of functional connectivity, capturing linear and nonlinear interactions in both time and frequency-domains. Multivariate machine learning and progressive feature elimination was run to discriminate AD from HCs, and vFTD from HCs, based on joint analyses of i) EEG frequency bands, ii) complementary frequency-domain metrics (e.g., instantaneous, lagged, and total connectivity), and iii) time-domain metrics with different linearity assumption (e.g., Pearson correlation coefficient and mutual information). Less than 10% of all possible connections were responsible for the differences between patients and controls, and atypical connectivity was never captured by more than 1/4 of all possible connectivity measures. Joint analyses revealed patterns of hypoconnectivity (patientsHCs) in both groups was mainly identified in frontotemporal regions. These atypicalities were differently captured by frequency- and time-domain connectivity metrics, in a bandwidth specific fashion. The multi-metric representation of source space whole-brain functional connectivity evidenced the inadequacy of single-metric approaches, and resulted in a valid alternative for the selection problem in EEG connectivity. These joint analyses reveal patterns of brain functional interdependence that are overlooked with single metrics approaches, contributing to a more 59 reliable and interpretable description of atypical functional connectivity in neurodegeneration.

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