Alterations of Effective Connectivity Patterns in Mild Cognitive Impairment: An MEG Study

Article type: Research Article

Authors: Gómez, Carlos^{a; *} | Juan-Cruz, Celia^b | Poza, Jesús^{a; c; d} | Ruiz-Gómez, Saúl J.^a | Gomez-Pilar, Javier^a | Núñez, Pablo^a | García, María^a | Fernández, Alberto^{e; f} | Hornero, Roberto^{a; c; d}

Affiliations: [a] Biomedical Engineering Group, University of Valladolid, Spain | [b] Department of Radiation Oncology, Netherlands Cancer Institute, Amsterdam, The Netherlands | [c] IMUVA, Instituto de Investigación en Matemáticas, University of Valladolid, Spain | [d] INCYL, Instituto de Neurociencias de Castilla y León, University of Salamanca, Spain | [e] Department of Psychiatry, Faculty of Medicine, Complutense University of Madrid, Spain | [f] Laboratory of Cognitive and Computational Neuroscience, Center for Biomedical Technology, Complutense University of Madrid and Technical University of Madrid, Spain

Correspondence: [*] Correspondence to: Carlos Gómez, Biomedical Engineering Group, E. T. S. Ingenieros de Telecomunicación, Universidad de Valladolid, Paseo Belén 15, 47011 Valladolid, Spain. Tel.: +34 983 423981; E-mail: carlos.gomez@tel.uva.es.

Abstract: Neuroimaging techniques have demonstrated over the years their ability to characterize the brain abnormalities associated with different neurodegenerative diseases. Among all these techniques, magnetoencephalography (MEG) stands out by its high temporal resolution and noninvasiveness. The aim of the present study is to explore the coupling patterns of resting-state MEG activity in subjects with mild cognitive impairment (MCI). To achieve this goal, five minutes of spontaneous MEG activity were acquired with a 148-channel whole-head magnetometer from 18 MCI patients and 26 healthy controls. Inter-channel relationships were investigated by means of two complementary coupling measures: coherence and Granger causality. Coherence is a classical method of functional connectivity, while Granger causality quantifies effective (or causal) connectivity. Both measures were calculated in the five conventional frequency bands: delta (δ, 1–4 Hz), theta (θ, 4–8 Hz), alpha (α, 8–13 Hz), beta (β, 13–30 Hz), and gamma (γ, 30–45 Hz). Our results showed that connectivity values were lower for MCI patients than for controls in all frequency bands. However, only Granger causality revealed statistically significant differences between groups (p-values < 0.05, FDR corrected Mann-Whitney U-test), mainly in the beta band. Our results support the role of MCI as a disconnection syndrome, which elicits early alterations in effective connectivity patterns. These findings can be helpful to identify the neural substrates involved in prodromal stages of dementia.

Keywords: Coherence, connectivity, Granger causality, magnetoencephalography (MEG), mild cognitive impairment, neuroimaging

DOI: 10.3233/JAD-170475

Journal: Journal of Alzheimer's Disease, vol. 65, no. 3, pp. 843-854, 2018