title: Complexity analysis of spontaneous brain activity in Alzheimer disease and mild cognitive impairment: an MEG study.
abstract: Nonlinear analyses have shown that Alzheimer disease (AD) patients' brain activity is characterized by a reduced complexity and connectivity. The aim of this study is to define complexity patterns of mild cognitive impairment (MCI) patients. Whole-head magnetoencephalography recordings were obtained from 18 diagnosed AD patients, 18 MCI patients, and 18 healthy controls during resting conditions. Lempel-Ziv complexity (LZC) values were calculated. MCI patients exhibited intermediary LZC scores between AD patients and controls. A combination of age and posterior LZC scores allowed ADs-MCIs discrimination with 94.4% sensitivity and specificity, whereas no LZC score allowed MCIs---controls discrimination. AD patients and controls showed a parallel tendency to diminished LZC scores as a function of age, but MCI patients did not exhibit such "normal" tendency. Accordingly, anterior LZC scores allowed MCIs-controls discrimination for subjects below 75 years. MCIs exhibited a qualitatively distinct relationship between aging and complexity reduction, with scores higher than controls in older individuals. This fact might be considered a new example of compensatory mechanism in MCI before fully established dementia.
authors.affiliation: Centro de Magnetoencefalografía Dr. Pérez-Modrego, Facultad de Medicina, Pabellón, Universidad Complutense de Madrid, Madrid, Spain. aferlucas@med.ucm.es
authors.forename: Alberto
authors.initials: A
authors.lastname: Fernández
authors.forename: Roberto
authors.initials: R
authors.lastname: Hornero
authors.forename: Carlos
authors.initials: C
authors.lastname: Gómez
authors.forename: Agustín
authors.initials: A
authors.lastname: Turrero
authors.forename: Pedro
authors.initials: P
authors.lastname: Gil-Gregorio
authors.forename: Juan
authors.initials: J
authors.lastname: Matías-Santos
authors.forename: Tomás
authors.initials: T
authors.lastname: Ortiz
mesh_terms: D000368:Aged; D000375:Aging / Q000502:physiology; D000544:Alzheimer Disease / Q000503:physiopathology*; D001921:Brain / Q000503:physiopathology*; D003072:Cognition Disorders / Q000503:physiopathology*; D005260:Female; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D012680:Sensitivity and Specificity