title: Complexity analysis of spontaneous brain activity: effects of depression and antidepressant treatment.
abstract: Magnetoencephalography (MEG) allows the real-time recording of neural activity and oscillatory activity in distributed neural networks. We applied a non-linear complexity analysis to resting-state neural activity as measured using whole-head MEG. Recordings were obtained from 20 unmedicated patients with major depressive disorder and 19 matched healthy controls. Subsequently, after 6 months of pharmacological treatment with the antidepressant mirtazapine 30 mg/day, patients received a second MEG scan. A measure of the complexity of neural signals, the Lempel-Ziv Complexity (LZC), was derived from the MEG time series. We found that depressed patients showed higher pre-treatment complexity values compared with controls, and that complexity values decreased after 6 months of effective pharmacological treatment, although this effect was statistically significant only in younger patients. The main treatment effect was to recover the tendency observed in controls of a positive correlation between age and complexity values. Importantly, the reduction of complexity with treatment correlated with the degree of clinical symptom remission. We suggest that LZC, a formal measure of neural activity complexity, is sensitive to the dynamic physiological changes observed in depression and may potentially offer an objective marker of depression and its remission after treatment.
authors.affiliation: Departamento de Psiquiatría y Psicología Médica, Universidad Complutense de Madrid, Madrid, Spain. maria.mendez@kcl.ac.uk
authors.forename: María Andreina
authors.initials: MA
authors.lastname: Méndez
authors.forename: Pilar
authors.initials: P
authors.lastname: Zuluaga
authors.forename: Roberto
authors.initials: R
authors.lastname: Hornero
authors.forename: Carlos
authors.initials: C
authors.lastname: Gómez
authors.forename: Javier
authors.initials: J
authors.lastname: Escudero
authors.forename: Alfonso
authors.initials: A
authors.lastname: Rodríguez-Palancas
authors.forename: Tomás
authors.initials: T
authors.lastname: Ortiz
authors.forename: Alberto
authors.initials: A
authors.lastname: Fernández
mesh_terms: D000367:Age Factors; D000928:Antidepressive Agents / Q000627:therapeutic use*; D001921:Brain / Q000187:drug effects* / Q000503:physiopathology*; D003865:Major Depressive Disorder / Q000188:drug therapy* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008803:Mianserin / Q000031:analogs & derivatives / Q000627:therapeutic use; D008875:Middle Aged; D000078785:Mirtazapine; D009415:Nerve Net / Q000187:drug effects* / Q000503:physiopathology*; D012737:Sex Factors
chemical_list: D000928:Antidepressive Agents; D008803:Mianserin; D000078785:Mirtazapine