Fractal dimension analysis of states of consciousness and unconsciousness using transcranial magnetic stimulation

Autor(es)

Ruiz de Miras, J. ^[1] ; Soler, F. ^[2] ; Iglesias-Parro, S. ^[3] ; Ibanez-Molina, A. J. ^[3] ; Casali, A. G. ^[4] ; Laureys, S. ^{[5, 6, 7]} ; Massimini, M. ^{[8, 9]} ; Esteban, F. J. ^[10] ; Navas, J. ^[11] ; Langa, J. A. ^[12]

Afiliação do(s) autor(es):Mostrar menos -

^[1] Univ Jaen, Comp Sci Dept, Jaen - Spain

^[2] Univ Seville, Dept Philosophy Log & Philosophy Sci, Seville - Spain

^[3] Univ Jaen, Dept Psychol, Jaen - Spain

^[4] Univ Fed Sao Paulo, Inst Sci & Technol, Sao Josedos Dos Campos - Brazil

^[5] Univ Liege, Coma Sci Grp, GIGA Consciousness Res Ctr, Liege - Belgium

^[6] Univ Liege, Neurol Dept, Liege - Belgium

^[7] Univ Hosp Liege, Liege - Belgium

^[8] Univ Milan, Dept Biomed & Clin Sci Luigi Sacco, Milan - Italy

^[9] RCCS Fdn Don Carlo Gnocchi, Milan - Italy

^[10] Univ Jaen, Dept Expt Biol, Jaen - Spain

^[11] Univ Jaen, Dept Math, Jaen - Spain

^[12] Univ Seville, Dept Differential Equat & Numer Anal, Seville - Spain

• Tipo de documento: Artigo Científico
• Fonte: COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE; v. 175, p. 129-137, JUL 2019.
• Citações Web of Science: 1

Resumo

Background and objective: Knowing whether a subject is conscious or not is a current challenge with a deep potential clinical impact. Recent theoretical considerations suggest that consciousness is linked to the complexity of distributed interactions within the corticothalamic system. The fractal dimension (FD) is a quantitative parameter that has been extensively used to analyse the complexity of structural and functional patterns of the human brain. In this study we investigate FD to assess whether it can discriminate between consciousness and different states of unconsciousness in healthy individuals. Methods: We study 69 high-density electroencephalogram (hd-EEG) measurements after transcranial magnetic stimulation (TMS) in 18 healthy subjects progressing from wakefulness to non-rapid eye movement (NREM) sleep and sedation induced by different anaesthetic agents (xenon and propofol). We quantify the integration of thalamocortical networks by calculating the FD of a spatiotemporal voxelization obtained from the locations of all sources that are significantly activated by the perturbation (4DFD). Moreover, we study the temporal evolution of the evoked spatial distributions and compute a measure of the differentiation of the response by means of the Higuchi FD (HFD). Finally, a Fractal Dimension Index (FDI) of perturbational complexity is computed as the product of both quantities: integration FD (4DFD) and differentiation FD (HFD). Results: We found that FDI is significantly lower in sleep and sedation when compared to wakefulness and provides an almost perfect intra-subject discrimination between conscious and unconscious states. Conclusions: These results support the combination of FD measures of cortical integration and cortical differentiation as a novel paradigm of tracking complex spatiotemporal dynamics in the brain that could provide further insightsin to the link between complexity and the brain's capacity to sustain consciousness. (C) 2019 Elsevier B.V. All rights reserved. (AU)

• Processo FAPESP: 16/08263-9 - Padronização, validação e caracterização de uma nova medida de complexidade cerebral
• Beneficiário: Adenauer Girardi Casali
• Modalidade de apoio: Auxílio à Pesquisa - Jovens Pesquisadores