EEG, Alpha Waves and Coherence Metadata

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Title

  • Main Title EEG, Alpha Waves and Coherence

Creator

  • Author: Ascolani, Gianluca
    Creator Type: Personal

Contributor

  • Chair: Grigolini, Paolo
    Contributor Type: Personal
    Contributor Info: Major Professor
  • Chair: Krokhin, Arkadii
    Contributor Type: Personal
    Contributor Info: Co-Major Professor
  • Committee Member: Roberts, James A.
    Contributor Type: Personal
  • Committee Member: Weathers, Duncan L.
    Contributor Type: Personal

Publisher

  • Name: University of North Texas
    Place of Publication: Denton, Texas
    Additional Info: Web: www.unt.edu

Date

  • Creation: 2010-05

Language

  • English

Description

  • Content Description: This thesis addresses some theoretical issues generated by the results of recent analysis of EEG time series proving the brain dynamics are driven by abrupt changes making them depart from the ordinary Poisson condition. These changes are renewal, unpredictable and non-ergodic. We refer to them as crucial events. How is it possible that this form of randomness be compatible with the generation of waves, for instance alpha waves, whose observation seems to suggest the opposite view the brain is characterized by surprisingly extended coherence? To shed light into this apparently irretrievable contradiction we propose a model based on a generalized form of Langevin equation under the influence of a periodic stimulus. We assume that there exist two different forms of time, a subjective form compatible with Poisson statistical physical and an objective form that is accessible to experimental observation. The transition from the former to the latter form is determined by the brain dynamics interpreted as emerging from the cooperative interaction among many units that, in the absence of cooperation would generate Poisson fluctuations. We call natural time the brain internal time and we make the assumption that in the natural time representation the time evolution of the EEG variable y(t) is determined by a Langevin equation perturbed by a periodic process that in this time representation is hardly distinguishable from an erratic process. We show that the representation of this random process in the experimental time scale is characterized by a surprisingly extended coherence. We show that this model generates a sequence of damped oscillations with a time behavior that is remarkably similar to that derived from the analysis of real EEG's. The main result of this research work is that the existence of crucial events is not incompatible with the alpha wave coherence. In addition to this important result, we find another result that may help our group, or any other research group working on the analysis of brain's dynamics, to prove or to disprove the existence of crucial events. We study the diffusion process generated by fluctuations emerging from the same model after filtering out the alpha coherence, and we study the recursion to the origin. We study the survival probability of this process, namely the probability that up to a given time no re-crossing of the origin occurs. We find that this is an inverse power law with a power that depends on whether or not crucial events exist.

Subject

  • Keyword: Electroencephalogram
  • Keyword: complex system
  • Keyword: renewal events
  • Library of Congress Subject Headings: Electroencephalography.
  • Library of Congress Subject Headings: Alpha rhythm.
  • Library of Congress Subject Headings: Brain.

Collection

  • Name: UNT Theses and Dissertations
    Code: UNTETD

Institution

  • Name: UNT Libraries
    Code: UNT

Rights

  • Rights Access: public
  • Rights License: copyright
  • Rights Holder: Ascolani, Gianluca
  • Rights Statement: Copyright is held by the author, unless otherwise noted. All rights reserved.

Resource Type

  • Thesis or Dissertation

Format

  • Text

Identifier

  • OCLC: 664685015
  • UNT Catalog No.: b3865686
  • Archival Resource Key: ark:/67531/metadc28389

Degree

  • Degree Name: Doctor of Philosophy
  • Degree Level: Doctoral
  • Degree Discipline: Physics
  • Academic Department: Department of Physics
  • Degree Grantor: University of North Texas

Note