title: Age-related variation in EEG complexity to photic stimulation: a multiscale entropy analysis.
abstract: OBJECTIVE
  This study was intended to examine variations in electroencephalographic (EEG) complexity in response to photic stimulation (PS) during aging to test the hypothesis that the aging process reduces physiologic complexity and functional responsiveness.
  
  
  METHODS
  Multiscale entropy (MSE), an estimate of time-series signal complexity associated with long-range temporal correlation, is used as a recently proposed method for quantifying EEG complexity with multiple coarse-grained sequences. We recorded EEG in 13 healthy elderly subjects and 12 healthy young subjects during pre-PS and post-PS conditions and estimated their respective MSE values.
  
  
  RESULTS
  For the pre-PS condition, no significant complexity difference was found between the groups. However, a significant MSE change (complexity increase) was found post-PS only in young subjects, thereby revealing a power-law scaling property, which means long-range temporal correlation.
  
  
  CONCLUSIONS
  Enhancement of long-range temporal correlation in young subjects after PS might reflect a cortical response to stimuli, which was absent in elderly subjects. These results are consistent with the general "loss of complexity/diminished functional response to stimuli" theory of aging.
  
  
  CONCLUSIONS
  Our findings demonstrate that application of MSE analysis to EEG is a powerful approach for studying age-related changes in brain function.
authors.affiliation: Department of Neuropsychiatry, Faculty of Medical Sciences, University of Fukui, 23-3 Matsuokashimoaizuki, Eiheiji-cho, Yoshida-gun, Fukui 910-1193, Japan. takahash@u-fukui.ac.jp
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Takahashi
authors.forename: Raymond Y
authors.initials: RY
authors.lastname: Cho
authors.forename: Tetsuhito
authors.initials: T
authors.lastname: Murata
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Mizuno
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Kikuchi
authors.forename: Kimiko
authors.initials: K
authors.lastname: Mizukami
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Kosaka
authors.forename: Koichi
authors.initials: K
authors.lastname: Takahashi
authors.forename: Yuji
authors.initials: Y
authors.lastname: Wada
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging / Q000502:physiology*; D002540:Cerebral Cortex / Q000502:physiology*; D004569:Electroencephalography / Q000379:methods*; D019277:Entropy; D005074:Evoked Potentials, Visual / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009473:Neuronal Plasticity / Q000502:physiology; D010775:Photic Stimulation; D012677:Sensation / Q000502:physiology; D012815:Signal Processing, Computer-Assisted; D013997:Time Factors; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult