title: Dynamics of dynamics within a single data acquisition session: variation in neocortical alpha oscillations in human MEG.
abstract: BACKGROUND
  Behavioral paradigms applied during human recordings in electro- and magneto- encephalography (EEG and MEG) typically require 1-2 hours of data collection. Over this time scale, the natural fluctuations in brain state or rapid learning effects could impact measured signals, but are seldom analyzed.
  
  
  RESULTS
  We investigated within-session dynamics of neocortical alpha (7-14 Hz) rhythms and their allocation with cued-attention using MEG recorded from primary somatosensory neocortex (SI) in humans. We found that there were significant and systematic changes across a single ~1 hour recording session in several dimensions, including increased alpha power, increased differentiation in attention-induced alpha allocation, increased distinction in immediate time-locked post-cue evoked responses in SI to different visual cues, and enhanced power in the immediate cue-locked alpha band frequency response. Further, comparison of two commonly used baseline methods showed that conclusions on the evolution of alpha dynamics across a session were dependent on the normalization method used.
  
  
  CONCLUSIONS
  These findings are important not only as they relate to studies of oscillations in SI, they also provide a robust example of the type of dynamic changes in brain measures within a single session that are overlooked in most human brain imaging/recording studies.
authors.affiliation: McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America.
authors.forename: Qian
authors.initials: Q
authors.lastname: Wan
authors.forename: Catherine
authors.initials: C
authors.lastname: Kerr
authors.forename: Dominique
authors.initials: D
authors.lastname: Pritchett
authors.forename: Matti
authors.initials: M
authors.lastname: Hämäläinen
authors.forename: Christopher
authors.initials: C
authors.lastname: Moore
authors.forename: Stephanie
authors.initials: S
authors.lastname: Jones
mesh_terms: D000293:Adolescent; D000328:Adult; D001288:Attention; D001931:Brain Mapping / Q000379:methods; D003627:Data Interpretation, Statistical; D004569:Electroencephalography / Q000379:methods*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D015225:Magnetoencephalography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D019579:Neocortex / Q000473:pathology; D009991:Oscillometry / Q000379:methods; D012815:Signal Processing, Computer-Assisted