title: Origin, structure, and role of background EEG activity. Part 3. Neural frame classification.
abstract: OBJECTIVE
  To show that cortical responses to conditioned stimuli (CS) include intermittently induced spatial patterns of amplitude modulation (AM) of beta-gamma oscillation called frames.
  
  
  METHODS
  EEGs were recorded from 8x8 high-density arrays fixed on primary sensory cortices of rabbits trained to discriminate CS with reinforcement (CS+) from those without (CS-). EEG frames were located with a pragmatic information index, H(e). The spatial patterns of the first 3 frames on each of 37-40 trials were measured by the square of 64 analytic amplitudes from the Hilbert transform to give points in 64-space. The questions were asked: Did the frames from CS+ trials and CS- trials differ within each sequential group? Did the 3 frames differ from each other (form 3 clusters of points)?
  
  
  RESULTS
  EEG frames that were identified by high H(e) had AM patterns that could be classified with respect to CS+ and CS- well above chance levels. Two stages of correct frame classification occurred on each trial: 40-130 ms after CS onset with a gamma carrier frequency, and 450-550 ms with a beta carrier frequency. Peak power in the beta frames was double that in gamma frames, and mean pattern surface area of beta frames was nearly 4-fold greater.
  
  
  CONCLUSIONS
  Under the impact of a CS on a sensory neocortex, the background EEG activity reorganized in sequential frames of coordinated activity, first local and modality-specific, thereafter global.
  
  
  CONCLUSIONS
  The size, texture and duration of these AM patterns indicate that spatial patterns of human beta frames may be accessible with high-density scalp arrays for correlation with phenomenological reports by human subjects.
authors.affiliation: Department of Molecular & Cell Biology, University of California, Berkeley, 94720-3200, USA.
authors.forename: Walter J
authors.initials: WJ
authors.lastname: Freeman
mesh_terms: D000161:Acoustic Stimulation; D000465:Algorithms; D000818:Animals; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000502:physiology*; D003213:Conditioning, Psychological / Q000502:physiology; D004569:Electroencephalography; D010775:Photic Stimulation; D011817:Rabbits; D012815:Signal Processing, Computer-Assisted; D013003:Somatosensory Cortex / Q000502:physiology*