A new technique for the analysis of background and evoked EEG activity: time and amplitude distributions of the EEG deflections.
OBJECTIVE
The EEG during background activity and that evoked in response to sensory stimuli (evoked potential, EP) has traditionally been studied by averaging and by frequency analysis. These obscure trial to trial variability. A new analysis technique is presented here which leads to single trial analysis and to insight into the mechanisms of EP generation.


METHODS
This technique is based on the identification of the EEG deflections recorded on the scalp before (background) and immediately after visual stimuli. A statistical description of the time and amplitude distributions of these deflections is defined and leads to the differentiation between background and evoked activity.


RESULTS
In response to stimuli, the time and amplitude of ongoing deflections (background) are re-organized (time locking) and amplified, generating the EP. Not all stimulus trials are accompanied by an appropriate response. Separate analysis of those single trials that do contain a response deflection provides information on the exact timing, variability, amplitude, etc., of those EEG deflections which contribute to the EP.


CONCLUSIONS
New EEG analysis techniques are described which provide single trial EP analysis and insight into mechanisms of EP generation.
Rodionov
V
V
Department of Physiology, The Hebrew University - Hadassah Medical School, P.O. Box 12272, Jerusalem, Israel.
Goodman
C
C
Fisher
L
L
Rosenstein
G Z
GZ
Sohmer
H
H
D000161:Acoustic Stimulation; D000293:Adolescent; D000328:Adult; D004569:Electroencephalography / Q000379:methods*; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005074:Evoked Potentials, Visual / Q000502:physiology*; D006801:Humans; D008297:Male; D010775:Photic Stimulation; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D013997:Time Factors