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J Neurosci Methods. 2008 Aug 15;173(1):41-6. doi: 10.1016/j.jneumeth.2008.05.008. Epub 2008 May 21.

Method for detection of changes in the EEG induced by the presence of sensory stimuli.

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Department of Orthopaedic Surgery, LSU Health Sciences Center, Shreveport, LA 71130-3932, United States.


The onset and offset of sensory stimuli evoke transient changes in the electroencephalogram (EEG) that can be detected by linear and/or nonlinear analysis. However, there is presently no systematic procedure to quantify the brain-electrical-activity correlate of the presence of a stimulus (as opposed to its onset evoked potential). We describe a method for detecting a stimulus-related change in brain electrical activity that persists while the stimulus is present (presence effect). The method, which is based on phase-space embedding of the EEG time series followed by quantitative analysis of the recurrence plot of the embedded signal, was used to demonstrate the occurrence of a presence effect in separate groups of human subjects exposed to sound, a magnetic field, and light. Any form of law-governed dynamical activity induced in the EEG can be detected, particularly activity that is nonlinearly related to the stimulus. Salient mathematical features of the method were reproduced in a model EEG system containing known nonlinear determinism.

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