title: Measurement and definition of changes in the visual evoked potential to different stimulus intensities.
abstract: Visual evoked potentials (VEPs) were recorded from the vertex to 5 intensities of light flashes. Measures were taken of peak-to-trough, prestimulus baseline-to-peak, and timeband amplitude for P1, N1, and P2 waveforms. Augmenting/reducing was defined by traditional (amplitude/intensity slope, monotonicity) and non-traditional (strength of the nervous system, combined amplitude response) criteria. In support of Connolly and Gruzelier ([1982) Psychophysiology, 19: 599-608], analyses showed that data collected by traditional methods contravened assumptions underlying VEP augmenting/reducing methodology. Specifically, 20% of total peaks occurred outside designated timebands, amplitude/intensity slopes explained only 30-46% variance, and levels of agreement between different definitions were low. Researchers ought to ensure that VEPs are admissible before using them or consider employing non-traditional criteria to avoid rejecting large numbers of inadmissible data.
mesh_terms: D000293:Adolescent; D000328:Adult; D001143:Arousal; D004569:Electroencephalography; D005074:Evoked Potentials, Visual; D006801:Humans; D010775:Photic Stimulation; D011930:Reaction Time