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VEPs to Concentric Motion: Can we measure Behavioral Differences in Humans?

Molnar F. E.1,2, Bach M.2
11st Department of Ophthalmology, Semmelweis University, Budapest; 2Electrophysiology Lab, Ophthalmology Department, University of Freiburg

Purpose: Concentric motion stimuli have the advantage that they do not elicit optokinetic nystagmus responses. However, expansion vs. contraction have different behavioral relevance so we systematically compared motion VEPs to these stimuli.
Method: Using the “Freiburg Evoked Potentials” system, dartboard-like stimuli either contracted or expanded at 13°/s for 200 ms and then remained stationary for 1300 ms. The stimulus was viewed binocularely; it covered 40°x30° at 20% contrast and a luminance of 45 cd/m2. The EEG was derived from Oz, O1 and O2 vs. averaged ears in 32 normal subjects.
Results: Basic properties of the motion potentials were as described in the literature: a prominent negativity (N2) between 140 and 200 ms. Both motion types evoked clear N2-dominated VEPs. 6 subjects who had an Oz amplitude below 4.5 µV were excluded from analysis to avoid noise intrusion. The average Oz-N2 amplitude to expansion was 8.4±3.9 µV, to contraction 6.9±3.2 µV (p=0.058). The average lateral O1 or O2-N2 amplitude to expansion was 9.8±3.8 µV, to contraction 8.7±4.1 µV (p=0.072). There were no latency differences between expansion and contraction.
Conclusions: This research was part of optimizing our stimuli for measuring motion VEPs in amblyopia. Question was based on t

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