Different scalp localization of pattern onset and reversal visual evoked potentials

Area of Science:

• Neuroscience
• Ophthalmology
• Visual Electrophysiology

Background:

• Visual evoked potentials (VEPs) are crucial for assessing the integrity of the visual pathway.
• Understanding the scalp topography of VEPs aids in localizing visual processing areas.
• Source-sink analysis provides insights into the electrical current flow generating VEPs.

Purpose of the Study:

• To investigate the scalp distribution and origin of visual evoked potentials.
• To analyze the electrical source-sink dynamics during pattern onset and reversal.
• To examine the effect of check size on VEP components.

Main Methods:

• Monopolar and bipolar recordings of VEPs from electrodes placed between T3 and T4.
• Stimulation using checkerboard patterns (10° x 13.5°) with varying check sizes and high contrast.
• Application of source-sink analysis to VEP data.

Main Results:

• Pattern onset with small checks showed a C1 component (approx. 80 ms) with a contralateral source and midline sink.
• Pattern reversal revealed two phase reversals: an early one (approx. 80 ms) with a contralateral source, and a later one (approx. P100 latency) with a midline or ipsilateral source.
• Smaller check sizes enhanced the early phase reversal amplitude while reducing the later one.

Conclusions:

• VEP scalp topography and source-sink analysis differentiate responses to pattern onset and reversal.
• The findings suggest distinct neural generators for early and later VEP components.
• Check size significantly modulates VEP component amplitudes, impacting the interpretation of visual pathway function.