Extraction of M and P components from the visual evoked potential using pseudorandom stimulation with swept parameter technique

To develop a method of extract magnocellular (M) and parvocellular (P) components from VEP, the nonlinear system identification method using pseudorandom binary sequence (PRBS) stimulation combined with swept parameter technique was examined. VEP elicited by achromatic sinusoidal grating reverse based on PRBS was recorded and their binary kernels were calculated as cross-correlation between PRBS and VEP. To manipulate the magnitudes of M and P visual pathways responses in VEP, the spatial frequency of gratings were swept during the PRBS stimulation. VEP to this stimulation was recorded from 4 healthy participants and their binary kernels changes during the stimulation were evaluated. PRBS stimulation of 40950 ms period was repeated twice, and the spatial frequency was swept from 0.5 to 9 [c/d] or 9 to 0.5 [c/d] within the period. Binary kernel of each epoch was calculated by cross-correlating VEP with PRBS of 40950 ms duration. Different waveforms of binary kernels obtained from the former and latter half of the PRBS stimulation were confirmed, and the waveforms were continuously changed during the stimulation. The changes may reflect the M and P pathway contribution changes during the stimulation and depend on the spatial frequency sweeping. The suggested technique would be effective for studying and screening several eye and neurocognitive disorders which have been reported to relate with selective damage in M/P pathways.