The phase of PVEP in Maxwellian view: influence of contrast, spatial and temporal frequency

The temporal phase of the pattern reversal VEP has been investigated using stimulation with laser interference fringes in Maxwellian view. VEP phase was almost constant as function of spatial frequency (2-30 c/deg, 6.5 r/sec, 51 subjects). The phase function however shows a small phase increase at low spatial frequencies consistent with the existence of multiple temporal mechanisms. Contrast variation yields a smaller phase increase with decreasing contrast than conventional stimulation. The phase is linear as function of reversal rate (2-31 r/sec) for low and high spatial frequencies. The indication of more than one temporal mechanism has also been found when the test field diameter was varied. With decreasing test field size the phase increases at 6.5 r/sec, but decreases at 18 r/sec (for 12 c/deg).