In all cases, the display will be viewed through natural pupils (undilated) with optimal refractive correction in place. The viewing distance will be set to 1 m, yielding a total display viewing angle of 15.5 degrees. The square black/white checkerboard pattern reversal stimulus has a height and width of 27 cm with a red circular ring used as a fixation target. The diameter of the target is approximately 1.5 cm with a ring thickness of 1.5 mm. The target ring will be centered on the stimulus. The check size will be 29.0 minutes of arc. Two pattern contrasts will be used in the study, based on earlier studies that suggested that differential contrast stimulation could affect the NOVA-VEP (FP) waveforms. The first pattern will have a Michelson contrast of 15%. The second pattern will have a Michelson contrast of 85%. These two patterns are referred to as LC (Low contrast) and HC (High contrast) respectively.