time-course is analyzed by comparing point-by-point amplitude variability across trials, and also by computing the degree of inter-trial phase consistency across the time-course. In addition, variability of P1 amplitude, i.e., the consistency of P1 magnitude, and variability of P1 latency, i.e., the consistency of the time at which the peak occurs will be investigated. The P1 deflection is a positive going deflection within the VEP. It peaks between 100 and 160 ms after stimulus onset, is maximal over posterior leads and is generated within the extra-striate cortex. The P1 was selected for analysis as it is time-locked and phase-locked to stimulus onset. Therefore a “P1-like” increase in amplitude should be visible across single-trials, enabling variability between the two groups to be compared1.
