Visual evoked potentials associated with the verbal and non-verbal problem-solving processes

VEPs to six repetitive checkerboard and letter or number stimuli (presented in two triplets) were measured. The task solution process was separated into the store, retention, solve and post-solve stages. Three stimuli in intratrial stimulus positions 1, 2 and 3 were identical and another three in positions 4, 5 and 6 were also identical. The subject's task was either naming the letter-number or matching the checkerboard stimuli in two triplets. For both stimuli, the occipital P270 was almost the same in amplitude as positions 1 and 4. During the memory retention (at position 2) the P270 enhanced for the letter-number stimulus, but not for the checkerboard. During the post-solve stage (at positions 5 and 6) the P270 enhanced for both stimuli. The occipital P270 enhancement seems to correlate with the decrease in the degree of significance of the task relevant stimuli.