On and off contribution to the combined occipital on-off response to a pattern stimulus.

The hypothesis, derived from previous studies, that the off response forms the main part of the second positive wave (P2) in the occipital response to the presentation of patterns was tested by using stimuli of various durations. It was found that the off response merges with P2 of the on response in the combined on-off response. The question, however, whether the on response or the off response contributes most to the combined on-off response could not be answered. By applying hemifield stimulation, the experiments furthermore confirm the concept of the presence of a double dipole in the hemisphere contralateral to the stimulated side.