Fusional movements by peripheral retinal stimulation ('peripheral motor fusion')

Vertical fusional movements elicited by stimulation of the non-foveal retina cannot be distinguished from movements elicited by foveal stimulation, except for a difference in the ratio between the amplitude of the response and the amplitude of the stimulus. This ratio is dependent on target configuration and on the retinal area stimulated. In some circumstances, if the size and richness of contour balances against the object fixated at the fovea, bifoveal fixation can be disrupted. It can be assumed that the stimulus for the motor response is made up of foveal as well as peripheral retinal stimulation. it is plausible that there is a gradient over the retina: the influence of the stimulated retinal area decreases form the fovea towards the periphery.