Relations between Excitatory and Inhibitory Retinal Responses as determined by a Revised Apparatus for the Study of Induced Negative After-images

INDUCED negative after-images are of interest in that they reflect relations between inhibitery and excitatory retinal function. In 1897, Bidwell 1 reported that when a coloured, a white, and a black stimulus are repeatedly presented in that order for certain durations and at certain intensities, only the complement of the coloured stimulus is perceived. This effect facilitates certain after-image investigations as decisions as to reversal of colour are made more readily than are estimates of after-image duration or intensity. Suitable durations for coloured, white, and ‘black’ stimuli are 0.017, 0.10, 0.083 sec respectively; the matter of suitable brightness is the principal concern of this communication.