Flicker alternating potentials in the ERGs of insects in response to two different stimuli

Summary A special pattern of the flicker is studied in insects belonging to four Orders, i. e. the differential electrical synchronised response of the eye periodically stimulated by two slightly different alternating illuminations.After having checked that the flicker in response to a regular periodical stimulation at every frequency is made up of successive equal potentials, we use two slightly different alternate flickering flashes. It is established that the alternation of two periodical stimulations of a different duration, as well as the alternation of two periodical stimulations of a different intensity, results, over a certain frequency which depends on the insect studied, in the appearance of a flicker marked with the alternation of two potentials whose difference increases at the same time as the frequency of stimulation.The dependence of this phenomenon on modulation of the light flux is described. At a given frequency of stimulation, the alternation of a high and low potential is more obvious when the modulation is lower.A particular experiment allows us to admit that the differential threshold of electrical response to two different stimulations is under 0.25%, at the frequency 100 Hz, inCalliphora erythrocephala.All the phenomena observed can be explained by a mathematical theory which considers the characteristics of the amplitude of the response to sinusoidal stimulations of various frequencies, i. e. the characteristics of the transfer function of the frequencies.