Die Empfindlichkeit einzelner Photorezeptoren im Komplexauge vonCalliphora erythrocephala

An analog-digital feedback system for measuring photoreceptor properties with an equal response method

This paper describes a feedback system in which a neutral density wedge automatically controls the light flux applied to a photoreceptor, so that an intracellular recorded response is held constant. We describe here a "differential sampler" that subtracts the photoreceptors dark response from the light response induced by a chopped light source. The resulting signal drives the feedback system. The response time of the feedback system can be adjusted with a "digital integrator" to match a range of variable conditions that occur in different experiments.

Two late response components in on-off ganglion cells of the frog retina: the delayed response-generated by red rods; the second off-response-generated by green rods

Frog on-off retinal ganglion cells react to diffuse, large-sized stimuli not only with an "early response" and a "delayed response" but also with a "second off-response". The intensity at which the delayed response becomes visible coincides with the quantum amount necessary for saturating the red rod response. The spectral sensitivity of the delayed response fits the nomogram for the 502 nm pigment. Unlike the delayed response, the second off-response appears earlier with increasing stimulus intensity and follows the 433 nm nomogram. Therefore, it is most probably generated by the green rods.