A DIGITAL FEEDBACK CONTROLLER APPLICATION FOR STUDYING PHOTORECEPTOR ADAPTATION BY VOLTAGE-CLAMP BY LIGHT

We present a new digital feedback application for the study of the sen sitivity characteristics of photoreceptors. The amplitude of the recor ded membrane voltage of a cell is steered by changing the incoming lig ht intensity with a motor-driven circular, linear neutral-density wedg e (CFW). The voltage response is sampled and fed to a software positio n controller of the CFW. The controller determines the position of the wedge according to the desired (command) value of the response. The l ight intensity changes during steady-state represent the sensitivity c hange, the time-course of adaptation.