Phototransduction in Humans and Locusts
For Student Groups

Experiments

• Determination of the flicker fusion frequency in a self-experiment
• Determination of the flicker fusion frequency in the migratory locust
• Creation of stimulus response curves in the migratory locust

The speed of stimulus processing in the rods and cones of the human retina is examined in self-experiments. For this purpose, the frequency at which a series of light flashes is perceived as a continuous light (flicker fusion frequency) is determined at different light intensities. A minimum time is required for the transduction process in the photoreceptors. The transduction process consists of a sequence of biochemical processes that finally lead to a change in the receptor potential and is triggered by a light flash. If the time interval between two stimuli is shorter than this minimum time, the stimuli will not be perceived separately. The results are interpreted with respect to the physiological properties of the cones and rods. In order to quantify the electrical activity of the locust eye, so-called retinograms are generated by means of extracellular recordings from the locust eye. This allows to quantify the stimulus response. By stimulation with light flashes of different frequency and brightness the flicker fusion frequency is determined. Furthermore, the amplitude of the stimulus response is determined as a function of the light intensity, and the spectral sensitivity of the locust eye is investigated by stimulation with light of different wavelengths. The computerized control of the experiments and the analysis of the digitized stimulus responses allow a fast quantitative evaluation of the performed experiments.

Keywords

Retina, Signal transduction, Sense organ, Photoreceptor, Eye, Complex eye