There are mainly two parts in my presentation this time, results and analysis for the omitted stimulus response (OSR) experiment with spatial stimuli and some preliminary tests for photon counting in retina.

Some results from our experiments on OSR were shown in the slides. By holding the last state after terminating the periodic stimulus in an inverted manner (differ from the originally adapted brightness), OSR could be eliminated or shifted significantly in the latency. We’ll try to repeat the experiments a few more times, since such designed stimuli would tell us more about how ON and OFF pathways in the retina interact to produce OSR.

During the last two months, we started adding EGTA, a calcium chelator in the buffer and observed change in OSR. Surprisingly, period doubling occurred at some specific concentration, and didn’t abolish OSR. We think that EGTA affects the time scale in the whole retina activity.

As observed in my experiments, "achromatic" receptive fields may react similarly to blue or green light stimuli, which are the two observable colors in bullfrogs. However, under intermeshed blue and green light stimulus, we constantly (such experiment had been repeated for more than five times) see the activity of recorded ganglion cells synchronize to only one color. I suspect that the retina randomly "follow" a color, since the same retina could produce activity following blue or green light under a same stimulus, and uninfluenced by the starting color.