I saw the movie of the hangout and because of my lack of understanding of spoken English, I'd have some questions to ask to better understand all the interesting things said yesterday.
1. It seemed to understand that some components of the retina behave as hardware preprocessors on the contrary of photoreceptors that act as pure sensors. In particular the J cell preprocesses the downward movement. The question is: does it regardless of the photoreceptors or in some way (which?) they take into account the signals from the photoreceptors?
2. From the point of view of evolution is there any reason why the photoreceptors in the retina are arranged behind the neurons?
Thanks in advance
PS I'm sorry not having been able to follow the live hangout due to technical problems with my computer but it is probably better to follow you at a later time so I got the possibility to review the discussion in order to better understand what was being said.
PPS in the discussion did you refer to a Wikipedia page. Which one?