I know this is a basic question, but I can't find the answer anywhere. How can a cell that is not photoreceptive (eg LGN and retinal gangion cells) have a receptive field that is stimulated by "light" (as most textbooks explain it). Isn't it truer to say that they are stimulated by incoming neuronal inputs - in which case, how can they have a "circular surround"? Clearly I'm lost here, so all help appreciated! Thanks!

  • $\begingroup$ Indirectly, but effectively, they respond to light stimulus. "receptive field" is defined that way... $\endgroup$ – Memming Sep 14 '17 at 16:03
  • $\begingroup$ Thanks, so would I be right in thinking that the "center surround" phenomenon only happens at the photoreceptors and then, as their signals travel through the rest of the connections to any given ganglion cell (or even the LGN), the "field" of those later cells really refers to the network of signals sent by all of the earlier cells feeding into the process? Or does it work some other way? THANKS SO MUCH FOR ALL YOUR HELP! (cause so many even canonical writings say "the LGN cells also reacts to light on their center surround" - which is (literally) impossible yes? Thanks again! $\endgroup$ – confused Sep 15 '17 at 5:16

The (visual) receptive field of a neuron is the relation between the light that falls on the retina and the change in activity of that neuron, regardless of what happens in between the light and the neuron. Therefore, RGC, LGN, V1, or even higher order visual cortical neurons all have some sort of receptive fields. Not because they respond directly to patterns of light, but through cascade of signals that originate from the photoreceptors. So, yes, many LGN neurons would have center-surround receptive fields.

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    $\begingroup$ Thanks so much again, Memming! I really appreciate the time you spent to clarify this for me. I hope you can see why a newcomer to this would be confused, as many textbooks (at least on the introductory level) use the words "are responsive to light on their center-surrounds" too ambiguously, IMHO. Thanks again! - "Less Confused" $\endgroup$ – confused Sep 16 '17 at 3:20
  • $\begingroup$ You're welcome. Feel free to "accept" the answer! $\endgroup$ – Memming Sep 16 '17 at 16:05

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