How do mammalian retinal ganglion cells respond differently from frog retinal neurons in darkness?

In the study of receptive fields, the primary difference between mammalian retinal ganglion cells and frog retinal neurons in darkness lies in their baseline activity levels.

While frog retinal neurons typically exhibit distinct "on," "off," or "on-off" responses to light stimuli without a notable background discharge, the mammalian retina maintains a continuous background of activity in the dark. Consequently, in mammals, "on" and "off" effects are manifested as either accentuations or diminutions of this existing normal discharge rather than as a transition from complete inactivity.1

Furthermore, the mammalian receptive field is more complex than that of the frog. It is organized into a concentric structure where the peripheral area provides an opposite response to the center, creating a system of mutual inhibition. During dark adaptation, the surrounding area of opposite activity in the mammalian retina becomes less effective, causing the receptive field to shrink in terms of inhibitory influence, which effectively increases the regions over which summation can occur.1