Signal-to-noise comparisons for X and Y cells in the retina and lateral geniculate nucleus of the cat.

The spike trains of X and Y retinal ganglion cell axons and neurons in the lateral geniculate nucleus (LGN) of cats were compared to determine if the visual signal could be better discriminated from the maintained activity in the LGN relative to the retina. Curves for relative or receiver operating characteristics (ROC) were derived from the interspike interval data of the spike trains using maintained activity as "noise" and visually-driven activity as the "signal". Analyses were also made using spike densities and more restricted time intervals. Although it was expected that neurons in the LGN might better distinguish the signal from the noise, the results of the ROC curve and spike density analyses did not bear out this expectation; that is, neither the X or Y cells in the LGN provided better discrimination of the visually-driven activities from the maintained activities compared to the incoming retinal information. Thus, at least in the anesthetized preparation, the LGN does not play a role in increasing the signal-to-noise ratio.