Figure 4.
Stimulus representation changes from retina to LGN. a, b, Normalized MID filters for the RGC (red) and LGN neuron (black) are temporally altered, as revealed by subtracting the filters (blue). MID1 yields the most information, while MID2 represents an orthogonal stimulus dimension adding maximal information to the first. Error estimates computed over data subsets had average SEMs <0.01 for each point along all filters (data not shown). c, d, Spike rate gain measures how far above the mean firing rate (at gain = 1) any stimulus can drive the cell, plotted as a function of projection value distributions (see Materials and Methods for details). Filter combinations significantly increase the spike rate gain of the LGN neuron (d) over the RGC (c). Projection values with positive SDs represent stimuli with increasing resemblance to the filters. e, Population data comparing RGC and LGN peak spike rate gains for all filters (e.g., the peaks in supplemental Fig. 1g–i, available at www.jneurosci.org as supplemental material), normalized to the peak RGC STA rate gain. The combined MID filters exhibited the highest gains. f, Peristimulus time histograms of spike rate gains for 3 cells, in response to the same repeated stimuli. Stimulus segment is the same as shown in Figure 1d. When LGN gains (black) are above the unity gain line (gray), they exceed RGC gains (red); and when below unity, they are lower than RGC gains, suggesting a greater modulation range for LGN neurons. The information transmission ratios for these cell pairs were: magno ON = 1.0; magno OFF = 0.74; parvo ON = 0.75.