Figure 2.
Stimulus representations in the SC of β2-/- mice are broader than in wt animals. A, B, Single-position maps obtained with five stimulus sizes (side length, 12, 15, 20, 24.5, and 30°) presented at the same position in visual space from a wt (A) and β2-/- (B) animal. The patch area increases with stimulus size, but responses in β2-/- animals are larger and blurrier for a given stimulus size. The dotted line outlines the border of the SC, which in these experiments was not exposed fully. Scale bar, 1 mm. C, Quantification of the SC response area. Mean patch area values for each of the five stimulus sizes from wt and β2-/- animals. **p < 0.01; ***p < 0.001; t test. D, Mean, normalized semi-profiles of patches evoked by 12° stimuli in wt (black) and β2-/- (gray) animals. Note that, in β2-/- mice, there is a shallower decline of response with distance from patch center and that patch width is broader for all values below the peak response. Error bars represent SEM.