Article Figures & Data
Figures
- Figure 1.
Parasol and midget RF mosaics and anatomical prediction. A, Previous anatomical findings indicate that parasol cell dendritic fields overlap substantially, with the tips of each dendritic field reaching the soma of its neighbors in the mosaic, while midget cell dendritic fields abut at their boundaries. B, Each panel shows the RFs of simultaneously recorded ON and OFF parasol and midget cells from one retina, with each RF represented as the 1 SD contour of a Gaussian fit to the RF center. Note that this does not represent the full extent of the RF (see text for details). Black rectangles indicate the outline of the recording array. Gaps in the mosaic probably represent unrecorded cells. Retinal temporal equivalent eccentricity: 6.4 mm. C, Same as in B for a second preparation; temporal equivalent eccentricity 9.0 mm.
- Figure 2.
Quantitative analysis of RF overlap. The normalized nearest neighbor distance (NNND) expresses RF spacing relative to RF size; if two mosaics have the same degree of RF overlap, they will have the same NNND. A, NNND values for the mosaics of parasol and midget cells shown in Figure 1B, with the modal NNND indicated on the abscissa. Because the recordings did not sample every cell in the mosaic, the modal NNND was computed using the mean of the densest 75% of values, which excluded outlying points. The robustness of this calculation was confirmed by subsampling analysis (see Materials and Methods). B, Similar data, for the preparation in Figure 1C. C, Data summarizing the RF overlap of 36 mosaics. Modal NNND values of simultaneously recorded parasol and midget mosaics are compared separately for ON cells (open circles) and OFF cells (filled circles). Solid line indicates equality, dashed line indicates the prediction from anatomical findings that NNND should be approximately twice as large for midget cells. D, NNND values as a function of retinal eccentricity, for ON (open) and OFF (filled) cells of both midget (triangle) and parasol (circle) types.
- Figure 3.
Nearest neighbor RF profiles for ON and OFF parasol and midget cells. A, For each cell type, the average RF profiles of a cell and its nearest neighbor were computed directly by interpolation of the spatial receptive field (see Materials and Methods). Distance and amplitude were normalized to focus on the RF profile shape independently of absolute size, spacing, and sensitivity. Distance between centers (vertical bars) was normalized for each pair of nearest neighbors (see Materials and Methods). Sensitivity was normalized to have the same variance across cell types (see Materials and Methods). Data are from the preparation shown in Figure 1C. B, Same as A, from a second preparation (temporal equivalent eccentricity 9 mm).
