Figure 3. Classical alpha RGCs and their “mini” counterparts.

a, functional “fingerprint” of classical transient OFF alpha cells (G_8a,b). Light-evoked Ca²⁺ responses of n=80 cells (a₁): heat-maps (top) of individual responses, response averages and firing rates estimated from Ca²⁺ signals below (cf. Extended Data Fig. E1). a₂, left, G_8a,b somata (yellow) and receptive fields (RFs, dotted) indicated in example experiment (cf. Fig. 1a₂). Grey circles mark cells with RFs above quality criterion (Methods). Sample morphology of a G_8a,b cell filled after electrical single-cell recording (a₂, right). For details, see SI Data 2₈. b_1,2, G₉ RGCs (n=68), dubbed transient OFF mini alpha because of their similarity in light response to G_8a,b RGCs (cf. a_1,2). c_1,2, G₂₄ RGCs (n=44), identified as classical ON alpha. d_1,2, G₂₃ RGCs (n=113), dubbed ON mini alpha (cf. c_1,2). Mini alphas have smaller RF diameters than classical alphas (median in μm, 95% confidence interval): G₉,280 (270–293) versus G₈, 306 (294–315) with p=0.01232), and G₂₃, 236 (218–256) versus G₂₄, 319 (290–352) with p=0.00026 (rank-sum test). e, overlay of OGB-1-stained cells (green) and SMI-32 (magenta). SMI-32-positive RGCs include classical alphas (e₁, solid contours; n.r. indicates a non-responsive cell), one large-soma non-alpha cell (green, dotted contour) as well as weakly-labeled ON-OFF DS cells (dashed contours) and starburst-ACs (asterisks). Mini alpha cells (blue, dotted contours) are SMI-32-negative. Chirp-evoked Ca²⁺ responses (e₂) for 5 cells in (e₁). f, SMI-32 statistics (OFF tr.: alpha, n=16, mini, n=3; ON: alpha, n=6, mini, n=15; OFF sus. alpha, n=14; ON tr. large, n=7; other, n=957; means with 95% confidence intervals, **, p≤0.01; ****, p≤0.0001, logistic regression).