Figure 1 ∣. AII ACs make chemical synapses onto OFFα GC somas.

(A) Retina schematic (modified⁸¹). ♦♦, gap junctions; ►●, chemical synapses. 1, AII synapses onto OFF CB axon terminals; 2, AII synapses onto OFF GC dendrites; 3, proposed output synapses onto OFF GC somatic region. R, rod photoreceptor; C, cone photoreceptor; RB, rod bipolar cell, AII, AII amacrine cell; On CB, ON cone bipolar cell; Off CB, OFF cone bipolar cell; Off GC, OFF ganglion cell; On GC, ON ganglion cell; ONL, outer nuclear layer; OPL, outer plexiform layer; INL, inner nuclear layer; IPL, inner plexiform layer; GCL, ganglion cell layer.

(B-C) SBFSEM micrographs showing AII synapses onto a s-OFFα soma (B) and a t-OFFα dendrite (C). Scale bar applies to (B,C). See Figure S1 for serial EM sections. See Table S1 for quantitative summary.

(D) Skeletonized s-OFFα with all inhibitory inputs annotated. Lower panel, transverse view; gray plane indicates ON-OFF border in IPL²⁶. See Figure S2 for annotated excitatory inputs.

(E) Histogram showing dendritic stratification of identified OFFαs in the EM dataset, relative to those of identified ON and OFF starburst amacrine cells (SACs).

(F) Soma locations of AIIs providing inputs to s-OFFα in the OFF (black circles) and/or ON layers (blue squares) of the IPL. Gray circles and gold squares indicate AIIs connected to the t- OFFα. See Figure S3 for inputs from other ACs.

(G) Summary plot showing the total synaptic contacts from AIIs to the s-OFFα versus retinotopic (x-y) distance between AII and GC somas. Diamonds indicate the number of ON/GCL contacts.

(H-J) As in (D,F,G) for the t-OFFα. Scale bar in (H) applies to (D,F,H,I).

(K-L) 3D images of s-OFFα (K) and t-OFFα (L) GC somatic region. AIIs inputs are color-coded to indicate those arising from the same AII. Scale bar applies to both panels. Please mention Figures S1-S3 and Table S1.