Fig. 1.

Wiring diagrams of retinal direction selectivity. A: model of null-direction inhibition. Left: schematic shows side view of glutamatergic bipolar cell (BP) inputs to the proximal dendrites of ON and OFF starburst amacrine cells (SACs) and GABA release (orange circles) from SAC distal dendrites to two ON-OFF direction-selective ganglion cells (DSGCs) of opposite preferred directions (pref dir). The preferred directions of ON-OFF DSGCs are represented by the green and red arrows. Directional inhibition from SACs to the DSGC depends on two properties: 1) centrifugal (CF) direction selectivity of SAC dendrites (CF direction (CF dir) of SAC dendrites is represented by black arrows) and 2) asymmetric wiring between SACs and DSGCs. SAC dendrites oriented to the right form GABAergic synapses with the DSGC whose preferred direction is to the left. Right: Top view shows the asymmetric inhibition from a SAC (center) to four DSGCs that prefer four different cardinal directions. Each SAC dendritic quadrant preferentially forms GABAergic synapses with the DSGC with the same color. B: schematic shows anatomically and/or functionally identified connections in the inner plexiform layer that participate in the direction-selective circuit. Top: ON pathway. Bottom: OFF pathway. Excit, excitatory; Inhib, inhibitory; VGluT3, vesicular glutamate transporter 3; VIP, vasoactive intestinal polypeptide; WAC, wide-field amacrine cell.