Connectome of a human foveal retina.

What makes human brains distinctive? The answer is hidden at least partially in the myriad synaptic connections made between neurons - the connectome. The foveal retina is a primate specialization which presents a feasible site for deriving a complete connectome of a human CNS structure. In the fovea, cells and circuits are miniaturized and compressed to densely sample the visual image at highest resolution and initiate form, color and motion perception. Here we provide a draft connectome of all neurons in a human fovea. We found synaptic connections, distinct to humans, linking short-wavelength sensitive cones to color vision pathways. Moreover, by reconstructing excitatory synaptic pathways arising from cone photoreceptors we found that over 95% of foveal ganglion cells contribute to only three major pathways to the brain. Our study reveals unique features of a human neural system and opens a door to a complete foveal connectome.