Detecting visual features in the environment such as motion direction is crucial for survival. The circuit mechanisms that give rise to direction selectivity in a major visual center, the superior colliculus (SC), are entirely unknown. Here, we optogenetically isolate the retinal inputs that individual direction-selective SC neurons receive and find that they are already selective as a result of precisely converging inputs from similarly-tuned retinal ganglion cells. The direction selective retinal input is linearly amplified by the intracollicular circuits without changing its preferred direction or level of selectivity. Finally, using 2-photon calcium imaging, we show that SC direction selectivity is dramatically reduced in transgenic mice that have decreased retinal selectivity. Together, our studies demonstrate a retinal origin of direction selectivity in the SC, and reveal a central visual deficit as a consequence of altered feature selectivity in the retina.

The novel, hemilabile (phosphinoalkyl)arene ligands ArX(CH2)2PPh2 (1a, Ar = C6H5, X = O; 1b, Ar = C6H5, X = CH2; 1c, Ar = FC6H4, X = CH2) were synthesized and complexed to Rh(I) to form the bis(phosphine), η6-arene piano stool complexes [(η6:η1-ArX(CH2)2PPh2)Rh(η1-ArX(CH2)2PPh2)]BF4 (2a−c). Complexes 2a−c were fully characterized in solution, and complex 2a was characterized by single-crystal X-ray diffraction methods. Two of these complexes, 2a,c, undergo an unusual, degenerate η6-arene, free arene exchange reaction which was studied by 2-D NMR EXSY experiments. A mechanism for the exchange reaction of 2a which involves the formation of a square planar, cis-phosphine, cis-ether Rh(I) complex, [Rh(η2-PhO(CH2)2PPh2)2]BF4 (13), is proposed.

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Detection of salient objects in the visual scene is a vital aspect of an animal’s interactions with its environment. Here, we show that neurons in the mouse superior colliculus (SC) encode visual saliency by detecting motion contrast between stimulus center and surround. Excitatory neurons in the most superficial lamina of the SC are contextually modulated, monotonically increasing their response from suppression by the same-direction surround to maximal potentiation by an oppositely-moving surround. The degree of this potentiation declines with depth in the SC. Inhibitory neurons are suppressed by any surround at all depths. These response modulations in both neuronal populations are much more prominent to direction contrast than to phase, temporal frequency, or static orientation contrast, suggesting feature-specific saliency encoding in the mouse SC. Together, our findings provide evidence supporting locally generated feature representations in the SC, and lay the foundations towards a mechanistic and evolutionary understanding of their emergence.