How specific features in the environment are represented within the brain is an important unanswered question in neuroscience. A subset of retinal neurons, called direction-selective ganglion cells (DSGCs), are specialized for detecting motion along specific axes of the visual field1. Despite extensive study of the retinal circuitry that endows DSGCs with their unique tuning properties2, 3, their downstream circuitry in the brain and thus their contribution to visual processing has remained unclear. In mice, several different types of DSGCs connect to the dorsal lateral geniculate nucleus (dLGN)4, 5, 6, the visual thalamic structure that harbours cortical relay neurons. Whether direction-selective information computed at the level of the retina is routed to cortical circuits and integrated with other visual channels, however, is unknown. Here we show that there is a di-synaptic circuit linking DSGCs with the superficial layers of the primary visual cortex (V1) by using viral trans-synaptic circuit mapping7, 8 and functional imaging of visually driven calcium signals in thalamocortical axons. This circuit pools information from several types of DSGCs, converges in a specialized subdivision of the dLGN, and delivers direction-tuned and orientation-tuned signals to superficial V1. Notably, this circuit is anatomically segregated from the retino-geniculo-cortical pathway carrying non-direction-tuned visual information to deeper layers of V1, such as layer 4. Thus, the mouse harbours several functionally specialized, parallel retino-geniculo-cortical pathways, one of which originates with retinal DSGCs and delivers direction- and orientation-tuned information specifically to the superficial layers of the primary visual cortex. These data provide evidence that direction and orientation selectivity of some V1 neurons may be influenced by the activation of DSGCs.
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Extended data figures and tables
Extended Data Figures
- Extended Data Figure 1: The retino-geniculo-cortical pathway links retinal cells and circuits to the brain. (100 KB)
a, Diagram of retina, dorsal lateral geniculate nucleus (dLGN) and primary visual cortex (V1). The optic tract which carries retinal ganglion cell (RGC) axons and thalamocortical (dLGN to V1) pathway also shown. b, Diagram of retinal layers: PRL, photoreceptor layer; opl, outer plexiform layer; INL, inner nuclear layer; ipl, inner plexiform layer; GCL, ganglion cell layer; nfl, nerve fibre layer. c, Retina diagram with cells shown (labels same as in b).
- Extended Data Figure 2: Approach for assessing laminar specificity of mouse geniculocortical projections. (108 KB)
a, Focal retrograde tracer injection to V1. Scale bar, 3 mm. b, Diagram of the three different injection depths used to generate data in Fig. 2. c, Percentage of fluorescence in V1 from superficial (black line) versus deep (grey line) injections. Superficial, peak intensity occurs at 25 μm from pial surface (4 mice). Deep, peak intensity occurs at 350 μm from pial surface. Gray shaded regions, s.e.m. (superficial vs deep = ***P < 0.0001; two-way ANOVA). d, Assessment of retrogradely labelled cells across the width of the dLGN. 0% is at optic tract, 100% is at medial border (see Fig. 2g–i).
- Extended Data Figure 3: Retrograde tracers to superficial V1 label cells in the DSGC-RZ. (410 KB)
a–c, Same dLGN as in main Fig. 2f but with GFP+ On-Off DSGC6 axons shown. a, most of the retrogradely labelled cells (magenta/dashed circles) reside in the DSGC-RZ (green terminals). Asterisk, labelled cell outside the DSGC-RZ. Scale bar, 200 μm. b, c, High magnification views of retrogradely labelled dLGN neuron cell bodies with potential contact from GFP+ DSGC axons (arrow in b); c, this cell is in vicinity of DSGC axonal boutons (arrowheads). b, c, Scale, 15 μm. d, Diagram of laminar-specific connections between DSGC-RZ and superficial V1 and dLGN core and deeper V1 layers 4 and 6.
- Extended Data Figure 4: Analysis of dLGN neurons retrogradely infected from superficial V1. (320 KB)
a–f, Example serial sections of anterior, middle and posterior portions of dLGN in a mouse with GFP expressing On-Off DSGC axons that was injected with ΔG-RABV-mCherry in superficial layers of V1. a, DAPI to show cytoarchitectural landmarks and dLGN borders. b, GFP+ DSGC axons and AAV2-Glyco-hGFP-infected cell bodies (see main Fig. 4 and text). c, Mask of GFP+ DSGC axons (Methods). d, ΔG-RABV-mCherry+ dLGN relay neurons. e, GFP+ DSGC axon mask superimposed with mCherry signal; this was used to determine colocalization. f, mCherry and GFP signals merged. Scale bar, 200 μm.
- Extended Data Figure 5: Putative sites of contact between DSGC axons and a dLGN neuron retrogradely infected from superficial V1. (526 KB)
a–i, GFP+ On-Off DSGC axons (green in all panels except black in b) and mCherry+ dLGN relay neuron (magenta in all panels except white in c) infected by injection to superficial V1. Framed region in a is shown at higher magnification in b–d. Arrowhead (a), thalamocortical axon of mCherry+ dLGN cell. Scale bar in a, 50 μm. Yellow boxed region in c, d, is shown at higher magnification in e–i. Scale bar in d, 15 μm. e–i, Some DSGC axon–dendrite contacts contain VGLUT2 (blue). f–i, Arrowhead, site of GFP/mCherry co-localization that does not contain VGLUT2; arrow, GFP/mCherry/VGLUT2+ contact.
- Extended Data Figure 6: The axons of GFP+ On-Off DSGCs and dLGN neurons infected with AAV2-Glyco-hGFP can be distinguished on the basis of their cellular localization. (563 KB)
High magnification view of DSGC-RZ in mouse with GFP+ posterior-tuned On-Off DSGCs that was injected 14 days earlier with AAV2-Glyco-hGFP. Glyco-hGFP+ neurons have nuclear GFP labelling (arrows), whereas DSGCs have GFP in axon terminals (arrowheads). Dashed line, lateral border of dLGN. OT, optic tract. Scale bar, 50 μm.
- Extended Data Figure 7: Signature anatomical and physiological characteristics of GFP-tagged On-Off DSGCs. (277 KB)
a, b, Flat-mount retina with GFP+ On-Off DSGCs (a) and co-stained with DAPI (b). c, Positions of GFP+ RGCs. Scale bar in c, 150 μm. d–f, High magnification views. Scale bar, 12 μm. g, Targeted fill of a GFP+ DSGC. Scale bar, 50 μm. h, Schematic of On-Off DSGC stratification and starburst amacrine cells (magenta). Labelling as in Extended Data Fig. 1. i, j, Higher magnification of framed region in g stained for VAChT (starburst amacrine processes). Asterisk, ‘looping arborizations’; dashed line, GFP arborization, which matches VAChT plexus. Scale bar, 10 μm. k, l, Side (x–z plane) views of cell in g. GFP+ dendrites co-stratify with both the On and Off sublayers. Scale bar, 5 μm. m, Direction-tuned response of a GFP+ On-Off DSGC targeted for recording and receptive field characterization. The spike count is highest for bars moving towards ~270° in the cardinal axes.
- Extended Data Figure 8: Injections of ΔG-RABV-mCherry into both superficial and deep V1 combined with AAV2-Glyco-hGFP infection of dLGN core. (484 KB)
a, mCherry+ neurons in the DSGC-RZ and the core of the dLGN. b, AAV2-Glyco-hGFP: many neurons throughout the dLGN, but mostly along the medial border and not in the shell/DSGC-RZ express Glyco-hGFP. DSGC-RZ marked by axons of GFP+ On-Off DSGCs. c, Merged of a, b. Scale in a, 100 μm. Boxed regions with arrows: two dLGN neurons; both RABV-mCherry+ and AAV2-Glyco-hGFP+. One or both of these cells infected their presynaptic partner, the RGC shown in Fig. 4 (panels cc-ee) of the main text. Scale bar, 15μm.