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. 2023 May 22;17:1193949. doi: 10.3389/fnana.2023.1193949

FIGURE 2.

FIGURE 2

Schematic of example LGN-V1-MT circuit. Dense projections from the retina, to LGN and in turn to V1, form the main visual input pathway. From V1, the densest dorsal stream projections reach MT via V2. However, a smaller projection from V1 (layer 4B) directly to MT, also exists. Furthermore, direct projections from LGN to MT, and LGN to V2 then to MT, bypass V1 entirely. An additional retinal output to pulvinar nucleus (Pul) and the stronger connections to the Pul via the superior colliculus (SC) also project directly to MT. Optogenetic probing of the LGN to MT projection requires simultaneous silencing of alternate projections from V1, V2, and Pul. High magnification factors in V1 and V2 in comparison to MT, mean large areas of tissue will need to be illuminated to silence these projections, making optogenetic silencing infeasible. Employing classical cooling of V1 and V2 (blue outline) will effectively remove V1 and V2 related circuits, allowing for the manageable modulation of remaining direct MT projections. Figure created with Biorender.com.