Volume 28, Issue 1, Pages 114-120.e5 (January 2018) Feature-Specific Organization of Feedback Pathways in Mouse Visual Cortex  Carey Y.L. Huh, John P. Peach, Corbett Bennett, Roxana M. Vega, Shaul Hestrin  Current Biology  Volume 28, Issue 1, Pages 114-120.e5 (January 2018) DOI: 10.1016/j.cub.2017.11.056 Copyright © 2017 Elsevier Ltd Terms and Conditions

Figure 1 CAV2-Cre-Mediated Labeling of Feedback Neurons Projecting to V1 (A) Tangential section showing retrograde labeling of neurons in areas providing projections to V1 using CAV2-Cre (left) and CTB-488 (middle; right: merged). AL, anterolateral; AM, anteromedial; LI, laterointermediate; LM, lateromedial; P, posterior; PM, posteromedial; RS, retrosplenial; S1, somatosensory. (B) Coronal sections showing laminar distribution of feedback neurons. (C) Percentage of CTB-488 co-labeling in CAV2-Cre+ cells (red) and that of CAV2-Cre co-labeling in CTB-488+ cells (green). (Top) All layers are shown. (Bottom) L5 only is shown. Error bars represent mean ± SEM in 3 mice. See also Figure S1. Current Biology 2018 28, 114-120.e5DOI: (10.1016/j.cub.2017.11.056) Copyright © 2017 Elsevier Ltd Terms and Conditions

Figure 2 Channelrhodopsin-2 Guided Targeted Recording of AL and PM Feedback Neurons In Vivo (A) Experimental approach. (B) Laser responses of feedback (blue) versus neighbor (magenta) neurons in terms of change in firing rate during laser and latency of first spike during laser period. Some cells could not be classified (yellow). AL, circles; PM, triangles; filled, cells with spiking during laser; open, cells without spiking during laser period (no response). (C–F) Example AL feedback neuron. (C) Response to laser is shown. (D) Spatial frequency (SF) turning curve is shown. PrefSF, preferred SF, based on Gaussian fit (red). (E) Spike time histogram and raster plot during 0.01-cpd grating is shown. (F) Temporal frequency (TF) tuning curve is shown. Gray lines, baseline firing rate (solid, mean; broken, mean ± SEM). (G–J) Example PM feedback neuron with same layout as in (C)–(F). (K–M) Visual properties of feedback versus neighbor neurons in AL (red circles) and PM (cyan triangles). (K) Peak SF, (L) peak TF, and (M) linearity are shown. Error bars represent mean ± SEM; ∗∗p < 0.01. See also Figure S2. Current Biology 2018 28, 114-120.e5DOI: (10.1016/j.cub.2017.11.056) Copyright © 2017 Elsevier Ltd Terms and Conditions

Figure 3 Functional Impact of Silencing AL versus PM Feedback on V1 Neurons (A and B) Experimental approaches 1 (A) and 2 (B). For AL feedback silencing, both approaches were used. For PM feedback silencing, approach 2 was used. (C–E) Control experiment showing direct silencing effects on putative feedback PM neurons (4 cells). (C) Normalized firing rates in laser-off (black) versus laser-on (green) trials are shown. Solid, mean; broken, mean ± SEM. Change in firing rate (%) during laser as a function of time in 250-ms bins (D) and laser power (E) is shown. (F–I) Effects of silencing AL feedback. (F) SF tuning curve of a V1 neuron preferring 0.04 cpd with/out AL feedback silencing (black, control; green, laser) is shown. Raster plot (G) and spike time histogram (H) of the cell’s response to 0.04-cpd gratings with/out laser are shown. (I) Change in firing rate for preferred stimulus during AL feedback silencing for V1 neurons preferring low versus high SF is shown. Blue, results using approach 1; black, results using approach 2; bold, neurons with statistically significant laser modulation; numbers in parentheses, number of neurons. (J–M) Effects of silencing PM feedback with same layout as (F)–(I). For (C)–(F) and (J), error bars represent mean ± SEM; ∗∗∗p < 0.001; ∗∗p < 0.01; ∗p < 0.05; nsp > 0.05. See also Figures S3 and S4. Current Biology 2018 28, 114-120.e5DOI: (10.1016/j.cub.2017.11.056) Copyright © 2017 Elsevier Ltd Terms and Conditions