Whether mouse visual cortex contains orderly feature maps is debated. The overlapping pattern of geniculocortical (dLGN) inputs with M2 muscarinic acetylcholine receptor-rich patches in layer 1 (L1) suggests a non-random architecture. Here, we found that L1 inputs from the lateral posterior thalamus (LP) avoid patches and target interpatches. Channelrhodopsin-assisted mapping of EPSCs in L2/3 shows that the relative excitation of parvalbumin-expressing interneurons (PVs) and pyramidal neurons (PNs) by dLGN, LP and cortical feedback are distinct and depend on whether the neurons reside in clusters aligned with patches or interpatches.Paired recordings from PVs and PNs shows that unitary IPSCs are larger in interpatches than patches. The spatial clustering of inhibition is matched by dense clustering of PV-terminals in interpatches. The results show that the excitation/inhibition balance across V1 is organized into patch and interpatch subnetworks which receive distinct long-range inputs and are specialized for the processing of distinct spatiotemporal features. S1), and measured EGFP intensity in patches (top 3 rd ) and interpatches (bottom 3 rd ). We then normalized the pixel values in interpatches to the mean intensity in patches and plotted the counts in different intensity bins. We found that the fluorescence intensity in patches was 2.1 ± 0.024fold (p = 8x10 -18 , Komolgorov-Smirnov test [KS]) higher in patches than interpatches ( Figure 1D). Similar to our previous findings, patches and interpatches in L1 were 60-80 µm wide and their centroids were 120-140 µm apart. dLGN projections to L4, and 5/6 appeared uniform (data not shown). Inputs to L1 from the LP thalamus exhibited a strikingly different pattern, showing 1.6 ± 0.14-fold (p = 1.33x10 -4 , KS) stronger projections to M2-interpatches ( Figure 1E-H).Simultaneous tracing of dLGN and LP inputs with AAV2/1hSyn.tdTomato.WPRE.bGH and AAV2/1.hSyn.EGFP, respectively, confirmed the interdigitating pattern of projections from primary and higher order thalamic nuclei, showing denser LP input to interpatches (p = 7.95 x 10 -4 , KS) ( Figure 1I-M).
Clustering of intracortical inputs to L1 of V1We next compared feedback projections from the higher visual cortical ventral stream lateromedial area, LM, to V1 with inputs from the dLGN. Double viral tracings from the dLGN (AAV2/1.hSyn.EGFP) and LM (AAV2/1hSyn.tdTomato.WPRE.bGH) showed that inputs from both sources overlapped in presumtive M2+ patches of L1 ( Figure 1A-C; 2A). Quantitative analysis showed that LM inputs to patches were 1.7 ± 0.05-fold denser than to interpatches (p = 1.45x10 4 , KS) ( Figure 2B). We have shown previously that inputs from the dorsal stream anterolateral area, AL, terminate in M2+ patches (Ji et al., 2015), raising the question whether M2+ patches are the preferred targets of cortical feedback. To address this, we traced the connections to V1 from the posteromedial area, PM, another member of the dorsal stream (Wang et al. 2012). We found that inputs from PM were non-uniform, overlapped i...