Fig. 2.

Retrograde transsynaptic tracing of inputs to the POm → S1 pathway. (A) Schematic of the anatomical labeling strategy for labeling presynaptic inputs to the POm → S1 pathway (see Results and Materials and Methods for details) (B) Representative images of POm, with GFP+ (B, i) and mCherry+ (B, ii) “starter” cells double labeled (yellow arrows) in POm only (overlay in B, iii). (C) Higher magnification image of a double labeled “starter” cell in POm, Top Left, GFP; Top Right, mCherry; Bottom Left, DAPI; Bottom Right, overlay. (D–H) Representative epifluorescence images of GFP+ presynaptic “input” cells, projecting to the POm → S1 pathway. Cortical layers are labeled L2/3, L4, etc. Abbreviations: BC, barrel cortex S1, TRN, thalamic reticular nucleus; SC int, SC intermediate layers; MRN, midbrain reticular nucleus. (I) Location of presynaptic GFP+ input cells as a proportion of the number of input cells found in each mouse (n = 4 animals). Of note are labeled input cells in layer 5 of several cortical areas and a lack of labeling in brainstem nucleus SpV.