SAT drives compartment-specific changes in PSD95 puncta on L5 Pyr dendrites. A, Image of an optical stack showing Citrine-labeled PSD95.FingR puncta in L5a from S1 barrel cortex from an acclimation control (Acc) mouse. B, All PSD95 puncta reconstructed from FOV in A. C, Schematic showing an FOV of reconstructed PSD95.FingR puncta (yellow). D, Left, Schematic showing PSD95.FingR puncta in L1. Middle, Cumulative distribution histogram of randomly selected L1 PSD95.FingR puncta from Acc (dashed black line; 6600 puncta; 11 mice) and SAT1 (blue line; 3600 puncta; 6 mice) animals. K–S test, p = 0.015. Right, Averaged mean puncta surface area + SEM by animal (solid dots); N = 12 Acc and 7 SAT1 mice. Unpaired t₍₁₇₎ = 0.23; p = 0.82. E, Same as in D but for L5a FOV. Left, Schematic showing PSD95.FingR puncta in L5a. Middle, Cumulative distribution histogram of randomly selected L1 PSD95.FingR puncta from Acc (dashed black line; 11,000 puncta; 11 mice) and SAT1 (blue line; 6000 puncta; 6 mice) animals. K–S test, p = 2.65 × 10⁻¹⁰. Right, Averaged mean puncta surface area + SEM by animal (solid dots); N = 12 Acc and 7 SAT1 mice. Unpaired t₍₁₇₎ = −1.29; p = 0.21. F, As in A but with tdTomato-labeled POm axons. G, As in B but showing only digitally detected PSD95 puncta (yellow) contacting POm axons (red). H, Schematic showing puncta touching POm axons. Note the inclusion of interbouton segments either fused to or independent of the nearby boutons. I, As in D but for POm-assigned PSD95 puncta in L1 (left). Middle, Cumulative distribution histogram of randomly selected puncta from Acc (dashed black line; 6600 puncta; 11 mice) and SAT1 (blue line; 3600 puncta; 6 mice) animals. K–S test: p = 0.0031. Right, Averaged mean puncta surface area + SEM by animal (solid dots); N = 12 Acc and 7 SAT1 mice. Unpaired t₍₁₇₎ = 0.066; p = 0.95. J, As in I but for POm-assigned PSD95 puncta in L5a (left). Middle, Cumulative distribution histogram of randomly selected L5a PSD95.FingR puncta from Acc (dashed black line; 11,000 puncta; 11 mice) and SAT1 (blue line; 6000 puncta; 6 mice) animals. K–S test, p = 3.78 × 10⁻⁶. Right, Averaged mean puncta surface area + SEM by animal (solid dots); N = 12 Acc and 7 SAT1 mice. Unpaired t₍₁₇₎ = −0.68; p = 0.50.