(a) Typical field of view of L2/3 neurons (green) stained with OGB-1 AM and imaged with in vivo two-photon microscopy. Sulforhodamine 101 was used to stain glia (yellow). Sum intensity projection (*xyt*) of a representative calcium imaging movie (3 min, 3.9 Hz) from a P15 mouse.

(b) Automated detection of neuronal cell bodies obtained through algorithmic segmentation of the image shown in *a*.

(c) Raw ΔF/F calcium traces of 6 different L2/3 neurons from representative movies at P9-11, P14-16 and P30-40. Gray arrows and vertical dashed lines represent times of synchronous firing.

(d) Mean correlation coefficients for all cell pairs vs. distance separating cell pairs in unanesthetized WT mice at different ages (n = 12, 9, 8 mice at P9-11, P14-16, and P30-40, respectively). The largest difference in correlation coefficients between P9-11 and P14-16 occurred for cell pairs <100 μm apart (Bonferroni corrected *p < 0.0001, two-way ANOVA).

(e) Mean correlation coefficients for all cell pairs within 100 μm of each other for WT (black) and *Fmr1*^{–/–} (red) mice at different ages. For *Fmr1*^{–/–} mice, n = 9, 10, 8 at P9-11, P14-16, and P30-40, respectively. Both age and genotype significantly affected correlation coefficients (*p < 0.05 after Bonferroni correction, two-way ANOVA). The difference in correlation between WT and *Fmr1*^{–/–} was largest at P14-16 (*p = 0.039, t-test). Error bars indicate the standard error of the mean (s.e.m.).

(f) Mean correlation coefficients vs. distance for WT and *Fmr1*^{–/–} mice at P14-16. Dashed lines indicate s.e.m. boundaries.

## PubMed Commons