Figure 3.

Connectivity frequency is unchanged with postsynaptic Fmr1 deletion at P15 when incorporating an increase in “silent,” NMDAR-mediated connections. A, Example average uEPSCs that are AMPA:KA-R mediated (top) and silent (bottom). B, C, Connectivity frequency based on AMPA:KA-R-mediated currents (B) and on silent, NMDAR only, connections (C). D, Total connectivity based on adding B and C. E, uEPSC amplitude of silent connections. F, AMPA:KA-R/NMDAR ratio of uEPSCs that were not silent (one WT and two KO uEPSCs had no detectable NMDAR-mediated response and are not included). G, Idealized schematic of our data showing the connectivity of L5A pyramidal neurons through development, which depends on postsynaptic expression of FMRP. This schematic incorporates both silent and AMPA:KA-R-mediated connections and the gray box indicates the estimated time window of exuberant silent connections with Fmr1 deletion. Error bars in B–D indicate 95% confidence interval; in E and F, error bars indicate SEM.