FIG. 5.

Local excitation between excitatory neurons is decreased, but to a lesser extent. A: examples of EPSCs targeting layer 4 excitatory neurons in slices obtained from 2-wk-old animals. Scale bars: 1,000 and 10 pA, 50 ms. B: connection frequency was not detectably different at either 2 or 4 wk of age but showed a similar trend. C: connection frequency is decreased in the Fmr1 KO when 2 and 4 wk data are pooled. D: no detectable change in amplitude with pooled data (shown) and unpooled data (not shown). E: excitatory drive is decreased in the KO. F: no change in short-term plasticity with both pooled (not shown) and unpooled data (for 2 wk: n = 20,15; for 4 wk, n = 16,16). Short-term plasticity was dependent on age (P < 0.01). G: example of EPSCs in a WT somatostatin-positive (Som+) inhibitory neuron evoked by a 20-Hz train of action potentials in a presynaptic pyramidal neuron. APs are not shown. Scale bars: 10 pA, 100 ms. H: no difference in local excitatory drive targeting Som+ neurons was detected (left, based on EPSC₈), but there was an increase in inhibitory drive provided by Som+ neurons (right). *P < 0.05.