A: MGN evoked EPSCs with increasing stimulation currents at 3 ages. Traces are shown on the left. Peak EPSC amplitudes as functions of stimulus strength (IO-curve) are shown on right. For comparison, stimulus strength was normalized to the maximum stimulus strength used in a particular cell. Note the limited dynamic range of EPSC amplitudes at young ages. Dashed lines indicate where saturation was reached. Note the occasional disynaptic responses (red traces). B: Graph shows a superposition of the IO curves in A normalized to maximum EPSC and saturation stimulus level. Note the steeper increase in the IO curve from threshold to saturation at younger ages. C: Quantification of EPSC amplitudes. Box plots show EPSC amplitude at threshold (minimal reliably evoked EPSC), maximal evoked EPSC, and the ratio of these values. Box plots show median (line), mean (square) and the 25% and 75% quartiles. The threshold EPSC amplitude does not change (P1/4: 14.6±7.2 pA N=9; P5/9: 19.9±8 pA N=12; P10/13: 17.45±11.8 pA N=8), while maximal EPSC amplitude (P1/4: 42.4±18.1 pA; P5/9: 121±105 pA; P10/13: 184±149 pA) and the ratio (P1/4: 3.1±1.2; P5/9: 4.3±5.6; P10/13: 10.1±6.5) increase from P2/4 to P5/9 and P10/13 (‘*’ indicate P<0.05). D: Latencies of the monosynaptic EPSC (time to peak). Box plots show median (line), mean (square) and the 25% and 75% quartiles. Peak latencies were similar at all ages (P1/4: 11.6 ± 3.2 ms, P5/9: 13.66 ± 5.76 ms, P10/13: 14.74 ± 4.32ms, all P > 0.1).