<p>Supplementary Fig. 1 Maffei et al. manuscript # 2005-09-11010A</p><p>Supplementary Fig. 1. IPSC reversal potential was not affected by VD. a. Example perforated patch recording showing evoked IPSCs at holding potentials ranging from –</p><p>110 mV to +40 mV. b. IV curves showing evoked current (black squares, measured at time indicated by thin grey box in a) and holding current (black triangles, measured at time indicated by thick grey box in a). The calculated IPSC reversal is at the intersection between the IV curves33. c. Average IPSC reversal potential in Control (black bar) and </p><p>Deprived hemispheres (white bar). N = 3 each condition. Supplementary Fig. 2 Maffei et al. manuscript # 2005-09-11010A</p><p>Supplementary Fig. 2. FS to FS connections are not affected by VD and by LTPi induction. b. Bar plot showing IPSC amplitude of FS to FS connections (as diagramed in a). c. Time course of FS to FS connections during successful LTPi induction onto star pyramids. d. Bar plot showing % changes of FS to FS IPSP and Gap junction amplitude following LTPi induction at FS to star pyramids synapses. Supplementary Fig. 3 Maffei et al. manuscript # 2005-09-11010A</p><p>Supplementary Fig. 3. Peak-scaled non-stationary fluctuation analysis. A. Example of a unitary FS to star pyramid connection, showing variation in the individual current amplitude across trials (for 50 repetitions); the black line indicates the average IPSC. </p><p>Decay kinetics were very uniform across trials. B. Example of one trial (in black) overlayed with the peak-scaled average current (smooth red trace); the subtraction current (representing the variance about the mean) obtained by subtracting the two traces is also shown (variable red trace). C. Plot of average variance around the mean (in pA2) against the mean current. Black line represents the best fit to a parabolic equation (F(x) = i –i2/n </p><p>+ b); from this fit was extracted an estimate of the single channel current (i), the number of channels open at the peak of the IPSC (n), and the background variance (b); single channel conductance (gamma, or g) was calculated from i. Note that the background variance was not subtracted and was 9.4 pA2 for this example; background variance ranged from 2-10 pA2 for these experiments. Supplementary Fig. 4 Maffei et al. manuscript # 2005-09-11010A</p><p>Supplementary Fig. 4. In the control hemisphere, pairing depresses an already potentiated synapse. a. Time course of the IPSP of a single FS to Pyr connected pair from the control hemisphere; arrows indicate times at which the pairing protocol was applied. b. Bar plot shows average (n = 3 pairs) percent changes of IPSP amplitude before pairing (black bar), 10 minutes after the first pairing (white bar) and 10 minutes after the repetition of the same pairing (grey bar). The second pairing depressed the connection, suggesting that saturation (or washout) of LTP unmasks a competing depression; this depression may reflect an LTD-like process akin to that in the deprived hemisphere, or a depotentiation process. Time course of the IPSP of a single connected pair from the deprived hemisphere; arrows indicate times at which the pairing protocol was applied. d. Bar plot showing the average percent change (n = 2 pairs) of IPSP amplitude before pairing (black bar), 10 minutes after the first pairing (white bar) and 10 minutes after the second pairing (gray bar). Supplementary Fig. 5 Maffei et al. manuscript # 2005-09-11010A</p><p>Supplementary Fig. 5. Summary of microcircuitry changes in layer 4 following VD during the critical period. Diagram illustrates the circuitry in Control (left) and Deprived </p><p>(right) layer 4. Deprivation increases EPSC amplitude from star pyramids onto FS cells approximately 3 fold (thick red axons), and also increases the amplitude of feedback </p><p>IPSC from FS cells onto star pyramids approximately 3 fold (thick green axon). Synapses between star pyramids are unaffected. VD thus shifts the balance between excitation and inhibition within layer 4 to favor inhibition.</p>