A saturating period of MD reduces both excitatory and inhibitory responses to closed eye stimulation.

<p><b>A</b>. Examples of excitatory (g_E, red) and inhibitory (g_I, green) responses of 4RSNs (left: normal; right: MD) upon stimulation with optimally oriented light bars. The total membrane conductance (G_tot) is shown in blue and the V_m response in absence of current injection is in black (top traces). Dotted lines: 0 nS. Gray shadow: 95% confidence intervals of the g_E and g_I estimates obtained by bootstrap analysis. <b>B</b>. Amplitudes of the visually-driven g_E (green) and g_I (red) responses in normal (open boxes) and MD (dashed boxes) rats. MD reduced both excitatory and inhibitory conductances upon contralateral eye (closed in MD rats) stimulation and increased both excitatory and inhibitory conductances upon ipsilateral eye (open in MD rats) stimulation (Mann-Whitney Rank Sum tests, p<0.05). <b>C</b>. The excitatory-inhibitory balance of visually-driven responses, expressed by the K_EI index, was not affected by MD (dashed boxes vs open boxes) for both contralateral and ipsilateral responses (Mann-Whitney Rank Sum tests, p>0.7).</p

Sub- and supra-threshold effects of MD in 4RSNs of rat V1.

<p><b>A</b>. Figure S1. Examples of anatomically recovered layer 4 star pyramids. 100 µm thick coronal sections were reacted for cytochrome C to reveal layer 4 and byocitin-filled cells were recovered with peroxidase-based histochemistry. Calibration bar: 100 µm. <b>B</b>. Left: the ocular preference shift –as assessed by the decrease of the ODI- caused by MD (P20–P30) was larger for AP responses (open boxes) compared to PSP responses (dashed boxes). Middle: at the level of PSP responses, depression of responsiveness to the deprived eye was larger (Mann-Whitney Rank Sum test, p<0.05) compared to potentiation of open eye responses (Mann-Whitney rank Sum test, p = 0.1). Right: at the level of AP responses, both depression of responses to the deprived eye and potentiation of open eye responses were significant (Mann-Whitney Rank Sum tests, p<0.05). For a more detailed analysis of date presented in this figure see also<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0082044#pone.0082044-Iurilli1" target="_blank">[41]</a></p

Estimate of visually-driven excitatory and inhibitory synaptic conductances.

<p><b>A</b>. Visual responses to an optimally oriented moving light bar of a 4RSN recorded under 1 mM QX314 while injecting different steady currents. The black, continuous line are the recorded V_m values, whereas the blue, dashed trace shows the reconstructed V_m values obtained by inserting back the estimated g_E and g_I values into the fundamental membrane equation. The instantaneous total synaptic conductance is calculated based on the instantaneous slope of the current-voltage relation (G_tot, blue). The time-dependent excitatory (g_E, green) and inhibitory (g_I, red) conductances are plotted below. Gray traces represent the 95% confidence intervals obtained by bootstrapping of the data (see Methods). Conductance measurements began after the response to the injected current was at steady state (after 200 ms). Resting conductances were calculated in absence of visual stimulation (dashed line: stimulus end). <b>B</b>. Visually-driven PSPs vary linearly with the injected current. Plot showing the linearity of the relationship between the amplitude of the visually-driven PSP response and the value of the injected current (r = −0.97) for a 4RSN (this plot refers to the example shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0082044#pone-0082044-g002" target="_blank">Figure 2</a> of the Main Text). Means ± standard erros are shown. The median of the correlation coefficients for all the recorded neurons was −0.94 (25^th–75^th percentiles: −0.88 − −0.99). <b>C</b>. Plot of the recorded <i>vs</i> reconstructed V_m values obtained by inserting back the estimated g_E and g_I into the membrane equation. The linearity of the cell and the accuracy of the V_m reconstruction is shown by the fact that data points align along the line of steepness 1 and intercept 0 in the plot. <b>D</b>. Temporal intervals between the peaks of g_E (green) and g_I (red) and that of the V_m response. For each cell, values for both contralateral and ipislateral responses are plotted. Note that in the vast majority of cases the conductance values have been obtained in close proximity of the V_m peak response (within 200 ms, dashed lines). <b>E</b>. Example of a voltage clamp recording (see Methods) following visual stimulation with a moving bar in the preferred direction. By clamping the cell at the reverse potential for inhibition (−80 mV when considering a liquid junction potential of approximately 14 mV) only excitatory currents can be seen (green: average response overlapped to single trials, shown in gray). Conversely, clamping the cell at the reversal potential for inhibition (+14 mV when considering the liquid junction potential) reveals the presence of inhibitory currents (red: average response overlapped to single trials, shown in gray).</p

Relationship between synaptic and conductance-based ODIs.

<p><b>A</b>. Raster plot showing the relationship between synaptic ODIs (ODI PSP) and ODIs for excitatory and inhibitory conductances (respectively ODI ge, in green and ODI gi, in red), for animal in the control (N) group. Dashed lines indicate the result of the linear fit between synaptic and conductance-based ODIs (ODI-ge vs. ODI-PSP: r = 0.73, p<0.01; ODI-gi vs. ODI-PSP: r = 0.47, p = 0.06). <b>B</b>. Same as in A for rats in the MD group (ODI-ge vs. ODI-PSP: r = 0.67, p<0.01; ODI-gi vs. ODI-PSP: r = 0.47, p = 0.06).</p

MD does not alter the ratio of excitation and inhibition measured at the excitation peak.

<p>The values of the ratio between g_E and g_I measured at the peak of the excitatory conductance are plotted for each experimental group. MD does not significantly modify the ratio values for both contralateral (left) and ipsilateral (right) eye responses (Mann-Whitney Rank Sum tests, p>0.6).</p

Basic biophysical properties of 4RSNs.

<p>± S.E.M. are given. No significant differences between Control and MD rats for all parameters (t-tests, p>0.2). Means </p

Effects of offsetting equilibrium potentials V_E and V_I on g_E and g_I estimates.

<p>^th–75^th percentiles). All comparisons along any column between normal (N) and MD rats were significant (Mann-Whitney Rank Sum tests, p<0.05). V_E and V_I are the estimated equilibrium potentials for excitation and inhibition (see methods section), V_E+ and V_I+ are V_E and V_I offset by +10 mV; V_E− and V_I− are V_E and V_I offset by −10 mV. Data are reported as follows: median (25</p