Figure S7.
Rbp4-Cre neurons display spontaneous excitatory synaptic potentials, and correlated activity which does not extend across the population, related to Figure 6
(A–F) Spontaneous excitatory synaptic potentials are found in both active phases of embryonic development, at E14.5 (A – C) and E18.5 (D – F).
(A and D) Traces recorded in current clamp mode during in vivo two-photon targeted patch clamp recordings from Rbp4-Cre neurons, following the application of TTX to the surface of cortex. Synaptic potentials were defined as deflections greater than 5 mV (dotted line: event threshold).
(B and E) Distribution of amplitudes greater than the event threshold.
(C and F) Average across events, normalized to the peak voltage of each event, showing the characteristic shape of a synaptic potential. Decay time (τ) shown in ms. Black line: mean; gray shading: SEM.
(G and H) Population activity across Rbp4-Cre neurons is less correlated than activity across pairs of Rbp4-Cre neurons. (G) Schematic comparing the “correlation between pairs” of neurons (black), and “correlation with the sum” of neuronal activity (blue) within all neurons recorded in an imaging field (top). Pairwise correlations of neuron 1 with each other neuron among all imaging field (middle). Correlation of the activity of neuron 1 with the sum of activity in all other neurons in the imaging window (bottom).
(H) From E14.5 to E18.5, the distribution of correlations between pairs of neurons (that are significantly greater than random) (black shaded area) is compared to the distribution of correlations with the sum (for all recorded neurons) (blue shaded area). Probability: Wilcoxon rank-sum test. Correlations computed from recordings in 9 (E14.5), 5 (E15.5), 4 (E16.5), 5 (E17.5), and 6 (E18.5) embryos.
(I–M) Pairwise correlations of spontaneous calcium activity, that are significantly greater than random, between Rbp4-Cre neurons, on each embryonic day from E14.5 to E18.5, do not decrease with distance.
(N) Combining all pairwise correlations, significantly greater than random, across all embryonic days.
(I–N) Red line: best fit trend of correlations across distance (red: R2 quality of fit); n = number of pairs from recordings in 9 (E14.5), 5 (E15.5), 4 (E16.5), 5 (E17.5), and 6 (E18.5) embryos.
Scale bars: 5s and 2.5 mV (A), 50 ms and 25% of peak (C), 5s and 2.5 mV (D), 50 ms and 25% of peak (F).