Figure 5. Presynaptic cooperativity increases spike transmission probability.
A. Pyramidal neuron pairs which share a postsynaptic target (green) synchronize more at short ISIs than pairs lacking a common postsynaptic target (gray). B. Mean CCGs between synchronous events for pairs of convergent PYR and INT. Color code is summed transmission probability for connections to common interneuron. C. Schematic illustrating how spike transmission probability was assessed after convergent spiking. D. During spontaneous activity, spike transmission is highest following temporally synchronous spiking of pairs of pyramidal neurons for which both are presynaptic (green), as compared to pairs of pyramidal cells in which one is connected and the other is not (grey) (shaded area is SEM). Dashed line is the mean expected linear summation of the transmission probabilities for the two PYR in the convergent case. Solid lines below traces indicate ISIs with significant differences between the convergent and independent case (black), or the convergent case and the arithmetic mean indicated by the dashed line (red). Wilcoxon rank sum test, p < 1.25−3. E. During optogenetically induced presynaptic activity a similar gain through cooperativity was observed, indicating that the synchrony of the two presynaptic cells, and not hidden third parties, explained the overall boost in spike transmission. Shaded area is SEM.