Bidirectionally Connected Pairs Contain Connections That Are Stronger and Correlated

<div><p>(A) Synaptic connections in bidirectionally connected pairs are on average stronger than those in unidirectionally connected pairs. The probability density distribution for both the reciprocal (red solid, p(w) = 0.41exp(−(ln w + 0.60)²/(2 × 0.976²)/w) and nonreciprocal (blue dashed, p(w) = 0.47exp(−(ln w + 0.81)²/(2 × 0.834²)/w) connections are shown.</p> <p>(B) In bidirectionally connected pairs synaptic connection strengths are moderately but significantly correlated (<i>R</i> = 0.36, <i>p</i> < 0.0001).</p> <p>(C) Scatter plot of the strength of synaptic connections that shared no pre- and postsynaptic neurons in the same quadruple recording. There might be other connections in the quadruplet besides these two connections. No significant correlation is observed (<i>R</i> = 0.068, <i>p</i> = 0.48). All correlations calculated using Pearson's <i>R</i> method in log space.</p> <p>(D) Average connection strength for bidirectional connections does not vary systemically with interneuron distance (one-way ANOVA, <i>p</i> = 0.068). Numbers on top of data points are the number of connections. Error bars are standard errors of the mean.</p>