Emergence of strong connections in branching neurons

Across the brains of many different animals, a unifying feature is the heavy-tailed distributions of connection strength: compared to the average connection between neurons, some rare connections are orders of magnitude stronger. While these strong connections are critical for neural function, it remains unclear how they emerge in the brain. Here, we show that the branching growth of neurons naturally gives rise to a preferential attachment mechanism, whereby new synapses are more likely to form between pairs of neurons that are already strongly connected. This preferential attachment of synapses, in turn, leads to the emergence of very strong connections. Comparing across connectomes from multiple species and neural systems, we find that a minimal model of neuronal branching produces distributions of connection strength that quantitatively match those in experiments. Together, these results suggest that universal features of large-scale brain structure may arise from the fine-scale structure of individual neurons.