Brain stimulation preferentially influences long-range projections in primates

Advances in brain stimulation have made it possible to target smaller and smaller regions for electromagnetic stimulation, in the hopes of producing increasingly focal neural effects. However, the brain is extensively interconnected, and the neurons comprising those connections may themselves be particularly susceptible to neurostimulation. Here, we test this hypothesis using single-unit recordings from alert non-human primates receiving transcranial electrical stimulation. We find that putative long-range projections (i.e., axons) are more strongly affected by stimulation than other cell types. These data suggest the need for alternate stimulation strategies that target the edges, rather than nodes, of neural networks.