Eigenmodes in the brain explain how local perturbations evolve into long-range effects
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Local perturbations of neural activity, for example via transcranial magnetic stimulation, can affect activity in distant regions of the brain. This propagation has been linked to neuroanatomy and functional organizational principles including the brain hierarchy of timescales. However, a general account of the mechanisms explaining how focal perturbations are integrated is missing. To address this knowledge gap, we combined multimodal neuroimaging and brain stimulation with advanced biophysical modelling. Specifically, we showed that neural perturbations in two specialized brain regions located at the extremes of the visual hierarchy (V1 and FEF) caused marked changes in eigenmodes, the global functional modes defined by neuroanatomy. Strikingly, the long-term and global effects of these local perturbations were largely captured by a limited number of eigenmodes. Using a biophysical interpretation of these global states, we explain how an acute and local neural perturbation evolves into a global effect that depends on brain anatomy and eigenmode energy. These results advance fundamental knowledge of large-scale brain communication and have implications for understanding and treating brain disorders.