When the brain is stimulated, for example, by sensory inputs or goal-oriented tasks, the brain initially responds with activities in specific areas. The subsequent pattern formation of functional networks is constrained by the structural connectivity (SC) of the brain. The extent to which information is processed over short- or long-range SC is unclear. Whole-brain models based on long-range axonal connections, for example, can partly describe measured functional connectivity dynamics at rest. Here, we study the effect of SC on the network response to stimulation. We use a human whole-brain network model comprising long- and short-range connections. We systematically activate each cortical or thalamic area, and investigate the network response as a function of its short- and long-range SC. We show that when the brain is operating at the edge of criticality, stimulation causes a cascade of network recruitments, collapsing onto a smaller space that is partly constrained by SC. We found both short- and long-range SC essential to reproduce experimental results. In particular, the stimulation of specific areas results in the activation of one or more resting state networks. We suggest that the stimulus-induced brain activity, which may indicate information and cognitive processing, follows specific routes imposed by structural networks explaining the emergence of functional networks. We provide a lookup table linking stimulation targets and functional network activations, potentially useful in diagnostics and treatments with brain stimulation.
Significance Statement Systematic exploration via stimulation of all cortical and subcortical brain areas can only be performed in silico. We have performed a detailed parametric exploration of dynamically responsive networks of a large-scale brain network model to stimulation and developed a stimulation map indicating which brain areas need to be stimulated to place the brain in a particular state at rest. Brain stimulation is one of the upcoming novel tools in the treatment of neurological disorders. The stimulation map will be critical in guiding these studies and allow for the development of theory guided stimulation protocols.
Authors report no conflict of interest.
James S. McDonnell Foundation and the European Union Seventh Framework Programme.