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. Author manuscript; available in PMC: 2022 Dec 15.
Published in final edited form as: Clin Neurophysiol. 2022 May 18;140:59–97. doi: 10.1016/j.clinph.2022.04.022

Fig. 4. Network effects of transcranial magnetic stimulation (TMS) and state-dependency.

Fig. 4.

Focal TMS can induce neural activity in nodes of the brain network connected with the targeted cortical region. Excitation of connected regions occurs through axonal and transsynaptic conduction of the regionally induced action potentials to anatomically connected cortical and subcortical regions. Axonal spread may also involve antidromic excitation. The propagation of neuronal excitation throughout the network depends on its physiological state at the time of stimulation. This is illustrated conceptually in the network diagram. Depending on whether TMS is applied in state A or state B, the network propagation that is evoked by a physically identical TMS pulse given over exactly the same cortical region (red) with the same intensity, may differ substantially not only in magnitude but also in spatial pattern. State dependence may be more relevant to orthodromic propagation as compared to antidromic propagation throughout the targeted brain network.