Table 2.

Pros and cons of potential strategies for increasing the effect of non-invasive brain stimulation.

Strategy	Pros	Cons
Stimulation of iM1	• Direct enhancement of the reduced participation in the incompletely recovered motor network after stroke	• Higher risk of adverse effects due to induction of excitotoxicity in the penumbra and shunting of electrical current
Stimulation of cM1	• Stimulation of intact cortical areas	• Inhibitory stimulation might also impair complex motor function
Stimulation of secondary sensorimotor areas	• Stimulation of intact cortical areas	• More difficult to target
	• Modulation of cortico-cortical connections to M1
Stimulation of the cerebellum	• Stimulation of intact cortical areas	• More difficult to target
	• Alternative target within the motor learning network	• Comparable high discomfort of cerebellar rTMS protocols
Simultaneous application of a motor training paradigm	• Simultaneous modulation of LTP-/LTD-like mechanisms	• Unfavorable homeostatic interactions
		• Not feasible for most rTMS protocols
Stimulation in the acute or sub-acute phase	• Enhanced adaptive plasticity	• Higher risk of adverse effects
Stimulation in the chronic phase	• More stable deficit	• Reestablished growth/plasticity inhibition
	• Lower risk of adverse effects
Multi-session stimulation	• Enhancement of plasticity, e.g., induction of late-phase LTP/LTD-like neuroplasticity	• More complex and time-consuming
Multifocal stimulation	• Modulation of multiple nodes of the motor network	• Higher risk of adverse effects, e.g., shunting of current
	• Induction of additive or supra-additive effects
Sequential stimulation	• Time-dependent modulation of multiple nodes of the motor network	• More complex setup
Patterned rTMS protocols	• Shorter delivery time	• Higher risk of adverse effects
	• Proposed potent modulatory aftereffect	• Need of a more complex and expensive setup
		• Mixed results