Table 1.

TMS-evoked potential (TEP)-based indices as possible biomarkers in stroke.

Index	Quantity indexed	Potential implications for neurophysiology of stroke and stroke recovery
Multi-channel TEPs (amplitude and waveform)	Local excitability and spread of activation (see also: Figures 1.3,1.6)	Characterize excitability profiles in (non-motor) cortical regions using the summated TMS-related event potential response
Specific TEP components (amplitude and latency)	Local intracortical facilitation and inhibition (e.g., N45 and N100 of the M1-TEP for GABA-A- and GABA-B-ergic inhibition) (Figures 1.2,1.3)	Assess the integrity of intra-cortical facilitatory and inhibitory circuits
State-dependency of TEP waveform and components	Influence of functional brain state on cortical excitability and connectivity (Figure 1.3)	Measure influence of functional/arousal state (e.g., during paretic arm movement vs. rest)
Global mean field power (GMFP)	Variance of response magnitude across multiple channels (high values for topographically diverse responses) (Figure 1.1B)	Estimate of cortical excitability and large-scale network reactivity
TMS-evoked oscillations (time frequency representation of average TEP)	Synchronized rhythmic neuronal activity in response to perturbation (Figures 1.4,1.5)	Aberrant oscillatory activity (power or frequency) may be a sensitive marker of abnormal information processing. Can be analyzed and manipulated online.
Interregional coherence of TEP	Effective connectivity between stimulated and other brain regions (Figure 1.6)	Abnormal causal cortical connectivity may identify ineffectual signal propagation in functional brain networks