Table 1.

Five critical factors

Factor	Why is this factor important?
Site of stimulation	Downstream effects of M1 or V1 stimulation may lead to different results for these sites compared with others
Task vs rest	TMS may have different effects based on whether a subject is at rest or engages in a task
Intensity and amount of stimulation	Higher intensities and more pulses may be more likely to affect the BOLD activity
Image artifacts	Spatial artifacts and signal dropout may occur near the TMS coil and mask genuine increases in BOLD activity at the site of stimulation
Precision of TMS localization and type of analyses	Imprecise localization of the site of stimulation increases the possibility for both false positives and false negatives; analyses on precisely localized ROIs are likely to be most informative

The table lists factors likely to be critical for establishing the direct effect of TMS at the site of stimulation and reasons for the importance of each factor. The first three factors relate to aspects of stimulation likely to affect the BOLD signal, whereas the last two factors are methodological.