Table 2.

Studies using TMS to examine M1 excitability before and after inhibitory NIBS techniques in healthy participants.

#	Study	Group	N	MEP	NIBS technique	Measurement	Compared with the baseline or sham condition	Difference between BDNF genotypes	Comments
1	Cheeran et al. (2008)	Val/Val	9	FDI	cTBS	MEP	↓	SD
		Non-Val/Val	9				→
2	Guerra et al. (2019)	Val/Val	13	FDI	cTBS	MEP	→	NS	cTBS+sham tACS condition
		Non-Val/Val	13				→
3	Jannati et al. (2017)	Val/Val	12	FDI	cTBS	MEP	?	SD	Only group data was compared by a t-test
		Val/Met	6				?
4	Marsili et al. (2017)	Val/Val	36	FDI	cTBS	MEP	↓↓	SD
		Non-Val/Val	14				↓
5	McDonnell et al. (2013)	Val/Val	10	FDI	cTBS	MEP (% Max M-wave)	→	NS
		Non-Val/Val	15				→
6	Mastroeni et al. (2013)	Val/Val	15–17	FDI	cTBS	MEP	↓	NS	Intervention: cTBS+cTBS Monophasic TMS for single-pulse MEP
		Val/Met	10–12				↓
		Val/Val	15–17	FDI	cTBS	MEP	↓	NS	Intervention: cTBS+cTBS Biphasic TMS for single-pulse MEP
		Val/Met	10–12				↓
		Val/Val	15–17	FDI	cTBS	MEP	↓	NS	Intervention: cTBS+iTBS Monophasic TMS for single-pulse MEP
		Val/Met	10–12				↓
		Val/Val	15–17	FDI	cTBS	MEP	↓	NS	Intervention: cTBS+iTBS Biphasic TMS for single-pulse MEP
		Val/Met	10–12				↓
7	Antal et al. (2010)	Val/Val	11	FDI or ADM	C-tDCS	MEP	↓	NS
		Val/Met	8				↓
1	Cheeran et al. (2008)	Val/Val	8	FDI	C-tDCS	MEP	↓	NS
		Non-Val/Val	8				↓
8	Di Lazzaro et al. (2012)	Val/Val	21	FDI	C-tDCS	MEP	↓	NS
		Non-Val/Val	8				↓
9	Strube et al. (2014)	Val/Val	10	FDI	C-tDCS	MEP	↓	NS
		Non-Val/Val	12				↓
10	Nakamura et al. (2011)	Val/Val	5	FDI	QPS	MEP	↓	NS
		Non-Val/Val	7				↓

The NIBS effects are indicated by the arrow direction based on the statistical data (i.e., facilitatory effect: ↑; no change: →; inhibitory effect: ↓, or Not available: ?). In addition, when either of the genotype groups had a greater effect on the direction of the inhibition, two arrows were added to express this enhanced effect (i.e., ↓↓). ADM, abductor digiti minimi; BDNF, brain-derived neurotrophic factor; cTBS, continuous theta burst stimulation; C-tDCS, cathodal transcranial direct current stimulation; FDI, first dorsal interosseus; iTBS, intermittent theta burst stimulation; NIBS, non-invasive brain stimulation; Non-Val/Val, Val/Met+Met/Met; NS, not significant; MEP, motor-evoked potential; QPS, quadri-pulse transcranial magnetic stimulation; rTMS, repetitive transcranial magnetic stimulation; SD, significant difference; tACS, transcranial alternating current stimulation.