Heritability of Intracortical Inhibition and Facilitation

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Figure 1.
Mean (±SE) values of intracortical excitability in 16 MZ, 16 DZ twins, and 20 UP subjects measured by the PP TMS technique. Mean changes in MEP amplitude expressed as the ratio between conditioned responses at different ISI divided by test (unconditioned) responses. Horizontal line indicates MEP amplitude at baseline. Error bars, SEM.

Table 1.

r_ICC of corticospinal excitability

	MZ	DZ	UP	MZ versus DZ		MZ versus UP		DZ versus UP
	MZ	DZ	UP	Z	p	Z	p	Z	p
LT	r_ICC = 0.79	r_ICC = 0.69	r_ICC = −0.08	0.35	0.36	1.98	0.02	1.58	0.06
MT	r_ICC = 0.72	r_ICC = 0.70	r_ICC = −0.04	0.06	0.47	1.62	0.05	1.55	0.04
UT	r_ICC = 0.65	r_ICC = 0.79	r_ICC = −0.03	−0.47	0.32	1.37	0.08	1.88	0.03

r_ICC of corticospinal measures for LT, UT, and standard MT, within MZ and DZ twin pairs and UP. Results of the significance testing on the difference between r_ICC of MZ, DZ, and UP are also reported (p ≤ 0.05, uncorrected for multiple comparisons).

Table 2.

r_ICC of intracortical excitability

	MZ	DZ	UP	MZ versus DZ		MZ versus UP		DZ versus UP
	MZ	DZ	UP	Z	p	Z	p	Z	p
1 ms	r_ICC = 0.37	r_ICC = 0.25	r_ICC = 0.44	0.21	0.42	−0.14	0.44	−0.37	0.36
3 ms	r_ICC = 0.78	r_ICC = 0.11	r_ICC = −0.19	1.48	0.07	2.11	0.02	0.52	0.30
7 ms	r_ICC = 0.87	r_ICC = 0.25	r_ICC = 0.35	1.70	0.04	1.65	0.05	−0.19	0.42
12 ms	r_ICC = 0.62	r_ICC = 0.31	r_ICC = −0.01	0.64	0.26	1.25	0.10	0.56	0.29

r_ICC for the intracortical excitability values, measured by the PP technique, within MZ and DZ twin pairs and UP. Results of the significance testing on the difference between r_ICC of MZ, DZ, and UP are also reported (p ≤ 0.05, uncorrected for multiple comparisons).