Inducing LTD-Like Effect in the Human Motor Cortex with Low Frequency and Very Short Duration Paired Associative Stimulation: An Exploratory Study

Table 1

Baseline characteristics of all PAS protocols.

	0.2 Hz 2 min	0.25 Hz 1 min		0.25 Hz 2 min	0.5 Hz 1 min	0.5 Hz 2 min	1 Hz 1 min
		Prior 6 subjects	Total of 11 subjects^+
Number of pairs	24	15	15	30	30	60	60
Age (years; mean ± SD)	45.50 ± 14.14	34.33 ± 8.87	35.82 ± 10.90	36.67 ± 11.79	28.67 ± 3.98	35.67 ± 14.72	34 ± 7.69
RMT (%; mean ± SD)	59.67 ± 7.71	54.17 ± 8.38	57.73 ± 7.73	56.17 ± 8.47	63.50 ± 16.02	56.83 ± 9.93	57.00 ± 10.56
S50 (%; mean ± SD)	76.67 ± 9.27	70.00 ± 12.68	72.18 ± 10.01	66.83 ± 8.30	78.50 ± 11.33	67.50 ± 12.69	80.17 ± 12.17
200% perceptual threshold (mA; mean ± SD)	7.60 ± 4.09	8.80 ± 2.49	7.78 ± 2.51	9.40 ± 0.83	7.20 ± 2.01	7.53 ± 4.27	6.67 ± 1.95

One-way ANOVA did not show statistically significant difference compared to each baseline characteristics among 6 protocols (-value < 0.05) and ⁺combined additional 5 subjects to prior 6 subjects. PAS = paired associative stimulation at interstimulus interval of 10 ms, min = minute(s), SD = standard deviation, RMT = resting motor threshold, S50 = the intensity that can elicit MEP amplitudes equal to 50% of the maximal MEP, perceptual threshold = intensity of electrical stimuli at the median nerve over right wrist area that triggered subjects to start feeling the stimulation, and mA = milliamp.