Table 1.
Participant demographics.
Table 2.
Study parameters and rules for data extraction.
Fig 1.
Distribution of SAI data for individual studies and data from all studies.
SAI values from each of the studies included in the main analyses are shown with (A; n = 148) and without (B; n = 130) instances where no inhibition (ratios >1) occurred. The distribution of pooled SAI data (n = 148) is shown in C, and MEPCSTS (gray) and MEPTS (black) amplitudes are shown in D (also n = 148) for 20% bins between SAI = 0 and SAI = 1.0, and for SAI > 1.0. * p < 0.01 significant result of a Mann-Whitney U post-hoc comparison between study A and study H (A). * p < 0.01 significant difference indicated by Wilcoxon signed rank tests and for paired comparisons of MEPCSTS and MEPTS amplitudes within each bin (D). All error bars represent the mean and standard error of the mean.
Fig 2.
Distribution of LAI data for individual studies and data from all studies.
LAI values from each of the studies included in the main analyses are shown with (A; n = 117) and without (B; n = 108) instances where no inhibition occurred. The distribution of pooled LAI data (n = 117) is shown in C, and MEPCSTS and MEPTS amplitudes are shown in D (also n = 117) for 20% bins between LAI = 0 and LAI = 1.0, and for LAI > 1.0. * p < 0.01 significant result of a Mann-Whitney U post-hoc comparison between study A and study H (A). * p < 0.01 significant difference indicated by Wilcoxon signed rank tests and for paired comparisons of MEPCSTS and MEPTS amplitudes within each bin (D). All error bars represent the mean and standard error of the mean.
Fig 3.
Correlations and gender comparisons for SAI and LAI data.
Nonsignificant correlations of SAI with age (18–35 years; n = 113), and time of day (n = 148) are shown in A and B respectively. No difference in SAI with respect to biological sex is shown in C. Similarly, LAI did not correlate with age between 18 and 35 years (D; n = 81), or time of day (E; n = 117) and was not different between males and females (F). All error bars reflect standard error of the mean.
Fig 4.
Reproducibility of SAI and LAI.
The absolute size of between-session differences for studies with repeated baseline measures are shown on the left and individual SAI and LAI values are shown on the right. Between-session differences in SAI for each study (A; n = 92) are represented in the open bars while the average across all included studies is shown by the gray bar. Individual SAI data from the same studies is presented in B. Subjects who exhibited at least one SAI value > 1 are highlighted in dark gray while the rest are shown in light gray. Between-session differences in LAI for each study (C; n = 62) are represented in the open bars while the average across all studies is shown by the gray bar. Individual LAI data from the same studies is presented in D. All error bars reflect standard error of the mean.
Fig 5.
TS Intensity and inhibition-facilitation fluctuations.
Panel A and B show the association between test stimulus intensity and between-session differences for log-transformed SAI and LAI, respectively. In panel C and D, between-session differences when the mean TS intensity was >120%RMT versus <120%RMT is shown for SAI and LAI, respectively. Panel E shows between-session differences in log transformed SAI and LAI ratios, separated into cases where participants always exhibited inhibition (light blue), always showed facilitation (dark blue), or crossed between inhibition and facilitation (red). Participants from Study E and F, who were assessed at multiple ISIs for SAI and/or LAI appear on the plot once for each assessed ISI.
Fig 6.
Reliability and heterogeneity measures.
Panel A shows the SAI and LAI ICC values with 95% confidence intervals for each study included in dataset 2. Vertical dashed lines reflect the border between low, moderate, strong, and excellent reliability, from left to right. Panel B shows the sample sizes and coefficients of variation, calculated in baseline data from each included study. A = Tsang et al. 2014; B = Tsang et al. 2015; C = Bailey et al. 2016; D = Turco et al. 2017; E = Turco et al. 2018; F = Turco et al. 2019; G = Toepp et al. 2019. H = Harasym et al. 2020.
Fig 7.
Panel A and B shows the reliability of measurements performed at each ISI for SAI and LAI, respectively. ICC values with 95% confidence intervals are shown for each ISI tested in the studies that comprise dataset 2. Vertical dashed lines reflect the border between low, moderate, strong, and excellent reliability, from left to right. * Indicates a that the ICC and 95% confidence interval for Study F are referenced from Turco et al., [14]. A = Tsang et al. 2014; B = Tsang et al. 2015; C = Bailey et al. 2016; D = Turco et al. 2017; E = Turco et al. 2018; F = Turco et al. 2019; G = Toepp et al. 2019. H = Harasym et al. 2020.