Table 4.
Comparison of the effects of spatial smoothing on t-statistics from the GLM output and significantly activated voxel counts for all 15 subjects. T-statistics: as spatial smoothing extent increased, peak t-statistics (in parentheses) decreased and statistically significant (voxel-based thresholding, 5% FWER corrected) increases in t-statistics (* and † symbols) were observed across all grey matter ROIs. The mean t-statistic in all ROI increased after 3 mm smoothing compared to no smoothing, and increased in PoCG and thalamus after 5 mm smoothing compared to 3 mm # active voxels and % white matter: as smoothing extent increased, the number of statistically significant voxels increased, measured using three thresholding approaches. Voxel is FDR corrected; cluster and TFCE are FWER corrected. ACC = anterior cingulate cortex; PoCG = postcentral gyrus; TFCE = threshold free cluster enhancement; * and † = statistically significant difference.
| 0 mm FWHM | 3 mm FWHM | 5 mm FWHM | ||
|---|---|---|---|---|
| T-statistics | ACC | 1.956 (5.392) | 2.104* (4.030) | 2.066 (3.102) |
| Insula | 2.674 (6.222) | 2.977* (5.224) | 2.968 (4.317) | |
| PoCG | 2.423 (8.778) | 2.959* (6.987) | 3.265 (5.874) | |
| Thalamus | 1.928 (7.467) | 2.565* (6.797) | 2.927 (5.389) | |
| # active voxels | Voxel | 14,484 | 66,984 | 140,389 |
| Cluster | 48,332 | 82,837 | 109, 137 | |
| TFCE | 25,226 | 66,756 | 93,852 | |
| % white matter | Voxel | 13,353 | 17.598 | 21.309 |
| Cluster | 4.616 | 5.400 | 7.192 | |
| TFCE | 2.319 | 4.687 | 6.148 | |