Table 2. Time–frequency clusters with significant group differences.
| Cluster label | Time range | Peak time | Peak frequency | Statistic | Direction of group difference |
|---|---|---|---|---|---|
| Phase locking (ITC) | |||||
| Initial stimulus pre-N1 delta/theta | −22 to 30 ms | −4 ms | 5 Hz | t(27)=3.37, P=0.002 | FXS>CON |
| Initial stimulus N1 gamma | 20 to 210 ms | 56 ms | 35 Hz | t(27)=3.19, P=0.004 | CON>FXS |
| Initial stimulus N2 delta/theta | 254 to 322 ms | 297 ms | 5 Hz | t(27)=3.51, P=0.002 | CON>FXS |
| Repetition 1 N1 alpha/beta | 556 to 658 ms | 642 ms | 13 Hz | t(27)=3.09, P=0.005 | FXS>CON |
| Repetition 1 N1 gamma | 530 to 598 ms | 556 ms | 36 Hz | t(27)=4.05, P<0.001 | CON>FXS |
| Repetition 1 N2 delta/theta | 796 to 918 ms | 849 ms | 4 Hz | t(27)=2.79, P=0.009 | CON>FXS |
| Repetition 2 N1 alpha | 1056 to 1186 ms | 1134 ms | 10 Hz | t(27)=3.33, P=0.003 | FXS>CON |
| Repetition 2 N2 delta/theta | 1350 to 1522 ms | 1392 ms | 3 Hz | t(27)=2.90, P=0.007 | CON>FXS |
| Repetition 3 N1 alpha | 1660 to 1720 ms | 1685 ms | 11 Hz | t(27)=3.02, P=0.005 | FXS>CON |
| Repetition 3 N1 gamma | 1574 to 1616 ms | 1591 ms | 42 Hz | t(27)=4.14, P<0.001 | CON>FXS |
| Repetition 3 N2 delta/theta | 1806 to 2030 ms | 1867 ms | 5 Hz | t(27)=3.91, P<0.011 | CON>FXS |
| Repetition 3 N2 gamma | 1806 to 1910 ms | 1884 ms | 49 Hz | t(27)=4.36, P<0.001 | CON>FXS |
| Single trial power | |||||
| Overall gamma | −220 to 2350 ms | 1798 ms | 39 Hz | F(1,27)=10.1, P=0.004a | FXS>CON |
| Baseline-corrected single trial power | |||||
| Initial stimulus N1 gamma | 64 to 124 ms | 108 ms | 50 Hz | t(27)=3.21, P=0.003 | CON>FXS |
| Repetition 1 N1 gamma | 512 to 564 ms | 539 ms | 48 Hz | t(27)=2.42, P=0.02 | CON>FXS |
| Repetition 2 N1 delta/theta | 1030 to 1176 ms | 1073 ms | 2 Hz | t(27)=4.69, P<0.001 | FXS>CON |
| Repetition 2 N1 gamma | 934 to 1150 ms | 961 ms | 37 Hz | t(27)=3.27, P=0.003 | CON>FXS |
| Repetition 3 N1 alpha/beta | 1600 to 1702 ms | 1668 ms | 13 Hz | t(27)=2.93, P=0.007 | FXS>CON |
Abbreviations: ANOVA, analysis of variance; CON, control; ERP, event-related potential; FXS, Fragile X Syndrome; ITC, inter-trial coherence.
Cluster names are identified by stimulus number (Initial stimulus or repetition 1, 2 or 3), ERP associated with the time period (if applicable) and frequency band. Time ranges are given relative to initial stimulus onset, to provide equivalency with the x-axes in Figure 2. Repetitions occurred every 500 ms. Cluster peaks are identified for highest t-values, not for peaks of activity. For overall gamma single trial power, a peak statistic is reported, however, it should be noted that group differences were remarkably stable throughout the time period.
Number of trials retained was significantly correlated with overall gamma single trial power in FXS, so number of trials was included as a factor in an ANOVA for this group comparison only. Group differences remained significant.