Table 1.
Summary of different types of spectral power.
| Type of spectral power | Phase-locking to stimulus/response | Relationship to PLF+ | Typical Analysis* |
|---|---|---|---|
| Evoked | High | Positively correlated | Average in time domain, then spectral analysis |
| Induced (Total) | Indeterminate | Varies. PLF can allow one to view this measure and decide whether power is evoked or induced | Spectral analysis on individual trials, then average |
| Induced (-Evoked) | Low | Negatively correlated | Take result of Evoked analysis and subtract from Induced, either from average Induced or from individual trials |
| Spontaneous | Indeterminate | Indeterminate | Cut continuous EEG/MEG data into segments, compute spectrum on segments, then average |
Notes
+
The term phase-locking factor (PLF) is used here for the reasons outlined in Roach and Mathalon {Roach:2008ib}. PLF is also sometimes referred to as inter-trial coherence (ITC) and inter-trial phase-coherence (ITPC).
*
Analyses are varied and these examples are meant to convey common approaches, not all approaches.