My colleague and I started exploring EEG processing and, especially, functional connectivity. We decided to try the Phase Slope Index (PSI) and conducted a simple experiment as follows: it consists of three steps, research participant should raise his left hand (1), then his right one (2), then both (3). The description is simplified a bit but shows what the experiment was. We expected to see the information flow between the pre-motor cortex and primary motor cortex but we seemed to fail. The data was pre-processed (filtered at [0.25; 40] Hz, re-referenced to the average electrode, segmented into three pieces according to three stages of experiment; also blink artefacts were removed, so were motion ones). Then we computed the all-to-all PSI matrix and what we have had is depicted on the pictures (if needed and more appropriate, I could add the graph representation). All in all, we haven't seemed to reach what we aimed and now we're trying to figure out whether the fail refers to the interpretation, or experiment design, or both, or something else. My questions are:
- Can one guess what stage of experiment every matrix refers to? If so, how? I mean, do they at least look like the result of the experiment described? If they do, how can one interpret them?
- What could be an experiment that would show the noticeable PSI for two areas given beforehand? I mean, we had two areas given, pre-motor cortex and primary motor cortex, and we supposed that we would find a synchronization between them in such a motion experiment; something's gone wrong, though. If the problem is in the design of experiment, what design would be better?