As we approach the end of the summer, we have transitioned into the more exciting data analysis stage. The initial steps of data analysis consist of cleaning up the data. First, you select the sections of the raw data of importance (usually the segments immediately following stimulation). Then from these segments, we remove artifacts – recorded activity from the EEG that do not originate from the cerebral region, such as eye blinks or eye movements. Then…
Well a lot more stuff. Stages of analysis becomes a wonderland the further you get (fitting since our lab is exploring natural sentence processing using the story “Alice in Wonderland”). I’ve stopped at the artifact rejection stage because that is the bulk of what we are working on at this time. Through frequent meetings with the rest of the group, we have been training on how to separate good data from noisy data, how to judge which and how many artifacts to reject so that there is limited noise but enough data remaining, and how to tie what we see in this analysis stage to how we can prevent some noise in the collecting stage.
The reason I’ve dubbed this stage as “exciting” is because artifact rejection allows us to perceive the experiment we have been running all summer in a more introspective way. It’s interesting to see that the nature of this experiment – a natural listening session to a story being read out loud – produces very different results from, say, our previous experiment that involved subjects completing a task of answering a question. For example, since the pace of our experiment travels at the average pace of an individual speaking, any movement or significant blinks carry over multiple stimuli – multiple words – because of the fast rate of the experiment. The patterns we are observing in result of this are are unlike what I have seen before. Additionally, perhaps the most fascinating observation we have made is that some of the components the EEG picks up indicates the signal of the subject’s heartbeat – an EKG signal!
All in all, I can feel that more exciting things are to come.