I'm thinking of a way to describe what's happening to a single channel EEG/MEG sensor output. I've noticed that there is significant difference in the readings from a quiet observations, versus a person who's engaged in a conversation. I'm looking for some way to quantify the two distinct states, so a computer algorithm may have a chance of distinguishing the two. Potentially, in the future I would like to compare readings from one individual to the next, or compare the arousal of two individuals engaged in a conversation.
It would be helpful to know what are the names of metrics that may be used to measure the overall arousal/excitation of a person, that person's nervous system or brain. I can think of Actigraphy (the study of human motion) as one, its units are arbitrary activity count, or m/s^3. These are scored as "zero point crossings", or "area under the curve" of an accelerometer graph. But are there any other metrics or units of human activity/excitation? Maybe some of them are related to an EEG/EMG readings? Like an obscure algorithm named after some scientist?