Mapping Sustained Attention on the brain (EEG) I am doing a study to the effects of sustained attention on Situation Awareness, i.e. how well one perceives and understands the relevant information in their direct environment (in both space and time) and the ability to make predictions about the near future. I want to use EEG to measure the participants sustained attention by calculating the mean power in the Alpha frequency band, over two second periods.

I am in doubt however, over which channels I should calculate this average. Perceptual related brain responses usually occur in the occipital lobe and other more posterior located regions, but where do I draw the line? Are there some references that may support such a decision?
You should consider using subject-specific alpha channels and frequency ranges. There are differences between individuals in alpha peak frequency. Also the placement of the EEG cap as well as small differences in orientations of cortex can affect which channels pick up perceptual activity.

One way to do this would be to record data from the subject with their eyes open and then their eyes closed, say for 60 seconds each. Then you can find the channels where there is a significant difference in power around the alpha range between these two conditions. You can also use this data to determine the peak frequency of each subject's alpha.