A clinical study published in 2015 on P300 and Alzheimer's disease is just the latest demonstrating your point.
"A clinical trial to validate event-related potential markers of Alzheimer's disease in outpatient settings "
That study is a recapitulation of many academic center findings to show similar results can be had in the outpatient setting. Its findings have nothing to do with assessing drug effects on these parameters. I think we are discussing very different things...there is a difference between observing the well-known AD effects on P300 (on both amplitude and latency) and being able to use them to measure drug effects.