Yes, we are looking at the divergence between the 'simultaneous' and 'sum' ERP, that is correct. But, what I need to be clear on is how to obtain the 'sum' ERP for the two unimodal conditions. I can get a sum wave (of sorts) by just taking my epochs for Auditory stimulation and Visual stimulation and averaging them together like that, but I wondered if I did it this way or if I some how add the Grand Averages together by doing a peak analysis and then re-plotting on the basis of that. Cheers, Atlanta indicated auditory-visual (AV) neural response interactions. -----Original Message----- From: human-electrophysiology-bounce@xxxxxxxxxxxxx [mailto:human-electrophysiology-bounce@xxxxxxxxxxxxx] On Behalf Of T Elliman Sent: 06 August 2007 10:54 To: human-electrophysiology@xxxxxxxxxxxxx Subject: [human-electrophysiology] Re: Any ideas about summing ERPs? So shouldn't the formula be something like: D = Y - (A + V) where Y = the response to audiovisual stimuli, A = response to audio only, V = response to visual only, and D = the difference between presenting the stimuli together, and the sum of presenting them apart I don't know too much about processing the ERPs, so can't answer the second part. It was the equation that threw me, because it seemed to be a circular one. Toby --On 06 August 2007 09:48 +0100 Atlanta Flitton <a.flitton@xxxxxxxxxxxxx> wrote: > AV = (A+V)-AV ---------------------- T Elliman psxte@xxxxxxxxxxxxx