Please see the attached image for the channel data recorded using neuroscan. All the channel data seems following similar trend. 100% sure that there is no extra gel spreading across channels. Any solutions ?
There is the chance that there could be some minor bridging of electrodes, but it's also important to remember what you are actually recording with EEG. Theoretically it is safe to assume that the signals at each channel are picking up very similar information, so it is not uncommon for them to appear like this. If you think that this is problematic for any of your analyses (especially if using ICA) then perform a rank calculation on the data, say something like R = rank(EEG.data(:,:,1)) - that is assuming you are using matlab (as it does look like an eeglab plot). This will tell you how similar the channels of your data set are (http://stattrek.com/matrix-algebra/matrix-rank.aspx)
Where is the reference electrode in this Neuroscan 32 electrode cap? All channels will be influenced equally by electrocortical activity near the reference electrode. One way to mitigate this effect is to re-reference to the average reference (i.e. average across channels and subtract that average potential from each electrode, see the attached book chapter). Or you could calculate a spline-Laplacian/"current source density" estimate that is not influenced by reference choice.
Chapter Electroencephalography (EEG): neurophysics, experimental met...
I agree with Stephen- that is normal EEG data. In fact, you can see that EEG is NOT same across all your channels. I presume the scale here is 512 microvolt. You can change scale in neuroscan by up and down arrows (in Scan- EDIT). My questions to you are- what is the stimulus & what were you hoping to record? You won't see any responses (ERPs) until you process the raw EEG appropriately.
Your EEG data is normal. As Pragati says , epoching and averaging your data will help you see the ERP.
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