can you point the exact cue onset and cue offset times on the picture? there seems to be nice P1-N1 response peaks in the region of cueoffset and onset inscription.

another question, are you going to exactly pick each of P1-N1-P2-N2 complex peak latency and amplitudes? or is P2-N2 responses is the question of interest but not only N1?

do you see the visual evoked P1/N1/P2 response over occipital electrodes? If so, you may try looking at the Fz,Pz,Oz electrodes separately and plot based on the cue information (i.e. low, medium, high chances of winning). To me it looks like the late positive complex/P3 activity. I would predict that occipital P1/N1 would be similar between cue information but the Pz positivity would be graded.

Hello Katharina,

From my experience your resulting ERP looks more like a CNV (Contingent Negative Variation) than a P300.

The only thing speaking against it, is the polarity. But, maybe at some point the polarity was reversed: recording or visualising the data. I suggest to verify that point to see if this is the case.

You only provided a short description of the procedure. As I read it now, this could indeed generate a CNV instead of P300. More detail on your procedure might shed some light on this point.

Daniel

Hi! 

I'm not sure that your paradigm elicits a N1-P2-N2 response, because the large P3 response that seems to be present. But, the ERP shown is extremely large duration, so maybe you need some more preprocessing of those signals.  Do you try to remove common average reference (CAR) and a linear detrending of each epoch? It seems that the responses you're looking for is hiding by the large P3.

 Additionally, that component is of larger amplitude in the occipital and parietal electrodes.  

Regards

Hi Katharina, 

actually your plot looks similar to the results of Alpay et al (2009). They only have reversed polarity. So there's probably nothing to worry about. Would be interesting though, to figure out when the complex is found for cues and when there's only a P3. In my own data I find more than one peak at Fz, but I never really cared about that. Might it have something to do with whether the cue already contains specific information about the response to be performed? (Sorry, random speculation.) I agree with the CNV/SPN interpretation mentioned in an earlier comment, but I think it follows the P3. Winning chances... cues reward positivity with me and backpropagation of reward to cue. Actually that might overwrite the other components. See Clay Holroyd's work, also feedback correct related positivity.

Good luck with your results!

Alpay, G., Goerke, M., & Stürmer, B. (2009). Precueing imminent conflict does not override sequence-dependent interference adaptation. Psychol Res, 73(6), 803-816. doi:10.1007/s00426-008-0196-9

Dear Katharina,

I agree with Anthony, that you should expect a P1/N1/P2 over occipital leads given the visual paradigm. If you have Oz recorded you may try to reference it against Fz. Based on the polarity reversal of the visual P1 over frontal leads, you may better see this. It seems to me from the plot, though, that the Pz is in fact more negative in the P100-latency range than in Fz. It also confuses me that the CNV-like potentials preceding cue 2, little also before cue 1 onset, is als more negative in Pz, although CNV are typicall greater at Fz and Cz than Pz. The P3-like component following cue 1 onset, on the other hand, is greater over Pz as one expects. I am not sure, whether my thoughts are helpful. In any case the data looks clean. Best wishes, Jürgen

Hi Katharina,

The pre-processing (sampling rate, etc..) you did is perfectly standard and it is right for ERP analysis, so you shouldn´t worry about that.

Regarding your results, I can actually see the component N1 and P2 at Fz electrode,  while the positive deflection at Pz (that fits with a P3b component) might some times hide the visibility of other components (in this case P2 and N2)

In my opinion, I think your ERPs are ok and you should go ahead with your analysis ;)

Cheers,

Mario

HI Katharina,

After taking a look to your plot, I think your results could be perfectly ok. In this respect, I have a massive amount of examples with control subjects performing some kind of task in which you only can see the visual ERP components N1 and P3. In addition:

- Sometimes P2/N2 may be hidden or masked by a massive P3. However, you have a nice/fast P2 peaked at +/- 200 ms over Fz, and this is fine.

- A CNV may usually appear after your P3 and other long-latency ERP as a preparation of the subjects for the next trial.

However, and although perhaps this gambling paradigm might result in this kind of waveforms, I have indeed some concerns about this plot:

a) Some researches attribute the more anterior visual N1 (and N2) solely to response preparation processes because it could be eliminated by not requiring a motor response and decreased SOA. Was any kind of motor response required during your task?

b) The visual N1 between frontal and posterior sites should be different. Thus, in my opinion, you should have a visual N1 occurring at 100-150 ms over the frontal/central midline and another visual N1 present at +/-165 ms over the posterior sites. Therefore, your plot does not show this, so you should be sure that you are not having any problem with your current montage or setup.

c) If the montage is ok, then I strongly recommend you the application of spatial filtering based on principal component analysis (PCA) to detect ERP, which might be a very useful tool in assisting the ERP detection for non-standard paradigm.

Cheers,

Javier

I think that the N1 and the P2 are actually present in your plot.

The P1 could be just not visible from those electrodes. Could you show also Oz, PO7 and PO8 (or closer)? Could you also show some topographical maps?