[FieldTrip] ft_lateralizedpotential question

Caspar, Emilie e.caspar at ucl.ac.uk
Fri Jun 12 15:19:26 CEST 2015

Dear Nietzsche,

Sorry for the missing letter! Indeed, it slightly changes the meaning x)

I have tried with different electrodes for avg Left and Right

cfgL             = [];
cfgL.channel = {'A*'}
avgL = ft_timelockanalysis(cfgL, clean_data);
cfgR             = [];
cfgR.channel = {'B*'}
avgR = ft_timelockanalysis(cfgR, clean_data);

And then I have asked for ft_lateralizedpotential:

cfgT             = [];
cfgT.channelcmb={'A13' 'B18'};
cfgT             = [];
cfgT.xlim = [-2 1];
cfgT.ylim = [-12 10];
ft_singleplotER(cfgT, lrp)

I agree that avgL and avgR are more logical now. However, the plot is still not working, with the following error:

Error using fixdimord (line 85)
the data does not contain a dimord, but it also does not resemble raw or component data

I still do not really understand what is wrong. My script/data work very well without the ft_lateralized. I have already looked at the results for the readiness potential. I just want to look now for the lateralized RP.



On 12 juin 2015, at 13:07, "Lam, N.H.L. (Nietzsche)" <n.lam at donders.ru.nl<mailto:n.lam at donders.ru.nl>>

Hi Emilie,

We won't be ripping any fields anytime  ("Fieldrippers")  ;)

(1) Assuming your data has been calculated correctly, then the issue is the input argument you gave to ft_singleplotER

You should probably try:  <ft_singleplotER(cfg,lrp)  % giving ft_singleplotER only the 'plotlabel' field is incorrect because the function expects a struct (i.e. the structure of timelock of freqdata).

(2) Your second question is a bit vague, but logically speaking you will not find a difference between avgL and avgR if both are computed from the same dataset.  1-1 = 0, no difference.
Not sure what your pipeline looks like, but I suspect that you need timelocked data for only the left sensors in one data set (Lavg), and timelocked data for only the right sensors in a separate dataset (Ravg).

Good luck,

From: fieldtrip-bounces at science.ru.nl<mailto:fieldtrip-bounces at science.ru.nl> [fieldtrip-bounces at science.ru.nl<mailto:fieldtrip-bounces at science.ru.nl>] on behalf of Caspar, Emilie [e.caspar at ucl.ac.uk<mailto:e.caspar at ucl.ac.uk>]
Sent: 12 June 2015 12:53
To: fieldtrip at science.ru.nl<mailto:fieldtrip at science.ru.nl>
Subject: [FieldTrip] ft_lateralizedpotential question

Dear Fieldrippers,

I have a small question about ft_lateralizedpotential.
I am currently trying to compute a LRP. Thus, I wrote:
avgL = ft_timelockanalysis(cfg, cleandata);
avgR = ft_timelockanalysis(cfg, cleandata);
cfg             = [];
cfg.layout      = 'biosemi64.lay';
cfg.channelcmb={'A13' 'B18'};
cfg             = [];
cfg.xlim = [-2 1];
cfg.ylim = [-12 10];
ft_singleplotER(cfg, lrp.plotlabel)

There is apparently something wrong with the plot because I get the following error message:

Error using ft_checkdata (line 461)
This function requires timelock or freq data as input.

I have also tried to add a new avgLRP = ft_timelockanalysis(cfg, lrp);
and then to compute the plot based on that, but it is not working. If anyone has an idea!

Second question:, ft_lateralizedpotential only works (apparently) with two outputs (avgL and R, for instance). Thus, I computed the same ft_timelockanalysis with two different names, but I am not sure this is correct. Is someone able to answer?

Thank you in advance for your help!

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