[FieldTrip] calculating behavioural-power correlation

Tue Feb 17 15:18:11 CET 2015

Dear Arjen,

Thanks! It works well now.

I plotted the results using ft_clusterplot, and it only shows the
significant clusters that show significant correlation of power and
behavioural measure, right? Or is there a better way I can display the
results?

Thanks again.

Cheers,
Hweeling

On 17 February 2015 at 11:45, Stolk, A. (Arjen) <a.stolk at donders.ru.nl>
wrote:

>  Hey Hweeling,
>
> "Just to ensure that I get this right, I should create a variable for the
> behavioural measure such that the variable contains a powspctrm field with
> the behavioural information for every frequency?"
> > indeed
>
> "What I'm confused is that in the walkthrough website, under the
> subsection on correlation, it is suggested to create the cfg.design with
> the behavioural measure that one wants to correlate. So is this information
> in the walkthrough website incorrect?"
> > the walkthough may refer to a GLM-based statistical implementation, for
> which the FT implementation differs from the correlationT statfun. Namely,
> the former uses the behavioral measure as a regressor in a data model
> whereas the latter uses the behavioral measure as a datapoint series for
> correlation with another datapoint series (and then converts to a T value).
> The correlationT statfun is relatively 'new', hence not yet addressed in
> the walkthrough.
>
> Yours,
> arjen
>
>  ------------------------------
> *From:* fieldtrip-bounces at science.ru.nl [fieldtrip-bounces at science.ru.nl]
> on behalf of Hwee Ling Lee [hweeling.lee at gmail.com]
> *Sent:* Tuesday, February 17, 2015 11:34 AM
> *To:* FieldTrip discussion list
>
> *Subject:* Re: [FieldTrip] calculating behavioural-power correlation
>
>   Dear Arjen,
>
>  Thanks for the prompt reply again!
>
>  Just to ensure that I get this right, I should create a variable for the
> behavioural measure such that the variable contains a powspctrm field with
> the behavioural information for every frequency?
>
>  What I'm confused is that in the walkthrough website, under the
> subsection on correlation, it is suggested to create the cfg.design with
> the behavioural measure that one wants to correlate. So is this information
> in the walkthrough website incorrect?
>
>  Cheers,
> Hweeling
>
>
> On 17 February 2015 at 11:23, Stolk, A. (Arjen) <a.stolk at donders.ru.nl>
> wrote:
>
>>  Hey Hweeling,
>>
>> It seems you're only inserting one input variable into the statistics
>> function, i.e. "[c200_delta_stat] = ft_freqstatistics(cfg,
>> sub_LF_c200{:});"
>>
>> Could you try something along this line: ft_freqstatistics(cfg, freq1,
>> freq2)
>>
>> where freq1 is the original freq data, and freq2 is a copy of freq but
>> with the relevant values (say, in powspctrm) replaced with behavior values
>> (ensure this behavior matrix is matched in terms of size and dimensions to
>> the original freq values).
>>
>> Hope this helps,
>> Arjen
>>
>>  --
>> Donders Institute for Brain, Cognition and Behaviour
>> Centre for Cognitive Neuroimaging
>> Radboud University Nijmegen
>>
>> Email:  a.stolk at donders.ru.nl
>> <https://mail.ru.nl/owa/redir.aspx?C=aE7VYn0S90OKCrgPeLfE1S7ZybNAtNEIa36fR052GideznKNfSHe2KSW6d9DoW6tEIOMlaBdT-s.&URL=mailto%3aa.stolk%40donders.ru.nl>
>> Phone:  +31(0)243 68294
>> Web:    www.arjenstolk.nl
>> <https://mail.ru.nl/owa/redir.aspx?C=aE7VYn0S90OKCrgPeLfE1S7ZybNAtNEIa36fR052GideznKNfSHe2KSW6d9DoW6tEIOMlaBdT-s.&URL=http%3a%2f%2fwww.arjenstolk.nl>
>>   ------------------------------
>> *From:* Hwee Ling Lee [hweeling.lee at gmail.com]
>> *Sent:* Tuesday, February 17, 2015 10:33 AM
>> *To:* Stolk, A. (Arjen)
>> *Cc:* FieldTrip discussion list
>> *Subject:* Re: [FieldTrip] calculating behavioural-power correlation
>>
>>    Dear Arjen,
>>
>>  Thanks for the prompt reply. I keep getting an error message when I set
>> up my correlation cluster statistics, and I'm not sure what I could have
>> done wrong. Here's my script:
>>
>>  cfg = [];
>> cfg.layout = 'EEG1010.lay';
>> cfg.neighbours = neighbours;
>> cfg.channel = 'all';
>> cfg.latency = 'all';
>> cfg.avgovertime = 'no';
>> cfg.avgoverchan = 'no';
>> cfg.avgoverfreq = 'yes';
>> cfg.parameter = 'powspctrm';
>> cfg.method = 'montecarlo';
>> cfg.statistic = 'ft_statfun_correlationT';
>> cfg.correctm = 'cluster';
>> cfg.clusteralpha = 0.05;
>> cfg.clusterstatistics = 'maxsum';
>> cfg.minnbchan = 2;
>> cfg.tail = 0;
>> cfg.clustertail = 0;
>> cfg.alpha = 0.025;
>> cfg.numrandomization = 1000;
>> cfg.ivar = 1;
>> cfg.uvar = 1;
>>
>>  % design matrices
>> clear design;
>> % change in MMSE score relative to baseline
>> design(1,:) = [0.095238095 -0.045454545 -0.533333333 0.238095238
>> -0.157894737 0.117647059];
>> design(2,:) = 1:6;
>> cfg.design = design;
>>
>>  % for delta band
>> cfg.frequency = [2 4];
>> [c200_delta_stat] = ft_freqstatistics(cfg, sub_LF_c200{:});
>> [c210_delta_stat] = ft_freqstatistics(cfg, sub_HF_c210{:});
>>
>>  Here's the output from Matlab:
>>
>>  computing statistic over the frequency range [2.000 4.000]
>> the call to "ft_appendfreq" took 0 seconds
>> the call to "ft_selectdata" took 0 seconds
>> using "ft_statistics_montecarlo" for the statistical testing
>> using "ft_statfun_correlationT" for the single-sample statistics
>> constructing randomized design
>> total number of measurements     = 6
>> total number of variables        = 2
>> number of independent variables  = 1
>> number of unit variables         = 1
>> number of within-cell variables  = 0
>> number of control variables      = 0
>> using a permutation resampling approach
>> repeated measurement in variable 1 over 6 levels
>> number of repeated measurements in each level is 1 1 1 1 1 1
>> computing a parametric threshold for clustering
>> Error using ft_statfun_correlationT (line 90)
>> Invalid specification of the design array.
>> Error using ft_statistics_montecarlo (line 254)
>> could not determine the parametric critical value
>> for clustering
>>
>>  Error in ft_freqstatistics (line 319)
>>   [stat, cfg] = statmethod(cfg, dat, cfg.design);
>>
>>  Would you please tell what I have done wrong in this case?
>>
>>  Thanks!
>>
>>  Cheers,
>> Hweeling
>>
>>
>> On 17 February 2015 at 10:18, Stolk, A. (Arjen) <a.stolk at donders.ru.nl>
>> wrote:
>>
>>>  Hi Hweeling,
>>>
>>> Have a look at the help of ft_statfun_correlationT, which might be the
>>> function you're looking for. This function calculates correlations between
>>> two variables (e.g. subjects' behaviors and brain activities) and converts
>>> the resulting correlation coefficients to t-statistics.
>>>
>>> Best,
>>> arjen
>>>
>>>  --
>>> Donders Institute for Brain, Cognition and Behaviour
>>> Centre for Cognitive Neuroimaging
>>> Radboud University Nijmegen
>>>
>>> Email:  a.stolk at donders.ru.nl
>>> <https://mail.ru.nl/owa/redir.aspx?C=aE7VYn0S90OKCrgPeLfE1S7ZybNAtNEIa36fR052GideznKNfSHe2KSW6d9DoW6tEIOMlaBdT-s.&URL=mailto%3aa.stolk%40donders.ru.nl>
>>> Phone:  +31(0)243 68294
>>> Web:    www.arjenstolk.nl
>>> <https://mail.ru.nl/owa/redir.aspx?C=aE7VYn0S90OKCrgPeLfE1S7ZybNAtNEIa36fR052GideznKNfSHe2KSW6d9DoW6tEIOMlaBdT-s.&URL=http%3a%2f%2fwww.arjenstolk.nl>
>>>   ------------------------------
>>> *From:* fieldtrip-bounces at science.ru.nl [fieldtrip-bounces at science.ru.nl]
>>> on behalf of Hwee Ling Lee [hweeling.lee at gmail.com]
>>> *Sent:* Tuesday, February 17, 2015 10:06 AM
>>> *To:* FieldTrip discussion list
>>> *Subject:* [FieldTrip] calculating behavioural-power correlation
>>>
>>>
>>> Dear all,
>>>
>>>  I read on the "walkthrough" that it is possible to calculate
>>> behavioural-power correlation across subjects. However, I was not sure what
>>> type of descriptive statistics (i.e. cfg.statistics) I should use when
>>> performing correlation cluster statistics.
>>>
>>>  Would someone please enlighten me which type of statistics I should
>>> input for cfg.statistics?
>>>
>>>  Thanks!
>>>
>>>  Best regards,
>>> Hweeling
>>>
>>>
>>
>>
>> _______________________________________________
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>>
>
>
>

-- 
=================================================
Dr. rer. nat. Lee, Hwee Ling
Postdoc
German Center for Neurodegenerative Diseases (DZNE) Bonn

Email 1: hwee-ling.lee<at>dzne.de
Email 2: hweeling.lee<at>gmail.com

https://sites.google.com/site/hweelinglee/home

Correspondence Address:
Ernst-Robert-Curtius Strasse 12, 53117, Bonn, Germany
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