[FieldTrip] Different way of calculating the covariance for LCM

Yuval Harpaz yuvharpaz at gmail.com
Tue Mar 22 05:47:38 CET 2011

Dear Jean Michel
As far as I know you can do it on an averaged data structure (item 1) or do
the same with the data structure before averaging (3). I did not understand
what you meant by 2.


On 21 March 2011 22:58, Jean-Michel Badier <jean-michel.badier at univmed.fr>wrote:

>  Dear fieldtrip users,
> There are different ways of estimating the covariance for LCMV calculation.
> If I am correct:
> 1. As suggested in one of the tutorial one can apply the calculation of the
> covariance directly on the average data (for the different periods of
> interest that are at least a base line and the period of interest).
> 2. Estimate the covariance from the average of the covariance rather than
> the covariance of the average using cfg.keeptrials = "yes"
> 3. Estimate the covariance from the whole trials concatenated together.
> Is there an easy way to do that in fieldtrip (beside create a new data set
> of one trial constituted of all the trials)?
> Thanks
> Jean-Michel
>  -- Jean-Michel Badier PhD
>  Laboratoire de MagnétoEncéphaloGraphie INSERM U751. Aix
> Marseille Université 33 (0)4 91 38 55 62  *jean-michel.badier at univmed.fr*<jean-michel.badier at univmed.fr>
>  Service de Neurophysiologie Clinique. CHU Timone 264 Rue
> Saint-Pierre, 13005 Marseille-France
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a link to the BIU MEG lab:

 " Why, Dan," ask the people in Artificial Intelligence, "do you waste your
time conferring with those neuroscientists? They wave their hands about
information  processing and worry about where it happens, and
which neurotransmitters are  involved, and all those boring facts, but
they haven't a clue about the computational requirements of higher
cognitive functions."  "Why," ask the neuroscientists, "do you waste your
time on the fantasies of Artificial Intelligence? They just invent
whatever machinery they want, and say unpardonably ignorant things about the
brain." The  cognitive psychologists, meanwhile, are accused of concocting
models with neither biological plausibility nor proven computational powers;
the anthropologists wouldn't know a model if they saw one, and the
philosophers, as we all know, just take in each other's laundry, warning
about confusions they themselves have created, in an arena bereft of both
data and empirically testable theories. With so many idiots working on the
problem, no wonder consciousness is still a mystery.* Philosopher Daniel
Dennet, consciousness explained, pp. 225*
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