[pymvpa] Hemodynamic lag shift

[Yaroslav Halchenko]

there are a few options you have...

in a block design experiment you can either
1. discard volumes on the boundaries of the blocks -- look at 
idsonboundaries
method of a dataset to figure out which volumes you need to discard

2. shift labels to account for  the hemodynamic response... lets say
with TR=2 and desired shift of 6 seconds, just shift labels by 3 and
discard first 3 volumes... smth like (just typed in... not tested ;))

dataset.labels[3:] = dataset.labels[:-3]
dataset = dataset.selectSamples(range(3, dataset.nsamples))

3. use BoxcarMapper mapper to just get a mean activation pattern of the
block (or simply use that ERNiftiDataset in the fashion similar to
ER-dataset analysis)



On Wed, 29 Apr 2009, Vadim Axel wrote:

>    Hi guys,
>    I wonder whether you are making hemodynamic lag shift in pyMVPA? Here
>    it the thread, where you discussed this issue with regard to Haxby's
>    dataset.
>    [1]http://www.mail-archive.com/pkg-exppsy-pymvpa@lists.alioth.debian.or
>    g/msg00173.html
>    I think it's a critical procedure, especially when designed consists of
>    short blocks (like 10-15 secs), where you might miss considerable
>    amount of information. As far as I remember in Princeton MVPA matlab
>    toolbox such a option existed.
>    Thaanks,
>    Vadim

> Ссылки

>    1. http://www.mail-archive.com/pkg-exppsy-pymvpa@lists.alioth.debian.org/msg00173.html

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-- 
Yaroslav Halchenko
Research Assistant, Psychology Department, Rutgers-Newark
Student  Ph.D. @ CS Dept. NJIT
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