[Mne_analysis] Head movement correction as a pre-processing step

[Mainak Jas]

Hi Qiong,

`mne_map_data` uses Minimum Norm Estimate. You project your data onto a
sphere and project it back to the new sensor locations. Actually, you
should be able to find the Mathematical details in Matti's 1994 paper:
http://link.springer.com/article/10.1007%2FBF02512476?LI=true.

Mainak

On Mon, May 1, 2017 at 5:32 PM, <qiongz at andrew.cmu.edu> wrote:

> Hi Alex,
>
> Thanks so much for the information. I really appreciate it. I have looked
> into papers during that period of time by matti Hämäläinen, with the most
> relevant material in this chapter
> <https://mycourses.aalto.fi/pluginfile.php/123749/mod_resource/content/1/2002-Hämäläinen-BrainMappingMethods.pdf> p237
> last paragraph in section 3 providing some understanding of the problem:
>
> "The continuous records of the head movements can then be utilized in
> different correction methods. If the signal-to-noise ratio is so good that
> unaveraged signals can be modeled, one can simply use a different
> coordinate transformation between the anatomical and device coordinate
> frames at each time instant. The situation is more complicated if signals
> are averaged or if continuous data segments containing signals from
> supposedly identical source distributions are compared. Uutela et al.
> (2001) have recently explored several alternative computational approaches
> applicable to signal averaging and source modelling in situations with
> significant head movements during the data acquisition.
>  "
>
> As the name 'mne_map_data' suggests the use of simple transformation and
> is often applied by sessions/blocks, correct me if I'm wrong, it seems to
> implement different transformations between the anatomical and device
> coordinate frames using data averaged within those sessions/blocks. As a
> result, the sensor data is transformed as if they are recorded from the
> same anatomical positions across these sessions/blocks.
>
>
> Best,
> Qiong
>
>
> On Mon, May 1, 2017 at 8:53 AM, Alexandre Gramfort <
> alexandre.gramfort at telecom-paristech.fr> wrote:
>
>> hi,
>>
>> mne_map_data is based on Matti's paper from the early 90's AFAIK.
>>
>> for some reason mne_map_data seems to be absent from the MNE website
>> and even from the original MNE manual...
>>
>> Alex
>>
>>
>> On Fri, Apr 28, 2017 at 7:43 PM, <qiongz at andrew.cmu.edu> wrote:
>>
>>> Dear MNE users,
>>>
>>> I am trying to understand the difference between using MaxFilter (SSS
>>> based) and using 'mne_map_data' to correct for head movement.  Does anyone
>>> know what algorithm is implemented for 'mne_map_data'?
>>>
>>> Thanks in advance for any help!
>>>
>>> Best,
>>>
>>> Qiong
>>>
>>> ---------------------------------------------------------
>>>
>>> Qiong Zhang
>>>
>>> PhD Student
>>> Machine Learning & Neural Computation
>>> Carnegie Mellon University
>>>
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