[Mne_analysis] computing head position information

Ramakrishnan, Nithya Nithya.Ramakrishnan at bcm.edu
Tue Oct 20 14:01:38 EDT 2020
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Hi,

I would like to find out if there is a manual or if you could point me to literature on the effect of different input parameters in mne.chpi.compute_chpi_head_pos ( info, chpi_locs, dist_limit=0.005, gof_limit=0.98, adjust_dig=False, verbose=None)

This is because I am using a few datasets with movement compensation performed with Elekta maxfilter (-movecomp with default parameters such as HPI-fit parameters for each every 200ms) and a few datasets where movement compensation is performed within MNE. What I  am finding is some head position calculations with default goodness of fit (0.98) gives me an empty matrix and a "cannot determine the transformation" error for all coils. While, if I reduce the goodness of fit, or if I set the t_step_max=0.2 (which I am assuming is comparable to Maxfilter -movecomp) for calculation of chpi locations ( mne.chpi.compute_chpi_locs), I do get an head_pos array of a decent size.

Nithya Ramakrishnan
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