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getting_started:neuromag [2013/11/12 20:34]
getting_started:neuromag [2017/08/17 11:21] external edit
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 {{tag>​elekta neuromag dataformat meg}} {{tag>​elekta neuromag dataformat meg}}
-====== Getting started with Elekta-Neuromag data ======+====== Getting started with Elekta/Neuromag data ======
 ===== Introduction ===== ===== Introduction =====
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 ===== Special issues ===== ===== Special issues =====
 +  * if you have STI001 up to STI008, the TTL values (single bits) in those channels will be combined into an event of type '​Trigger'​ with an integer value between 0 and 255. 
   * Reading .fif mri-data with fieldtrip and making a single shell headmodel (example script can be found [[example/​read_neuromag_mri_and_create_single-subject_grids_in_individual_head_space_that_are_all_aligned_in_mni_space|here]]).   * Reading .fif mri-data with fieldtrip and making a single shell headmodel (example script can be found [[example/​read_neuromag_mri_and_create_single-subject_grids_in_individual_head_space_that_are_all_aligned_in_mni_space|here]]).
-Not yet documented or fixed but encountered:​ +  ​The default behavior of ft_read_event is that it assumes that event values ​below 5 are noise. ​However, in the new systems ​(Elekta Neuromag VectorView ​or Triux (306 channels both) this is seldom ​the case. 
-  ​read_trigger,​ this function ​assumes that event_values ​below 5 are noise. ​In the new system ​(Elekta Neuromag VectorView 306) this is not always ​the case. +
 +===== Frequently Asked Questions ===== 
 +    - Can I do source reconstruction with combined planar and magnetometer channels? ​
 +        *Yes, by specifying cfg.coilaccuracy=1 or 2 during ft_preprocessing
 +    - Can I do source reconstruction with combined MEG and EEG channels? ​
 +        * Almost!
 +    - How can I visualize planar gradient data? 
 +        *After combining, but also by pulling them apart in side-by-side layouts
 +    - How can I do stats with clustering on data from the planar gradiometers? ​
 +        * After combining, or using some smart (still to be defined) neighbourhood definition
 +    - Can I do stats with clustering on combined planar and data? 
 +        *Yes, using two (non-neighbouring) concatenated neighbourhood definitions
 +    - Can I combine multiple runs of an experiment (over multiple files)? ​
 +       *Yes, by using ft_appenddata...but see next question
 +    - How can I deal with rank-deficient maxfiltered data from multiple datasets/​runs? ​
 +        *After combining data from separate runs using ft_appenddata,​ you can run PCA using ft_componentanalysis followed by ft_rejectcomponent such that the rank of your covariance matrix is a number less than 64.
 +    - Should I use or avoid using MaxFilter? ​
 +        *It depends on several factors, including the level of noise in your recording, the presence of artefacts from outside the helmet and large amounts of head movement. Optimising source-localisation for Maxfiltered data is still under development. N.B. If you used Internal Active Shielding (IAS) running Maxfilter is obligatory