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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 | ||