# Weighted Phase Lag Index  
###### see [\[1\]](https://pubmed.ncbi.nlm.nih.gov/21276857/) for further information about the measure

This license [CC BY 4.0](ground_truth_wpli/LICENSE.txt) covers the artificial 
LFP-data and calculated ground truth data.  \
This license [BSD-3](scripts/LICENSE.txt) covers the provided script codes. 

## Description

This folder contains subfolders for:
* 1. the WPLI related artificial LFP datasets in 'wpli_specific_artificial_data'
* 2. the ground truth data calculated by 'ft_connectivity_wpli' function from 
     MATLAB package FieldTrip (see 
     [\[2\]](https://pubmed.ncbi.nlm.nih.gov/21253357/) ) in 'ground_truth_wpli' 
* 3. the scripts used for calculating the ground truth, slicing the 
     [R2G-data](../../../dataset-4/R2G_slices) and creating the artificial 
     LFP-data in 'scripts'.

NOTE: *.mat files can't contain units, there for we provide the units explicitly

The _artificial_LFPs_{i}.mat_ files in 'wpli_specific_artificial_data' contain 
the artificial LFP-signals with the fields: 
* 'lfp_matrix': multi-trial LFP-data with shape (150(trials) x 2500(samples); 
  implicit unit: uV)
* 'times':  time-vector (1 (aligned trials) x 2500 (time-points); 
  implicit unit: msec)
* 'sf': sampling frequency of the recording (1000; implicit unit: Hz)

There is also a _cross_spectrum_of_artificial_LFPs_1_and_2.mat_ file containing 
the cross-spectrum of signal 1 and 2 with the fields:
* 'cross_spectrum_matrix': multi-trial cross-spectrum with shape 
  (150(trials) x 1251(cross-spectrum))
* 'frequencies': positive, real-valued frequencies with shape 
  (1 (aligned trials) x 1251 (frequency); implicit unit: Hz)  

The *.csv files in 'ground_truth_wpli' contain the function-dependent ground truths calculated by  
the reference implementation:
* data-shapes:
  
  * real data: 1 (aligned trials) x 1051 (WPLI values)
  * artificial data: 1 (aligned trials) x 1251 (WPLI values)
   

* For WPLI the reference implementation is ft_connectivity_wpli() from the MATLAB
package 'FieldTrip' (see [\[1\]](https://pubmed.ncbi.nlm.nih.gov/21276857/) for 
  the reference method publication and 
  [\[2\]](https://pubmed.ncbi.nlm.nih.gov/21253357/) for the toolbox publication). \
Used versions of MATLAB & FieldTrip:\
    MATLAB          Version 9.9         (2020b)\
    FieldTrip       fieldtrip-20210128 
  
## References
1. Vinck, Martin et al. “An improved index of phase-synchronization for 
   electrophysiological data in the presence of volume-conduction, noise and 
   sample-size bias.” NeuroImage vol. 55,4 (2011): 1548-65. 
   doi:10.1016/j.neuroimage.2011.01.055
2.  Oostenveld, R., Fries, P., Maris, E., Schoffelen, JM (2011). 
    FieldTrip: Open Source Software for Advanced Analysis of MEG, EEG, and 
    Invasive Electrophysiological Data. 
    Computational Intelligence and Neuroscience, 
    Volume 2011 (2011), Article ID 156869, doi:10.1155/2011/156869