Neural Flows: estimation of velocities, detection and classification singularities in 3D+t brain data

If you use this toolbox, please cite:

Brief Description

This is neural-flows, a library to estimate wave velocities and singularities in 3D+t in neuroimaging data.
The figure below gives you an idea of a typical workflow you can run with this toolbox:
Each link of the path is a component of the core/ namely:

• data interpolation,
• flow estimation,
• singularity detection and classification, and
• streamline tracing.

The toolbox has a number of ancillary modules, including:

• io/ that handles read and write operations of .json and .mat files.
• visualisation/ contains lots of plotting functions including some that produce movies like the one you can see at the end of this document.
• external/, which contains code implemented by others, the most prominent being C-NEM invoked by so-called meshless methods, and the Hungarian method used track singularities; and finally,
• utils/ which gathers small standalone functions that support the main modules.

Getting started

Dependencies:

MATLAB

• tested on R2018b & R2020a
• in principle should work on any OS that MATLAB supports; tested on Windows 10, Debian 10, Ubuntu 20.04, Ubuntu 16.l4, OpenSuse 15.1

CNEM, https://m2p.cnrs.fr/sphinxdocs/cnem/index.html

• only relevant if you want to use the phase-gradient method for calculating flows and meshless method for tracing streamlines.
• meshless methods speed up calculations significantly but installing cnem can be tricky.
• used version (v03, 2014-05-04) available here: https://ff-m2p.cnrs.fr/frs/?group_id=14
• aka cnemlib: https://au.mathworks.com/matlabcentral/linkexchange/links/3875
• if you have trouble, contact the author of the library (mail can be found on the cnrs.fr website linked above) who has been super helpful when we had issues.

Installation:

If you download the zip folder, first unzip and then ...

• Windows 10: see the instructions here.
• Linux: on the terminal change directory to neura-flows folder, then start matlab. That's it. The toolbox paths should be appended automatically.

If you clone the repo, same rules as above apply.

What can the toolbox do?

A bunch of things, mostly the ones described in the diagram above.

To get started follow the next steps (timestamp: Tue 29 Jun 2021 14:49:38 AEST):

Out of the box examples

0. (Optional) Inside directory neural-flows/, make a new directory called scratch/ (by default we will store results there, you can change it later ...). If this directory doesn't exist the toolbox will print a warning message and then proceed to create it.

1. Call the following function from within the top level directory neural-flows/

fmri_waves()

or

rotating_wave()

The first example takes about 7 minutes to run everything and then it pops up figures with flow mode decomposition and singularity tracking! The second one takes about 9 minutes. The execution times are estimated using a high-end workstation (circa 2018). On a laptop it can take 2.5 longer to run (o.O it's heavy stuff).

Flow mode decomposition

Singularity statistics

Movies

Movies are not produced by default as they require more computational resources. However, we provide the visualisation tools to make movies like this one:

What if I want to use my own data? Input data format

The toolbox reads data from a .mat file. It will expect the following variables to be stored.

- `data`: a 2D array of size [number of timepoints x number of ROIs/nodes/sources] with the neuroimaging data for unstructured datasets (i.e., source reconstructed EEG/MEG data, whole-brain models/brain networks, parcellated fmri data) 
- `locs`: a 2D array of size [number of ROIs/nodes/sources x 3] with the x,y,z coordinates of ROIs/nodes/sources, expressed in mm or m.
- `ht`  : sampling period expressed in ms or s.