This code implements the theoretical dissertation about a new Brain-Heart interaction model, published in: [1] Catrambone Vincenzo, Alberto Greco, Nicola Vanello, Enzo Pasquale Scilingo, and Gaetano Valenza. "Time-Resolved Directional Brain/Heart Interplay Measurement Through Synthetic Data Generation Models." Annals of biomedical engineering 47, no. 6 (2019): 1479-1489.

This function quantifies directional Brain-Heart Interplay (BHI) through the model proposed by Catrambone et al.(2019) [1].

INPUT variables:

• TFR_EEG = Time course of EEG power spectral density (PSD). This must be a matrix (Dimension: Channels X time samples). Each series in each row should be filtered in the desired frequency band of interest (psi)
• TFR_HRV = Time course of HRV PSD (Dimension: 1 X time samples). This should be filtered in the desired frequency band of interest (phi: e.g., LF or HF band).
• FS = Sampling Frequency of the two TFRs
• RR = HRV time series (expressed in seconds)
• win_RR = windows length (expressed in seconds) in which the heartbeat generation model (IPFM) is reconstructed (default = 15 s)
• window = windows length (in seconds) in which the parameters are calculated (default: window*FS >= 15 )

OUTPUT variables:

• HeartToBrain = Functional coupling index (c_rrTOeeg(T)) from HRV Phi-band to EEG Psi-band
• BrainToHF, BrainToLF = Functional coupling indices from EEG Psi-band to HRV-LF or HRV-HF bands
• HeartToBrain_sigma, HeartToBrain_mc = model parameters to be used for fitting evaluation [1]

This software assumes that input series are all artifact free, e.g., heartbeat dynamics free of algotirhmic and/or physiological artifacts; e.g. EEG series free of artifacts from eye blink, movement, etc.

Copyright (C) 2019 Vincenzo Catrambone, Gaetano Valenza

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.

If you use this program in support of published research, please include a citation of the reference above. If you use this code in a software package, please explicitly inform the end users of this copyright notice and ask them to cite the reference above in their published research.

To use the software from Matlab or Octave, simply call the BHImodel function in the src/folder. Type 'help BHImodel' from the Matlab/Octave command window for help on the command's syntax and input/output arguments.

The software does not come with a GUI. Assuming the series sampled at 1 Hz, with 'x' as the time-varying PSD of a given EEG channel integrated in the theta band (4-8 Hz) and 'y' as the time-varying PSD of an HRV series integrated in 0.04-0.4 Hz, and 'z' as the HRV series, the following example performs the BHImodel analysis (with default parameters) and plots the function outcomes:

Fs = 1;

[HeartToTheta, ThetaToHF, ThetaToLF] = BHImodel(x,y,Fs,z);

figure, hold all

plot(1:length(HeartToTheta))'/Fs, HeartToTheta);

plot(1:length(ThetaToHF))'/Fs, ThetaToHF);

plot(1:length(ThetaToHF))'/Fs, ThetaToLF);