The Auditory Modeling Toolbox

Applies to version: 0.9.8

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KELVASA2015 - Localization model in cochlear-implant listeners (Kelvasa and Dietz, 2015)

Usage

[results] = kelvasa2015(insig,fs);

Description

KELVASA2015(insig,fs) implements the ACE signal processing strategy upon the two channel input signal to produce bilateral electrodograms. This is further processed through an electrode nerve interface to generate spike times of a population of AN neurons. A chosen localization model from Kelvasa and Dietz 2015 is then used to map the two channel (right and left) outputs to a predicted azimuthal position.

Input parameters

'',insig
Can be either: [N x 2] two channel audio signal
or results structure of preProcessed data
'',fs sampling rate (Hz)
'',varargin structure with all parameters required for model. If this is not included, default paramters are loaded.

Output parameters

'',results A structure containing the processed electrodograms, AN spike times, and model predicted azimuthal locations
The output structure "results" has the following fields:
electrodogramCHAN1 : [NxM] matrix of CI electrode current output
in mA(???) with N = number of CI electrodes and M = time
APvecCHAN1 : [Nx2] matrix of [Nx1] indices of spiking AN
fibers [Nx2] spike times in seconds

electrodogramCHAN2 : same but for second channel

APvecCHAN2 : same but for second channel

SpkSumPerBin : [NxM] matrix of Right and Left Spike Rate
differences in spikes per second with N= number of AN frequency bands and M = time bins

SpkDiffPerBin : same but for Right and Left spike rate differences

ANbinPredictions : [NxM] matrix of azimuthal angle bin predictions in
degrees with N= number of AN frequency bands and M = time bins
weightedPredictions : [1xM] matrix of bin weighted azimuthal angle
bin predictions in degrees with M = time bins
mappingData : Structure containing data used to calibrate and
implement the chosen localization model as detailed in kelvasa2015calibratemodels.m

The steps of the binaural model to calculate the result are the following :

  1. Process two channel input signal through a CI strategy as detailed

    in (Hamacher, 2003) and (Fredelake and Hohmann, 2012) to produce bilateral electrodograms.

  2. Process electrodogram through an electrode nerve interface and

    auditory nerve model as detailed in (Fredelake and Hohmann, 2012)

  3. Compute bilateral spike rate differences over chosen AN frequency

    bands and time windows as detailed in (Kelvasa and Dietz, 2015)

  4. Calibrate the chosen localization model with a chosen calibration

    signal. This step can take several hours so preProcessed calibration is loaded for "Speech Shaped Noise" at 55dB as detailed in (Kelvasa and Dietz, 2015)

  5. Map the spike rate differences for each AN frequency band to a

    predicted azimuthal angle using the chosen localization model as detailed in (Kelvasa and Dietz, 2015)

Parameters implemented in the model processing stages are set through AMT using the following files: arg_kelvasa2015ciparams.m, arg_kelvasa2015anparams.m, and arg_kelvasa2015locationmodelparams.m in which thorough descriptions of the input parameters are given.

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