This repository contains the source code for my final-year project in my BEng degree, 'Musical Pattern Recognition in Spiking Neural Networks'. The title of the project should hopefully be self-descriptive as to the purpose of the project. The report accompanying the project is available at http://amid.fish/beng_project_report.pdf.

As seems to be the case with pretty much all final-year projects, only a small portion of what was originally intended was actually achieved. This code implements the first layer of the model proposed in the report: a layer of spiking neurons which can differentiate between individual notes in a series of simple monophonic test audio sequences.

The architecture of the network comes from Peter Diehl's model in Unsupervised learning of digit recognition using spike-timing-dependent plasticity.

First, in order to properly clone the repository and all the associated data, you'll need to to install Git Large File Storage: https://git-lfs.github.com.

Then you'll need:

• Python
• Brian 2 (http://briansimulator.org)
• Brian 1, if you want to generate new input spike sequences
• (The Brian 1 Hears bridge is used for input spike generation)
• NumPy
• matplotlib
• ffmpeg for animation generation

• test_inputs contains a number of test sequences in .wav files, generated by gen_test_inputs.py using the Mingus music library and the Fluid R3 SoundFont (https://musescore.org/en/handbook/soundfont). The .pickle files are spike-coded representations of these sequences in .pickle files, generated by gen_audio_spikes.py.
  • (comptine*.wav is a test sequence based on the first few chords of Yann Tiersen's 'Comptine d'un autre été', generated by a script not supplied.)
• stdp_sounds.py is the main simulation script. See params/*_cmdline.txt for examples of usage for each test sequence. The simulation script will record the parameters used in params, save results in results (if run with --save_results), and save figures generated in figures (if run with --save_figs).
• modules contains Python modules used for the simulation.
• input-layer1e-weights.pickle is a cache of the random initial synaptic weights used in the simulation, for repeatability.
• prepare_movie_with_sound.sh uses write_movie.py and the results of a single simulation run with --vis --save_results (as stored in results/monitors_<test sequence name>.pickle) to generate an animation showing the input spikes, neuron membrane potentials and weight changes over time, then combine it with the corresponding audio track using ffmpeg. Examples of these animations are included in results.

To generate spikes for an audio file:

$ ./gen_audio_spikes.py test_inputs/two_notes_0.5_s.wav
...
Writing spike files...
done!

To then run a simulation:

$ python -i stdp_sounds.py --input_spikes_file test_inputs/two_notes_0.5_s.pickle
...
done!
<observe pretty figures>

If the simulation uses too much memory, you can decrease the resolution of state variable recordings by increasing --monitors_dt.

Alternatively, run a simulation using a saved set of parameters:

$ python -i stdp_sounds.py --parameters_file params/two_notes_0.5_s.txt

Note that all other arguments are ignored when using --parameters_file.

The code includes a few basic tests:

• LIF test, run with python -i stdp_sounds.py --test_neurons. This sets up a simple network of regularly-firing input neurons and a bunch of output neurons, then plots graphs of input/output spikes and membrane potential of the output neurons. Graphs can then be inspected to check that LIF dynamics/threshold adaptation is working correctly.
• Winner-take-all inhibitory connections test, run with python -i stdp_sounds.py --test_competition. This runs the same thing as the LIF tests but with inhibitory connections enabled.
• STDP curve test, run with python -i stdp_sounds.py --test_stdp_curve. This plots the STDP curve. A heavily-potentiation skewed STDP curve is used here because for the rate-coded input setup used it's actually much simpler to just do Hebbian-like learning.