644 Homework 2

In this homework, you will choose from one of the existing, functional code base and (1) replicate previous results, and (2) make small modifications and run a small set of new experiments. Some of these are small in scale, suitable to be developed later into an individual project. The more complex ones can become a team project.

Choose one task from below, and I will provide you with the details on an individual basis (or in groups of those who are interested in the same task), plus the working code. Please choose your preference by Friday, 3/30/07.

Codebase Environment Replicate previous results Modifications Experiments
Coupled integrate-and-fire neuron in XPPAUT (from homework 1
[Use your own code]
XPPAUT Get both synchronization and desynchronization from excitatory (and inhibitory) coupling, by adjusting parameters (mostly the PSP time constant). Revise equation to keep firing rate constant (or at least within a range), regardless of PSP amplitude. Do a study where you change the simulation parameter systematically and record and analyze the results. Does the behavior change smoothly or abruptly?
Choe's Thalamocortical circuit model in XPPAUT:
[Download: thalcor.tar.gz]
XPPAUT: use your own code from homework 1 Run all experiments in Choe (2004) Instead of exponentially decaying PSP, use alpha function. Run the same simulations with the revised model, adjusting parameters to get the same qualitative behavior.
Sensory-invariance-driven action code:
[Download: sida-nat.tar.gz]
Octave Run the basic simulation for autonomous learning of internal state, on synthetic and natural images. Learn RF using a random policy and Hebbian weight adaptation. After RF learning is complete, learn R(s,a). Run the same simulations with the revised model.
Simple neuroevolution code for feedforward neural networks:
[Download: ga.m]
Octave Run the basic simulation for learning boolean functions. Modify network to have context layer (hidden layer feeding back to itself). Experiment with temporal sequence learning (supervised).
[Download: download page]
Topographica Run two tutorial simulations: Tutorial page Add integrate-and-fire neuron types to the code base. Extend the coupled-neuron experiment and get synchronization/desynchronization behavior
Sarma and Choe's orientation energy code for contour saliency detection and associated code
Octave Run code on new images and compare to your own perceptual experience. Derive and implement a neural network to learn response threshold. Use a square-root activation function at some stage during the process. Train and test using the human data set.
Your own codebase, relating to cortical networks ? ? Discuss with the instructor Discuss with the instructor

Thu Mar 29 03:22:27 CDT 2007 Yoonsuck Choe