Rapid tutorial - Nonlinear transformations

In this tutorial, you will connect groups of neurons to create a system that can multiply two numbers together. You will then modify this network to compute a new function.

  1. Open the partially completed multiplication network

  2. Go to File->Open from file and select partial multiplication.nef.

  3. Connect the network

  • The basic components of the network have been constructed for you. Connecting components tells the system to compute the necessary synaptic connection weights to optimally realize the desired function.
  • Connect input 1 and input 2 to the inputs for neural ensembles A and B.
  • Connect A and B to the two inputs of H.

  • Connect the product output of H to the input of Z.

  • Run the network

  • Right-click on the background in the Network Viewer and select Interactive plots.

  • Click the play button (in the bottom-right corner). The grey squares show the firing rates of the neurons.
  • The graph displays the decoded output of the network. This should be approximately 40, since the input sliders are currently set to 8 and 5.

  • Move the sliders up and down to adjust this input. The output will change accordingly.

  • Change the function being computed

  • Close the Interactive Plots window.

  • Right-click on the H population and select Add decoded origin. Change the name to my function and click Set functions (dimension should be 1). Select user-defined function from the drop down and click set.
  • Type in a new function. Try x0*x0+cos(x1). You can also use your own function, but the neurons in this example are only optimized for representing values between -100 and 100. Click OK three times.
  • Disconnect the product projection from H to Z and connect the new origin called my function in its place.
  • Right-click on the Network Viewer and select Interactive plots.
  • Adjust the sliders to confirm that the new function is being calculated.
  • To compare the behaviour of neurons to the ideal calculation of this function, we can switch simulation modes. Click on the down-arrow at the bottom of the interactive plots. Change the mode from default to direct. This will bypass the neurons, producing an exact result.