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University of Plymouth | Centre for Theoret. and Comput. Neuroscience | Home
Example 4: Carandini Ringach Model for Orientation Tuning
This example is presented only, because it displays a further type of view, the "function". The C&R-model is a one-dimensional non-linear neural field of neurons with non-local laterally decaying interactions which are positive for near-by cells and negative for more distant cells. The coupling kernel, thus, is of Mexican hat type. The model can be formulated as a functional differential equation. This and related models are useful to explain dynamic tuning phenomena in receptive fields of cortical neurons (see e.g. my publication list and research interests).Below you find an image of a running simulation.
On the top left the field phi(x,t) of potentials of the neurons is displayed as a raster plot similar to previous examples. f(phi) results from the field of potentials after application of a rate-function. Whereas the left frame shows the fields as functions of time (obviously a steady state, because every unit is displayed by a constant grey-level over time), the right re-displays them as functions at the current simulation step. The main control frame allows to set various simulation parameters like the input strength, excitatory and inhibitory coupling strengths, the membrane time constant, the exponent of the squashing function, and the threshold potential of the neurons (the rate-function f(phi) is zero for phi smaller than theta and polynomial with exponent "power" for phi larger than theta). If the Switch "spikes" is activated the graded neurons are replaced by probabilistic spiking neurons, or, in mathematical terms, by rate-modulated Poisson processes. The Switch "empty" does nothing.
As usual every control element and view can be declared by a single line of code. These declarations also already include the individual control popups for element and display scale selections. Those are not shown in the figure, but always hidden behind buttons above each data view.
Downloads
Statically linked executable (Right-click and store using "Save Link Target .." or similar. Start by clicking on it after download.)
Environment file (Put this file into a subdirectory "env" in the directory of the executable, which will then start with appropriate parameters.)
Shared library executable (Right-click and store using "Save Link Target .." or similar.)
Note 1: If the statically linked executable does not start, you might need to make it executable by setting the right permissions. It might also be that you don't have all necessary libraries (none of which is, however, very exotic). Try "ldd cr" on the command line to see if something is missing.
Note 2: To run the shared library executable you need to install the felix runtime libraries; to compile the source code you need to install in addition the felix development tools. See HERE for more info.
© 2004 by -thowe-