MT area

The <area> object defines a rectangular coordinate frame with respect to the stimulus pixel coordinates. Below is an example of an area that is used in setting the geometry of a small MT population in this model.

  <area>
    name   mt          # Area name
    x0    14           # Origin w.r.t. the stimulus grid
    y0    14           #
    xn     4           # width
    yn     4           # height
    umx   20.0 (um)    # microns per grid unit (stimulus grid)
  </area>

The name parameter can be chosen arbitrarily and is used to refer to this area.

The x0 and y0 values specify the location of the lower left corner of this rectangular region in terms of the stimulus grid (the stimulus grid is defined by the global xn and yn at the top level of the model parameter file).

The xn and yn values specify the size of the rectangle in number of units. Here a 4 by 4 rectangle is defined.

The rectangular coordinate frame thus defined is shown in the figure below. The black dots indicate the pixels in the 32 by 32 stimulus frame. The red circles indicate the locations of the centers of the RFs of the MT units in the area defined above.

The umx parameter (above) defines the number of microns that should correspond to one grid unit along the x (horizontal) axis. This parameter may be left out, but if present, it can be useful if axonal connections are to be specified or limited in terms of their projection distances in microns. This is an optional conversion factor that can allow biologically meaningful units to be used in configuring the model. A value for umy can also be specified, but it if is not (as is the case here), then it will default to the value given for umx.