Maps
----
Maps, such as orientation or ocular dominance maps, can be applied to
populations of cells to set attributes of those cells. Maps are
applied to a population based on the size of the area assigned to the
population. Maps can be written to a text file for inspection by setting the parameter
*write_as_text* to a file name (any string other than "null" or "NULL").
Orientation
***********
The following parameters govern the orientation map. Default values
are specified in parentheses. Note, the phase shifts below refer to
some fraction of a full cycle (0 to 360 deg), and the unit of
``deg`` here does **not** refer to the 0-180 degree orientation
scale. [This can be confusing, and perhaps a range of 0.0 to 1.0
should be used instead.]::
A particular algorithm for assigning orientations (from 0 to 180) is
implied by the ``type`` parameter. This should be described
here.
Direction
*********
Currently, the orientation map sets a value that is interpreted as a
direction, but only covers directions from 0-180. When forming direction
selective (DS) cells, the direction can be changed by using a flag
parameter, as follows::
map_dir_flag ori # "ori", "ori_invert", "ori_alt_z", ...
where values have the following meaning:
* ``ori`` - use the orientation map value for the reference direction
* ``ori_invert`` - add 180 deg to the orientation map value
* ``ori_alt_z`` - alternate between ori and ori+180 for z=[0,1]. This
allows the construction of multiple sheets of cells with opponent
directions, consistent with the underlying orientation map.
Ocular Dominance
****************
The following defines an ocular dominance map::
Receptive Field Position
************************
The following map defines how to align receptive field positions when an
ocular dominance map is used::
Spatial Frequency
*****************
The following defines a spatial frequency map::
The optional parameter *renorm* allows the user to specify the shape
of a target SF distribution using a list of numbers. The sequence of N
values that follows *renorm* specifies the amount of weight given to
each of N contiguous regions that are evenly spaced along the SF axis from
*sf_min* to *sf_max*. The *renorm_rule* can be set to 0 to limit SF values to distinct bands, or to 1 to allow a more uniform distribution.