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.]:

<map>
  name   orimap       # Name to identify this map [exit]
  type   ori          # Type of map, determines the orientation pattern [exit]
  ncol_x   2          # Number of orientation columns along x-axis [2]
  ncol_y   2          # Number of orientation columns along y-axis [ncol_x]
  phase_x  0.0        # (0-360 deg) shift pinwheels along x-axis [0.0]
  phase_y  0.0        # (0-360 deg) shift pinwheels along y-axis [0.0]
  phase_p  0.0        # (0-360 deg) rotate ori around pinwheel [0.0]
  write_as_text null  # Filename to write map to a text file [null]
</map>

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:

<map>
    name odmap          # Name to identify this map [exit]
    type ocdom          # Type of map [exit]
    ncol_x   4          # Number of OD columns in X-direction
    phase_x  1.0        # (0-360 deg) Phase of OD map on X-axis
    write_as_text null  # Filename to write map to a text file [null]
</map>

Receptive Field Position

The following map defines how to align receptive field positions when an ocular dominance map is used:

<map>
   name rfxmap         # Name to identify this map [exit]
   type rfx            # Type of map
   ncol_x   4          # Number of OD columns in X-direction
   phase_x  1.0        # Phase of OD map on X-axis (deg)
</map>

Spatial Frequency

The following defines a spatial frequency map:

<map>
    name sfmap           # ID for reference
    type sf              # Type of map
    ncol_x    28.6       # Number of ori columns in X-direction
    ncol_y    14.3       # Number of ori columns in Y-direction
    phase_x 180.0        # Phase of orimap on X-axis
    phase_y 180.0        # Phase of orimap on Y-axis
    sf_min    1.0        # Minimum SF value
    sf_max    3.0        # Maximum SF value
    renorm  1 2 3 4 5 6 3 1  # Target shape for SF distribution
    renorm_rule          # 0-centered, 1-uniform random distribution
    renorm_seed 5551212  # For random uniform renormalization
    renorm_plot NULL     # Set a non-NULL string for filename to append plots
    round_to_unit 1      # Adjust column to integer number of units
    write_as_text null   # Filename to write map to a text file [null]
</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.