table of contents
LIPSIA     List of local activation maxima
vzmax
The program 'vzmax' produces a list of local maxima in the zmap.

Example:

vzmax -in tcgbsAC1T.v -pos 3.1 -neg -3.1 -out BtcgbsAC1T.v -radius 5 -minsize 81 -report AC1T_list.txt -system talairach -threshold 0.3

The output image 'BtcgbsAC1T.v' marks the locations of the local maxima. The list of local activation maxima is contained in the text file 'AC1T_list.txt'.

A pixel is considered a local maximum, if its value is above the given threshold (-pos or -neg), and if it is the largest value within the specified radius. Only activation areas of size larger than '-minsize' are considered, '-minsize' is given in units of mm^3. For example, if the spatial resolution is 3x3x3mm, then a minsize of 81 corresponds to three voxels (81 = 3 x 27 = 3 x (3x3x3)).

The parameter '-threshold' facilitates the inclusion of adjacent voxels into the output image, provided they do not differ by more than the specified amount from the local maximum. In the example, '-threshold' is set to 0.3. If a local maximum has a value of 4.1, then adjacent voxels with values above 3.8 are included in the output file:


The parameter '-system' determines the coordinate-system that will be printed in the list. Possible values are:

Caution: The use of 'vzmax' only makes sense for registered 3D data (otherwise, Talairach coordinates are not available).
Parameters of 'vzmax':
-help
Prints usage information.
-in
Input file. Default: (none)
-out
Output file. Default: (none)
-pos
Positive threshold on zmap. Default: 3
-neg
Negative threshold on zmap. Default: -1000
-threshold
Height threshold for local maxima. Default: 0
-system [ mm | voxel | talairach ]
Coordinate system. Required.
-radius
Radius in mm for identifying local maxima. Default: 12
-minsize
Minimal size in mm^3 of activation areas. Default: 81 ( = 3 x 27 = 3 x (3x3x3)).
-report
File containing output report. Default: (none= screen output)


Max Planck Institute for Human Cognitive and Brain Sciences. Further Information: lipsia@cbs.mpg.de
Copyright © 2007 Max Planck Institute for Human Cognitive and Brain Sciences. All rights reserved.