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• atlasVolume: uchar (8bit) grayscale Nissl volume of the reconstructed brain at 25 µm resolution.
• annotation: uint (32bit) structural annotation volume without fiber tracts at 25 µm resolution. The value represents the ID of the finest level structure annotated for the voxel. Note: the 3-D mask for any structure is composed of all voxels annotated for that structure and all of its descendents in the structure hierarchy.
• annotationFiber: uint (32bit) fiber tracts annotation volume at 25 µm resolution.
• averageTemplate: ushort (16bit) average brain template used as registration target at 25 µm resolution.
• gridAnnotation - 100 µm: uint (32bit) combined structural and fiber tract annotation volume at grid (100 µm) resolution for projection analysis.

Volumetric All volumetric data is stored in an uncompressed format with a simple text header file in MetaImage format. The raw numerical data is stored as a 1-D array as shown in the figure below. Image Added
Figure: Packing of 3-D volumetric data into a 1-D numerical array.

Example Matlab code snippet to read in the 25µm atlas and annotation volumes:

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