Hi SPM users

I had a very naive question about downsampling the MRI atlas for registration with functional data.

The Zebra finch MRI atlas has the following dimensions(256x256x256), 0.8x0.8x0.8 (voxel size). My functional data has dimensions( 64x64x15 ) and voxel size (0.39x0.39 x0.75)

Initially i had registered the functional data to atlas space which made each file having dimensions as 256x256x256. That took up  a lot of disk space. So I downsampled the atlas to 64x64x16 and voxel size 93.2x3.2x12.8).

I then used the rescaled atlas to register functional data.

Does the downsampling of atlas before registration  affect the analysis in SPM?

I would be grateful if someone could clear my doubts.

thank you

Best

Payal