[pymvpa] Group analysis - surface searchlight

[Nick Oosterhof]

On 12 Apr 2015, at 00:53, Mike E. Klein <michaeleklein at gmail.com> wrote:

> I’m trying to run a sample top-level analysis on surface-based searchlight data using Nick’s afni_surface_alphasim script. I’ve never tried this before, and am getting a ZeroDivisionError (bottom of output). I tried re-running the script, leaving out some subjects (in case there is a bad file/vertex somewhere), but get the same result. […]
> 
> Here is my bash input/output: […]
> 
> ++ 3dbucket: AFNI version=AFNI_2011_12_21_1014 (May  1 2014) [64-bit]
> ** FATAL ERROR: Dataset /Volumes/deep_thought/fmri/mvpa2/april_analyses/subs/06/suma_surfaces_deoblique/zeroed_soundVrest_NEW-minimal_ico32-128_mh_50vx.niml.dset differs in size from first one

This error suggests that the number of vertices is not matched across subjects. Probably there are nodes that have values from some subjects but not others (e.g. when running a searchlight analysis with partial brain coverage, i.e. when the functional data does not contain all of the surface node in some subjects).

Try using the “--pad_to_node” option in afni_surface_alphasim. In your case, ico32 means 10*(32*32)+2=10240 nodes per hemisphere, and you use merged hemispheres. The value for pad_to_node is then (10*(32*32)+2)*2-1=20479, where the “-1” is for the 0-base indexing used by afni.

Please let us know if that solves the problem.