Hi, 

There following codes can be used to convert your txt file to nifti file: 

hdr = spm_vol('Reslice_ch2.nii');
vol = spm_read_vols(hdr);
vol_new = zeros(size(vol));
value = load('ThreDeltaLoc.txt');
loc = load('location.txt');
loc = loc';
loc(4,:) = 1;
loc = round(hdr.mat\loc);
ind = sub2ind(hdr.dim,loc(1,:),loc(2,:),loc(3,:));
vol_new(ind) = value;
hdr_new = hdr;
hdr_new.fname = 'ThreDeltaLoc.nii';
hdr_new.dt(1) = 64;
hdr_new.descrip = '';
spm_write_vol(hdr_new,vol_new);

I also attached relevant files. I resliced the nifti file to a 5mm resolution according to your coordinates, you can use different resolution in other cases.

Best,
Mingrui