Overcomplete ICA
What if we have more independent sources than data
components? (independent \= orthogonal)
The data no longer specifies a unique vector of
source activities. It specifies a distribution.
This also happens if we have sensor noise in square case.
The posterior over sources is non-Gaussian because
the prior is non-Gaussian.
So we need to approximate the posterior:
MCMC samples
MAP (plus Gaussian around MAP?)