Think I caught a long-standing bug in my momentum update code: I was re-assigning TensorVariables to the self.updates dict, when instead I should have been adding the
theano.shared values of that same dict to the mod_updates dict passed to the theano.function calls in pretraining, finetuning functions to perform the parameter update
tracking.  This might simplify my NAG update code.  I've included param name debugging to try and find if I'm assigning the updating properly.