Neuroscience explains only functional things it does not explain consciousness

Neuorscience seems to explain only things defined in functional terms. Consciousness cannot be given a functional definition so it cannot be neuroscientifically explained

Neuroscience is very useful and can of course be used to explain 

many things. For instance, memory in sea slugs is explainable in terms of synaptic strength and gene expression. 

But it seems only things defined in functional terms can be explained (e.g.the neural mechanism that explains memory function).The problem is then the following: consciousness cannot be given a functional definition so it cannot be neuroscientifically explained.