It seems to happen only when she gets knocked out in battle and NEVER HAPPENED before Amon knocked her out by hitting her Chi point on her forehead. 

I’m still of the opinion that Amon is trying to force her into the Avatar State and what we’re seeing might be what Aang did to bury the Avatar State deep within Korra.

I think Aang did something horrible and changed what it means to be The Avatar. Perhaps we’re already State-less and that’s going to surprise Amon as much as it surprises Korra.

We have no evidence Korra has ever accessed the Spirit World. EVER, so I don’t think she’s in contact with Aang at all at this point.

Oh Aang, you always change EVERYTHING. 

… even The Simpsons:

-Da7e-