Paul E. Schoen wrote:

And it appears that he is making some progress at becoming better
socialized now that he is interacting with caring people. That is not
"total shutdown", which would be, essentially, a coma.

You have no experience with dogs who are (or have been) in total
shutdown.

So far, except for myself and Sparrow, only JH has attempted to supply some
actual advice and encouragement.

Bad advice is worse than none at all.

I haven't offered any because although I did rescue for 10 years nothing
in my experience is particularly relevant to what this poster is describing
- most of my fosters were Briards, OES and Beardies, which are temperamentally
QUITE different than Eskies.

The two closest we Chloe (an OES that I permanently adopted) had been
subjected to near-complete sensory deprivation as had the dog the OP was
describing, but her response was the complete opposite of that dogs: initially
any stimulation sent her into screaming hysterics. It took several years to
get her settled down, but she eventually turned into a fine dog although she
remained permanently less stress-tolerant than I would consider typical.

Chester was a Briard and I was told nothing of his early life by the &*($#@!
owner who gave him up to me (who conveniently told me absolutely nothing about
his extreme shyness). I drove 8 hours to pick up a dog that turned out to be
nearly catatonic to the point that I couldn't get him out of the crate when
I got home. (My mantra the first few weeks was "please, dog, PLEASE don't
make me have to put you down...") Obviously he was so f'ed up that he ended
up having to be a long-term foster (9 months). I pretty much let him take
things at his own pace and he eventually turned out to be a sweet and even
attention-soliciting dog, though again he was never as reslient as I would've
liked. Ironically, I ended up placing him in a therapy-dog home where he
turned out to excel at his job.

But again, those were both herding dogs, bred to bond strongly with humans,
and quite different from northern breeds like Eskies. And none of the 20 or
so other foster dogs I had had anything in common with what the OP described.

So that's just FWIW.

Dianne