Wow! Your question is a very interesting one!
I don't have a degree in dog psychology but have been around dogs my whole life and am very aware of what they do. So here's a story that just might help you.
I have a giant breed dog 10yrs old, with arthritis in his spine and he's 3 yrs post surgery for a 'blown out knee'. Every once in awhile he starts limping for unknown reasons. It usually dissapears in a day or so. About 3 months ago he started limping again and it wasn't going away. He's a velcro dog and always comes upstairs with me during he day while I work on the computer and also to sleep in my bedroom. One day I heard him come up a few stairs and then yelp. He went back down immediately. I started him on Rimadyl. (pain, anti-inflamatory) and he stopped limping but refused to come upstairs, actiing like he was afraid of the stairs.No amount of coaxing or temptations with bones, etc would get him to come up more that a few stairs. He didn't come up the stairs for about a month, and I began thinking that he was 'just too old' and I'd never have my buddy around me again. One day we had a thunderstorm, and my poor dog has always been afraid of thunder. Lo and behold.....he comes upstairs like it's nothing. Been coming upstairs ever since without any problems at all, and he's been off the rimadyl for a long time.
Moral of the story........I definitely think they can 'associate' a place in the home that depress or scares them and causes them to 'act differently'. If I were you, I'd begin feeding him outside, giving pills outside, find a toy or bone or something that he really likes and play with him outside with it like nothing is wrong with him and you just love him like he's still a puppy. Then after a few days or so, bring the toy inside where he acts listless and try to play with him. I'd also begin acting like that place in your home is a happy place and give him lots of attention, playing, silly noises, playful belly rubs, etc. Anything that you know makes him 'act like a puppy' when you do it. My hopes are that, like my dog, he'll get his mind off of thinking that inside the house is a bad place, where he gets pills, pain, etc. and will begin acting like he used to. It's all just a guess of course, but I have no other explanation for what happened with my dog, so I offer my 'advice' to you.
I'd really like you to write back to me after you try my suggestions (if you do) and tell me how it went. I wish you best of luck and a long life for your dog.
Sandy