Is this a central control issue?

On move 13...Nxe5, I got blasted by the computer as making a mistake. I really need to understand why? My thought in taking the knight here was to not allow the white knight to hang out in such an annoying post. I also wanted to attempt to break up the pawns in the middle. Fortunately the computer deemed my opponents next move as a mistake too, so I should have been able to redeem myself. Regardless, I'm curious on some additional thoughts on 13...Nxe5 and why this is a mistake. What is logically better? I know what the computer says is better but I want to hear it from humans. Thanks in advance to everyone who participates here...in my previous posts your feedback has been very helpful. 

Without consulting an engine...  (I think the engine's suggestions here might be quite revealing) ... Nxe5 certainly looks worth considering: His N on e5 is obviously good, your N on d7 obviously less good, so why not exchange? Well, I think I'd reject Nxe5  because the pawn structure after the recapture looks worrying. I'm not even sure dxe5 is his correct response after NxN. I think fxe5 might be even stronger (I'm truly not sure... I'd ponder that one a while as White... but dxe5 or fxe5, having that pawn planted on e5 can really cramp a game. Your move might be a "mistake" not because it's an outright terrible move, but because you had better. The e2 square with Be2;Bc4 is intriguing. (That Bishop looks like it might have some long term problems if White gets aggressive on the Kingside) This leads to the idea of kicking his N on c3 to free up the e2 square, and suddenly b4! looks attractive all on it's own: that Nc3 doesn't have any good squares -- and the position gets extremely interesting IMO -- after his N moves the b pawn will need protecting, but really mobilizing the queenside pawns seems like it has lots and lots of possibilities. Transfering the Bh5;e2;c4 looks interesting. I really like b4! An engine probably says 0-0 is right :(

*darn it mr.gottlieb, must you always post while I'm composing!

I didn't look at Qb6 at all... hmmm... *strokes chin meaningfully*

Did you just give the board a quick glance and see Qb6?  That was actually the engine move. Is it the pin on the pawn that lead you to that conclusion or just from experience as you mention that Qb6 is a move worth looking at? I never even considered that move (in any game for that matter) I tend to look at Rc8 to stack the queen and rook in this type of position. Anyhow, Qb6 does look good after poking around with it a bit....I kind of like Rc8, castle and b4 after that if possible. 

Aside from Qb6 being a better move, that still begs the question why does the engine consider Ne5 a mistake?  I think you had the opportunity of making white have an isolated pawn by exchanging pawns with dxe4, which leaves white's d pawn isolated and difficult to defend.  Instead, by Nxe5, that sets up d or fxe5, driving your knight off f6 (it either needs to retreat or go to the temporary g4 post from which it can again be driven off), giving white tempo, and allowing white to later play exd5 causing black to now have the isolated pawn after recapturing exd5.

I got a second opinion from Chessmaster X. The original computer was the chess.com engine. Top 3. 

1. Qb6
2. b4
3. Nxe5

very interesting to see my move in the top 3 and be called a mistake on chess.com. Although chessmaster gave it a full point toward the white side.  

But it is a mistake and b4 is certainly an inaccuracy -- the best that can be said of it is that it might be surviveable.  That's not uncommon, there are many positions where one move is forced and anything else is a dreadful mistake. But this position is interesting in that it is illustrative position of the difference between computers and people.  Neither Nxe5 and b4 or anything else are 'positional' errors to the computer.  The engine refutes them tactically winning material for White down deep variations (stockfish after a few minutes, btw, sees Qb6 as leading to a forced draw.) To a human the position is complicated enough that one relies on positional judgment rather than exactly calculated variations to say 'oh Nxe5 doesn't look so hot' -- but the engine sees, clearly, that there is only one move that puts enough pressure on White to keep White from unleashing his own strong moves. According to Stockfish 1.9.1 one second best move from Black and White gets a winning game here. It doesn't look that way to me, or to most humans I'll wager, because we don't play 3000 elo chess. 

Correction, 2.Kf2! wins.