"i then pointed out that gold reached its peak at the end of 2011"
Gold peaked in August/September 2011, thats Q3 so not the end of 2011.
Central banks buy/sell gold via OTC transactions, not via the spot markets of futures exchanges, their transactions have very little bearing on the price or volumes you or I can see (queue timber1956 to explain it 500 times better than I can).
The below may help answer your questions (???????) regarding if they have stopped buying, article posted yesterday on Reuters.