WINDERMERE, Fla. ( Stockpickr) -- Professional traders running mutual funds and hedge funds don't just look at a stock's price moves; they also track big changes in volume activity. Often when above-average volume moves into an equity, it precedes a large spike in volatility. >>5 Bargain Stocks to Buy Before 2013 Major moves in volume can signal unusual activity, such as insider buying or selling -- or buying or selling by "superinvestors." Unusual volume can also be a major signal that hedge funds and momentum traders are piling into a stock ahead of a catalyst. These types of traders like to get in well before a large spike, so it's always a smart move to monitor unusual volume. That said, remember to combine trend and price action with unusual volume. Put them all together to help you decipher the next big trend for any stock. With that in mind, let's take a look at several stocks rising on unusual volume today. Abiomed Abiomed ( ABMD) is a provider of mechanical circulatory support devices and it offers a continuum of care in heart recovery to heart failure patients. This stock is trading up 5.8% at $14.41 in recent trading. Today's Volume: 2.06 million Average Volume: 679,236 Volume % Change: 412% From a technical perspective, ABMD is trending higher here with above-average volume. This move is coming following a large gap down that took ABMD from $20 to $13.12 with heavy volume. That plunge has now pushed ABMD into oversold territory, since its relative strength index (RSI) reading is now 26. Oversold can always get more oversold, but ABMD could continue to spike higher if it takes out its gap down day high. Traders should now look for long-biased trades in ABMD once it manages to sustain a move or close above its gap down day high of $15.90 with volume that hits near or above 679,236 shares. If that breakout triggers soon, then look for ABMD will have a great chance to re-fill some or its entire gap down zone that started near $20. Focus Media Focus Media ( FMCN) is engaged in selling out-of home television advertising time slots on its network of flat-panel television advertising displays located in high traffic areas such as commercial locations and in-store network. This stock is trading up 3.7% at $24.75 in recent trading.