Corporate insiders sell their own companies' stock for a number of reasons. ¿

They might need the cash for a big personal purchase such as a new house or yacht, or they might need the cash to fund a charity. Sometimes they sell as part of a planned selling program that they have put in place for diversification purposes, which allows them to sell stock in stages instead of selling all at one price.

Other times they sell because they think their stock is overvalued and the risk/reward is no longer attractive. Some even dump their own stock because they have inside knowledge that a competitor is eating their lunch and stealing market share. ¿

But insiders usually buy their own shares for one reason: They think the stock is a bargain and has tremendous upside.

The key word in that last statement is "think." Just because a corporate insider thinks his or her stock is going to trade higher, that doesn't mean it will play out that way. Insiders can have all the conviction in the world that their stock is a buy, but if the market doesn't agree with them, the stock could end up going nowhere. Also, I say "usually" because sometimes insiders are loaned money by the company to buy their own stock. Those loans are often sweetheart deals and shouldn't be viewed as organic insider buying.

At the end of the day, it's institutional money managers running big mutual funds and hedge funds that drive stock prices, not insiders. That said, many of these savvy stock operators will follow insider buying activity when they agree with the insider that the stock is undervalued and has upside potential. This is why it's so important to always be monitoring insider activity but twice as important to make sure the trend of the stock coincides with the insider buying.

Recently, a number of companies' corporate insiders have bought large amounts of stock. These insiders are finding some value in the market, which warrants a closer look at these stocks.

Barnes & Noble Education

One specialty retailer that insiders are active in here is Barnes & Noble Education(BNED) - Get Report , which retails educational content and tools in the U.S. Insiders are buying this stock into large weakness, since shares have dropped sharply by 36.6% over the last six months.

Barnes & Noble Education has a market cap of $451 million and an enterprise value of $236 million. This stock trades at a reasonable valuation, with a trailing price-to-earnings of 42.6 and a forward price-to-earnings of 29.2. This is a cash-rich company, since the total cash position on its balance sheet is $214.28 million and its total debt is zero.

A beneficial owner just bought 488,348 shares, or about $4.3 million worth of stock, at $8.77 per share.

From a technical perspective, Barnes & Noble Education is currently trending below both its 50-day and 20-day moving averages, which is bearish. This stock recently gapped-down sharply lower from around $13.50 to under $9.50 a share with heavy downside volume flows. Following that move, shares of Barnes & Noble Education have now attempted to form a double bottom chart pattern, since shares have found some buying interest at $8.15 to $8.54 a share. This stock is now starting to spike within range of triggering a near-term breakout trade.

If you're bullish on Barnes & Noble Education, then I would look for long-biased trades as long as this stock is trending above those recent double bottom support levels and then once it breaks out above some near-term overhead resistance levels at $10 to $10.30 a share with high volume. Look for a sustained move or close above those levels with volume that registers near or above its three-month average action of 445,327 shares. If that breakout hits soon, then this stock will set up to re-test or possibly take out its next major overhead resistance level at its gap-down-day high from December at $11.31 a share. Any high-volume move above $11.31 will then give this stock a chance to re-fill some of its previous gap-down-day zone that stared near $13.50 a share.

Tuesday Morning

Another discount variety stores player that insiders are jumping into here is Tuesday Morning(TUES) - Get Report , which operates as a retailer of upscale decorative home accessories, housewares, seasonal goods and gifts in the U.S. Insiders are buying this stock into massive weakness, since shares have plunged by 49.2% over the last six months.

Tuesday Morning has a market cap of $237 million and an enterprise value of $210 million. This stock trades at a reasonable valuation, with a trailing price-to-earnings of 22.5 and a forward price-to-earnings of 13. Its estimated growth rate for this year is 8.3%, and for next year it's pegged at 57.7%. This is a cash-rich company, since the total cash position on its balance sheet is $23.28 million and its total debt is zero.

The CEO just bought 1,055,467 shares, or about $5.42 million worth of stock, at $5.12 to $5.14 per share.

From a technical perspective, Tuesday Morning is currently trending below both its 50-day and 200-day moving averages, which is bearish. This stock has been consolidating and trending sideways over the last three months and change, with shares moving between $5.02 on the downside and $7.36 on the upside. Any high-volume move above the upper-end of its recent sideways trending chart could trigger a big breakout trade for shares of Tuesday Morning.

If you're in the bull camp on Tuesday Morning, then I would look for long-biased trades as long as this stock is trending above its recent low of $5.02 a share and then once it breaks out above its 50-day moving average of $6.22 to some more near-term overhead resistance at $6.50 to $6.65 a share with volume that hits near or above its three-month average action of 629,108 shares. If that breakout fires off soon, then this stock will set up to re-test or possibly take out its next major overhead resistance levels at $6.90 to $7.36, or even $7.83 to $8.22 a share.

Aquinox Pharmaceuticals

One clinical-stage pharmaceutical player that insiders are snapping up here is Aquinox Pharmaceuticals (AQXP) , which engages in discovering and developing targeted therapeutics for diseases in the areas of inflammation and immuno-oncology. Insiders are buying this stock into massive strength, since shares have ripped higher by 412.7% over the last six months.

Aquinox Pharmaceuticals has a market cap of $158 million and an enterprise value of $41.4 million. This stock trades at a fair valuation, with a price-to-book of 1.39. Its estimated growth rate for this year is 34.9%, and for next year it's pegged at 3.4%. This is a cash-rich company, since the total cash position on its balance sheet is $117.41 million and its total debt is zero.

A beneficial owner just bought 202,623 shares, or about $1.67 million worth of stock, at $7.91 to $8.56 per share.

From a technical perspective, Aquinox Pharmaceuticals is currently trending below both its 50-day and 200-day moving averages, which is bearish. This stock has been downtrending badly over the last five months, with shares falling sharply off its high of $24.50 to its recent low of $7.64 a share. During that downtrend, shares of Aquinox Pharmaceuticals have been making mostly lower highs and lower lows, which is bearish technical price action. That said, this stock has now started to spike higher off its recent low of $7.64 a share, and it's beginning to trend within range of triggering a near-term breakout trade.

If you're bullish on Aquinox Pharmaceuticals, then I would look for long-biased trades as long as this stock is trending above its recent low of $7.64 a share then once it breaks out above some near-term overhead resistance at $10 a share with high volume. Look for a sustained move or close above those that level with volume that registers near or above its three-month average action of 236,784 shares. If that breakout develops soon, then this stock will set up to re-test or possibly take out its next major overhead resistance levels at its 200-day moving average of $10.76 to its 20-day moving average of $11.15, or even its 50-day moving average of $11.82 a share.

Northern Oil & Gas

One independent energy player that insiders are in love with here is Northern Oil & Gas(NOG) - Get Report , which engages in the acquisition, exploration, development, and production of oil and natural gas properties in the U.S. Insiders are buying this stock into large weakness, since shares have plunged by 54% over the last six months.

Northern Oil & Gas has a market cap of $160 million and an enterprise value of $1 billion. This stock trades at a fair valuation, with a price-to-sales of 0.68. Its estimated growth rate for this year is -18.9%, and for next year it's pegged at -128.6%. This is not a cash-rich company, since the total cash position on its balance sheet is $7.04 million and its total debt is $867.68 million.

A beneficial owner just bought 780,724 shares, or about $2.30 million worth of stock, at $2.84 per share. That same beneficial owner also just bought 436,682 shares, or about $1.36 million worth of stock, at $3.05 per share.

From a technical perspective, Northern Oil & Gas is currently trending below both its 50-day and 200-day moving averages, which is bearish. This stock has been downtrending badly over the last three months and change, with shares moving sharply lower off its high of $5.95 to its new 52-week low of $2.51 a share. During that downtrending, shares of Northern Oil & Gas have been making mostly lower highs and lower lows, which is bearish technical price action. That move has now pushed this stock into extremely oversold territory, since its current relative strength index reading is 22.9. Oversold can always get more oversold, but it's also an area where a stock can experience a strong bounce higher from if buyers step back into the name.

If you're bullish on Northern Oil & Gas, then I would look for long-biased trades as long as this stock is trending above some its new 52-week low of $2.51 a share and then once it breaks out above some near-term overhead resistance levels at $2.90 to $3 a share and then above more resistance at $3.25 a share with high volume. Look for a sustained move or close above those levels with volume that registers near or above its three-month average action of 1.52 million shares. If that breakout develops soon, then this stock will set up to re-test or possibly take out its next major overhead resistance levels at its 20-day moving average of $3.53 to $4, or even $4.20 a share.

Lionbridge Technologies

One final stock with some decent insider buying is business services player Lionbridge Technologies (LIOX) , which provides language, content and testing solutions worldwide. Insiders are buying this stock into big weakness, since shares have dipped sharply by 32% over the last six months.

Lionbridge Technologies has a market cap of $264 million and an enterprise value of $312 million. This stock trades at a cheap valuation, with a trailing price-to-earnings of 25.7 and a forward price-to-earnings of 9.7. Its estimated growth rate for this year is 69.2%, and for next year it's pegged at 90.9%. This is not a cash-rich company, since the total cash position on its balance sheet is $30.93 million and its total debt is $94.15 million.

A beneficial owner just bought 307,367 shares, or about $1.28 million worth of stock at $4.11 to $4.24 per share. From a technical perspective, Lionbridge Technologies is currently trending below both its 50-day and 200-day moving averages, which is bearish. This stock has been downtrending badly over the last two months and change, with shares moving sharply lower off its high of $6.26 to its new 52-week low of $3.93 a share. During that downtrend, shares of Lionbridge Technologies have been consistently making lower highs and lower lows, which is bearish technical price action. That said, this stock has now started to spike a bit off that $3.93 low, and it's now beginning to move within range of triggering a near-term breakout trade.

If you're bullish on Lionbridge Technologies, then I would look for long-biased trades as long as this stock is trending above its new 52-week low of $3.93 a share and then once it breaks out above some near-term overhead resistance levels at $4.20 to $4.30 a share with high volume. Look for a sustained move or close above those levels with volume that hits near or above its three-month average volume of 239,442 shares. If that breakout gets set off soon, then this stock will set up to re-test or possibly take out its next major overhead resistance levels at $4.40 to its 20-day moving average of $4.48, or even $4.60 to $4.80 a share. Any high-volume move above $4.80 will then give this stock a chance to trend north of $5 a share.

Disclosure: This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.