5. Stock-based Compensation

The Company recognized stock-based compensation on all employee and non-employee awards as follows:

The following table summarizes the stock option activity during the three months ended March 31, 2021:

(1) The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying stock option awards and the closing market price of our common stock as of December 31, 2020 and March 31, 2021, respectively.

Total unrecognized compensation cost related to unvested stock options was $1,163,496 as of March 31, 2021 and is expected to be recognized over a weighted-average period of less than two years.

As of March 31, 2021, 537,901 shares of common stock are available for future awards under the 2012 Equity Incentive Plan (the “Plan”).

Each executive officer and non-employee director receiving equity-based awards is subject to a minimum dollar value stock ownership holding requirement with respect to the awards received as well as all prior equity awards under the Plan which requirements are intended to align the ability to sell shares with the performance of the Company’s stock price. The executive officer recipients each have a minimum dollar value stock ownership holding requirement threshold equal to two times (2x) their then base salaries below which dollar threshold they would be precluded from selling any shares of Company stock obtained from the Company under its Plan. Also, the non-employee directors are each subject to a minimum dollar value stock ownership holding requirement threshold equal to six times the annual Board retainer ($270,000) below which dollar threshold they would be precluded from selling shares of Company stock acquired from the Company under its Plan.