The Company recorded approximately $93,000 and $11,000 of stock-based compensation related to employee and non-employee stock options for the three months ended March 31, 2015 and 2014, respectively. As of March 31, 2015, there was $2,266,000 of unrecognized compensation cost related to outstanding options that is expected to be recognized as a component of the Company’s operating expenses over a weighted average period of 1.1 years.

As of March 31, 2015, an aggregate of 53,599,046 shares of common stock were reserved for issuance under the Company’s 2007 Equity Incentive Plan, including 21,143,880 shares subject to outstanding common stock options granted under the plan and 31,157,015 shares available for future grants. The administrator of the plan determines the times when an option may become exercisable at the time of grant. Vesting periods of options granted to date have not exceeded five years.  The options generally will expire, unless previously exercised, no later than ten years from the grant date. The Company is using unissued shares for all shares issued for options and restricted share awards.

The following schedule presents activity in the Company’s outstanding stock options for the three months ended March 31, 2015 (in thousands, except per share amounts): 

The aggregate intrinsic value of outstanding and exercisable options at March 31, 2015 was calculated based on the closing price of the Company’s common stock as reported on the Over-the-Counter Bulletin Board and the OTCQx markets on March 31, 2015 of $1.46 per share less the exercise price of the options. The aggregate intrinsic value is calculated based on the positive difference between the closing fair market value of the Company’s common stock and the exercise price of the underlying options.