12.         Stock-based Compensation

The Company's Amended and Restated 2014 Equity Incentive Plan (the "2014 Plan") expired on  January 31, 2024. Following such expiration, no grants  may be made under the 2014 Plan, but the grants in effect prior to such expiration were not impacted by the expiration. 

Stock Options

The following table summarizes information about the Company’s stock options outstanding as of March 31, 2024, and activity during the three months then ended:

There were no stock options awarded during the three months ended March 31, 2024 and 2023, and no unrecognized compensation cost related to unvested stock options as of March 31, 2024.

Restricted Stock Units

The Company issues time-based restricted stock units (“RSUs”) and performance-based restricted stock units ("PSUs") to employees and non-employee members of the Board. Each RSU and PSU represents the right to receive one share of the Company’s common stock upon vesting and subsequent settlement. PSUs vest upon achievement of performance targets based on the Company's annual operating plan. The fair values of RSUs and PSUs are determined based on the closing price of the Company’s common stock on the date of grant.

Combined RSU and PSU activity for the three months ended March 31, 2024 is summarized below:

As of March 31, 2024, $1,007 of total unrecognized compensation expense related to unvested RSUs and PSUs was expected to be recognized over a weighted average period of 1.30 years.

Compensation Expense

Stock-based compensation expense is included in the condensed consolidated statements of operations and comprehensive loss in general and administrative, research and development, or sales and marketing expenses, depending on the nature of the services provided. Stock-based compensation expense related to options, RSUs and PSUs was recorded as follows:

401(k) Plan Share Match

During the three months ended March 31, 2024, the Company issued 163 shares of common stock with a fair value of $237, to eligible employees’ deferral accounts for the 401(k) Plan matching contribution representing 50% of each eligible employee’s elected deferral (up to the statutory limit) for the years ended December 31, 2023. No shares related to the 401(k) Plan matching contribution were issued during the three months ended March 31, 2023. 

The expense for the 401(k) Plan share matching was $29 and $93 for the three months ended March 31, 2024 and 2023, respectively.