bxSlider hover images

bxSlider hover images

Hi, I have a images bxSlider.

I'd like to change the selected image on hover.

Here is my code:

      <!-- Avatars bxSlider -->
      <div class="slider">
           <div class="slide">
                  <a href="#" data-toggle="tooltip" title="first tooltip">
                        <img src="_include/img/avatar_nat.png" alt="" title="">
                  </a>
            </div>
      </div>

How I can change avatar_nat.png image on hover ?

Thanks in advice.

-Antonio