Triggered on mouseover :

function() {


  clearInterval(interval);
  clearInterval(secondInterval);

  interval = setInterval(function() {
    for (var j = 0; j < step; j++) {
      var tmpIndex = lettersIndex + j;
      if (tmpIndex < lettersLength)
        jQuery(letters[tmpIndex]).addClass('red-letter');

      var tmpReverseIndex = lettersLength - (tmpIndex + 1);
      if (tmpReverseIndex >= 0)
        jQuery(letters[tmpReverseIndex]).addClass('ae-underline');
    }

    lettersIndex += step;
    if (lettersIndex >= lettersLength) {
      lettersIndex = lettersLength;
      clearInterval(interval);
      /*secondInterval = setInterval(function(){
         jQuery(letters[lettersIndex2]).addClass('red-bg');
         lettersIndex2++;
         if(lettersIndex2 >= lettersLength)
           clearInterval(secondInterval);

      }, speed);
      */
    }

  }, speed);

}

Triggered on mouseout :

function() {
  clearInterval(interval);
  clearInterval(secondInterval);

  interval = setInterval(function() {


    /*jQuery(letters[lettersIndex]).removeClass('red-letter');
    jQuery(letters[lettersLength - (lettersIndex + 1)]).removeClass('ae-underline');
    */

    for (var j = 0; j < step; j++) {
      var tmpIndex = lettersIndex + j;
      if (tmpIndex < lettersLength)
        jQuery(letters[tmpIndex]).removeClass('red-letter');

      var tmpReverseIndex = lettersLength - (tmpIndex + 1);
      if (tmpReverseIndex >= 0)
        jQuery(letters[tmpReverseIndex]).removeClass('ae-underline');
    }

    lettersIndex -= step;
    if (lettersIndex < -1) {
      clearInterval(interval);
      lettersIndex = 0;
    }

    /*
    jQuery(letters[lettersIndex2]).removeClass('red-bg');
    lettersIndex2--;
    if(lettersIndex2 < 0){
      clearInterval(interval);

      secondInterval = setInterval(function(){
         jQuery(letters[lettersIndex]).removeClass('red-letter');
         lettersIndex--;
         if(lettersIndex < 0 )
           clearInterval(secondInterval);

      }, speed);


    }
    */

  }, speed);
}