jQuery SerialScroll:添加类的活动项目

我使用Ariel Flesler的serialScroll脚本，并想添加一个类的活动，或突出显示的项目，所以我可以用CSS样式。在阅读文档时，我发现了notify触发器，但我不确定如何/是否可以使用它来完成此操作。

这是我的代码:

jQuery

jQuery(function( $ ){
    $('#slideshow').serialScroll({
        items:'li',
        prev:'#screen2 a.prev',
        next:'#screen2 a.next',
        offset:-180,
        start: 0,
        duration:1200,
        force:true,
        stop:true,
        lock:false,
        cycle:false,
        jump: true
    });
});

    <div id="screen2">
    <div id="buttons">
        <a class="prev" href="#">Previous</a>
        <a class="next" href="#">Next</a>
        <br class="clear" />
    </div>
    <div id="slideshow">
        <ul>
            <li><img src="http://www.stockvault.net/data/s/113497.jpg" /></li>
            <li><img src="http://www.stockvault.net/data/s/100177.jpg" /></li>
            <li><img src="http://www.stockvault.net/data/s/101916.jpg" /></li>
            <li><img src="http://www.dreamstime.com/animal-steps-in-snow-thumb12853223.jpg" /></li>
            <li><img src="http://www.dreamstime.com/animal-eggs-thumb15876342.jpg" /></li>
            <li><img src="http://www.dreamstime.com/animal-cat-thumb15385101.jpg" /></li>
            <li><img src="http://www.dreamstime.com/green-nature-thumb596309.jpg" /></li>
            <li><img src="http://www.dreamstime.com/office-in-nature-thumb3256171.jpg" /></li>
            <li><img src="http://www.dreamstime.com/nature-tree-thumb16030502.jpg" /></li>
            <li><img src="http://www.dreamstime.com/gift-of-the-nature-thumb15977958.jpg" /></li>
            <li><img src="http://www.dreamstime.com/nature-abstract-thumb3615419.jpg" /></li>
            <li><img src="http://www.dreamstime.com/nature-path-in-forest-with-sunshine-thumb8241130.jpg" /></li>
            <li><img src="http://www.dreamstime.com/nature-walk-thumb8436665.jpg" /></li>
            <li><img src="http://www.dreamstime.com/save-the-nature-thumb15696583.jpg" /></li>
        </ul>
    </div>
</div>

我是否误解了通知触发器的功能?如果有的话，有没有别的方法可以达到我的目的?

onBefore:function( e, elem, $pane, $items, pos ){
    /**
    * 'this' is the triggered element 
    * e is the event object
    * elem is the element we'll be scrolling to
    * $pane is the element being scrolled
    * $items is the items collection at this moment
    * pos is the position of elem in the collection
    * if it returns false, the event will be ignored
    */
    //those arguments with a $ are jqueryfied, elem isn't.
}