There is a sample in our samples browser that shows exactly how to do this:
http://samples.infragistics.com/2008.2/webfeaturebrowser/default.htm
Under Aikido/WebImageViewer: Both the "Customizing the Header" and "Client-Side Events" samples use this method:
var item = imageViewer.get_items().getItem( 4 );
imageViewer.get_scrollAnimations().get_nextItemAnimation().moveItemIntoFocus(item);
The code above shows how to scroll the 5th item into view.
Hope this helps:
-SteveZ