On the December 16, 2014 tip I discussed 5 challenges facing the audience. The January 15, 2015 tip addressed the first challenge, "multi-tasking."
The second challenge is "information overload." The audience is limited in what it can understand. They don't know what slide is coming up next and it takes them a while to reorient with each new slide. As a start, take a look at the "slider sorter" view and ask yourself if the audience can possibly comprehend what you are about to present in 30 or 40 minutes.
Information overload also occurs at the level of the individual slide. The typical biomedical research slide is chock full of data, graphs, and images, most of which the speaker never discusses. If you don't discuss something, why is it on the slide? It only causes confusion.
The key to solving the information overload is to first establish the minimum amount of information you want to convey. Do this for the entire presentation and for each individual slide. For each slide ask yourself what you hope the audience will gain by looking at the slide and cut out any superfluous data or images. You can then be very deliberate and incremental about going above and beyond the minimum. There is a tendency for scientists to grab all their slides and power through them. That is starting with the maximum and the audience is almost always lost. See the September 2, 2014 "tip" about how to establish your minimum.