OK, imagine a mouse in a cage. With Promethion, you can monitor that mouse’s position to within a calculated centroid of 2.5 mm (several times higher resolution than legacy systems). You do this with an infrared light array. So, what do you do with those data?
Well, you can of course calculate the time which the mouse spends in various areas of the cage. Depending on your research goals, this can be quite informative. Here’s a graphic representation. Note that in these views, you should mentally move the running wheel a bit to the left; the spot shown in the running wheel is actually just to the right of it, and corresponds to the mouse’s last recorded position before it entered the wheel.
Well, that gives you some information regarding the mouse’s favored positions. But what is the metabolic state of the mouse in each of these areas? With Promethion, it’s easily possible to find out because all of the data from all of the sensors in the system are synchronized. How about VO2 vs. position?
Now we’re seeing something interesting. This mouse was measured at 29 oC, within its thermal neutral zone, so its resting metabolic rate was around 0.6 ml O2 min-1. There are certain areas characterized by much lower, or higher, VO2s than others. Wouldn’t it be informative to know the characteristic RQs at each location, which would tell us about its respiratory substrate utilization across space? Certainly.
…and this visualization tells us a lot more about the metabolic nature of this mouse, and shows us its resting areas (low RQ) very clearly. Now, think of the applications of this type of visualization for thermogenesis research (hello, BAT)?
Update! For an interactive, graphic exploration of how multiplexing distorts metabolic data, be sure to visit the multiplexing visualization page on this site. Have fun!
As usual, thanks to Thomas Förster, Ph.D., Sable Systems International’s expert in-house data analysis and data presentation consultant, for creating the graphs.
— John Lighton