While the McGriddle is a tasty creation, the most pleasurable thing about the sandwich isn't the pancake or the bacon: it's the calories. According to a recent paper in Neuron, the brain also receives rewarding input from metabolic processes that have nothing to do with the tongue. When you eat at McDonald's, a big part of the pleasure comes from the fact that the food is sustenance, fuel, energy. Even mediocre food is a little rewarding.
The scientists at Duke came up with a clever paradigm for isolating this more indirect rewarding pathway: they studied mice without a functional TRPM5 channel, which is essential for detecting sweetness. As a result, these mutant mice showed no immediate preference for sugar water. But here comes the cool part of the experiment. The scientists then allowed the mice to spend some time with the sugar water and normal water. After a few hours, it became clear that the mutant mice greatly preferred the sugar water, even though they couldn't taste the sugar. (A control experiment with sucralose, an artificial sweetener, demonstrated that the rats were responding to the caloric intake, not the sweet taste.)
Finally, the scientists measured dopamine levels (via in vivo microdialysis) in the nucleus accumbens (a brain area that processes rewards) in the mutant mice and normal mice.* While normal mice exhibited an increase in dopamine in response to both fake sugar and real sugar - the reward was the sweet taste - the mutant mice only demonstrated a dopaminergic spike when consuming genuine sugar water. What they enjoyed were the calories.
At last count there were 150 colleges and universities featured on iTunesU, the section of Apple’s iTunes music store devoted to higher education. There’s great free downloadable content here — lots of lectures and entire courses, but sorting through all this material can be daunting. Unfortunately, most of the colleges offer little more than online brochures, with virtual campus tours and the like. (Newbies can get up to speed by reading The easiest ways to find classes.)
So here is a guide to the good stuff.
(Go here to read a list of some of the good lectures/courses offered!)
Perhaps the solution to this is a junk food tax. Ezra Klein thinks its unlikely to work because food is already so ridiculously cheap you'd need to jack up the price by too much., and points to this RAND-affiliated study as evidence.
Someone should write a play or novel about the brief moment in the antebellum south when American History when Chinese Coolie laborers were brought in to work the plantations. If you wanted to start researching such a thing, perhaps this book would be a good starting point.