Exercise 4.19 on page 232 describes a study investigating the effects of exercise on cognitive function. Separate groups of mice were exposed to running wheels for 0, 2, 4, 7, or 10 days. Cognitive function was measured by Y-maze performance. The study was testing whether exercise improves brain function, whether exercise reduces levels of BMP (a protein which makes the brain slower and less nimble), and whether exercise increases the levels of noggin (which improves the brain’s ability). For each of the results quoted in parts (a), (b), and (c), interpret the information about the p-value in terms of evidence for the effect.

(a) ‘‘Exercise improved Y-maze performance in most mice by the 7th day of exposure, with further increases after 10 days for all mice tested (p < .01).”

(b) ‘‘After only two days of running, BMP. . . was reduced . . . and it remained decreased for all subsequent time-points (p < .01).”

(c) ‘‘Levels of noggin . . . did not change until 4 days, but had increased 1.5-fold by 7–10 days of exercise (p < .001).”

(d) Which of the tests appears to show the strongest statistical effect?

(e) What (if anything) can we conclude about the effects of exercise on mice?

Exercise 4.19

It is well established that exercise is beneficial for our bodies. Recent studies appear to indicate that exercise can also do wonders for our brains, or, at least, the brains of mice. In a randomized experiment, one group of mice was given access to a running wheel while a second group of mice was kept sedentary. According to an article describing the study, ‘‘The brains of mice and rats that were allowed to run on wheels pulsed with vigorous, newly born neurons, and those animals then breezed through mazes and other tests of rodent IQ” compared to the sedentary mice. Studies are examining the reasons for these beneficial effects of exercise on rodent (and perhaps human) intelligence. High levels of BMP (bone-morphogenetic protein) in the brain seem to make stem cells less active, which makes the brain slower and less nimble. Exercise seems to reduce the level of BMP in the brain. Additionally, exercise increases a brain protein called noggin, which improves the brain’s ability. Indeed, large doses of noggin turned mice into ‘‘little mouse geniuses,” according to Dr. Kessler, one of the lead authors of the study. While research is ongoing in determining which effects are significant, all evidence points to the fact that exercise is good for the brain. Several tests involving these studies are described. In each case, define the relevant parameters and state the null and alternative hypotheses.