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Exercise and the Brain Exercise 4.19 on page 232 describes a study investigating the effects of exercise on cognitive function. \(^{28}\) 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 7 th 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?

Step by step solution

01

Interpret Result (a)

Result (a) saw exercise improving Y-maze performance by the 7th day of exposure, with further increases after 10 days for all mice tested \(p<.01\). A p-value of less than 0.01 indicates that the probability of observing these results (or more extreme), given that the null hypothesis is true, is less than 1%. Thus, there is strong evidence against the null hypothesis that exercise has no effect on Y-maze performance, and in favor of the alternate hypothesis that exercise does improve Y-maze performance.

02

Interpret Result (b)

Result (b) saw levels of BMP reduced after only two days of running and it remained decreased for all subsequent time points \((p<.01)\). A p-value of less than 0.01 suggests that the probability of seeing these results, assuming the null hypothesis that exercise has no effect on BMP levels, is less than 1%. This provides strong evidence against the null hypothesis and in favor of the alternate hypothesis that exercise does decrease BMP levels.

03

Interpret Result (c)

Result (c) saw levels of noggin didn't change until 4 days, but had increased 1.5 fold by 7-10 days of exercise \((p<.001)\). The p-value less than 0.001 indicates that the probability of observing these results, given the null hypothesis is true (i.e., exercise has no effect on noggin levels), is less than 0.1%. Hence, there is overwhelming evidence against the null hypothesis and in favor of the alternate hypothesis that exercise significantly increases noggin levels.

04

Identify Strongest Statistical Effect

Comparing the p-values from the three tests, the noggin test shows the strongest statistical effect because it has the smallest p-value. This suggests that the observed difference is very unlikely to have occurred by chance, therefore, it provides strong evidence for the alternate hypothesis that exercise increases noggin levels.

05

Conclude Effects of Exercise

Based on these results, it can be concluded that exercising has beneficial effects on mice, particularly in enhancing cognitive function (improved Y-maze performance), reducing levels of BMP (a protein that hinders brain function), and increasing levels of noggin (a protein that boosts brain ability).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Exercise and Brain Function

Regular physical activity has been shown to have numerous effects on the brain and its functions. When it comes to cognitive skills, exercise can be a real game-changer. How so? Well, the brain's functioning is enhanced through exercise as it can improve memory, learning, and even mental agility.
Among the molecules influencing cognition is BMP, which exercise reduces. This protein's presence is generally associated with slower brain responses. By decreasing BMP levels, exercise accelerates brain activity, making it more efficient.
Additionally, exercise in mice increased noggin, a protein renowned for enhancing brain capabilities. By interacting with brain cells, noggin supports the formation and maturation of neurons. This increase was particularly noted after prolonged physical activity, as highlighted in the study's results after 7 to 10 days of exercise.
Overall, regular exercise can improve the speed of learning and problem-solving capabilities, thus boosting cognitive function.

Statistical Significance

Statistical significance is a critical concept in research and science. It helps determine whether the findings of a study are likely due to chance or if there is indeed an important effect present.
In this exercise, the researchers used different p-values to assess the significance of changes due to exercise in mice. A result is typically considered statistically significant if its p-value is below a certain threshold, often 0.05. This threshold represents a 5% probability that the results observed happened by random chance, assuming the null hypothesis is true.

• If a result is statistically significant, it means it is probably not just a fluke.
• The lower the p-value, the stronger the evidence against the null hypothesis, indicating a true effect exists.

In this study, BMP and Y-maze performance improvements showed a p-value of less than 0.01, while noggin levels had an even smaller p-value of less than 0.001. These low p-values suggest strong statistical significance, supporting the hypothesis that exercise affects these areas.

P-Value Interpretation

Understanding p-values is vital in interpreting scientific results. In this exercise, p-values help determine the strength and validity of the results obtained through testing. A p-value measures how likely it is to observe results at least as extreme as studied, assuming the null hypothesis is true.
Here's how to interpret p-values:

• A p-value less than 0.05 usually indicates statistical significance, suggesting real effects beyond chance.
• Lower p-values mean stronger evidence against the null hypothesis. Thus, a p-value less than 0.01, as in this study for BMP reduction and Y-maze performance, shows very strong evidence of a true effect.
• An even smaller p-value, like the one indicating noggin increases ( <0.001), suggests overwhelming evidence of an effect.

Thus, interpreting these p-values, the results consistently demonstrate that exercise impacts brain function in mice significantly. Understanding and correctly interpreting p-values is crucial for drawing valid conclusions and guiding further scientific inquiry.