LR Question 17 Explanation, by LSATHacks
QUESTION TEXT: Science writer: The deterioration of cognitive faculties…
QUESTION TYPE: Strengthen
CONCLUSION: Microglia (immune cells in the brain) cause Alzheimer's.
REASONING: Microglia attack the proteins that build up during Alzheimer’s, poisoning the brain in the process. Also, acetylsalicylic acid (aspirin) can slow Alzheimer’s, but we’re not told how.
ANALYSIS: Part of the argument is okay. If microglia release poison when removing proteins from the brain, then maybe this could cause Alzheimer’s. This doesn’t prove the conclusion, but at least it shows how the brain could get hurt. We could strengthen this part of the argument by showing that microglia’s removal of PA proteins is the actual cause of Alzheimer’s.
But what does Aspirin have to do with it? The argument didn’t say how anti-inflammatories prove that microglia cause Alzheimer’s. We can strengthen the argument by showing how Aspirin proves that microglia cause Alzheimer’s. The right answer tells us that Aspirin reduces the amount of immune cells in the brain.
This is a hard question, with unfamiliar words. Note that I had to read this 2.5 times before I looked at the answer choices. If you read this, felt confused, but looked at the answer choices anyway, you made the mistake the LSAC wanted you to make.
The answers choices are no good to you if you don’t understand what you’ve read. You should always reread any stimulus you don’t understand. Even a quick look-over can do wonders for your understanding of the question.
___________
- This explains why proteins buildup in the brain, but it doesn’t prove that microglia cause Alzheimer’s. It’s true that microglia are part of the brain’s immune system, but maybe another part of the system causes the protein buildup. This also doesn’t help prove that PA proteins are part of the real cause of Alzheimer’s.
- CORRECT. Microglia are immune cells in the brain. If Acetylsalicylic acid gets rid of them and improves Alzheimer’s then maybe microglia are a cause of Alzheimer’s. It’s still weak evidence, but this at least explains why the argument mentioned Acetylsalicylic acid.
- This might slightly weaken the argument. The argument said Alzheimer’s patients suffer from a buildup of BA protein. This answer means that microglia help effectively combat one symptom of Alzheimer’s. We already know that microglia poison the brain, but this answer suggests there’s at least one benefit to the poisoning.
- This suggests that BA might be the cause of Alzheimer’s. So maybe microglia do the brain a favor by getting rid of BA, even if they have to use a bit of poison. This weakens the argument, slightly.
- So? This doesn’t tell us if microglia cause those diseases or whether the microglia are helping fight the diseases.
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Different analysis of D here: It seems to me it would strengthen the argument because it gives a mechanism for cognitive decline (which the prompt does not), but it says “directly” rather than “associated with Alzheimers”–am I wrong?
The conclusion of the argument in the stimulus is that the cognitive deterioration is caused by microglia. The argument supports this by saying microglia damage the brain while removing BA deposits.
If the BA deposits are causing the damage to cognitive function, the microglia are less responsible so the argument’s conclusion is weakened. So while you’re right that it gives a mechanism for cognitive decline, it’s not the mechanism that the argument is concluding, so the conclusion is weaker.
“it doesn’t prove that microglia cause Alzheimer’s.”
“This also doesn’t help prove that PA proteins are part of the real cause of Alzheimer’s.”
Hi Graeme, I’m not sure how you got to this. The way I see it is as follows
Deficiency in Brains Immune System Causes Brain’s Inability to Eliminate BA Proteins, which causes Microglia to attack these Protein Deposits according to the stimulus, which causes Deterioration of the Brain associated with Alzheimers.
How does this not prove that Microglia causes Alzheimers .. when the premise literally says Micgoglia’s attack causes the deterioration of the brain?
The stimulus is arguing that Alzheimer’s is caused by the activities of microglia. Answer A (saying that the buildup is due to an immune deficiency) doesn’t actually contribute to this argument.
Providing an explanation for the buildup doesn’t strengthen the idea that microglial response to the buildup causes the cognitive deficiency we see in Alzheimer’s patients.