In a recent study of stroke patients, those who exhibited continuing

In a recent study of stroke patients, those who exhibited continuing deterioration of the nerve cells in the brain after the stroke also exhibited the highest levels of the protein glutamate in their blood. Glutamate, which functions within nerve cells as a neurotransmitter, can kill surrounding nerve cells if it leaks from damaged or oxygen-starved nerve cells. Thus glutamate leaking from damaged or oxygen-starved nerve cells is a cause of long­ term brain damage resulting from strokes.

Which one of the following, if true, most strengthens the argument?

(A) Any neurotransmitter that leaks from a damaged or oxygen-starved nerve cell will damage surrounding nerve cells.

(B) Stroke patients exhibit a wide variety of abnormal chemical levels in their blood.

(C) Glutamate is the only neurotransmitter that leaks from oxygen-starved or physically damaged nerve cells.

(D) Leakage from damaged or oxygen-starved nerve cells is the only possible source of glutamate in the blood.

(E) Nerve cells can suffer enough damage to leak glutamate without being destroyed themselves.

LSAT

Premises:
- We noticed that those who exhibited continuing deterioration of the nerve cells in the brain after the stroke also exhibited the highest levels of the protein glutamate in their blood.
- We know that Glutamate can kill surrounding nerve cells if it leaks from damaged or oxygen-starved nerve cells

We concluded - Glutamate leaking from damaged or oxygen-starved nerve cells is a cause of long-term brain damage resulting from strokes.

Note how premises lead to conclusion - because Glutamate levels were high in the blood, and we know that a certain kind of Glutamate can cause brain damage, we concluded that this type of Glutamate is what is causing brain damage.
We want to strengthen this.

Option (D) says that this is the only type of Glutamate. Well, then we know that this type pf Glutamate does cause brain damage and it is there in the blood. Hence it strengthens the conclusion.

What does option (C) say? That nothing else leaks from oxygen starved nerve cells. Well, even if something else does leak, does it cause brain damage? We don't know. Other things leaking out of oxygen starved nerve cells don't have a direct link with Glutamate and brain damage. Hence it doesn't help much in our analysis of the conclusion.

(A) Any neurotransmitter that leaks from a damaged or oxygen-starved nerve cell will damage surrounding nerve cells.
Brings into question that Glutamate is the cause. Does not strengthen.

(B) Stroke patients exhibit a wide variety of abnormal chemical levels in their blood.
Again, brings into question that Glutamate is the cause. Does not strengthen.

(E) Nerve cells can suffer enough damage to leak glutamate without being destroyed themselves.
The argument already tells us this - Glutamate leaks from damaged nerve cells. This doesn't add much information.

Answer (D)

Rishav, the reason (C) is not correct is that other neurotransmitters leaking out of damaged nerve cells have no connection to the Glutamate and brain damage relation.
We don't know anything about the other neurotransmitters, what happens when they leak etc. Other neurotransmitters leaking has no impact on our conclusion that Glutamate leaking out of damaged nerve cells causes brain damage.

Merging topics. Please search before posting. Thank you.

EASY

In a recent study of stroke patients, those who exhibited continuing deterioration of the nerve cells in the brain after the stroke also exhibited the highest levels of the protein glutamate in their blood. Glutamate, which functions within nerve cells as a neurotransmitter, can kill surrounding nerve cells if it leaks from damaged or oxygen-starved nerve cells. Thus glutamate leaking from damaged or oxygen-starved nerve cells is a cause of long-term brain damage resulting from strokes.


The key phrase is: In a recent study of stroke patients, those who exhibited continuing deterioration of the nerve cells in the brain after the stroke also exhibited the highest levels of the protein glutamate in their blood.



Which one of the following, if true, most strengthens the argument?

(A) Any neurotransmitter that leaks from a damaged or oxygen-starved nerve cell will damage surrounding nerve cells. (NOT CONCERNED)
(B) Stroke patients exhibit a wide variety of abnormal chemical levels in their blood. (OUT OF SCOPE )
(C) Glutamate is the only neurotransmitter that leaks from oxygen-starved or physically damaged nerve cells. (SO WHAT ? IT DOESNT STRENGTHEN)
(D) Leakage from damaged or oxygen-starved nerve cells is the only possible source of glutamate in the blood. CORRECT
(E) Nerve cells can suffer enough damage to leak glutamate without being destroyed themselves. (OUT OF SCOPE)

In defense of Option (C) what if the damaged nerve cells leak glutamate and another additional protein called "whynotmate". And it is the whynotmate protein that is the real cause of the nerve damage to other nerve cells.

However, in the tests, we only look for and hence we only find glutamate and thus conclude that it is glutamate that causes the damage.

Would then not the knowledge of Option C - "... only glutamate is released from damaged nerve cells" remove the possibilty of such a "whynotmate" protein being the behind-the-scenes reason for nerve damage?

Someone, please comment.

Best,
Gladi

Thanks a lot for your detailed explanation. I have a small doubt. I got the answer correct but I want to be sure that I reached to the answer for the right reasons.

Inferences in the passage:

• those who exhibited continuing deterioration of the nerve cells in the brain after the stroke also exhibited the highest levels of the protein glutamate in their blood
○ This means the deterioration of the nerve cells in the brain and highest levels of protein G ( glutamate) in blood are correlated in the examined stroke patients.

• Glutamate, which functions within nerve cells as a neurotransmitter, can kill surrounding nerve cells if it leaks from damaged or oxygen-starved nerve cells
○ Now it says that G can kill surrounding nerve cells if it leaks from damaged or oxygen-starved cells

• glutamate leaking from damaged or oxygen-starved nerve cells is a cause of long-term brain damage resulting from strokes.
○ From this we know that, leaking of glutamate can cause a long term brain damage resulting from strokes and this is our conclusion.


So:
X causes Y
X => glutamate leaking from damaged or oxygen-starved nerve cells
Y => long-term brain damage resulting from strokes

X causes Y

In option C, we say that the G that is leaking is the only neurotransmitter.
○ Now what can we infer from that?
§ Is it that the damage caused the leakage of G.
§ Or the leakage of G caused the nerve damage and subsequently the brain damage.
□ We can only say that the other cells are damaged.
○ If we check the Option C, we see that either way it is possible.


Option D, gets rid of this dilemma by saying that the leaking of the glutamate is coming from the damaged and oxygen starved nerve cells and we see that okay this leaking ( the process) is responsible for brain damage.


So basically, I think to validate the conclusion or raise our belief in the conclusion, we need to say that this (process) has lead to the brain damage.

Option C only talks about the G leaking from the cells, and hence we are not focusing on the process
While in Option D, we have focused on the process of the leaking and hence I believe the answer is D?



Please let me know if my understanding is in-line with what you explained?

Regards,
Rishav

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