Raj30
Can you explain why answer of Q6 is c?
We are sure of a differential oxygen use but how can we be sure that metabloic activity and use of oxygen is directly proportional?
For question #6, the question stem asks us to find which answer choice is "
most strongly supported by the passage." So we do not necessarily need to "be sure" that (C) is fully supported by the passage -- we only need to determine that it is more strongly supported than are the rest of the answer choices.
With that in mind, your best bet on this question is POE to eliminate all of the incorrect options. Let's go through the answer choices:
Quote:
(A) Although there are important exceptions, most cognition does in fact depend on independent modules located in specific regions of the brain.
This is essentially the opposite of the author's main idea, which is that "it may in fact be that neither mental activity, nor the physical processes that constitute it, are decomposable into independent modules." (A) is out.
Quote:
(B) The modular theory of mind holds that regions of the brain that are not engaged in a specific cognitive task have a rate of oxygen use that is close to zero.
This contradicts the information in the passage, which examines the "subtractive method" of interpreting brain scans. The author notes that "this method obscures the fact that the entire brain is active in both conditions." So, the passage does not support the idea that some regions of the brain have a rate of oxygen use close to zero when not engaged in a specific task. Eliminate (B).
Quote:
(C) During the performance of certain cognitive tasks, the areas of the brain that are most metabolically active show a rate of oxygen use that is higher than that of the rest of the brain.
Notice that this answer choice is
not making a statement about scans using the subtractive method. Instead, it is merely claiming that during certain tasks, the most "metabolically active" areas of the brain show a higher rate of oxygen use than the rest of the brain.
From the passage, we know that "the fMRI is usually interpreted as a map of the rate of oxygen use in different parts of the brain,
which stands as a measure of metabolic activity." So, the parts of the brain that are most metabolically active show the highest rate of oxygen use. (C) is the correct answer.
It is easy to get turned around in this answer choice by attempting to apply it to the differential scans. For example, what if a certain region of the brain is always highly active, and maintains this high level of activity during any given cognitive task? It could be the most active region of the brain, but not be "lit up" at all on a differential scan, because the baseline measurement would be the same as the second measurement. However, this doesn't change the fact that the most metabolically active region of the brain will show the highest rate of oxygen usage.
This is why it is important to look at the
exact wording of the answer choice. (C) is our answer.
Quote:
(D) The baseline measurements of oxygen use taken for use in the subtractive method show that some regions of the brain have high metabolic activity at all times.
The passage explains that "baseline measurement is... subtracted from the on-task measurement" to give a differential reading. However, it does not give any specific information about what the baseline levels for any region of the brain actually are. For this reason, (D) is out.
Quote:
(E) When a brain scan subject experiences anger, the subtractive method shows several regions of the brain as "lit up" with metabolic activity.
Here is the piece of the passage relevant to answer choice (E):
Quote:
"It cannot be said, for instance, that the amygdala is the seat of emotion and the prefrontal cortex is the seat of reason, as the popular press sometimes claims. For when I get angry, I generally do so for a reason. To cleanly separate emotion from reason-giving makes a hash of human experience.
Here, the author argues that one cannot cleanly separate anger into one specific region of the brain, which seems to support the idea that "when a brain scan subject experiences anger, the subtractive method shows
several regions of the brain as 'lit up,'" as expressed in (E).
However, the passage does not reveal how anger would
actually appear on an fMRI readout. Maybe the result would support the author's contention, and maybe it would not. Because this information is not given, we cannot say that answer choice (E) is well supported by the passage.
This leaves us with (C) as the "most strongly supported" answer choice.
I hope that helps!