Scientific advances in the latter half of the twentieth

[rahul.gmat]

Scientific advances in the latter half of the twentieth century have allowed researchers to study the chemical activities taking place in the human brain during the sleep cycle in more detail. In the 1970s, Jacobs employed these advances to postulate that dreams and hallucinations share a common neurochemical mechanism with respect to the neurotransmitters serotonin and norepinephrine that accounts for the observable similarities between the two states of mind. To test the theory, researchers attempted to elucidate the role of these transmitters in the normal sleep cycle and the effect of hallucinogenic drugs on them.
Although scientists still have much to discover about the chemical complexities of the brain, serotonin appears important for managing sleep, mood, and appetite, among other important functions, while neurons release norepinephrine to facilitate alertness and mental focus. Both are discharged in high quantities only during waking states. At the onset of sleep, the activity levels of neurons that release both the neurotransmitters drop, allowing the brain first to enter the four non-rapid eye movement (Non-REM) stages of sleep. When the brain is ready to enter the fifth stage, REM, which is associated with dreaming, the levels of these two chemicals drop virtually to zero. The Jacobs hypothesis held that the absence of norepinephrine was required to enable the brain to remain asleep, while the absence of serotonin was necessary to allow dreaming to occur.
Lysergic acid diethylamide, or LSD, is a semi-synthetic psychedelic drug which causes significant alteration of the senses, memories and awareness; at doses higher than 20 micrograms, it can have a hallucinogenic effect. LSD mimics serotonin well enough to be able to bind at most of the neurotransmitter’s receptor sites, largely inhibiting normal transmission. In addition, the drug causes the locus ceruleus, a cluster of neurons containing norepinephrine, to greatly accelerate activity. If the drug stimulates norepinephrine, thereby precluding sleep, and inhibits serotonin, which Jacobs had postulated was a necessary condition for dreaming, then the resulting hallucinations could merely be "dreaming while awake." The research thus far is promising but inconclusive; future scientific advances should allow this theory to be tested more rigorously.




Clearly, last sentence of para 2 says that absence of serotonin (S) is required for dreams and absence of norepinephrine (N) is required for sleep. In case of LSD, S is absent so dreams occur and N is present so the person dosent sleep and day dreams. Why is this inconsistent to with the theory.

[esledge]

Hi Rahul,

It may help for you to post the entire question and answer choices, if your doubt relates to a particular question.

I don't think that what you (and the passage) say about S and N ARE inconsistent with Jacob's theory, so I am interested in whether a particular question/explanation made such a claim. Please give some more background on your doubt...

[akhp77]

Which best represents the author's attitude towards the presented theory?
A: passionate but unbiased
B: optimistic and persuasive
C: pessimistic and dismissive
D: hopeful and conciliatory
E: supportive but objective

OA: E

Please explain.

[RonPurewal]

Which best represents the author's attitude towards the presented theory?
A: passionate but unbiased
B: optimistic and persuasive
C: pessimistic and dismissive
D: hopeful and conciliatory
E: supportive but objective

OA: E

Please explain.

you'll be pleased to know that these types of questions -- in which the question calls explicitly for the tone of the passage -- do not, as far as we can tell, appear on the test. therefore, we have removed all questions of this type from our CAT exams as well.

still, an explanation:

in this particular problem, the passage is very positive ("The research thus far is promising"). of the five mood-based adjectives that appear in the choices -- passionate, optimistic, pessimistic, hopeful, and supportive -- only (b) optimistic and (e) supportive convey this sense. ("hopeful" is also a word with a positive connotation, but it is not ordinarily used unless the positive thoughts exist against a negative background.)

(b) is incorrect because the passage is not persuasive; it basically just reports the current findings about the science described, in a very objective fashion. hence (e).