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# Scientific advances in the latter half of the twentieth

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04 Nov 2010, 17:35
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Question 1
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40% (03:47) correct 60% (02:08) wrong based on 158

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Question 2
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44% (01:35) correct 56% (00:28) wrong based on 171

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Question 3
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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.
1. According to the passage, which of the following is true of the drug lysergic acid diethlyamide?
A)Research into the drug is promising but inconclusive.
B)The neuron receptor sites that normally bind serotonin will also bind the drug.
C)The locus ceruleus causes the drug to affect bodily systems more rapidly than normal.
D)The drug stimulates norepinephrine and serotonin.
E)A person who ingests more than 20 micrograms of the drug will have hallucinations.

[Reveal] Spoiler:
B

2. Which of the following best represents the author's primary goal in writing the passage?
A)to outline a theory and suggest options for further research
B)to act as an advocate for additional research to help elucidate a particular theory's validity
C)to introduce a theoretical construct that has not yet been sufficiently proven
D)to demonstrate the complexities involved in conducting a certain type of scientific research
E)to articulate a hypothesis and lay out the case for proving it

[Reveal] Spoiler:
C

3. Which of the following, if true, would most undermine the central premise of the Jacobs hypothesis?
A)LSD does not cause as much long-term neurological damage as previously thought.
B)Serotonin and norepinephrine rise and fall in tandem.
C)Researchers prove conclusively that the level of norepinephrine in the brain is a significant factor in enabling the brain to sleep.
D)Some semi-synthetic hallucinogenic drugs other than LSD do not inhibit serotonin.
E)The first four stages of sleep are as crucial to the process of dreaming as is the fifth stage.

[Reveal] Spoiler:
D

4.According to the passage, all of the following are true EXCEPT
A. Norepinephrine and serotonin are discharged only during waking states.
B. Ingesting more than 20 micrograms of LSD will cause some people to hallucinate.
C. Rapid eye movement is the stage of sleep during which people dream.
D. LSD causes neurons to increase the rate at which they discharge norepinephrine.
E. The absence of serotonin seems to be necessary in order to enable the brain to dream.

[Reveal] Spoiler:
A

[Reveal] Spoiler: Question #1 OA
[Reveal] Spoiler: Question #2 OA
[Reveal] Spoiler: Question #3 OA
[Reveal] Spoiler: Question #4 OA

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Last edited by Skywalker18 on 05 Sep 2016, 10:27, edited 1 time in total.
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09 Nov 2010, 11:25
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Can someone who got #3 correct please provide an explanation? I chose E.
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09 Nov 2010, 18:31
MLF44 wrote:
Can someone who got #3 correct please provide an explanation? I chose E.

According to the passage:
LSD "inhibits serotonin, which Jacobs had postulated was a necessary condition for dreaming".

Therefore existance of any other hallucinogenic drug that does not block serotonin, but causes dreams would weaken the theory. Which is "D".
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14 Jun 2011, 16:12
Why is Option B wrong in Q3?If serotin and norepinephrine rise and fall in tandem rise and fall then person wont fall asleep and wont have a dream...the levels have to fall and not rise and fall....

3. Which of the following, if true, would most undermine the central premise of the Jacobs hypothesis?

LSD does not cause as much long-term neurological damage as previously thought.
Serotonin and norepinephrine rise and fall in tandem.
Researchers prove conclusively that the level of norepinephrine in the brain is a significant factor in enabling the brain to sleep.
Some semi-synthetic hallucinogenic drugs other than LSD do not inhibit serotonin.
The first four stages of sleep are as crucial to the process of dreaming as is the fifth stage.
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14 Jun 2011, 16:17
Why is A wrong in 1?

The last line of the para says this:- The research thus far is promising but inconclusive; future scientific advances should allow this theory to be tested more rigorously.
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14 Jun 2011, 16:27
Why is A wrong in Q2? Also, whats the difference between "theory" and "theoretical construct"
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08 Aug 2011, 23:50
Can somebody please answer why A is wrong in Q1. Last line of the passage says pretty much the same thing as in A.
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23 Aug 2011, 01:04
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1. B

A) the research is being done on the “ dream process” and not the drug so this option gets ruled out
B) it has been clearly mentioned that LSD mimics serotonin well enough to be able to bind at most of the neurotransmitter’s receptor sites
C) The locus ceruleus which will increase the alertness and mental focus which is the function of norepinephrine
D) LSd simulates norepinephrine and inhibits serotonin
E)can have hallucinations…not mandate that it will happen

2.

First passage: Jacob postulated some theory which is further taken up by the researchers to have undersatanding of role of transmitters on normal sleep and effect of hallucinogenic drugs on them.
Second :theory is described. Function of transmitter on normal sleep and the whole process how is dreaming and sleeping occur. (first part of the research)
Third passage:How LSD effect on transmitters which can result in hallucination(second part of the research)
In the end of third passage, author states that the research done in this field is promising but inconclusive.

to outline a theory and suggest options for further research( theory is outlined but no suggestions have been provided for further research)
to act as an advocate for additional research to help elucidate a particular theory's validity ( if author is advocating the research then the last statement of third passage would be not in place)
to introduce a theoretical construct that has not yet been sufficiently proven
to demonstrate the complexities involved in conducting a certain type of scientific research( no complexities involved in conducting the research have been discussed…only the theory has been explained)
to articulate a hypothesis and lay out the case for proving it( it can be considered as hypothesis but no case have been put forward to prove itas the last line suggests …theory is promising but inconclusive…which means not proved fully)

3.

Central premise would be: 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.

A)LSD does not cause as much long-term neurological damage as previously thought.( this somehow does not go with the context so I eliminated this option)
B) Serotonin and norepinephrine rise and fall in tandem.( which goes with the theory, both needs to be absent for dreaming)
C) Researchers prove conclusively that the level of norepinephrine in the brain is a significant factor in enabling the brain to sleep. ( yes it is as absence of this would only cause to sleep but in last passage it is given that there can be chances of person dreaming when awake when norepinephrine is accelerated and Serotonin is restrained but still it is a significant factor which very well goes with passage)
D) Some semi-synthetic hallucinogenic drugs other than LSD do not inhibit serotonin.
E) The first four stages of sleep are as crucial to the process of dreaming as is the fifth stage. ( which is also fine)
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25 Aug 2011, 19:28
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this passage are sooooooooooooo dense..............unbelievable

in max 6 minutes..........generally I go well on RC but sometime I'm completely lost...........maybe is the LSD
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27 Mar 2012, 18:40
only one correct...totally lost in this one took around 7 min.
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30 Mar 2012, 03:32
I also don't understand why B would be wrong in 3. If serotonin and norepinephrine rise and fall in tandem, it means that that serotonin, which is supposed to be the reason for dreaming is active on the first four stages of sleep, in which dreaming doesn't occur.
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08 Apr 2012, 05:03
B///A....c...b....took about 9min - this is one of those types that I'm not good at comprehending, too many biological terms.
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17 Apr 2012, 09:40
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i took 7 minutes and got answers
b
c
b

but as per OA 3rd one is D

Ok B is also strong
but D it should be because in passage it is mentioned that LSD which inhibits serotonin induces dreams
so if we have a semi-hallucinogenic drug that induces hallucination(dreams while awake) without inhibiting serotonin then Jacob's central premise that amount of serotonin needs to be less for dreaming falls flat.

Yeah it was a toughie
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04 Jun 2012, 01:40
This passage looked easy but turned out quite tricky. Got 2 wrong out of 3 because of careless mistakes.
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31 Jul 2012, 03:24
Even I've got the answer BCB, third one is wrong, I think following might be the explaination of third answer:

"hallucinogenic drugs other than LSD do not inhibit serotonin", So there are drugs which do not inhibit Sertonin and cause hallucinogenic effect. As per claim by Jacob , Serotonin must be 0 for dreaming. Again it is stated in the start of paragraph that "dreams and hallucinations share a common neurochemical mechanism". So, answer of third question is "D" instead of "B"
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17 Aug 2012, 06:45
i got B C C
can anyone pls help me how is C incorrect for #3 ...
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19 Aug 2012, 11:54
Hi,

For question number 1, the answer is B. As written - LSD mimics serotonin well enough to be able to bind at most of the neurotransmitter’s receptor sites, largely inhibiting normal transmission.

although I mi ticked E - silly mistake as it can happen only above 20mg....
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06 May 2014, 18:21
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.
"norepinephrine was required to enable the brain to remain asleep"
question 3 anyone pls tell me why option c is wrong , but from above sentence we can conclude that absence of norepinephrine = asleep , this shows that "c" is correct...
Re: Scientific advances in the latter half of the twentieth   [#permalink] 06 May 2014, 18:21

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