REM (rapid eye movement) Sleep, also called "Paradoxical" Sleep Because of its Neurologically Aroused Character

Reading Passage Question

REM (rapid eye movement) sleep, also called "paradoxical" sleep because of its neurologically aroused character, is best known as the sleep phase during which intense dreams occur in humans. It has been found to have a surprisingly close relationship with the waking state. The electroencephalogram (EEG), which records general electrical activity in the brain, indicates that REM sleep displays high-frequency, low-amplitude waves all but identical to those of wakefulness. This is in contrast to the slow-wave (low-frequency, high-amplitude) patterns of dreamless sleep. Additionally, neurological activity in various subunits of the brain is essentially similar in both REM sleep and the awakened state. Especially revealing is a pattern of waves in a part of the cerebral cortex called the hippocampus. This "theta rhythm" is manifested regularly throughout both REM sleep and wakefulness, and it contrasts with the irregular activity of the hippocampus during slow-wave sleep. Measurements of brain temperature indicated a third similarity: brain temperature decreases slightly during slow-wave sleep, then rises in REM sleep to about the same level as in wakefulness.

A recent, accidental discovery substantially augmented our understanding of the connection. PGO spikes (short-lived, high-amplitude electrical waves observed most frequently in the pons, a region in the brain stem) were thought to occur almost uniquely in REM sleep and to occur spontaneously, without external stimulus. However, when a laboratory worker accidentally struck an EEG recording cage while a cat's slow-wave sleep was being traced, a PGO spike appeared in the record almost instantly. A subsequent study indicated that both sounds and touch could easily produce PGO spikes in either REM or slow-wave sleep. Far from being spontaneous and unique to REM sleep, PGO spikes seem to be general alerting responses occurring in several slow sleep phases.

This finding in tum has prompted a reevaluation of waves called eye-movement potentials (EMPs), which occur in the waking state. These were believed to depend on environmental levels of light, but in the EEG record, they appeared identical to PGO spikes. Reasoning that a cat in a darkened cage might be bored, a worker directed the odor of tuna fish through the cage and presently observed EMPs identical to PGO spikes. Sharp noises produced the same result. Both PGO spikes and eye movement potentials are now seen as varieties of a general alerting response, which can be stimulated during REM sleep, slow-wave sleep, and wakefulness.

“REM (rapid eye movement) sleep, also called "paradoxical" sleep because of its neurologically aroused character”- is a GMAT reading comprehension passage with answers. Candidates need a strong knowledge of English GMAT reading comprehension.

This GMAT Reading Comprehension consists of 4 comprehension questions. The GMAT Reading Comprehension questions are designed for the purpose of testing candidates’ abilities in understanding, analyzing, and applying information or concepts. Candidates can actively prepare with the help of GMAT Reading Comprehension Practice Questions.

Solution and Explanation

1. The author is primarily concerned with

A) proving that brain wave activity occurs during REM sleep
B) studying the functions of brain subunits during various sleep phases
C) exploring inconsistencies in current accounts of brain-wave activity in various mind states
D) establishing that most sleep states involve patterns of electrical activity
E) demonstrating the neurologically aroused character of various stages of consciousness

2. According to the passage, which of the following is true of both wakefulness and REM sleep?

A) Slow-wave patterns predominate.
B) Brain temperature tends to drop.
C) Sensory contact with the environment is intensified.
D) Low-amplitude waves can be observed in the pons.
E) Brain wave patterns vary in response to environmental stimuli.

3. It can be inferred that the odor of tuna fish was directed through a darkened cage in order to determine which of the following?

A) Do eye movement potentials occur in REM sleep?
B) Can EMPs occur as a response to stimuli other than environmental levels of light?
C) Are EMPs identical to PGO spikes?
D) Are relaxed animals as neurologically alert as excited animals?
E) Do EMPs occur only in response to external stimuli?

4. The author implies that eye-movement potentials, which appear identical to PGO spikes in the EEG, were reevaluated because

A) PGO spikes were discovered to be responses to specific external stimulation
B) both responses appeared randomly and spontaneously in the EEG .
C) EMPs had been thought to occur in the absence of external stimuli
D) both responses occurred only in REM sleep
E) neither response occurred during slow-wave sleep

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