Download The human brain will return to an “ancestral state” when we sleep or

On The Neurological State During Dreaming and Sleeping
Abstract
The human brain will return to an “ancestral state” when we sleep or dream. In
the “ancestral state,” only the mammalian brain (the limbic system) is active,
while the rest of the human brain “shuts down” or becomes less functional. This
brain state is very similar to an undeveloped brain. This hypothesis is tested
through a literature review. There are similarities and differences in mental states
when humans are conscious and when they are unconscious. A conscious mental
state is when humans are awake; the unconscious refers to the mental state
during dreaming and sleeping. The mental state of an unconscious brain turns out
to be more complex than an undeveloped brain. Emotions, memory, daily
experiences, and unconscious cognition all play important roles during sleep.
YiYing Zhu
Ross School, East Hampton, N.Y.
Evolutionary History
of the Brain
Human
Mammalian
Brain
Reptilian
Brain
Background
Visual perception, in general, is the neurological process within the brain that integrates and interprets
the external visual stimuli received from the eyes. However, in the situation of dreaming, in which
external visual stimuli are lacking, images are somehow still perceived. This situation seems to be a
paradox. Nevertheless, images derived from dreams are neither imaginations nor a result of visual
perception as when we are conscious or awake. A plausible reason is that many parts of the brain
become less alert compared to the conscious brain.
Anatomy of the
Visual Pathways of
the Conscious Brain
The How Pathway
Parietal Lobe
The Where Pathway
Superior
Colliculus
Retina
Optic Nerve
Lateral
Geniculate
Nucleus
A prevalent theory today describes dreams
as side effects resulting from physiological
changes during REM sleep (Figure 1,
Hobson, 2000). Electrical activities in the
motor and visual areas of the brain during
REM sleep engender dreamlike
hallucinations. The brain is still involved in
thought processes, but to a lesser degree.
Thought processes connect one
hallucination with another in order to
decipher them (Gray, 2007). The series of
hallucinations becomes what is known as a
dream. The irrational nature of the dream
can be explained by the reduction in mental
capacity during sleep.
Figure 1
The Process of Generating Emotions
Emotions are cerebral responses generated in the limbic system. One theory (Bower, 1990) describes
dreaming mainly as an unconscious emotional release, which is restrained in the day. Cerebral activity that is
responsible for registering emotions is present during dreaming. There are two pathways for generating
emotions.
OR
Emotional stimuli  Amygdala 
Hypothalamus  Rest of the body  Physical
responses  Somatosensory cortex  Frontal
cortex
Temporal Lobe
The What Pathway
The Evolutionary Sequence of the Visual
Pathways (Ramachandran, 2008)
1st: The Where Pathway
2nd : The How and What Pathways
Percept and Mental Images
While we are dreaming, the brain functions differently than when we are awake. Thus, the images we
construct in our dreams are different from the percept—images we perceive when we are awake. In
the waking state, the where pathway that allows orientation, exploration and adjustment, is
constantly interacting with the what and how pathways that projects to the visual cortex or the
occipital lobe in the back of the brain. However, in sleep, the inputs of the optic nerves are missing,
since our eyes are closed, and there are no external visual stimuli to be received and processed. As a
result, the how and what pathways of the perceptual system are running free. Those two pathways
are more spontaneous and dynamic during sleep. The rapid-eye-movements (REM), see Figure 1, in
dreams can be explained (Gibson, 1970) as frustrated efforts of the perceptual system to perceive.
“The dreamer is trying to look.” Dream images are a result of the internal perceptive system. Since our
eyes are closed during sleeping and dreaming, these images are different from conscious sensepercepts because there is no external stimuli.
People who are born blind have no
visual imagery in their dreams,
since they are not able to
experience any visual imagery in
waking life. Their dreams are often
associated with other senses, such
as hearing and touch. People who
become blind before the age of 4
show a general trend of a lack of
visual imagery in their dreams.
People who become blind after that
may still hold remnants of visual
imagery in their dreams. This
pattern shows that dreaming is a
gradual cognitive achievement, in
which visual, spatial and other
imagistic abilities need to be
evolved. In other words, the parts
of the brain that are involved with
those imagistic abilities must be
developed for dreaming (Kerr &
Domhoff, 2004 ).
REM
Emotional stimuliAmygdalaFrontal Cortex
The Visual
Cortex
Born Blind
Neurological State during Dreaming
Neurological Activities during Sleeping
According Stickgold and Ellenbogen (2008), during sleep, our brain engages in data analysis, from
strengthening memories to solving problems. While we are sleeping, our brain processes the daily
information we received and improves and strengthens memory. Extraneous information is filtered
out, while the essential facts remain. In 1994, neurologists Avi Karni and Dov Sagi demonstrated how
rapid-eye-movement (REM) sleep (Figure 1) improves memory. They depicted the REM sleep as a
“permissive state.” This state allows changes to occur, such as altering memories developed during
the daytime or those already stored in the hippocampus a long time ago. Stickgold (2000) expanded
on this theory, proposeing that sleep—in all its phases—does something to improve memory that
being awake does not do. In 2007, Ellenbogen was able to show that our brain learns during sleep.
Memory processing appears to be the only function that requires sleep. This unconscious cognition
seems to demand a complete block out of the external environment. There cannot be any neuronal
activities related to processing incoming sensory signals. Sleep seems to be the perfect condition,
since all external stimuli are blocked out.
Conclusion
During sleep, many parts of the brain, such as the limbic system, work in similar
ways as when we are conscious. However, this is not the only part of the brain
that is functioning. Many parts of the brain, such as the cerebrum, do not “shut
down” at all, but merely work differently than when we are conscious. Part of
the cerebral cortex that registers emotions is still effective, while other parts of
the cortex are engaged mainly in memory processing. Nevertheless, the limbic
system, a more ancestral part of our brain, is rather prevalent when we sleep.
During sleep, functions of the mammalian brain are heightened, and the cortex
turns to an unconscious state, mainly devoted to unconscious cognition. The
fundamental and biochemical mechanisms underlying unconscious cognition
still remain unclear. These questions need to be further investigated.
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