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continued from the Brain Page of
Nervous System Contents
Neurons and Nerves
neurotransmitter
The Brain & Spinal Cord
Cranial Nerves
Peripheral Nervous System
Autonomic Nervous System
Senses:
Eye diagrams,
Hearing,
Smell,
Taste, Taste
& Tongue Sensation,
Balance
Memory ,
Memory types, Creation of Memory,
Higher Functions
Altered States
[Top]
It is not possible to divide states of being into the neat
categories of consciousness and unconsciousness. Too many curious
and interesting states lie between, challenging a simple definition.
These altered states of consciousness defy objective description
because they are intensely personal. Nevertheless, these
experiences, which range from the mild distraction of a daydream to
wild, drug-induced hallucinations, can have certain common
characteristics related to the change of perceptions of the self and
the outside world. The term "altered states" covers a number of
phenomena. Some arise naturally and
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automatically (dreaming, for example, is
thought to be common to all mammals). Others are attained
through learned techniques such as meditation. Some are
induced by drugs. Other still - the vision and trance states
- are highly controversial, and many people doubt their
existence. To understand altered states one must assess
subjective accounts of what it is like to "be in" these
states, along with objective research that tries to identify
their physiological basis and effects. Figure 33 shows the
brain scan for some of the altered states listed below.
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Dreaming - Vivid visual dreams light up the visual
cortex; nightmares trigger activity in the amygdala and the
hippocampus flares up from time to time to replay recent
events. The areas, which seem to be most commonly active are
the pathways carrying alerting signals from the brainstem
and the auditory cortex; supplementary motor area and visual
association areas - all of which produce the "virtual
reality" effect of dreaming. Activity is decreased in the
dorsolateral prefrontal cortex, the area of waking thought
and reality testing (Figure 33). Studies
have shown that dreaming sleep occurs in a wide range of
animal species. Figure 34 shows a dreaming cat. When its
pons is surgically removed to permit movement during REM
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sleep, the very nice cat becomes a vicious
tiger when it is dreaming and throws itself at imaginary
prey.
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Daydream - Many surveys suggest that ordinary men and
women, who are neither disturbed nor neurotic, spend a large
part of each day in some sort of fantasy, reverie or
daydream. This kind of quick fantasy rarely has a structured
narrative. It is the moment when we stop paying attention to
what we are seeing and hearing and switch into an inner
theatre of the imagination where we can play at wish
fulfillment (Figure 35). But there are other fantasies
qualitatively different from these "wouldn't it be nice if
..." stories. These are sustained fantasies, which often
seem to have been crafted, worked and reworked to meet some
more profound psychological need. When one daydreams, normal
inhibitions are bypassed. The
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evidence of the rather macabre biographies
of serial killers shows that they had frequently recurring
violent fantasies before they turned to murder.
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Meditation - One function of consciousness is to knit
together our sense of self-identity. But many religious
traditions believe that enlightenment can be achieved only
by breaking the shackles of self and attaining "purer"
states of consciousness through meditation (Figure 36). As
well as its psychological benefits, the meditative state has
marked physiological effects - these phenomena are
measurable and reliably repeatable, and thus are a suitable
object of scientific study. Such studies have revealed some
remarkable effects: meditation can lower a subject's
metabolic rate, decreasing blood pressure, pulse rate and
muscle tension. One study shows that the subject could
reduce his oxygen intake to one-third of the normal resting
state. Scans of people in a self-induced state of "passive
attention" have
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been shown to "turn off" areas of the brain
normally associated with seeking stimuli, including the
parietal, anterior and premotor cortexes (Figure
33).
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Hypnosis - Modern studies show that the brain waves of
hypnotized subjects are much like those of the waking state.
When subjects are hypnotized, they can speak, walk and carry
out instructions. Yet there are some noticeable changes from
normal consciousness: attention becomes very selective, with
the subject ignoring everything but the hypnotist's voice;
the subject rarely initiates thought or activity, but waits
for suggestions from the hypnotist; and fantastic ideas or
situations are more readily accepted as reality. It is
almost as if the willing, relaxed subject relinquishes
control over part of his or her consciousness to the
hypnotist. The classic method of hypnotism is to put a
subject into a relaxed frame of mind and ask him or her to
concentrate on an object, such as a swinging pocket watch
(Figure 37). Brain scans (Figure 33) show
increased activity during hypnosis in the motor and sensory
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areas suggesting heightened mental imagery.
Increased blood flow in the right anterior cingulate cortex
suggests that attention is focused on internal events. The
brain activity seen in this state is quite different from
that seen in normal waking or sleeping. |
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Sexual fantasy - This is the ability to use our
imaginations erotically. It is found that people spend a
surprising amount of time thinking about sex. There are vast
cultural differences in what different societies consider
acceptable material for sexual fantasy and fetishes. The
Victorians considered fetish to be shocking and dangerous,
the true dark side of sexuality; while the Freudian view
treats fetishism as the result of linking unresolved
childhood drives to object that seems "safe" such as the
high-heeled shoe. Many therapists now consider that it is
perfectly normal to have sexual fantasies, and some even
believe that they can be used to achieve a more fulfilling
sex life. Research into sexual fantasies is complicated and
must rely on what patients report to their therapists, but
some studies have found links with childhood events - either
sexual violence or a strict, repressed upbringing. There is
an obvious distinction between fantasy and action - a
fantasy does not harm others. However, some people who have
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fantasies that involves inflicting pain to
themselves or others (such as to the cat in Figure 38) claim
that they feel compelled to act them out. Sometimes people
with less extreme fantasies also choose to turn them into
realities such as in the form of cross dressing. |
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Addiction - Drug addiction is
caused by a similar train of events to hunger. However,
unlike most types of food, addictive drugs cause changes in
the receptors to which they bind, making them less
sensitive. This creates tolerance and addiction. Most
addictive drugs work by altering levels of neurotransmitters
in the brain's reward circuitry centered on the limbic
areas. Other brain areas are also involved and each type of
drug works in a slightly different way to produce its
characteristic effects. Opiates are drugs derived from the
dried resin of the opium poppy (Figure 39), or synthetic
versions of these chemicals, such as heroin, codeine and
morphine. All
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have been used medicinally at some time for
their pain-killing properties. They are used illegally for
similar reasons: heroin gives the user a "high", reducing
anxiety and producing a sense of temporary well-being. |
Schizophrenia (shattered mind) - There is evidence to suggest
that genetic vulnerability and environmental stressors can act in
combination to cause schizophrenia. Some researchers estimate
schizophrenia to be highly heritable. But a recent review of the
genetic evidence has suggested only a 28% chance of one identical
twin developing schizophrenia if the other already has it. A recent
study listed seven genes as likely to be involved in the inheritance
of schizophrenia or the risk of developing the disease. One of these
genes known as COMT is involved in encoding the dopamine catabolic
enzyme. This is interesting because of the known link between
dopamine function, psychosis, and schizophrenia. There is
considerable evidence indicating that stressful life events cause or
trigger schizophrenia psychosis. Childhood experiences of abuse or
trauma have also been implicated as risk factors for a diagnosis of
schizophrenia later in life. There is also consistent evidence that
negative attitudes towards individuals with schizophrenia can have a
significant adverse impact. In particular, critical comments,
hostility, and intrusive or controlling attitudes from family
members have been found to correlate with a higher risk of relapse
in schizophrenia across cultures. Factors such as poverty and
discrimination also appear to be involved in increasing the risk of
schizophrenia or
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schizophrenia relapse, perhaps due to the
high levels of stress they engender. The disease is
frequently accompanied by paranoia and delusions. Some may
experience extremely bizarre hallucinations. Ironically,
while some areas of the schizophrenic brain may be dead, in
other ways the sufferer's brain is overactive. Most
schizophrenics appear to have an excess of dopamine in the
brain, the neurons become overloaded and relay inappropriate
messages (see Figure 40 for a modern view). Lack of activity
in the frontal lobes is a feature of states of mind in which
consciousness is disturbed. This might account for the
state's common reduction in planned or spontaneous behavior
and social withdrawal. The anterior cingulate cortex -
thought to distinguish between external and internal stimuli
- is also underactive (Figure 33), which
may be one reason schizophrenics confuse their own thoughts
with outside voices. |
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Recently in 2006, it is found that those
with mutations in the PCM1 gene had a significantly lower
volume of grey matter in their
orbitofrontal cortex resulting in poor judgement,
inappropriate social behaviour and not keeping themselves
clean. PCM1 plays a role in cell division, which in the
brain occurs more actively at adolescence - an age at which
schizophrenia is commonly diagnosed.
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Dementia - Dementia is used to describe the organic
deterioration of the brain that affects the elderly. The main, but
not sole, form of dementia is Alzheimer's disease, and 25 percent of
people who live to be older than 85 will show some symptoms. One of
the hallmarks of Alzheimer's disease is the accumulation of amyloid
plaques between neurons in the brain. Amyloid is a general term for
protein fragments that the body produces normally. In a healthy
brain, these protein fragments would be broken down and eliminated.
In Alzheimer's disease, the fragments accumulate to form hard,
insoluble plaques (see Figure 41). Neurofibrillary tangles consist
of insoluble twisted fibers that are found inside of the brain's
cells. They primarily consist of a protein called tau, which forms
part of a structure called a microtubule. The microtubule helps
transport nutrients and other important substances from one part of
the nerve cell to another. In Alzheimer's disease the tau protein is
abnormal and the microtubule structures collapse (see Figure 41).
There is an overall shrinkage of brain tissue as Alzheimer's disease
progresses. In addition, the ventricles are noticeably enlarged. In
the early stages of Alzheimer's disease, short-term memory begins to
decline when the cells in the hippocampus, degenerate (see Figure
41). The ability to perform routine tasks also
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declines. As Alzheimer's disease spreads
through the cerebral cortex, judgment declines, emotional
outbursts may occur and language is impaired. Progression of
the disease leads to the death of more nerve cells and
subsequent behavior changes, such as wandering and
agitation. The ability to recognize faces and to communicate
is completely lost in the final stages. Patients lose bowel
and bladder control, and eventually need constant care. This
stage of complete dependency may last for years before the
patient dies. The average length of time from diagnosis to
death is 4 to 8 years, although it can take 20 years or more
for the disease to run its course. |
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Vision - It is virtually impossible to carry out research into
visions in the laboratory, because they do not happen on demand; as
a result, the only evidence that visions do exist is the accounts of
those people who have experienced them. Vision may occur in response
to stress. They are often central to religious experience.
Out-of-body experiences are not restricted to religious practices:
they seem to occur in response to some kind of emergency situation.
This is the case with near-death
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experiences. There have been thousands of
reports of near-death experiences, many noting the same
types of sensations. Subjects feel as though they have left
their bodies. Some people report travelling down a tunnel
toward a bright light (Figure 42), where benevolent
presences wait. Scientists have been unable to explain them
conclusively. Some physiologists have suggested that
hypoxia, or low oxygen levels in the brain, might cause a
consistent pattern of hallucination in all sufferers. Other
scientists argue |
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that the experience stems from an acute bout
of "REM
intrusion" into the partially awakening state (in time of
extreme stress) similar to narcolepsy - a neurological
disorder characterised by uncontrollable bouts of sleep that
can cause elaborate hallucinations and, sometimes,
out-of-body experiences.
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¶The challenge of finding an ideal
model animal in which a physical basis of memory formation might be
revealed was taken up in the 1960s by
E. R. Kandel,
who eventually received the Nobel Prize in Physiology or Medicine in
2000 for his efforts on investigating the nervous system with
Aplysia. The Aplysia did not share the prize, but his daughter
Minouche at the age of seven has written a poem to enshrine the
animal:
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An aplisa is like a squishy snail.
In rain, in snow, in sleet, in hail.
When it is angry, it shoots out ink.
The ink is purple, it's not pink.
An aplisa cannot live on land.
It doesn't have feet so it can't stand.
It has a very funny mouth.
And in winter it goes to the south.
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