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Neurology Anatomy Physiology

December 14, 2021

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

Memory

Memory
Higher Functions
Altered States

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Altered States

It is not possible to divide states ofIt 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

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. Figure 33 Altered States [view large image]

Dreaminge 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

Figure 34 Dreaming Cat [view large image]

sleep, the very nice cat becomes a vicious tiger when it is dreaming and throws itself at imaginary prey. Evidence of the rather macabre biographies of serial killers shows that they had frequently recurring violent fantasies before they turned to murder.

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 le="color: #000"> Figure 35 Daydream [view large image]

Meditations 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

Figure 36 Meditation [view large image]

been shown to "turn off" areas of the brain normally associated with seeking stimuli, including the parietal, anterior and premotor cortexes (Figure 33).

continued to altered states part-2

Go to the nervous system

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