Consciousness and Its Variations

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Chapter IV
Consciousness and its Variations

Intro: 4.1 Consciousness
Your immediate awareness of thoughts, sensations, memories, and the world around you represent the experience of consciousness.
William James described consciousness as a “stream” or “river.” Although always changing, consciousness is perceived as unified and unbroken much like a stream. Because his idea of structuralism was based off of introspection, many of the leading psychologists at the turn of the twentieth century emphasized with the study of overt behavior, which could be directly observed, measured, and verified.

In mid 90’s many psychologists once again turned their attention to the study of consciousness. This was due to two main reasons. First it was becoming clear that a complete understanding of behavior would not be possible unless psychologists considered the role of conscious mental processes in behavior. Second was because psychologist had devised more objective ways to stud conscious experiences. For example, they could often infer the conscious experience that seemed to be occurring by carefully observing behavior. Technological advances in studying brain activity were also producing intriguing correlations between brain activity and different states of consciousness. Different perspectives that psychologist are using to piece together a picture of consciousness are the role of psychological, physiological, social, and cultural influences.

Biological and Environmental “clocks” that regulate Consciousness.
Through the course of the day, there is a natural ebb and flow to consciousness. The most obvious variation of consciousness that we experience is the daily sleep-wake cycle. These daily cycles such as this are called circadian rhythms. You actually experience many different circadian rhythms that ebb and flow over the course of any given 24hr period. Normally your circadian rhythms are closely synchronized with one another. For example, the circadian rhythm for the release of growth hormone is synchronized with the sleep-wake circadian rhythm so that growth hormone is released only during sleep.

The suprachiasmatic Nucleus:
Your main circadian rhythms are controlled by a master biological clock-a tiny cluster of neurons in the hypothalamus in the brain. This tiny cluster of neurons is called the suprachiasmatic nucleus, abbreviated SCN. The SCN is the internal pacemaker that governs the timing of circadian rhythms. The most important environmental time cue is bright light, especially sunlight. The light is detected by special photoreceptors in the eye and is communicated via the visual system to the SCN. As the sun sets each day, the decrease in available light is detected by the SCN, and then in turn the CN triggers an increase in the production of a hormone called melatonin. Melatonin is manufactured by the pineal gland, an endocrine gland located in the brain. Increased blood levels of melatonin help make you sleepy and reduce activity levels. The levels of melatonin rise at night and peak around 0100 and 0300. Melatonin levels drop shortly before sunrises. The pineal gland stops producing melatonin, as the light from the sun is senesced by the SCN.

Circadian Rhythms and Sunlight: The 24hr day
Since the light from the sun helps regulate our circadian rhythm, what would happen if the external environmental factors were taken away? Well the circadian rhythm then will be referred to as a free-running condition, because the body’s internal clock runs freely and independently of external time cues. Without the external time cues researchers have found that our internal body clock drifts to its natural (or intrinsic) rhythm. They also found that our natural circadian rhythm is about 24.2 hours, or slightly longer than a day.

Also as our melatonin peaks, our body core temperature also drops to it’s lowest. But when deprived of all external environmental cues your body’s sleep-wake, body temperature,...
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