'When you think about brain activity it's correct to think about emergent properties at higher levels that depend on lower-level phenomena in the system.'Philosopher Patricia Churchland of the University of California (1)
The brain stem
The brain stem, sometimes called the reptilian brain, is the oldest part of the human brain.
The main purposes of the brain stem, including the cerebellum and some of the lower portions of the midbrain, are to warn us of incoming information; to adjust posture and coordinate all muscular movements in the body; and to perform involuntary behaviours such as activating muscular contractions in the heart, intestines and other organs of the body vital for our life support system. (2)
Damage to the brain stem either causes immediate death or permanent paralysis in certain parts of the body.
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The midbrain section
The midbrain section, sometimes called the mammalian brain because of its high state of development in all mammals, consists of the thalamus, limbic system or primal brain and basal ganglia.
The limbic system can be further subdivided into three other structures known as the pituitary gland, hypothalamus and hippocampus.
The basic function of the hypothalamus is to set up a biological clock that regulates the rate of muscular contraction in the body and the various biochemical reactions for controlling or alerting us of our instinctive need to eat, drink, sleep and wake, often on a regular, periodic basis. Furthermore, the hypothalamus also affects body temperature, water balance, bodily elimination and blood pressure. It achieves all these wide-ranging and vital functions by a combination of nervous impulse transmissions through the spinal cord and the secretion into the blood stream of a multitude of chemical hormones in the glands of the body through the master gland known as the pituitary gland. (3)
The removal or damage of the hypothalamus causes immediate death as the body cannot properly coordinate all of its functions in the right way on its own and the brain stem and cerebral cortex have not learned all the patterns needed to take over the functions of the hypothalamus for regulating basic bodily functions.
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The hypothalamus also provides one other benefit to a living organism: it affects how we feel which in turn affects how we think and behave. In other words, this important structure, together with the pituitary gland, holds the seat of the two most elementary physiological emotions of great survival importance (4). These two emotions are normally represented in our everyday language as pleasure and pain, happiness and sadness, positive and negative, the good side and the bad side and so on.
The hypothalamus can do this because it can release certain pleasurable hormones like endorphin, seratonin and enkephalin during moments of actual or imagined sexual ecstasy or even deep peaceful rest, or the more unpleasant hormones like the steroid cortisol, which rapidly increases heart rate, perspiration and our ability to fight infections when we are stressed.
The constant denial to pleasurable experiences over a long period of time may reduce or even stop the production of pleasurable hormones in the brain. The eventual result is chronic depression and only legal drugs such as prozac and SAM-e (avoid seroxat in the UK or paxil in the US and its equivalent aropax in Australia because of the potential to create serious hallucinatory problems in around 25 per cent of patients and a greater probability of suicide among young people below 18 years of age) can help safely trigger the brain to produce the pleasurable hormones for alleviating the depression.
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As for the hippocampus, this structure seems to be designed to behave like short-term memory (the nearest analogy to this would have to be the Random Access Memory or RAM of a computer) where information gathered by the nervous system over the last few days or even weeks is temporarily stored (and possibly drawn upon by other parts of the brain). It is also a place where the neurons of the hippocampus are able to manipulate the information stored there at a very rapid pace before transfering or returning the essential patterns extracted from the raw information to more permanent storage areas in the cerebrum (if considered important), or in order to perform some immediate action/behaviour if the pattern is already known and recognised.
Damage to the hippocampus does not necessarily cause death, but will make it virtually impossible for a person to learn and remember new patterns. Hence an adult with minor damage or deterioration (including shrinkage) of the hippocampus will look normal in every respect except that he/she will quickly forget such simple things like a new person's face, or where his new place of residence actually resides, as soon as the experience or knowledge of the new event is removed.
Children who are abused or traumatised may also suffer deterioration through shrinkage of the hippocampus according to the Stanford University study of 15 children. According to findings published in the March 2007 edition of Pediatrics, highly stressed children as measured by the amount of cortisol from saliva swabs appear to have their hippocampus regions shrunk when their brains were analysed. As the head of the study, Professor Victor Carrion, said:
'[The children, aged 8 to 14 years, had all suffered] traumatic events including witnessing violence, physical abuse, separation and loss, sexual abuse, physical neglect and emotional abuse.
'...[The findings] provide preliminary human evidence that stress may indeed damage the hippocampus.' (Robotham, Julie. Abuse can spur brain shrinkage in children: The Sydney Morning Herald. 3-4 March 2007, p.5.)
Researchers also noticed the shrinkage was highest among those children whose cortisol levels were at their highest.
To develop the functions of the hippocampus, exposing oneself to regular changes (ie. access to new experiences and knowledge) in a positive environment and applying the mind to remembering and testing the memory to recall those changes (perhaps about 15 minutes per day) will help strengthen short-term memory. And it should be done in a positive and fun way for the technique to work effectively.
## SPECIAL UPDATE ##
24 August 2006
People who use their brain to regularly solve problems and remember things causes the hippocampus region to stay large and active and this helps to protect older people from getting dementia.
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The structure called the basal ganglia is primarily concerned with initiating movement in the body. (5)
Finally, the thalamus is a major sensory integration centre and seems to be designed to help with, or initiate, consciousness with the outside world (6). In other words, the thalamus can control and rapidly process a great deal of information from the sensors of our body (except vision and smell, which go almost entirely to the cerebrum (7)) and to link this sensory information to other important functions in the brain.
The removal of the thalamus will probably cause death or instead the individual will be unable to process external stimuli of the sensors and therefore may withdraw entirely into the inner world.
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