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Reticular Activating System.

Extracts from this document...

Introduction

RETICULAR ACTIVATING SYSTEM + dreaming theories R.A.S. is very susceptible to damage. Is suppressed by chemicals during sleep. Acts as a filter of sensory messages passing through to the cerebral cortex. Function of R.A.S. Cut/lesion above R.A.S. This would cause a permanent coma. Cut/lesion below R.A.S. This would cause paralysis from the point below the lesion. Cut/lesion through RAS Damage to this will keep a person awake. Diagram including location of R.A S., pons, & Raphe nuclei. Chemical analysis of the RAPHE found SEROTONIN. (This was investigated to find a cur for coma victims). Serotonin is a neurotransmitter. This acts an inhibitor on the R.A.S. This leads to a gradual decrease in arousal. This is the mechanism for falling asleep. R.A.S. is also inhibited by nor-adrenalin, released by the pons. This closes the RAS system down further. Noradrenalin acts as and exitory agent on motor/sensory pathways and could cause REM/dreaming sleep. Havever found a system which reinhibits the motor pathwau after it has been stimulated by noradrenalin. (This stops you acting out your dreams.) He damaged this area in animals and they seemed to act out their dreams. (see animal experiments.) 2 There is a lot of complex bio-chemistry in the base of the brain controlling sleep. But they can hardly be there by accident of merely as remnants of past evolution! People on amphetamines (speed etc.) have difficulty on sleeping. These are given as an appetite suppressant. But patients soon get used to them and sleep normally. When they stop taking them they get a massive REM/Dream sleep rebound, (nightmares etc.) Line graph to show R.E.M. rebound and subsequent return to pre-amphetamine taking levels. _______________________________________________ 0 1 2 3 4 5 6 7 R.E.M. is maintained at a set level and therefore must be useful for something. Alcohol also caused lack of REM sleep. When prolonged drinking (heavy for several weeks) stops, REM sleep is increased to possibly and unpleasant level. ...read more.

Middle

He also believed that contact with the environment interacts with the biological structure. It is this interaction that leads to the dev. Of intellect. He focuses on how thinking changes in age-related stages and on what is common to all individuals as they pass through each of them. He became intrigued by the unexpected replies that children gave during his studies of intelligence and noted that there was a pattern to incorrect answers. He wanted to discover the thought processes behind them, as he believed that it was incorrect answers that would be the best indicators of how they think. Functional invariants are the aspects of the dev. Processes that remain constant and work in the same way throughout the stages. These include; assimilation applying existing schema to fit environment. Accommodation changing existing schema to fit the world. Brought about by a state of disequilibrium. ........................... equilibration Mental Balance achieved by matching objects and schemas The feature of development that does change is schemata. A schema can be thought of as the basic unit of intelligence. A baby s schema are of a reflex mature such as sucking, crying, rooting, gripping. 2 Schema cont. It is a way of organizing our experience, an internal representation of a sequence of actions, making the world more predictable. From birth existing schema are continuously used to interpret and cope with old and new situations. We try to make them fit. He called this assimilation. Inadequacies of existing schemas to deal with new situations force the change of one of more of them. He named this process accommodation. These two processes result in development. This can be expressed as the equation: assimilation + accommodation = adaptation Operation. This is a string of schema linked together, producing a more complex structure. This is acquired in middle to late childhood. 4 INVARIENT STAGES (continuous & universal) SENSORYMOTOR (0 to 2) ...read more.

Conclusion

Often the child will talk out loud until around 7 years-old when it becomes silent inner speech, internalized. The ability to use external symbols that converts elementary thought into higher thought. The effects of culture on higher mental functions was recorded by Gredler 1992. He noted a limited ability in coping with mathematical calculations amongst children of Papua, New Guinea. This, he believed, was due to the system of counting they are taught, which ends at 29. Vygotsky identified the Zone of Proximal/Potential Development. This is the distance between a childs current and potential abilities at any given time. He sees instruction by experts as wakening functions or abilities within the ZPD that may otherwise lay dormant. Without intervention the child will learn less. He claimed that, What a child can do with assistance today he/she can do by him/herself tomorrow. Peer tutoring was also seen by Vygotsky as an effective form of learning. 9 INFORMATION PROCESSING (Developmental Approach) Case 1974, suggested that the improved ability to process info. Occurs as children become able to use their mental space more efficiently. The M Space refers to the area of the brain where information is stored during processing. All cognitive activity can be divided into Figurative schemes, (equivalent to Piagets schemas), Operative schemes,(equivalent to Piagets operations), and Executive schemes that organize the other two to achieve a goal. Although there is a limit to how much info. the M space can hold, the amount the brain can process increases with age. This occurs because; Changes in the myelin sheath of the brains nerves lead to faster transmission of impulses. Strateges for info. Processing such a chunking become more automatic, freeing-up M space. Once schema are automatic children can think about an experience in more advanced ways and improve their problem solving techniques. Metacognitive skills (thinking and learning about how to acquire knowledge) usually follows the automation of schema and are important in cog. Dev. The effects of automation were demonstrated by Chi 1978. He found that children who were chess experts could recall more chess positions than non-expert adults. ...read more.

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