The information in this article may be used when explaining the principle of how the physiology and anatomy of the nervous system affects our behavior or the effect of neurotransmission on behavior. Here I will present a simplified view of how our brain affects behavior. Our brain consists of billions of neurons, connected in a complex network. The brain does does not have any central system, instead there are many interacting systems in this network. This parallel processing of the brain is different from the serial processing of most computers (however, the left brain hemisphere process information more serially than the right brain hemisphere). The brain and body also interact with the environment. In addition, information from our senses can trigger memories and influence behavior.
The interacting systems of the brain can sometimes work together, and sometimes work against each other. Sometimes, supposedly, we can have conflicting impulses, which may cause indecisiveness. For example, the sight of a cookie may trigger an impulse to eat the cookie, but the decision making processes in the frontal lobe may suppress this impulse because we are thinking of our weight. In order to understand how the brain can either suppress or activate certain behavioral tendencies, one should be aware of that neurons can either transmit or not transmit electrical impulses, but whether they do depend on the neurotransmission in the synapses. Different types of neurotransmitters, produced in different regions of the brain, can either excite or inhibit the activity of neurons. They do so by affecting different types of receptors in the neurons. Therefore, the neurotransmitters in the brain can excite or inhibit systems of the brain, which in turn will have an affect on our behavior. In one particular situation, some processes may be inhibited, whereas others are excited, which will produce a certain behavioral output. In the cookie example, the neurons that control our desire to eat the cookie were inhibited whereas the neurons that control our conscience were excited. GABA is the most common inhibitory neurotransmitter in the brain. This amino acid is found naturally in brown rice, and has a calming effect on the body. The major excitatory neurotransmitter in the brain is Glutamate, which is important for memory processes. As you know, there are also many other neurotransmitters. One example is Acetylcholine, which is related to learning, memory and movement. Another example is Dopamine, which is related to fine motor movement and pleasure. The effect of nerve gas demonstrates the importance of neurotransmission for behavior. Nerve gas destroys the synapses, preventing them from sending signals, so that the body and brain lose their functioning. The same is the case with the arrow poison Curare, which is used by the South American Natives. Curare paralyzes its victims, mainly because the chemical blocks the ability of the neurons to receive Acetylcholine. Besides Acetylcholine, Dopamine is also important for motor movement. Patients suffering from Parkinson´s disease, which primarily affects body movement, have an underproduction of Dopamine. In the 1960s, the neurologist Oliver Sachs managed to wake up a group of patients suffering from the Parkinson related disorder Encephalitis Lethargica (also called "sleepy sickness") by giving them L-Dopa. L-Dopa is a medicine that stimulates Dopamine production in the brain. After decades of sleep, these patients woke up from their catatonic state, trying to deal with a new life in a new time. However, after only a few weeks, they developed a tolerance to the drug, relapsing into their catatonic state. This true story has been dramatized in the movie Awakenings with Robin Williams and Roberto De Niro. Drugs can influence our behavior just because they influence neurotransmission. Drugs enter your bloodstream and are small enough to cross the blood-brain barrier. Because drugs imitate natural drug chemicals they bind to the same receptors and can therefore alter our consciousness. Alcohol prolongs the effect of GABA in the synapse, making us more relaxed. Cocaine blocks the reuptake of Dopamine of the presynaptic, increasing the effect of the transmitter (pleasure). Caffeine reduces the production of GABA, making us more aroused. Here are some animations on how neurotransmission works along with how drugs affect neurotransmission, should you be interested. Animation on how neurotransmission works Animations on how drugs affect neurotransmission It has sometimes been claimed that the biological view of behavior is deterministic and threatens our notion of free will. A number of studies that are challenging the notion of a conscious free will were conducted by Libet in the 1980s. Participants were seated in front of a computer screen with a moving dot. They were asked to carry out a simple action within a certain time frame. When they did it was voluntary. They were told to state where exactly the dot on the screen was when they consciously decided to take the action. Their motor movement in the hand and the brain activity was measured by EEG. Results demonstrated that the neurons in the hand and brain were activated before they had consciously decided to take the action (when they consciously decided to take the action could be estimated by the position of the dot on the screen). This study may challenge our view that free will is conscious. It may, however, still be unconscious. Other studies have challenged Libet´s assumption. In one study, patients undergoing awake brain surgery were electrically stimulated areas in the parietal region. Stimulating the areas triggered a strong intention and desire of the subject to move his limbs or talk. If stimulation intensity was increased, participants thought they had performed the movement. If the researchers stimulated some areas of the motor region which led to mouth or limb movement, patients denied that they had moved. This study and others suggest that conscious intention arises before movement, and that the intention process for motor movement can be found in the parietal lobe. Therefore, whether we have free will or not is still a question of debate.
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AuthorThis is my class blog for IB Psychology. Here I will publish reflections on psychology, reviews of psychology books, recommended links, lecture notes, and information on psychology topics that are not covered by the syllabus. You are free to add comments or ask me questions. Archives
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