Friday, May 20, 2016

Dopamine: Schizophrenia and Parkinson's disorder.

Dopamine and its Relationship to Parkinson’s Disorder and Schizophrenia

            Dopamine is one of the brain’s neurotransmitters (Carlson, 2013). This neurochemical performs an important role in concepts such as movement and motivation. The purpose of this essay is to explore the many functions of dopamine and its influence on behavior.
            The beginning of the subject of this essay starts when tyrosine is synthesized into dopamine (Cumming, 2009). Dopamine has been placed in the category of monoamines and in the subcategory of catecholamines, which is a class of amines that includes the above mentioned neurotransmitter, norepinephrine, and epinephrine. Moreover, the chemical Tyrosine hydroxylase is the enzyme (a catalyst that either breaks or combines components (Encyclopædia Britannica, n. d.)) involved in the biosynthesis of catecholamines (Kuhar, Couceyro, Lambert, n. d.). Its cofactor is biopterin, which is a common cofactor for enzymes, and uses molecular oxygen and tyrosine as its substrates.
 After Tyrosine, which is an amino acid, receives an oxygen and a hydrogen atom it becomes L-DOPA (Carlson, 2013). DOPA decarboxylase, which is another enzyme, removes the carboxyl group from DOPA in order for it to become dopamine (Kuhar et al., n. d.). Later, dopamine β-hydroxylase is used to synthesize epinephrine or norepinephrine, but for the purpose of this essay we are going to stop in the biosynthesis process here.


The image above shows the chemical structure of tyrosine. When tyrosine hydroxylase converts tyrosine into L-Dopa the structure changes and ends up looking like the structure below.

After DOPA decarboxylase acts upon L-Dopa, the following changes in the chemical structure take place., thus, becoming dopamine.

       The most important dopaminergic neurons are in the substantia nigra and ventral tegmental area (Carlson, 2012). The former and the latter are in the midbrain. It has been calculated that the dopamine cells in the substantia nigra measure on average 50 μm (Cumming, 2009). The measure that was just mentioned refers to the idea of a micrometer, or the millionth of a meter. In addition, they are usually pigmented, which is caused by neuromelanin granules in the cytoplasm of the cell. Moreover, it has been calculated that there are around 300, 500 dopamine neurons in each side of the substantia nigra and that around 8% is lost per decade due to aging (Cabello et al. 2002).

            The physiology of dopamine neurons is similar to other neurons. For example, they are polarized at -70mV and this is kept this way by the activity of sodium and potassium (Cumming, 2009). Nevertheless, something different is how they temporarily increase dopamine release by firing in bursts, which depends on the depolarization of the neurons (Grace, 1991). The dopaminergic cells mentioned in the paragraph above have their axons pointed towards the neostriatum, which has been accredited to be involved in movement. Another connection that involves movement is between the substantia nigra and the corpus striatum. This is why dopamine cells are connected with Parkinson’s disease. According to the National Institute of Health, when the neurons mentioned above die or become impaired there is less dopamine in the central nervous system, and this is what lead individuals to develop Parkinson’s disease (National Institute of Health, n. d.).

            In fact, it is possible to induce Parkinson’s disorder. Researchers, specifically biopsychologists, are able to explore more about the disease once it is induced in rats. One way of performing this technique is by intracerebral injections of the dopamine analog 6-hydroxydopamine (6-OHDA). This is a neurotoxin that damages dopamine pathways (Hanrott et al., 2005). Another way in which Parkinson’s disease can be induced is when MPTP, or meperidine analog 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine, enters the blood-brain barrier. This causes dopaminergic neurons to be poisoned and asphyxiate from the inside (Cummings, 2009).

            Another mental illness that is affected by dopamine is schizophrenia. One of the first connections discovered between dopamine and schizophrenia was with the use of chlorpromazine in 1952 (Ban, 2007). This drug was used by psychiatrists mainly to treat anxiety, however, it was also given to psychotic patients. It was not really efficient in the former, but it was for the latter. This happened because chlorpromazine is a dopamine antagonist, specifically it blocks D2 and D3 dopamine receptors (Carlson, 2012).

If dopamine antagonists are able to remove positive symptoms, then, people that are not schizophrenic would experience them after consuming agonists. This happens when individuals consume drugs such as amphetamine, cocaine, or L-Dopa. The first two block reuptake and the last one stimulates the synthesis of dopamine.

            The use of a dopamine antagonist used to treat psychosis and the idea that dopamine was also a neurotransmitter, and not only a precursor for norepinephrine, strengthen the idea that hyperactivity of dopamine was the cause of schizophrenia, at least for the positive symptoms (Brisch et al., 2014). There are three classifications of schizophrenic symptoms. They are positive, negative, and negative. The first category are symptoms that add something to the individual. This includes delusions, which are false ideals (Delusions, 2016), hallucinations, which are perceptions that are not real (Hallucinations, 2016), and thought disorders, which refer to a confusion in cognition (Thought-disorder, 2016). The negative symptoms refer to an absence or the decrease of a behavior. This includes being socially withdrawn, lack of affect, and reduced motivation (Carlson, 2012). The last category, which is cognitive symptoms, refers to those that add distortion to thinking. These symptoms include problems in memory, attention, learning, and problem solving (Carlson, 2012).

The Three Categories of Symptoms in Schizophrenia

Negative Symptoms
Social Withdrawal
Lack of Affect
Positive Symptoms
Cognitive Symptoms
Problems in Attention
Problems in Learning
Problems in Memory

            The hyperactivity of dopamine theory does not only mean that there is an excess of dopamine, but it can also indicate that the dopaminergic receptors are hypersensitive. This happens for several reasons. One of them is that because D2 dopamine receptors are blocked, usually because of anti-psychotic medication, their affinity increases (Seeman et al., 2014). All of the statements above are related to hyperactivity of dopamine and its relation to positive symptoms. However, the cause of the negative ones has not been explained.

Neurological damage is the believed cause, or at least the most supported theory, for the negative symptoms of schizophrenia. There are several reasons that support this fact. The first one is the similitude between other disorders that are caused by brain damage and the negative symptoms that are present in schizophrenics (Hall, 1998). The evidence of damage to the brain is seen in the large ventricles, which are spaces in the forebrain and brainstem that if large indicate loss of brain tissue (Purves, 2001), that are shown on computerized tomographic (CT) scans. The symptoms that are found in people with large ventricles, not only schizophrenics with negative symptoms, include catatonia, which is a lack of movement (Catatonia, 2016), and poor visual pursuit, which is a lack of ability in following an object with the eyes (Visual Pursuit, 2016).

            Usually, the damage has to occur in the prefrontal cortex in order for negative symptoms to be present (Hall, 1998). Other individuals that have damage in the same areas of the brain perform similarly to schizophrenics in the Wisconsin Card Sorting Test (WCST) (Everett et al., 2001). This test involves sorting cards into three categories: shape, color, and number of figures. If an individual shows no problems in arranging cards into one category, but presents difficulty when asked to change the classification, they would be categorized as being behaviorally inflexible. This refers to the notion that an individual or an animal can or cannot adapt their behavior (Brown & Tait, 2014).

            In addition, it is possible for an individual to present both types of symptoms. This involves both theories, the neurological damage in the prefrontal cortex and hyperactivity of dopamine or hypersensitivity of dopaminergic receptors, working together. This would mean that the brain damage that causes the negative symptoms is actually harming neurons that inhibit dopamine release, and thus causing the hyperactivity of dopamine.


Ban, T. A. (2007). Fifty years chlorpromazine: a historical perspective. Neuropsychiatric Disease and Treatment3(4), 495–500.
Brisch, R., Saniotis, A., Wolf, R., Bielau, H., Bernstein, H.-G., Steiner, J., … Gos, T. (2014). The Role of Dopamine in Schizophrenia from a Neurobiological and Evolutionary Perspective: Old Fashioned, but Still in Vogue. Frontiers in Psychiatry5, 47.
Brown, V., & Tait, D. (2014). Behavioral Flexibility: Attentional Shifting, Rule Switching and Response Reversal. Springer Reference. doi:10.1007/springerreference_169297
Cabello, C. R., Thune, J. J., Pakkenberg H., & Pakkenberg, B. 2002, “Ageing of substantia nigra in humans: cell loss may be compensated by hypertrophy”, Neuropathol. Appl. Neurobiol., vol 28, no. 4, pp. 283-291.
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Grace, A. A. (1991). “Phasic versus tonic dopamine release and the modulation of dopamine system responsivity: a hypothesis for the etiology of schizophrenia,” Neuroscience, Vol. 10, no. 2, pp. 333-348.
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Sunday, May 8, 2016

Behaviorism (Part 1)

For more information on the history of psychology please check out "A History of Modern Psychology," by C. James Goodwin.

Behaviorism is a school of thought in philosophy and psychology that focused on only studying concepts that were observable like behavior and ignoring those that were invisible to the eye such as the mind (1). The term was coined by John Watson.

Behaviorism before John B. Watson

People usually think that Watson was the one who invented the innovative ideas that pertained to behaviorism, but the truth was that they were appearing in different countries throughout time. The concept that outside experiences and not mental processes were what shaped individuals was central in British empiricism (2); it was also an important point of view in the discussion of nature vs nurture. Moreover, physiologists spread in the 19th century ideologies known as materialistic and mechanistic. The former is the idea that everything is either physical or can be reduced to a physical component (3). The latter is similar, it is the point of view that natural processes can be reduced to matter and motion (4). In addition, August Comte, a French philosopher, developed positivism, which is the notion that knowledge should only come from observable experience (5). A picture of John B. Watson can be found to the right. These ideas started to infiltrate psychology. For example, in experimental psychology, psychologists decreased the use of studies that required introspection and instead were interested in experiments that used animals such as maze studies. Additionally, there were statements like those of James McKeen Cattell that asserted that their laboratory focused very little on introspection, and that behavior, and not the study of mental processes, contributed more to the general pool of knowledge in psychology (6).

Ivan Pavlov

Many of you might have heard of Ivan Pavlov. He won the Nobel Prize for his research in digestion. Pavlov conditioned dogs to salivate when they heard the sound of a bell. He was the director of the Institute of Experimental Medicine and trained his new students, which usually were physicians that were trying to get their PhD, to replicate old studies about digestion. 

He designed several types of experiments. One of them was collecting stomach fluids by using a technique that is now known as the "Pavlov's Pouch." This is a cut made in the stomach that collects fluids without being contaminated by the food (7). The fluids were sold to other labs so they could study them too, as well as to the public because it was marketed as an elixir that helped with digestion. However, his most notorious experiment involves the recollection of saliva. Before we go into detail about Pavlov's conditioning experiment, it is important to describe one conducted by S. G. Vul'fson who was one of Pavlov's students. This experiment explored the amount of saliva produced by dogs when shown dry or moist food. After initial trials, the dogs started to salivate when they expected the food. This messed up the data, but interested Pavlov because the salivation was consistent. Thus, the Institute created a research laboratory known as the Tower of Silence. The name came to be because there were rooms that were soundproof so that the dogs would not be influenced by sound.

He reported this in the lectures that summarized 25 years of his work that were later translated to English by one of his students, G. V. Anrep. The English version of the lectures was titled Conditioned Reflexes: An Investigation of the Physiological Activity of the Cerebral Cortex." Pavlov explained that the salivation to food was a reflex and that the salivation to the stimulus that announced food became a learned reflex. He named this type of learned reflexes conditioning.

There were four terms that were central to his theory. To explain each concept the concept Unconditional stimulus (UCS), which is a stimuli that can cause a response, but does cause a learned reflex (In this case, the UCS is the food. The unconditioned reflex (UCR), is an unlearned response. In this case, the UCR is the salivation by the dog. The third term is conditioned stimulus (CS). This refers to a stimulus that would not have caused a response if it had not been conditioned. In this case, the CS is the bell. Finally, the conditioned reflex (CR), is the learned response to the CS. In this case, it would be salivation. In other words, a bell doesn't cause a dog to salivate (UCR), but food (UCS) does. However, when a bell and food are paired, the dogs starts to salivate (CR) when it hears the bell (CS) because it expects food.







6. "A History of Modern Psychology," by C. James Goodwin


Tuesday, May 3, 2016

The Use of Psychology as a Justification of Discrimination

The purpose of this essay is to explore the ways science was used in order to justify discrimination. An emphasis will be placed on psychology and Mexican-Americans living in the United States that were the targets of prejudices.
There were several areas of science that were used to discriminate individuals in the United States. The first one that will be explored is the intelligence test known as the Binet-Simon scales. It is important to note that a test bias is an error that can be found in the results of said tests in two ways. The first one is in the design of the test, such as the sample chosen or the operant definition of a variable. The second form of a test bias is seen socially. An example of the second form of bias is seen if a certain group, such as Chicanos or Mexicans living in the U. S., were not falling under the same regression line of the test.
There are four types of biases. The first one is called construct validity. This means that even though a test is supposed to measure a specific content, it is not accurately exploring it. In other words, a test is not investigating the same idea that is trying to measure. An example of this type of bias will be explored on the military test developed by American Psychological Association (APA) president Robert Yerkes.
The second type of bias is called content validity. This is when questions in the test are not fair for all participants. This can be caused by a lack of experience from a certain group. For example, Mexican Americans could be asked about food that is eaten traditionally in the south of America. But because they do not have the experience of eating that type of food within their culture, they should not be penalized or placed in a low category of mental intelligence. Another example of this type of bias can be seen in the wording or diction of tests. For example, if a question asks about instruments used for fishing, but Mexican Americans do not live, and thus have not experienced so far, in an environment surrounded of water bodies, the question would be considered to have a content validity bias.
The third bias is known as item selection. This refers to the notion, which is similar to content validity bias, that specific questions come from what the dominant group, in this case white Americans, are expected to know or perform. In other words, it is a narrowed type content validity bias, that ignores certain groups, such as Chicanos.
The last type of bias that will be explored is named criterion-related validity. This is the idea that the outcomes of a sample are not accurate in describing the population that is the target of the study. An example of this would be if Mexican Americans performed low in intelligence tests, would it mean that they would under-perform on job markets or would they not be successful employees because of their low intellect.
Before psychologist Ebbinghaus, who was known for his research in memory, explored a way to test intelligence, a measure known as the two-point threshold was correlated with academic performance. This measure explored how far two stimuli, such as the fingers of researchers placed on the backs of participants, had to be in order to be detected as two sources of physical stimulation instead of one.
What Ebbinghaus did was give students incomplete sentences so they could finish them in a complete manner. However, his test only divided students into strong and weak ones in terms of intelligence. Like Ebbinghaus, Binet thought that only cognitive processes such as memory tests and problem solving tasks, and not physical tests could determine intelligence.
            Students who were not academically competent were placed into three categories: The idiots, who were the worst of the worst, the imbeciles, who were better than idiots, but still performed poorly, and the debiles, who were the ones who were just below the average student, but still could be helped. The third category did not have a name; it was Binet who named it.
The Binet-Simon scale was the result of the development of Binet's test that involved cognitive processes and the help of his research assistance Theodore Simon. Both of them categorized tasks that someone of a certain age could perform, if the individual could not perform it, then they would be considered subnormal. Tasks for a three-year-old included showing were their facial feature where, for a five-year-old a task was to repeat a ten syllable sentence, for a seven-year-old it was to copy written sentences. Children who were nine years old had to arrange five weight in order (Dennis, 1984).
There are three things that are important to mention about Binet's opinion of his test. First, he did not think that intelligence was a unique component, but rather different types of skills interacting with each other. The second notion was that intelligence was not fixed, but rather a component of our lives that is always changing. Because of this idea, he developed material to help children increase their intelligence. The third belief was that his test would only be beneficial and useful in the educational context (Goodwin, 2015).
            The tests were used by other psychologists to classify undesired groups as mentally retarded people, especially in the 1900s. These groups included African Americans and Mexican American individuals. The discrimination occurred because there was a cultural bias in terms of the diction in the tests. This led intelligence to be challenged in the court. An example of this is the case of Larry P. v. Wilson Riles. The judge in the case ruled that the tests that were placing children on special education classes were biased. Nevertheless, the opposite happened in the case of Parents in Action in Special Education. The ruling in the latter found that tests were not used to discriminate and were not culturally biased.
            Psychologist Henry Goddard was the one who brought Binet’s test to the United States. He tried to use the leave the Binet scale and its techniques intact. However, he made the modification of renaming the category of debiles to morons. He used the Greek word moronia, which means foolish, as an inspiration to labeling the third category. This last category boosted the discrimination towards undesired groups of people in the U. S.
            This happened because groups that contained minorities, such as Chicanos, were said to be morons, and thus the cause of a lot of problems in their contemporary society. This meant, for eugenicists (the concept will be explained down below), that the answer would be to remove the undesired groups from the United States.
            However, the current IQ test is no longer culturally biased. The National Academy of Science created two panels and the American Psychological Association assembled a task force that found that neither the IQ nor other standardize tests under predict how Mexican American and other groups that are usually targets of discrimination would perform.
            The emphasis on the biological aspects of human beings was a result of the theory of Charles Darwin. He asserted that organisms changed throughout time by a process called evolution. This refers to the aided survival by mutations in the DNA that either helped living organisms avoid dying or helped them reproduce. The mutations could be beneficial or harmful. Francis Galton took the theory of Charles Darwin and explained that those mutations happened in individuals’ intelligence. Thus, there were groups, such as immigrants, that would never reach the intelligence of other groups.
            Galton, who was the cousin of Charles Darwin, introduced the concept and eugenics. This is the notion that human beings with desired attributes should be supported, encouraged, and protected, and the ones without those characteristics should not be allowed to live. This idea was central in the political system at the time. In fact, Hitler based his actions on the notion of eugenics. He described Eugenics as the “study of the agencies under social control that may improve or impair the racial qualities of future generations either physically or mentally” (1).
            An argument created against Galton was that the tests were limiting the resources of Chicanos because they were being penalized for having low scores on biased tests. Other arguments included that the tests’ language. For example, there are words that were commonly used by Americans in the north of the U. S., but unknown to the average Mexican American. Additionally, the tests were created using a normal distribution. Thus, if American students were used to generalize the intelligence test, the Mexican Americans would normally fall under the distribution. This means that the tests were not valid or reliable. According to the American Psychological Association and the American Educational Research Association, test should be fair and have as a purpose to help individuals, but as was seen before the Binet-Simon scales were not fair.
            Another form of intelligence tests that were target of controversy that revolved around Mexican American discrimination were those developed by President of the Psychological Association of America Robert Yerkes. He developed two types of tests: Alpha and Beta tests that were given to the military to test whether they were fit for combat. One of tests was given to literate individuals, which usually encompassed Americans. They had to read and answer questions related to word problem solving. The other test was given to illiterate people, which was usually groups of Mexican Americans. Participants had to finish incomplete picture and questions that revolved around completing patterns. This was biased and was not an efficient way to measure intelligence because the second test does not measure the same elements of the first test. This resulted in the bias known as construct validity.
            The tests created by Yerkes were used to discriminate immigrants coming from Europe during the first World War. People who followed the notion of eugenics did not wanted immigrants in the United States because they would alter the biological nature of intelligence in Americans. Therefore, the tests were used as evidence to support the desire of eugenicists to keep out the maximum number of immigrants coming to America. Nevertheless, it was not only used for European immigrants, but for Mexicans that were moving to the U. S. too.
            In conclusion, intelligence test developed by psychologists such as the Yerkes military alpha and beta tests and the Binet-Simon scale were used as a way to justify discrimination towards Chicanos. The tests were culturally and technically unfair and contained four types of biases that created a negative impact in the Mexican-American culture. Nevertheless, the tests have been revised and carefully crafted in order to avoid the prejudices that once existed in America.

Dennis, P. M. (1984). The Edison questionnaire. Journal of the History of the Behavioral Sciences, 20, 23-37.

Goodwin, C. J. (2015). A history of modern psychology. New York: J. Wiley.