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C3 Implications in the real world - Applications. Schizophrenia: Biological Explanation 1- Genes Schizophrenia – Biological Explanation 2: Structural Abnormalities (pg 116-117) What I will need to do: Be able to describe two biological explanations of schizophrenia (AO1) Be able to evaluate both of these explanations (AO3) Be able to apply these explanations to a novel scenario (AO2) First things first: some basic neuroanatomy Before we can look at the structural abnormalities in the brain that may lead to schizophrenia, it will be helpful to have a short tour of the three pounds of grey stuff you carry around in your head. This is just a very brief overview as neuroanatomy could be a whole A-Level by itself! A really useful website that can help you understand more about the brain (and a website we will be using in lessons) is www.finr.net/files/brain/index.htm. Here you can interact with a 3D brain and locate all of the key regions. Firstly, the brain can be split into three main sections. The cerebellum (“little brain”) is tucked underneath the cerebrum. This part of the brain is involved in motor control (movement). The brain stem regulates the body’s automatic processes (such as breathing) and also connects the brain to the spinal cord and the rest of the body. Using the picture on the board, colour in the four lobes. The cerebrum or cerebral cortex is the main part of the brain. This contains the thick top layer of brain called the cortex as well as the subcortical regions. The cortex is a thin layer of neurons around 2-4mm thick. It is folded many times to give it a huge surface area. As you should remember from Year 12, the cerebral cortex is separated into two hemispheres, and these each into four lobes (frontal, temporal, parietal and occipital). Each lobe has a number of functions that they perform. The occipital lobe for example is involved in vision and the temporal lobe with language. For a more detailed breakdown of what each part of the cortex is responsible for, refer to the sheet Anatomy and functional areas of the brain. If you were to peel back the cortex, you would find many subcortical regions. It includes the limbic system, containing amongst other parts, the hypothalamus, the hippocampus and the amygdala. The limbic system vital for emotions and motivation and also plays a role in memory. The two hemispheres are connected by the corpus callosum which enables communication between the two sides of the brain. The brain also contains a number of cavities filled with cerebrospinal fluid called ventricles. These ventricles help supply the brain with nutrients and remove waste. They apply internal pressure to help keep neurons in place inside the brain. When the brain is damaged or injured, these ventricles fill will fluid and enlarge to maintain the pressure that was lowered when neurons are destroyed. 1 C3 Implications in the real world - Applications. Schizophrenia: Biological Explanation 1- Genes Before we learn about what research has found about the brains of schizophrenics, what parts of the brain might you expect to be implicated in schizophrenia and why? Refer back to the handout on the characteristics of the illness to help you. Structural abnormalities in the brain and schizophrenia In the early days of psychology, schizophrenia was treated as a psychological illness, and as such was treated with psychological treatments such as therapy or psychoanalysis. However, once it was discovered that certain drugs could alleviate the symptoms of schizophrenia, the idea of the illness being (at least partly) biological began to be taken seriously. Psychologists began to look at the brains of schizophrenics; first after death in post mortems, and then as technology progressed they were able to look at living brains using scanners. These studies have shown that there may exist structural differences between the brains of schizophrenics and nonschizophrenic controls. Perhaps it is these structural differences that are the cause for schizophrenia? Cause and effect: neurodegenerative or neurodevelopmental? However, before we examine the evidence, and highlight those brain areas that may be responsible for schizophrenia, we have to bear in mind a very important issue; that of cause and effect. If the brains of schizophrenics differ from those of controls, it may be that these structural differences are the cause of the illness. However, it may be that the illness itself causes the brain changes. It may be a combination of the two. Maybe there are some initial brain abnormalities that cause the disorder, and then further changes in the brain occur as the schizophrenia progresses. This links in with the question as to whether schizophrenia is a neurodegenerative or neurodevelopmental illness. In neurodevelopmental illnesses, parts of the brain do not develop properly. This could be an issue of genes, prenatal development or events in childhood for example. If schizophrenia is neurodevelopmental, we would expect to find changes in the brain right from the start of the illness, and this damage would not change much over time. Therefore, we could say that the changes in brain structure have caused the schizophrenia. If schizophrenia was a neurodegenerative illness on the other hand, we would expect that there would be few brain changes at the start of the illness, but a progressive worsening of brain damage over time. Therefore, we would say that the changes in brain structure were caused by the schizophrenia. We will come back to this question of whether schizophrenia is neurodegenerative or neurodevelopmental once we have examined the evidence. 2 C3 Implications in the real world - Applications. Schizophrenia: Biological Explanation 1- Genes Brain ventricles One reliable finding from many studies that have used brain scans is that the brains of schizophrenics differ in the size of their ventricles. In schizophrenics, these ventricles tend to be bigger than in controls. Weinberger et al (1979) used CAT scans to compare schizophrenics with controls. Summarise his findings. An additional finding was that it did not matter how long they had suffered schizophrenia for, nor was it related to the type of medication they were taking. Look back to the information about ventricles on the first page. What might enlarged ventricles suggest? Cortical Atrophy The picture here shows a brain scan of a normal brain on the left, and a schizophrenic brain on the right. What differences can you see between these two images? What does the term cortical atrophy mean? What are the two ways that it can occur? 3 C3 Implications in the real world - Applications. Schizophrenia: Biological Explanation 1- Genes What did Vita et al (1988) do and find? So it seems that schizophrenic brains suffer from a loss of volume. However, it might not necessarily mean that there are fewer neurons (brain cells). It might be a reduction in the connections between these neurons (as argued by Feinberg ,1982). As well as neurons, the brain also contains support cells called glial cells. Reduction in brain volume may be due to the reduction of these glial cells rather than neurons. How might cortical atrophy explain the increased ventricle size? Reversed Cerebral Asymmetry Our brains are not totally symmetrical. The temporal, parietal and occipital lobes are usually larger on the left side of the brain, and the frontal lobe is usually larger on the right. The cortex also differs, with many parts of the left hemisphere having more folds than the right. More folds mean more surface are, so the left hemisphere seems to have more cortical space than the right hemisphere. However, this usual pattern of asymmetry is not seen in the schizophrenic brain. In many schizophrenics, the right hemisphere is larger than the left (the reverse of non-schizophrenic brains). As language function is located on the left hemisphere, this reversed asymmetry may account for some of the symptoms of schizophrenia such as alogia. What did Luchins et al (1979) do and find? How do these brain changes relate to the symptoms of schizophrenia? So there do seem to be some structural differences between the brains of schizophrenics and non- schizophrenics. But how do these structural changes actually relate to the symptoms of schizophrenia? These structural differences do not just affect one area of the brain; the differences tend to be global and multiple areas of the brain seem to be affected. Schizophrenia is clearly a complex and variable disorder, and to highlight every possible cognitive and social deficit present in schizophrenia and locate the area of the brain responsible would take days! The research below is just a flavour of the various ways in which structural abnormalities might explain the symptoms of schizophrenia. 4 C3 Implications in the real world - Applications. Schizophrenia: Biological Explanation 1- Genes Jibiki et al (1991) used EEG scanners on schizophrenics and found that there were disruptions to the visual processes in the occipital lobe, meaning that schizophrenics have a reduced capacity to detect motion. This could explain the misperceptions and hallucinations experienced in schizophrenia. Andreasen at al (1994) found that the metabolic rate (an indication of the amount of activity happening) of the thalamus is lower in people with schizophrenia. The thalamus is a subcortical part of the brain that is vital in directing sensory information, attention and memory, and is referred to as the “switchboard” of the brain, linking the cortex to subcortical regions. Damage to the thalamus could explain the confusion and illogical thinking of schizophrenics. Goghari et al (2011) found that schizophrenics had damage to temporal lobe structures, including reduced volume in the fusiform gyrus, a part of the brain responsible for facial recognition. Those with reduced volume in this area had problems with emotional recognition, a common symptom of schizophrenia. Neurodegenerative or neurodevelopmental? So, back to our original question; are the structural abnormalities present in the brains of schizophrenics neurodevelopmental (and therefore likely to be the cause of schizophrenia) or are they neurodegenerative (and likely to be a result of schizophrenia)? To determine the answer to this question, we need to look at results from longitudinal studies of schizophrenics to see if the structural abnormalities are stable or change over time. Oblai et al (2011) conducted a meta-analysis of longitudinal studies of schizophrenics. They found that the illness showed a clear progression with brain volume decreasing over time. An alternative to a longitudinal study is to could compare chronic schizophrenics with those who are at a high risk for schizophrenia, but have not developed the disorder. Chan et al (2011) reviewed the results of previous studies, and found that those at a high risk for schizophrenia had smaller brain volume and enlarged ventricles, even before showing any symptoms of psychosis. Those with chronic schizophrenia also showed this, but also had further damage to parts of the brain, for example, a smaller hippocampus. Do the studies above suggest that schizophrenia is neurodegenerative or neurodevelopmental? Explain why. Evaluation of theory One huge strength of the theory that schizophrenia is related to structural abnormalities in the brain is that the findings from the studies conducted are highly reliable. This means that the same structural abnormalities are found time after time when studies are replicated. This is strong evidence that structural brain abnormalities are at least involved in schizophrenia, even if they are not the ultimate cause. 5 C3 Implications in the real world - Applications. Schizophrenia: Biological Explanation 1- Genes o However, these structural abnormalities are not present in all schizophrenics. Also, factors such as age, gender and severity of symptoms can affect the prevalence and pattern of these structural differences. Therefore, we need to acknowledge that there may be other factors that may account for the illness. Another issue with this theory is that the structural abnormalities present in schizophrenia are also present in a number of other mental illnesses, such as bipolar disorder and schizoaffective disorder. There is a methodological problem with conducting brain scans on schizophrenics. It is highly likely that many of the schizophrenics in these studies will be on antipsychotic medication. Therefore, the structural abnormalities found may be the result of the medication that the patient is taking, and not the illness itself. Particularly, taking antipsychotics for a long period of time might account for the changes associated with neurodegenerative explanations of the illness. One of the biggest problem with this theory, and one to which there is still not a complete answer to is that of cause and effect. Are the structural abnormalities the cause of the schizophrenia, or are they caused by it.? This in turn poses more questions: o If the structural abnormalities caused the schizophrenia, what caused these abnormalities in the first place? o If the structural abnormalities were caused by the schizophrenia, then where did the schizophrenia come from? Also, how exactly does the schizophrenia cause these changes to occur? If we compare this theory to the genetic explanation, a weakness arises. If schizophrenia is caused by structural abnormalities alone, then why does it run in families? It is likely that any explanation of schizophrenia must incorporate genes into it for it to be a comprehensive theory. Perhaps the structural abnormalities that lead to schizophrenia are determined by genes. A strength of research into this area is that as technology advances, we learn more and more about the brain. In the early days of psychology, it was impossible to examine a living brain. All investigations had to be performed post mortem. However, brain scans allow us to see the living brain in action, and with every new study, we get closer and closer to the truth. Perhaps in the future, we will be able to put patients into a brain scanner to determine whether or not they have schizophrenia rather than have to rely on the sometimes inaccurate and subjective diagnosis methods of today such as the DSM-5 and the ICD-10. Brain scans are also a highly scientific method of investigation. They do not rely on subjective interpretation, and they enable replication. Overall evaluation of biological theories of schizophrenia There is a lot of evidence that schizophrenia is at least partly a biological illness. One major piece of evidence is that the illness has a biological basis is that the illness seems to run in families; even when children of schizophrenics are adopted into non-schizophrenic families they have a higher than normal risk of the disorder. o Also, schizophrenia responds well to biological treatments such as antipsychotic drugs. However, we should be careful when assuming that this means the illness itself is biological in nature. This is known as the treatment-aetiology fallacy. It is the same as the following metaphor: “I am sad so I eat some chocolate. I feel happy. I therefore conclude that my unhappiness was caused by lack of chocolate.” 6 C3 Implications in the real world - Applications. Schizophrenia: Biological Explanation 1- Genes However, a big issue with biological theories is that they ignore the social and cultural context of the illness and could be argued to be reductionist. Biological theories reduce an individual down into a set of measurable biological factors, ignoring the role that the family and society can play in both the causation and the maintenance of the illness. Also, culture can play a part in the development of schizophrenia, as in some cultural contexts, hearing voices may be seen as a positive experience. Biological theories are useful for developing treatments. If the biological basis for a disorder can be located, a treatment such as antipsychotic medication can be developed to target that biological cause. o However, biological explanations are highly nomothetic. This could have implications for treatment. If a person is seen as a list of symptoms rather than a unique individual, the treatment that they are given may not work. Perhaps taking a more idiographic approach may be more successful so that patients receive more personalised treatment that is tailored toward them. Biological explanations are also deterministic. They see schizophrenia as being completely outside the control of the individual. A person has no free will over their own mental health and is at the mercy of their genes or brain structures. o However, as undesirable as this seems, the day to day experiences of schizophrenics would support the deterministic nature of the illness. Schizophrenics will often have no control over their behaviour and symptoms. Insisting that a schizophrenic has free will may actually be detrimental to their recovery. 7 C3 Implications in the real world - Applications. Schizophrenia: Biological Explanation 1- Genes Exam Practice 1. Describe two biological explanations of schizophrenia. [10] See notes from the last handout for this question 2. Evaluate two biological explanations of schizophrenia. [15] See notes from the last handout for this question 3. Compare and contrast the strengths and weaknesses of two biological explanations of schizophrenia [10] This is testing your AO3 skills. This is the skill of evaluation and analysis. For the 10 marks, you will need to write about two sides of A4 and under timed conditions would be about 15 minutes. As it is an evaluation question you would gain no marks for describing the theories. It is important that in this question you are not just listing and discussing the various strengths and weaknesses of genes and structural abnormalities as explanations of schizophrenia. o You need to compare these evaluation points. o What you are being asked for is to assess the quality of these two theories and decide which of the two provides the best explanation. o Look for strengths and weaknesses that apply to both theories. o Also, are there any weaknesses in one theory that the other theory explains? For example, structural abnormalities cannot explain why schizophrenia runs in families, whereas the genetic explanation can. o A good conclusion to come to may be to argue that both theories could be combined into a more comprehensive theory. You should aim to use accurate terminology. Your answer needs both range and depth. 8