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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.
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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.
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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.
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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.
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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?
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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.
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C3 Implications in the real world - Applications. Schizophrenia: Biological Explanation 1- Genes
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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.
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C3 Implications in the real world - Applications. Schizophrenia: Biological Explanation 1- Genes
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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.”
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C3 Implications in the real world - Applications. Schizophrenia: Biological Explanation 1- Genes
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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.
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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.
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