Transcript Brain-Scansx

Biological Approach
Methods
Brain scanning techniques (CAT, PET, fMRI)
The use of brain scanning to investigate aggression
One twin study – Gottesman and Shields
Homework check
Research one brain scanning technique from
CAT, PET or fMRI. Scanning techniques could
be drawn out of a hat. Be ready to present
to the class
Learning objectives
1) To describe and evaluate three brain scanning
techniques (CAT, PET and fMRI) and be able to
teach the basics of these to others.
2) To investigate how brain scanning is used to
investigate aggression.
3) To become aware of one twin study (G&S) and
be able to learn the APRC and GRAVE the study.
4) To practice independent research and
questioning skills.
Links to Issues and Debates:
• Practical issues in the design and
implementation of research – e.g. issues in
scanning and measuring the complexity of the
brain.
• Psychology as a science – e.g. synaptic
transmission; brain scanning techniques.
• An understanding of how psychological
knowledge has developed over time – e.g.
development of scanning techniques up to fMRI.
• Issues of social control – e.g. using knowledge of
brain function to control individuals.
Computed Assisted Tomography Scan
(CAT Scan)
• CAT scans use a series
of X-ray beams passed
through the head,
creating cross-sectional
images of the brain
showing the structure,
but not the function.
How it happens
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You need to remove all jewellery
and glasses and all metal etc
You will be asked to lie on a scanner
table
You must keep still during the
procedure which takes about 20-30
minutes
The staff leave the room and
continue to talk to you through an
intercom
The scanner table then moves
through the scanner to take the
first picture and rotates in small
movements around your head to
take further pictures
It is a painless procedure
• You might need an injection or
injections as part of the
procedure. This will be discussed
with you before your scan.
• A dye is injected into the back of
your hand or into the crook of
your elbow and flows around
your bloodstream to highlight
the blood vessels in your brain or
spine.
• This helps to produce more
detailed pictures.
Positron Emission
Tomography
(PET)
• A scanner detects radioactive material that is injected or inhaled to produce
an image of the brain.
• Once in the bloodstream, it flows through the brain and oxygen and
glucose accumulate in brain areas that are metabolically active.
• As the glucose is used in the active parts of the brain, the radioactive
material breaks down and gives off a neutron and a positron.
• When a positron hits an electron, both are destroyed and two gamma rays
are released.
• Gamma ray detectors record the brain area where the gamma rays are
emitted.
• This method provides a functional view of the brain. E.g. language involves
a number of areas in the brain. By asking someone to think of words, read
words, or speak words researchers can find out which part of the brain
works for a particular language function.
PET scans
• They are mainly carried out
for medical purposes, e.g.
to check the damage made
by a stroke
• They can also be used to
research how the brain
works e.g. in individuals
with schizophrenia
• They can be compared with
‘normal’ individuals to learn
more about the illness
• Epilepsy and other
conditions can be studied
by looking at blood flow in
the brain.
Positron Emission Tomography
(PET)
Advantages
• A reasonably non-invasive way
of studding inside the brain (or
body) – although the
radioactive tracer is invasive
• Ethical
• Valid – the scan seems to
measure what it claims to
measure e.g. speech has been
consistently found to be
connected to Broca’s area
• It is reliable – it can be
repeated and the same
results found – the same
areas of the brain are
consistently found for
different activities
Positron Emission Tomography
(PET)
Disadvantages
• The use of the radioactive
tracer is invasive so there are
ethical issues – the researcher
must follow ethical guidelines
carefully (e.g. gained informed
consent, having a good reason
for doing the test.
• The scan itself is
claustrophobic – it must be
carefully explained to the
individual.
• It is difficult to isolate
different brain functioning
precisely. E.g. people can
read passages of text while
being scanned but they
would almost certainly be
using other parts of their
brain as well. It is valid to a
point.
• It is also expensive to use.
Magnetic Resonance Imaging
(MRI)
• MRI uses detection of radio
frequency signals produced
by displaced radio waves in
a magnetic field. It provides
an anatomical view of the
brain.
• The whole body is placed
inside a tube, which can be
claustrophobic.
• The process is noisy but not
painful.
MRI
• MRI scans are affected by
movement so the person
has to keep very still.
• MRI scans do not show
activity to the same degree
as PET scans, but they can
measure blood flow.
• Before an MRI scan, a dye
called a contrast medium, is
injected into the body to
help show up body organs
and relevant areas.
Magnetic Resonance Imaging
(MRI)
Advantages
• No X-rays or radioactive
material is used.
• Provides detailed view of the
brain in different dimensions.
• Safe, painless, non-invasive
(apart from the injected dye).
• No special preparation (except
removal of all metal) is
required from the patient.
• It is valid because what is
found in the scan is then often
found in reality. They are
accurate for checking
abnormalities in the brain and
the rest of the body.
• More ethical – animals do not
need to be used.
• Replicable – it can be repeated
and the same results found –
the results can be checked by
more than one person for
objectivity.
Magnetic Resonance Imaging
(MRI)
Disadvantages
• MRI scans are stressful
because an injection has to
be given, they are
extremely noisy and they
can be claustrophobic.
Stress should not be
imposed on a patient
without careful
consideration of ethical
guidelines and issues.
• MRI scanning only measures
particular things. There are
for example clear images of
soft tissue and body organs
but brain activity is not
measured. Knowledge from
such scans is limited.
Functional Magnetic Resonance
Imaging (fMRI)
• Functional magnetic
resonance imaging, or FMRI, is
a technique for measuring
brain activity.
• It works by detecting the
changes in blood oxygenation
and flow that occur in
response to neural activity –
when a brain area is more
active it consumes more
oxygen and to meet this
increased demand blood flow
increases to the active area.
• FMRI can be used to produce
activation maps showing
which parts of the brain are
involved in a particular mental
process.
• For fMRI, your head may
be placed in a brace
designed to help hold it
still. This brace may
include a mask that is
created especially for
you. You may be given
special goggles and/or
earphones to wear, so
that audio-visual stimuli
(for example, a projection
from a computer screen
or recorded sounds) may
be administered during
the scan.
fMRI scans
Advantages
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It can noninvasively record brain
signals without risks of radiation
inherent in other scanning
methods, such as CT or PET scans.
It has high spatial resolution. 2–
3 mm is typical but resolution can
be as good as 1mm.
It can record signal from all
regions of the brain, unlike
EEG/MEG which are biased
towards the cortical surface.
fMRI is widely used and standard
data-analysis approaches have
been developed which allow
researchers to compare results
across labs.
fMRI produces compelling images
of brain "activation".
Disadvantages
• Dispute over whether or not it
actual measures what it claims to
measure – e.g. increased levels of
oxygen could be in preparation for
neural activity, not because of it.
• Very noisy. (small signals and lots
of ‘noise’ make it difficult to pick
up changes in oxygenated blood
flow.
• The images produced must be
interpreted carefully, since
correlation does not imply
causality, and brain processes are
complex and often non-localized.
• Statistical methods must be used
carefully because they can
produce false positives.
Compare the three scanning
techniques
Issue
Non-invasive
Can scan brain
activity
Needs
interpretation
Scientific method
Validity
Reliability
MRI scan
PET scan
fMRI scan
Worksheet
• Complete the work sheet to show you
understand scanning techniques.
• Answer the exam questions.
How are brain scans used to
investigate aggression?
• What might brain scans show?
• Which areas/structures of the brain are
involved in aggression?
• Which type/s of scans would this show on?
Twin studies
• What are twin studies?
• How are they used in psychology?
Stretch and challenge:
Find about the TEDS study.
Where is it taking place? Who are the
participants? What do they hope to find?
Using twin studies
• One way of finding out whether a disorder has a genetic
component is to see whether it runs in families. If relatives of
sufferers have a higher than average risk of getting the
disorder themselves, then it may be that the disorder has a
genetic component.
• However, family members typically share similar
environments. Consequently, increased risk amongst close
relative may simply indicate that that are exposed to the
same set of environmental risks.
• An alternative approach is to do a twin study. This looks at the
concordance rate (degree of similarity) of twins with respect
to the disorder being considered. Concordance rates means
the probability of one twin having the disorder if the other
already has it expressed as a percentage.
• In a twin study, MZ (identical) and DZ (nonidentical) twins are compared. Whilst MZ twins
have a greater degree of genetic similarity, both
types of twin pair grow up in identical
environments.
• So if we discover that MZ twins have a higher
concordance, this cannot be because their
environments are more similar than those of DZ
twins; it must therefore be because their genes
are more similar.
Gottesman and Shields
• Read through the Gottesman and Shields twin
study.
• Make notes on the aim, procedure, results
and conclusion of the study.
• Complete the Sheet Describing and Evaluating
the study.
Gottesman and Shields (1966)
1) What was the aim of the study?
2) Who did they look at (who made up their
sample)?
3) What types of twins did they study?
4) List two results.
5) List at least one conclusion they drew from their
results.
6) What is a problem with this kind of research?
7) Why is this kind of research important?
8) How can it be applied today?
Links to Issues and Debates:
• Practical issues in the design and
implementation of research – e.g. issues in
scanning and measuring the complexity of the
brain.
• Psychology as a science – e.g. synaptic
transmission; brain scanning techniques.
• An understanding of how psychological
knowledge has developed over time – e.g.
development of scanning techniques up to fMRI.
• Issues of social control – e.g. using knowledge of
brain function to control individuals.
Can you spot the links to Issues and Debates in today’s lesson?
Homework
‘Flipped learning’ –
• What are adoption studies?
• Why are psychologists interested in them?
• Pupils should also find and read the
Adoption study by Ludeke et al (2012)
• Pupils should come up with three positives
about the study and three criticisms.