Biopsychology - ways to study the brain

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  • Created by: Anca.a
  • Created on: 09-04-18 15:17
Computed axial tomography(CT scanner):
used x-rays to take images of brain structures, details quite poor but major structures like abnormalities such as tumours could be seen.
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For taking static images of brain structures, what has replaced the CT scanner?
The magnetic resonance imaging(MRI) scanner.It is based on the magnetic properties of hydrogen in water found throughout the brain.By using a strong magnetic field & then applying radio waves,this can produce highly detailed images of brain structure
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Positron emission tomography:how does it work?
a radioactive substance such as glucose is introduced into the bloodstream,it travels to the brain where neurons use the glucose as a source of energy, so the most active brain regions will accumulate more glucose & the radioactivity emitted...
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....
is picked up by the PET scanner.The scanner uses the radioactivity to construct a functional map of the brain;this is a map showing the area's most active during the performance of a given task.
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What did the PET first allow psychologists to do?
it was the first scanning technique to take images of the brain in action & therefore help psychologists to link behaviour function to specific structures.
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Negatives of the PET:
the technique was both invasive and prolonged as imaging could only take place when radioactivity had accumulated in the brain structures.It has been almost completely replaced fMRI scans.
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BUT what is an example of it being useful in some specialised areas?
by using radioactive labelled drugs that bind to particular synaptic receptors, we can assess the distribution of neurotransmitter pathways in the brain.
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how do functional magnetic resonance imaging (fMRI) scanners work?
neurons most active during a given task will be using more energy & this requires glucose and oxygen, carried in the bloodstream.Therefore, the blood flow to active areas of the brain should increase
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How does fMRI indirectly measure blood flow through the conc. of oxygen in the bloodstream?
oxygen attached to haemoglobin in red blood cells.After oxygen is released for use by active neurons, haemoglobin becomes deoxygenated; so oxygenated and deoxygenated haemoglobin have different magnetic qualities.
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What can this difference be used for?
in combination with the powerful magnetic field applied to fMRI, this difference can be used to generate a signal representing blood flows in various parts of the brai, therefore indirectly measuring bloodflow through the conc. of oxygen in the blood
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What is the signal used in fMRI called?
BOLD (Blood Oxygen Level Dependent contrast).
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advantages of fMRI over PET:
not invasive as the patient only needs to lie still in the scanner,the time between stimulus and the BOLD signal is shorter,spatial resolution is far better,cognitive neuroscience is heavily dependant upon fMRI
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What other cognitive processes have been studied using fMRI?
attention, memory, face recognition, language processing, also used to study problems in development like autism and psychological problems such as schizophrenia
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Although this does not measure neuronal activity directly...
...they are revolutionising our understanding of brain function in relation to behaviour.
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How is information processed in the brain?
as electrical activity through action potentials and impulses travelling along the neuron
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Electroencephalogram(EEG):how does it work?
A number of small recording electrodes are distributed over the surface of the skull & these pick up the electrical activity of many neurons from the nerve impulses being transmitted along neurons.
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what basic properties does the EEG have that can be used to characterise particular brain states?
amplitude & frequency
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What is amplitude?
the size or intensity of the electrical activity
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what is frequency?
the speed of the electrical activity
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What are the 2 distinctive states of the EEG?
Synchronised pattern and desynchronised pattern
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What is a waveform?
it is a repeated pattern of electrical activity with a particular amplitude and frequency
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What is a synchronised pattern?
where a recognisable waveform can be identified in the EEG recording
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What is a desynchronised pattern?
this is where there is no recognisable waveform, although the frequency of electrical activity can still be determined.
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What is one contribution of the EEG?
It found that during sleep we have periods when the EEG shifts from a synchronised pattern of delta waves, to fast desynchronised activity similar to alert waking state
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What is this phase of sleep known as?
REM, because this EEG pattern is associated with rapid eye movement.It can also be known as dreaming sleep because participants usually report dreaming when waking up
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Event-related potentials (ERP's):
uses a similar array of electrodes like EEG, but a major stimulus like a picture or sound is presented and the psychologist looks for specific electrical responses to that stimulus.
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Why is this difficult?
because the specific responses may not standout from the background electrical activity of the brain
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What is the solution to this?
it is to present the stimulus several hundred times & the recordings for say, 5 seconds after each stimulus presentation, are superimposed on each other and a computer is used to add them together.
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The regular specific electrical response...
...gradually add together while the background noise cancels itself out.In this way, the event related potential emerges and this is called averaging.
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Post-mortem examinations:
Broca and Wernicke's work was entirely dependent on the study of brain damaged participants, followed by post-mortems of their brains to determine location and extent of damage. Since the 1970's, modern scanning techniques have replaced post-mortems
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Card 2

Front

For taking static images of brain structures, what has replaced the CT scanner?

Back

The magnetic resonance imaging(MRI) scanner.It is based on the magnetic properties of hydrogen in water found throughout the brain.By using a strong magnetic field & then applying radio waves,this can produce highly detailed images of brain structure

Card 3

Front

Positron emission tomography:how does it work?

Back

Preview of the front of card 3

Card 4

Front

....

Back

Preview of the front of card 4

Card 5

Front

What did the PET first allow psychologists to do?

Back

Preview of the front of card 5
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