Summary
Summary Brain Imaging, Brain scans, neuroimaging
- Module
- Imaging techniques
- Institution
- AQA
This is a detailed summary of brain scans; specifically, MRI, magneto-encephalography and transcranial magnetic stimulation
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Theory: fMRI: based on imaging blood oxygenation using an MRI machine; it provides information about thelocation and time course of brain processes. Infers neuronal activity
Background of theory Types of fMRI
Oxyhaemoglobin is converted into Event-related functional magnetic resonance imaging
deoxyhaemoglobin when neurons consume (efMRI): separate experimental elements to discrete time
oxygen, and deoxyhaemoglobin produces points in order to analyse associated brain responses
distortions in the local magnetic field. This independently (Huettel 2012).
distortion is assessed by fMRI, and provides a Event-related fMRI is generally very informative and
measure of the concentration of has become markedly more popular recently.
deoxyhaemoglobin in the blood
Drawbacks Strengths
Indirect measure of neuronal activity. Functional MRI has superior spatial and
Assumption where more oxygenated temporal resolution to PET.
blood = more activity measures BOLD
blood oxygen level-dependant contrast. v. good spatial resolution 1mm.
Temporal resolution = 2/3 seconds
Distortions in BOLD signal in some brain
regions e.g. close to sinuses/oral cavity)
Noisy scanner- hard for auditory
stimuli/ people sensitive to noisy
Claustrophobic.
Cooke et al. (2007) found 43% of
participants in an fMRI study were at
least a bit upset by the experience and
33% reported side effects (e.g.,
headaches).
Cant be used with any metal- some
tattoos
constraints on the kinds of
stimuli that can be presented
to participants lying in a
scanner.
constraints on the responses
they can be asked to produce
because even small
movements can distort the
BOLD signal.
Ig Nobel Prize in Neuroscience: the dead
salmon study (bennet et al 2010)
Relate to something in everyday life Aid understanding of mental health
MIND READING Often replacing PET in research due to superior
Haxby et al. (2001) asked participants to view pictures spatial resolution.
from eight different categories (e.g., cats, faces, houses)
while patterns of brain activity were assessed by fMRI.
Computer-based analysis of patterns of brain activity E.g. Wagner et a (1998) use efMRI whilst
allowed the researchers to predict accurately the partients learnt a list of words. More brain
category of object being viewed on 96% of trials! activity during learning for words remembered
later.
, • Functional MRI (fMRI) is used to ‘infer’ neural activity.
• Active neurons need energy. This is provided via an increase in blood flow, and a greater
amount of oxygenated haemoglobin.
• Blood oxygen level dependent (BOLD) imaging measures the difference in oxygenation
status of the blood between a resting and activated state.
• ‘Tasks’ are used to generate activity, and they must be repeated to get enough signal.
Resting state fMRI (rsfMRI) does not use tasks to generate activity, but instead searches for patterns
of synchronous BOLD activity among brain regions. Common patterns are interpreted as functional
connectivity between regions.
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