Brain scanning techniques Flashcards
(25 cards)
what does fMRI stand for
functional magnetic resonance imagery
how is fMRI more advanced than MRI
measures brain activty by detecting changes associated with blood flow
what does fMRI measure
- uses magnetic and radio waves to monitor blood flow
- measures which parts of the brain are most active during certain tasks compared to a baseline task
- based on th eprinciples: neurons that are active will be using energy in the form of glucose and oxygen, which are directed to the areas requiring it via the bloodstream (haemodynamic response), area with most blood flow during a task is the msot active
how do fMRI’s work
- powerful magnetic field is applied to the brain
- oxygentated blood has a different magnetic quality than de-oxygenated blood
- scanner generates a singal called BOLD contrast
- revals which neurons are currently using the most ozxygen and therefore which areas are most active
- produces a 3D image showing active parts of the brain in colour
strength fMRI: PET
- I: there are advantages of fMRI over earlier PET scanning
E: non invasive technique - doesn;t invlove the insetation of instruments into the body (like PET scans would). no exposure to potentially harmful radiation (PET invloves radiation)
better spatial resolution: produces images that depict detial by the mm. provides a clear image of how brain activty is localised
C: fMRI are used more frequently than pet scanning
strength fMRI: neuroscience
I: fMRI have contributed to the field of cognitve neuorscience
E: enabled the study us to study most cognitive processes like: attention. language, memory etc
it has also enabled us to identify neural abnormlaites undepinning psychological problems like: SZ, OCD depression
C: means that fMRI has contributed not only to our understadning of localisation of function but to the development of treatments for psychopathology
weaknesses: comparison
I: disadvantages of fMRI compared to other scanning techniques
E: fmri cannot meause brain activity directly likel EEG/ ERP’s can - only neausres blood flow in the brain
- fMRI is a very expensive technique comapred to EEG/ERP meaning trials only involove very small samples of ppts, reducing the validy of the findings
- only has low temporal resolution - meaning there is a time lag of around 5 seconds between the firings of the neurons and image seen on the screen, can lead to interpretor bias of the results
C: means that comapred to EEG/ERP’s fMRI could provide less detailed and valid reading of brain activty
what does EEG stand for
Electro EncephaloGram
what is an EEG
- provides a continous recording of brain wave activity
- records when there is a polarity of change ( negative or psotive charge), caused when neurotransmitters are recieved by the dendrites in the post synpatic neuron
- only can record activty of numerous neurons working together in ‘local field potential’
how does EEG work
- subject fitted with an EEG cap composed of electrodes placed on the scalp that meaure neuronal activty directly below where they are placed
- EEG amplifies and strengthens the signals as sends the data to a data acquisition computer
- EEG shows Gamma, Alpha, Beta and theta waves - strength is the amplification, speed of activty is the frequency
strength EEG: practical
I: have practical applications
E: this is beucase it can be used to diagnose conditions such as epilepsy - a disorder characterised by random bursts of electrical activty that can be detected on the data aquisition computer
diagnoisis then allos an appropriate treatment to be determined, allwoing for condition managment
C: means EEG is valuable in helping imrpove the lives of people in the real world
strength EEG: advantage fMRI
I: EEG’s have advantages over fMRI
E: better temporal resolution - no time lag between neuron activity and output seen on the screen. decect activty in 1/2 a millisecond
less expensive compared to fMRI which means trials are more likely to invlove larger sample sizes of ppts, improving validity
C: EEG prvoes a more detialed and precise recording of brain activity than fMRI
Weakness EEG: over general
I: provide crude and overly general measures of brain activty
E: poor spatial resoultion - it cannot record single neurons in one specifc location of the brain, instead it records thousands of neuron activty in general
C: this means it does not allow researchers to pinpoint the exact location of the activty, making it less useful in understadning localisation of function
what does ERP stand for
Event Related Potential
what are ERP’s
- types of brainwaves triggered by specifc stimuli (noises or images)
- show us the exact type of brain activty that is linked to differnt, specifc, cognitve images
how do ERP’s work
- a stimulus is presented during an EEG
- same stimulus is presented repeatedly (10/100’s times) at exactly the same interval for exactly the same time
- the brain wave pattern after each presentation is added to the previous, the computer progamme creates an average of the pattern
- process filters out all the extraneous brain activty, leaving just activty that is related to the stimulus ( ERP)
- allowing us to establish which wave is linked to the processing of certain stimuli
an example of ERP finding
N170 ( negative wave that occurs 170ms after the stimulus is thought to represent facial processing as the amplitude is stronger after a face is shwon than other stimuluses
Strength ERP: advantages
I: advantages over other techniques
E: compared to fMRI, ERP’s have higher temporal resoloution taking a reading every millisecond, meaning it can record brain actvty in real time rather than looking at a passive brain
compared to EEG’s ERP;s determine processes involved in specifc presentation of stimuli
C: provide more specifc and precise measurement of brain activty than other techniques
Stregnth ERP: neuroscience
I: contributed to the field of cognitve neuroscince
E: this is beucase researchers has been able to identify the role of differnt ERPs in various cognitve functions, for example, the N170 component has been linked to facial processing and the p300 component has been thogut to be involovedin working memory
C: ERP research has been valuable in developing our understadning of neural processes underlying congivtie functions
weakness ERP: methodology
I: flaws in the methodology used
E: lack of standardisation procedures across different research studies using this technique
not always possible to completely eliminate all the extraneous brain activty or ‘noise’ so the data is not as pure as it is assumed to be
C: difficult to confirm findings for ERP research - may not be reliable of valid
what is a post mortem
analysis of the subjects brain follwing their death
often for individulas with rare disroders who experienced deficits in metnal processes/ and or behaviour
how are post mortems conducted
- brain is dissected and examined in ordeer to establish possible cause of these deficits, such as which areas are damaged
- may involve comparisons with brains of control subjects ( neurotypical brains) in order to establish the extent of the difference
stregnth PM: advantages over other techniques
I: provide advantages over other techniques
E:* post moterms provide a detailed picture of the brains anatomical structure and the neurochemical adpects of the brain
* acess areas like this hypothalamus and hippocampus which other scanning techniques cannot, and therefore provide researchers with an insight into these deeper brain regions - providing a basis for further research
* iverson found higher levels of dopamine in the limbic system prompting research into neural correlates of SZ
C: post morterms have been valuable in helping improve medical knowledge and also helping to generate hypotheses for further studies
weakness PM: methodology
I: flaws in the methodology used
E: cannot establish causation as brain damage is not directly manipulated so we cant say the damage was responsible for problems with functioning whilst the patient was still alive
extraenous varibales as changes in neuronal activty could hae occured after dealth rather than before
C: means the technique may lack validity
