Ways of imaging the brain

Name the four ways you can study the brain

- fMRI

- EEG

- ERPs

- Post-Mortem Examination

what does fMRI stand for

Functional Magnetic Resonance Imaging

how does an fMRI work? (summary version)

is a brain scanning technique measuring blood flow in the brain when a person performs a task, they work on the premise neurons in the brain are the most active (during a task) use the most energy, it creates a dynamic 3D map of the brain highlighting which areas are involved in different neural activities

how does an fMRI work? (in depth version)

- a brain-scanning technique measuring blood flow in the brain when a person performs a task

- works on the premise the neurons in the brain are the most active during a task using the most energy

- energy requires glucose and oxygen

- oxygen is carried in the bloodstream attached to haemoglobin (which is found in red blood cells) and is released for use by active neurons, deoxygenating the haemoglobin

- deoxygenated haemoglobin has different magnetic qualities from oxygenated haemoglobin

- fMRI detects these differences and can be used to create a dynamic 3D map of the brain highlighting which areas are involved in different neural activity

- fMRI images show activity approximately 1-4 seconds after it occurs and are thought to be accurate within 1-2mm

- the increase in blood flow is response to the need for more oxygen to that area of the brain when it becomes more active suggesting an increase in neural activity

what are strengths of an fMRI

- non-invasive

- great spatial resolution

- supports localisation of brain function

how are fMRI's non-invasive? and what is the strength of this?

- fMRI is non-invasive as it doesn't use radiation or involve inserting instruments directly into the brain so is virtually risk-free allowing more p's to undertake the scans

- could help psychologists to gather further data on the functioning of the human brain and develop understanding on localisation of function

what is spatial resolution

refers to the smallest feature a scanner can detect and this is an important feature of brain scanning techniques meaning psychologists can determine the activity of different brain regions with greater accuracy when using fMRI

what is the spatial resolution of an fMRI

1-2mm which is better than other techniques

what are the limitations of fMRI

- poor temporal resolution

- poor in showing communication which takes place in different areas of the brain

- uncomfortable as they have to stay still

what is temporal resolution

accuracy of the scanner in relation of time or how quickly the scanner detects changes in brain activity

what is the temporal resolution of an fMRI

1-4 seconds which is worse than other techniques so psychologists cant predict with a high degree of accuracy of onset brain activity

what does EEG stand for

Electroenceohalogram

how does an EEG work? (summary ver.)

works on the premise information is processed in the brain as electrical activity in the form of action potentials or nerve impulses transmitted along neurons, EEG scanners measure the electrical activity through electrodes and are graphed over a period of time indicating level of activity in the brain

what are the four types of EEG patterns

- alpha waves

- beta waves

- theta waves

- delta waves

what are the two basic properties that pysychologists can examine

- amplitude

- frequency

what is amplitude

- intensity or size of the activity

what is frequency

- speed or quantity of the activty

what two distinctive states EEG patterns produce

- synchronised

- desynchronised

what is a synchronised pattern

where a recognised waveform can be detected

what is a desynchronised pattern

where no pattern can be detected

what did Dement and Kleitman 1957 find

they identified REM sleep which shows fast desynchronised brain activity (usually seen when awake) that is strongly indicative of dreaming and that non-REM sleep shows slower, synchronised patterns (theta waves in light sleep and delta waves in deep sleep, following relaxed waking alpha waves)

what illnesses and disorders can an EEG detected

epilepsy, sleep disorders, and Alzheimers

what is a limitation of an EEG

- electrical activity is often detected in several regions of the brain simultaneously so it can be difficult to pinpoint the exact area/region of activity making it difficult for researchers to draw accurate conclusions

what does ERP stand for

Event Related Potentials

how does an ERP work (summary)

they use electrodes that are attached to the scalp but the key differences is that a stimulus is presented to a P and the researcher looks for activity related to the stimulus

what is averaging

when the average response to a stimulus presented during an ERP is graphed in order to reduce any extraneous neural activity which makes specific response to a stimulus stand out

what is latency

time or interval between presentation of stimulus and response is reffered to as latency

do ERP's have short or long latency

short latency divided into two categories

what are the two categories of an ERP

- sensory ERP

- cognitive ERP

what is a sensory ERP

when a wave (response) can occur within 100 milliseconds following the presentation of a stimulus, demonstrate sensory response

what is a cognitive ERP

when a wave (response) occurs AFTER 100 milliseconds, demonstrate information processing

what is a strength of ERP's

- enable the determination of how processing is affected by a specific experimental manipulation

- more experimentally robust as it eliminates extraneous neural activity which something that other scanning techniques struggle to do

what are strengths of BOTH EEG's and ERP's

- non-invasive

- cheap

- good temporal resolution

why is non-invasive a strength of ERP and EEG

both do not use radiation or involve inserting instruments directly into the brain and are ergo virtually risk-free

why is cheap a strength of ERP and EEG

cheaper technique so more readily available allowing more patients to undertake ERP and EEG

why is temporal resolution a strength of ERP and EEG

they take readings every milliseconds meaning it can record brain activity in real time as opposed to looking at a passive brain leading to an accurate measurement of electrical acitivty when undertaking a task

what is a limitation of ERP and EEG

- poor spatial resolution

- uncomfortable

why is poor spatial resolution a limitation of ERP and EEG

only detect the activity in superficial regions of the brain so unable to provide information on what is happening in the deeper regions of the brain making this technique limited

why is uncomfortably a limitation of ERP and EEG

both are uncomfortable for the patient as electrodes are attached to the scalp resulting in unrepresentative readings as patients discomfort may affect cognitive responses to situations

what is a post-mortem examination (summary)

when researchers study the physical brain of a person who displayed a particular behaviour while they were alive that suggested possible brain damage

what is an example of a post-mortem

Broca and Tan

what have post-mortems successfuly investigated

the understanding of many disorders, including detailed examinations of anatomical and neurochemical aspects of the brain, allows researchers to examine deeper regions of the brain (hypothalamus, hippocampus)

what did Iverson do and find

examined the brains of deceased schizophrenic participants and found they all had a higher concentration of dopamine particularly in the limbic system when compared to brains without schizophrenia highlighting importance of these investigations

what are limitations of post-mortem examinations

- may not show causation as behaviour could be due to another illness rather than damage or deficits in the brain

- extraneous factors (age, time between death and examination, medication etc.)

- ethical issues over informed consent

what are strengths of post-mortem examinations

- detailed examination of anatomical structure and neurochemical aspects and can access deeper brain regions, useful basis for further research

- invasive but not an issue as patient is dead