Ways of Studying the Brain
- techniques for investigating brain are often used for medical purposes in diagnosis of illness. purpose of scanning in psychological research is often to investigate localisation - to determine which parts of the brain do what.
- evaluation of FMRI
- electroencephalogram (EEG)
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- functional magnetic resonance imaging (FMRI)
- works by detecting changes in both blood oxygenation and flow that occur as result of neural activity in specific parts of brain.
- brain area more active = consumes more oxygen & to meet increased demand, blood flow is directed to active area
(known as the haemodynamic response)
- FMRI produces 3-dimensional images (activation maps) showing which parts of brain are involved in specific mental processes - has important implications for our understanding of localisation of function.
- STRENGTHS
- doesn't rely on use of radiation like PET scans.
- is risk-free, non-invasive, and straightforward to use. when administered correctly
- produces images that have very high spatial resolution depicting detail by mm and providing clear picture of how brain activity is localised - means FMRI can safely provide a clear picture of brain activity.
- LIMITATIONS
- Expensive compared to other neuroimaging techniques
- has poor temporal (time) resolution because of 5 sec time lag behind image on screen & initial firing of neural activity - means FMRI may not truly represent moment-to-moment brain activity.
- measure electrical activity within brain via electrodes which are fixed to an individual's scalp using a skull cap.
- scan recording represent brainwave patterns which are generated from action of thousands of neurons, providing overall account of brain activity.
- often used by clinicians as diagnostic tool as unusual arrhythmic patterns of activity. (i.e. no particular rhythm) may indicate neurological abnormalities such as epilepsy, tumours or some sleep disorders.
- Evaluation of EEG
- STRENGTHS
- has been useful in studying stages of sleep & in diagnosis of conditions such as epilepsy, a disorder characterised by random bursts of activity in brain which can easily be detected on the screen.
- Has extremely high temporal resolution - today's EEG tech can accurately detect brain activity at a resolution of a single millisecond - shows the real-world usefulness of the technique
- WEAKNESSES
- main drawback of EEG lies in generalised nature of info received (that of many thousands of neurones)
- EEG signal isn't useful in pinpointing exact source of neural activity - therefore doesn't allow research to distinguish between activities originating in different adjacent locations
- Event-related potential (ERP)
- ERPs are a way of teasing out and isolating specific neural responses associated with sensory, cognitive, and motor events.
- ERPs work by using statistical averaging techniques, that filters out extraneous brain activity from the original EEG recording, leaving only the responses that relate to say, the presentation of a specific stimulus or performance of a specific task.
- Event-related potentials = types of brainwave that are triggered by particular events.
- Research has shown different forms of ERPs, linked to cognitive processes such as attention and perception.
- Evaluation of ERP
- STRENGTHS
- WEAKNESSES
- ERPs bring much more specificity to the measurement of neural processes than could be achieved using raw EEG data.
- As ERPs are derived from EEG measurements, they have excellent temporal resolution - led to their widespread use in the measurement of cognitive functions and deficits.
- Researchers have been able to identify many different types of ERP & describe the precise role of these in cognitive functioning including parts of working memory
- A lack of standardisation in ERP methodology between different research studies make it difficult to confirm findings.
- In order to establish pure data in ERP studies, background noise and extraneous material must be completely eliminated, which is not always easy to do.
EXTRA SPACE
- post-mortem examinations (PME)
- This is a technique that involves the analysis of a person’s brain following their death.
- Likely to be carried out on those who have a rare disorder and have experienced unusual deficits in mental processes or behaviour:
- Areas of damage within the brain are examined after death as a means of establishing the likely cause
- May also involve comparison with a neurotypical (healthy) brain in order to see the extent of the difference
- Evaluation of PME
- STRENGTHS
-WEAKNESSES
- Post-mortem (PM) evidence was vital in providing a foundation for early understanding of key processes in the brain.
- Both Broca & Wernicke relied on PM studies in establishing links between language, brain, and behaviour decades before neuroimaging began
- Still help to improve medical knowledge and help generate hypotheses for further study. (case of HM – memory)
Causation is an issue within these investigations:
Observed damage may not be linked to the deficits under review but to some other unrelated trauma or decay.
PM studies raise ethical issues of consent from the patient before death particularly informed consent
e.g. case of HM who lost his ability to form memories and was not able to provide such consent