Methods of studying the brain Flashcards
(12 cards)
What is FMRI
-fMRI works by detecting the changes in blood oxygenation and flow that occur as a result of neural
(brain) activity in specific parts of the brain.
-When a brain area is more active it consumes more
oxygen and to meet this increased demand, blood flow is directed to the active area
-fMRI produces 3-dimensional images showing which
parts of the brain are involved in a particular mental process and this has important implications for
our understanding of localisation of function.
Positives of FMRI
● Unlike other scanning techniques such as PET, it does not rely on the use of radiation. If administered correctly it is virtually risk-free, non-invasive and straightforward to use.
● It also produces images that have very high spatial resolution, depicting detail by the
millimetre, and providing a clear picture of how brain activity is localised.
Negatives of FMRI
● fMRI is expensive compared to other neuroimaging techniques and can only capture a clear
image if the person stays perfectly still.
It has poor temporal resolution because there is
around a 5-second time-lag behind the image on screen and the initial firing of neuronal
activity.
● fMRI can only measure blood flow in the brain, it cannot home in on the activity of individual
neurons and so it can be difficult to tell exactly what kind of brain activity is beingrepresented on screen.
What are EEG’s
-EEGs measure electrical activity within the brain via electrodes that are fixed to an individual’s scalp
using a skullcap.
- The scan recording represents the brainwave patterns that are generated from the action of millions of neurons, providing an overall account of brain activity.
- EEG is often used by clinicians as a diagnostic tool as unusual arrhythmic patterns of activity may indicate neurological abnormalities such as epilepsy, tumours or disorders of sleep.
Positives of EEGS
● EEG has proved invaluable in the diagnosis of conditions such as epilepsy, a disorder
characterised by random bursts of activity in the brain that can easily be detected on
screen.
● Similarly, it has contributed much to our understanding of the stages involved in sleep.
Unlike fMRI, EEG technology has extremely high temporal resolution. Today’s EEG
technology can accurately detect brain activity at a resolution of a single millisecond.
Negatives of EEG’s
The EEG signal is not useful for pinpointing the exact source of neural activity, and it does
not allow researchers to distinguish between activities originating in different but adjacent
locations = low spatial resolution
What are ERPS
-ERPs are types of brainwaves that are triggered by particular events.
- This data is taken from an EEG recording, which contains all the neural responses associated with specific sensory, cognitive and motor events.
-Using a statistical averaging technique, all extraneous brain activity from the original EEG recording is filtered out leaving only those responses that relate to, say, the presentation of a specific stimulus or performance of a specific task.
Positives of ERPS
● As ERPs are derived from EEG measurements, they have excellent temporal resolution,
especially when compared to neuroimaging techniques such as fMRI, and this has led to
their widespread use in the measurement of cognitive functions and deficits.
● Researchers have been able to identify many different types of ERP and describe the precise
role of these in cognitive functioning.
Negatives of ERPS
● In order to establish pure data in ERP studies, background noise and extraneous material
must be completely eliminated, and this may not always be easy to achieve.
What are psot mortem examinsations
-A technique involving the analysis, usually surgically, of a person’s brain following their death.
-Areas of damage within the brain are examined after death as a means of establishing the likely
cause of the affliction the person suffered.
-This may also involve comparison with a neurotypical
brain in order to ascertain the extent of the difference.
Positive sof post mortems
● Post-mortem evidence was vital in providing a foundation for early understanding of key
processes in the brain. EG Paul Broca and Karl Wernicke.
● Post-mortem examinations provide a detailed examination of the anatomical structure
and neurochemical aspects of the brain that is not possible with other scanning techniques (e.g. EEG, ERP and fMRI).
-Post-mortem examinations can access areas like the
hypothalamus and hippocampus, which other scanning techniques cannot, and therefore provide researchers with an insight into these deeper brain regions, which
often provide a useful basis for further research
-. They are performed on the deceased,
so no chance of causing problems for the patient.
Negatives of psot mortem
● Observed damage to the brain may not be linked to the deficits under review but to some
other unrelated trauma or decay. A further problem is that post-mortem studies raise
ethical issues of consent from the patient before death. Eg HM
