Lesson 10- ways of studying the brain Flashcards
Functional magnetic resonance imaging (fMRI)
Developed from MRI scanner
-neutrons most active during a given task will be using more energy requires glucose and oxygen carried in the bloodstream, therefore blood flow to active areas of the brain should increase over control levels
-directly measures blood flow through the concentration of oxygen in the bloodstream,signal used in fMRI is called the Blood Oxygen Level Dependent contrast
-innovative, emerging application in lie detectors
fMRI strengths
-does not rely on the use of radiation, non-invasive only require participant to remain still and quiet, virtually risk free, should allow more patients to undertake fMRI scans which could help gather further data, develop understanding
-good spatial resolution, refers to smallest feature that a scanner can detect, allows discrimination between different brain regions with greater accuracy, have spatial resolution of approx 1-2 mm, significantly greater than other techniques
fMRI weaknesses
-do not provide a direct measure of neural activity, only measures changes in blood flow therefore impossible to infer causation, unable to conclude whether the brain region is associated with a particular function, also argued that fMRI scans only show localisation of functioning within an area but are limited in showing the communication that takes place among the different areas of the brain, could be critical to neural functioning
-have poor temporal resolution, refers to accuracy of scanner in relation of time/how quickly the scanner detects changes in the brain activity, have temporal resolution of 1-4 seconds, worse than other techniques
-only provides information on what brain area is active during different cognitive tasks, cannot hone in on activity of individual neurones, does not provide a complete picture of brain activity
Electroencephalogram (EEG)
-provides an overall view of brain electrical activity, developed by Hans Berger in 1929
-large number of small recording electrodes distributed over the surface of the skull, pick up electrical activity of Amanda millions of neurones, basic properties used to characterise particular brain states: amplitude-size or intensity of electrical activity, frequency-speed or rapidity of the electrical activity
-two states:synchronised pattern-recognisable waveform can be identified, desynchronised-no recognisable waveform
-data can be used to detect various types of brain disorders or to diagnose other disorders that influence brain disease, eg disease/injury shows overall slowing of electrical activity, epilepsy-spikes of electrical activity
-awake but relaxed=rhythmic alpha, sleeping=delta and theta, used to extensively study sleep stages
-EEG shows alpha, beta, delta and theta waves
EEG evaluation
-provides recording of the brain activity in real time rather than still image, can accurately measure particular task or activity
-has helped provide invaluable diagnosis of conditions such as epilepsy, also contributed to understanding of stages in sleep
-can only detect activity in superficial regions of the brain, cannot reveal activity in deeper regions
-EEG signal not useful for pinpointing exact source of neural activity, does not allow researches to distinguish between activities originating in different but adjacent locations
Event related potentials (ERPs)
-small voltage changes in the brain that are triggered by specific events or stimuli
-procedure uses a similar array of electrodes as EEG however a stimulus is presented to the patient, and the psychologist looks for specific electrical responses to that stimulus
-may be difficult to separate particular electrical activity related to the task and overall activity of the brain, stimulus has to be presented many times
-regular specific electrical responses to stimulus gradually add together while the background electrical noise cancels itself out
ERP strengths
-interval between stimulus presentation and the beginning of erp is known as latency, has very short latency measured in milliseconds, fmri latency measured in seconds, can reflect very early stages of cognitive processing, such as face processing and working memory
-can measure processing of stimuli even in absence of behavioural response, erp recordings make it possible to monitor covertly the processing of a particular stimulus without requiring the person to respond to them
erp weakness
-poor spatial localisation, recording electrodes spread all over scalp means it is possible to localise componenets of the erp to general areas of the cortex, however not possible to localise to specific areas of cortex
-lack of standardisation in erp methodology between different research studies so findings lack reliability and generalisability
-correct data requires extraneous variables are minimised and not always possible in reality
post mortem examinations/autopsies
-a research may study a person while they are alive that suggests possible underlying brain damage, so when person dies research can compare brain to look for abnormalities that might explain that behaviour and compare to controls who do not show that abnormal behaviour
-Iverson examined brains of deceased schizphrenic patients and found they all had higher concentration of dopamine especially in limbic system compared with control brains, highlights how has contributed to understanding of disorders
-allow for more detailed examination of anatomical and neurochemical aspects of the brain than would be possible with other techniques, enables researches to examine deeper regions of the brain, something not easy with other methods
-can now carry out brain scans on deceased dont need to actually cut the brain
post mortem strengths
-allow more detailed examinations of anatomical and neurchemical asoects that is not possible with fmri and eeg, enables deeper region research
-Harrison (2000) claims post mortems have played central part in understandings of origins of schizophrenia and other mental illnesses eg Iverson
post mortem weaknesses
-too many individual differences in how people die, different stages of disease and circumstances, length of time between death and examination, drug treatments, age all confounding variables which can affect outcome of post mortem, cannot mkae generalisations about brain functioning
-ethical issues, is invasive but patient is dead, informed consent and whether patient provides consent before death, many post mortems carried out on patients with severe psychological deficits who would be unable to provide fully informed consent and yet post mortem carried out, raises ethical questions
