ways of studying brain

temporal resolution

• Temporal resolution = capacity of technique to tell researcher when activation in brain occurred

spatial resolution

• Spatial resolution = capacity of technique to tell researcher exactly which area of the brain is active (identifying localisation of function)

causation

• Causation - to what extent can each way of studying the brain allow researchers to establish cause and effect between particular brain areas and certain behaviour/cognitive functions

  • Or measure the effect of stimulus on brain activity

fMRI and uses

• fMRI uses magnetic field and radio waves to measure blood flow and oxygen levels in a particular area of the brain when a person performs a particular task or is exposed to a stimulus (changes are due to neural activity in those specific parts), can produce 3 dimensional images known as activation maps

  • Give insight into particular mental processes and how specific areas of the brain deal with these - important implications for our understanding of localisation of function

• Technical level

  • Increased blood flow means there is increased neural activity

  • If area becomes more active, there is increased demand for oxygen in that area (oxygenation)

  • Brain responds by increasing blood flow and delivering oxygen in red blood cells to the area of heightened neural activity (known as haemodynamic response)

  • As a result of these changes in blood flow, images can be produced which show which areas of the brain are being used when engaged in certain tasks

• Ppts may be asked to alternate between doing particular tasks and then control tasks

  • Identify where there is pattern of change between the 2 tasks and which brain areas are activated by stimulus

• Common uses include

  • Cognitive neuroscience: understanding brain regions involved in memory, language and decision-making and other cognitive processes

  • Clinical applications: diagnosing brain disorders like Alzheimer's, tumours and strokes

  • Neuromarketing: understanding consumer behaviour and product preferences

  • Neuroplasticity: studying how brain changes over time

strengths

fMRI = very high spatial resolution (depicts details btw 1-2 millimetre) - detailed pictures of where brain activity is located

non-invasive

• Do not use radiation or involve inserting instruments (electrodes) directly into the brain

• So they are virtually risk-free

• More ppts are willing to take part in research to allow researchers to gather data on the functioning human brain

other advantages and also RWA

• fMRI has been useful in diagnosis of conditions such as Alzheimer's disease, brain tumours and strokes

weaknesses

fMRI = poor as it has around a 1-4 second lag time behind the image on screen and initial increase in blood in particular brain area - may not truly represent moment to moment changes in brain activity

• unable to predict w high degree of accuracy onset of brain activity observed

other disadvantages

• Does not provide a direct measure of neural activity as they measure changes in blood flow which are a secondary marker - this means that small changes in activity may be missed

• Overlooks the networked nature of brain activity, as it focuses only on localised activity in the brain, they claim that it is not communication among the different regions that is most critical to mental function

• fMRI is expensive compared to other neuroimaging techniques

EEG

• EEG scanners measure electrical activity that's caused by brain cell activity, achieved via electrodes attached to scalp (skull cap)

• Scan recording represents brainwave patterns - detect electrical changes/charges which result from activity in thousands of brain cells/neurons (shows overall brain activity)

  • When small electrical charges are graphed over period of time this indicates the general level of brain activity

• Amplitude - intensity or size of the activity (high = delta)

• Frequency - speed or quantity of activity (high = beta)

  • EEG patterns produce two distinctive states - synchronised and desynchronised patterns

    • Synchronised = recognisable waveform (alpha, beta, delta, theta)

    • Desynchronised = no pattern can be detected

• Beta waves shown when person is physiologically aroused - shown in REM sleep

• Theta/delta waves are associated with deeper sleep

• Alpha waves - associated with relaxation and light sleep

• Uses - it is a diagnostic tool as unusual arrhythmic patterns of activity may indicate neurological abnormalities such as epilepsy, tumours or sleep disorders

  • EEG can be used to detect various brain disorders (epilepsy - where patients show spikes of brain activity)

  • Used to diagnose disorders that influence brain activity (Alzheimer's)

  • Have been used in sleep research which helped to identify the sleep cycle and used to diagnose sleep disorders

strengths

• EEG/ERP = detect brain activity at the resolution of a single millisecond, provides recording of the brain's activity in real-time rather than still image of the passive brain, means that researcher can accurately measure a particular task or activity with the brain activity associated with it (real-world usefulness)

  • ERP useful for measuring cognitive functions and deficits such as allocation of attentional resources and maintenance of working memory

non-invasive

• Do not use radiation or involve inserting instruments (electrodes) directly into the brain

• So they are virtually risk-free

• More ppts are willing to take part in research to allow researchers to gather data on the functioning human brain

other advantages

• EEG has been useful in studying stage of sleep and in the diagnosis of sleep conditions and epilepsy (disorder characterised by random bursts of activity in the brain that are easily detected on screen) - link to high temporal resolution

weaknesses

• EEG/ERP = superficial and only general regions

  • Not able to pinpoint exact source of neural activity as activity is detected by several neighbouring electrodes simultaneously so does not allow researchers to distinguish between activities originating in different but closely adjacent locations in the brain

  • Poor at measuring neural activity that occurs below the upper layers of the brain so activity in deeper regions of the brain remain undetected

causation - EEG - electrical activity is often detected in several regions, can be difficult to pinpoint exact region of activity

ERP

• Researchers have developed a way to use raw EEG data and filter all extraneous brain activity through a statistical averaging technique

• So only brain activity that is left relates to the presentation of a specific stimulus or performance of a specific task

• The brain activity that is left is referred to as ERPs

  • Types of brainwave triggered by particular events

  • Research reveals that many different forms of ERP and how these are linked to cognitive processes such as attention and perception

• Time or interval between the presentation of stimulus and brain response is referred to as latency

• ERPs are small voltage changes in the brain triggered by a specific event/stimulus (processing a sound or picture)

 

• ERPs diagrams are used to visualise the electrical activity of the brain in response to specific stimuli, each peak represents different components of the brain's response

• Horizontal axis in an ERP diagram is typically a time axis, represents the time elapsed from the presentation of the stimulus

• y-axis in an ERP diagram typically represents the amplitude of the electrical signal, amplitude measured in microvolts

  • ERPs that occur within 100 milliseconds after the stimulus is presented are referred to as sensory ERPs because they are associated the brain's sensory processing

  • ERPs that occur after 100 milliseconds after the stimulus is presented are referred to as cognitive ERPs because they are associated with cognitive processing (evaluation of the stimulus)

strengths

• EEG/ERP = detect brain activity at the resolution of a single millisecond, provides recording of the brain's activity in real-time rather than still image of the passive brain, means that researcher can accurately measure a particular task or activity with the brain activity associated with it (real-world usefulness)

  • ERP useful for measuring cognitive functions and deficits such as allocation of attentional resources and maintenance of working memory

non-invasive

• Do not use radiation or involve inserting instruments (electrodes) directly into the brain

• So they are virtually risk-free

• More ppts are willing to take part in research to allow researchers to gather data on the functioning human brain

causation

• ERP - possible to determine how processing is affected by specific experimental manipulation (processing in response to particular visual or auditory stimulus)

other advantages

• ERPs can determine how processing is affected by a specific experimental manipulation i.e. processing in response to a particular visual or auditory stimulus

  • Address limitations of EEG as they bring more specificity to measurement of neural processes

weaknesses

• EEG/ERP = superficial and only general regions

  • Not able to pinpoint exact source of neural activity as activity is detected by several neighbouring electrodes simultaneously so does not allow researchers to distinguish between activities originating in different but closely adjacent locations in the brain

  • Poor at measuring neural activity that occurs below the upper layers of the brain so activity in deeper regions of the brain remain undetected

other disadvantages

• ERPs - can be a lack of standardisation in ERP methodology between different research studies which makes it difficult to confirm findings 

• ERPs - removal of all extraneous brain activity is often difficult to achieve

similarities btw EEG and ERP

• Involve use of electrodes placed on scalp to measure brain's electrical activity

• High in temporal resolution but low in spatial resolution

• Neither can detect activity in deeper regions of the brain (e.g. hippocampus)

differences btw EEG and ERP

• EEGs represent sum of overall brain activity whereas ERPs represent brain activity in relation to a particular task/stimulus

• EEGs are commonly used to diagnose conditions that affect brain activity (e.g. epilepsy), ERPs are used to measure how electrical activity alters when performing a task

• ERPs use an averaging technique to record the brain's response to a specific stimuli whereas EEGs do not

post-mortem examination

• Researchers study the physical brain of a person (after death) who displayed a particular behaviour or who had unusual cognitive processes while they were alive

  • Might have had rare disorder or unusual deficits in cognitive/behavioural abilities during life

  • Areas of damage within the brain are examined as a means of establishing likely cause of the affliction

  • May also involve comparison with neurotypical brain in order to ascertain extent of the difference

• Idea is to link structure with unusual behaviours

  • Examples include Broca and Wernicke

  • Patient Tan had lesions in the area of the brain (posterior left frontal lobe) responsible for speech production

• Post-mortems have contributed to our understanding of many disorders

  • Ungerstedt and Iverson examined the brains of deceased schizophrenic patients, found higher concentration of dopamine especially in limbic system compared to non-schizophrenics

• Post-mortem studies allow for a more detailed examination of anatomical and neurochemical aspects of the brain than would not be possible with other techniques

strengths

• Retrospective

• No cause-and-effect

• Consent issues

• Detailed neuroanatomy

• Useful for rare cases

• Vital to providing foundation of early understanding of key processes in the brain, both Broca and Wernicke relied on PME in establishing links between language, brain and behaviour before neuroimaging ever became a possibility

  • PME - used to study HM's brain to identify areas of damage which could then be associated with his memory deficits

weaknesses

• PME - atypical behaviour/cognitive functioning a patient displayed during their lifetime may not only be linked to deficits found in the brain, may have been other causes in addition to neuroanatomical abnormality

  • Causation is difficult to establish due to this

• PME - raise ethical issues of consent of the individual before death

  • Ppts may not be able to give informed consent