Ways of investigating the brain

• Ways of investigating the brain

  Functional magnetic resonance imaging (fMRI)

  Works by detecting changes in blood oxygenation and flow that occur as result of neural activity in specific parts of brain. When brain area is more active it consumes more oxygen and to meet this increased demand, blood flow is directed to area (haemodynamic response). fMRI produces 3-dimensional images (activation maps) showing which parts of the brain are involved in particular a mental process - has important implications for our understanding of localisation of function.
• Ways of investigating the brain 2

  Electroencephalogram (EEG)

  EGGs measure electrical activity within the brain via electrodes which are fixed to an individuals scalp using a skull cap. The scalp 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 (no particular pattern) may indicate neurological abnormalities such as epilepsy, tumours or disorders of sleep.
• Ways of investigating the brain 3

  Event-related potentials (ERPs)

  Is crude and overly general measure of brain activity. But, within EEG data are contained all neural responses associated w/ specific sensory, cognitive and motor events that may be of interest to cognitive neuroscientists. Researchers have developed a way of teasing out and isolating these responses. Using statistical averaging technique, all extraneous brain activity from the original EEG recording is filtered out, leaving only event-related potentials: types of brainwave triggered by particular events.
• Ways of investigating the brain 4

  Post-mortem examinations

  A technique involving analysis of person's brain following their death. In psychological research, individuals whose brains are subject to post mortems are likely to be those who have a rare disorder and have experienced unusual deficits in mental processes or behaviour during lifetime. Areas of damage within the brain are examined after death to establish the likely cause of affliction the person experienced. This may also involve a comparison with a neurotypical brain.
• Ways of investigating the brain- evaluation

  fMRIs - Strengths

  • Unlike other scanning techniques (PET), does not rely on use of radiation.
  • If administered correctly is virtually risk-free, non-invasive and straightforward to use.
  • Produces images that have a high spatial resolution, depicting detail by the millimetre, and providing a clear picture on how brain activity is localised.
• Ways of investigating the brain- evaluation

  fMRIs - Weaknesses

  • Is expensive compared to other neuroimaging techniques and can only capture a clear image if a person stays perfectly still.
  • 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.
  • Can only measure blood flow in the brain, cannot home in on activity of individual neurons and so it can be difficult to tell exactly what kind of brain activity is being represented on screen.
• Ways of investigating the brain- evaluation

  EEG - Strengths

  • Has proved invaluable in diagnosis of conditions such as epilepsy, a disorder characterised by random bursts of activity in the brain that can easily be detected on screen.
  • Has contributed to understanding of stages involved in sleep.
  • Unlike fMRI, has extremely high temporal resolution. Today, can accurately detect brain activity at a resolution of a single millisecond.
• Ways of investigating the brain- evaluation

  EEG - Weaknesses

  • Generalised nature of info received. Not useful for pinpointing exact source of neural activity, and does not allow researchers to distinguish between activities originating in different but adjacent locations.
• Ways of investigating the brain- evaluation

  ERPs - Strengths

  • Bring more specificity to measurement of neural processes than could be achieved using raw EEG data.
  • As derived from EEG measurements, have excellent temporal resolution, especially compared to neuroimaging techniques like fMRIs, and this has led to their widespread use in measurement of cognitive functions and deficits.
• Ways of investigating the brain- evaluation

  ERPs - Weaknesses

  • Critics have pointed out lack of standardisation in ERP methodology between diff research studies which makes it difficult to confirm findings.
  • In order to establish pure data, background noise and extraneous material must be completely eliminated, and this may not always be easy to achieve.
• Ways of investigating the brain- evaluation

  Post-mortems - Strengths

  • Was vital in providing foundation of early understanding of key processes in the brain. Broca and Wernicke both relied on post-mortem studies in establishing links between language, brain and behaviour decades before neuroimaging became a possibility.
  • Improve medical knowledge and help generate hypotheses for further study.
• Ways of investigating the brain- evaluation

  Post-mortems - Weaknesses

  • Causation is an issue. Observed damage to the brain may not be linked to deficits under review but to other unrelated trauma or decay.
  • Raise ethical issues of consent from individuals before death. May not be able to provide informed consent. E.g., HM lost ability to form memories and was not able to provide such consent - nevertheless post-mortem research has been conducted on his brain.