Ways Of Studying The Brain

• Post-mortem examinations= the studying of the brain after death, and aims to correlate the features of the brain after death with what was known about the person's behaviour before they died- giving an insight into how brain structure relates to behaviour.
• Post-mortem examinations allow us to establish large scale structural differences (lesions, size changes), cellular abnormalities at a microscopic level (abnormal connectivity or altered density of neurons, disorganised patterns of neurons) or chemical activity (presence of toxins or altered levels of neurotransmitters/ hormones).
• Functional Magnetic Resonance Imaging (FMRI)- measures changes in living brain activity whilst the person is actually carrying out a task.
• FMRI measures minute (small) changes in blood flow, which indicates neural activity in a certain area because of the increased demand for oxygen.
• An FMRI scan involves being within a machine that creates a very strong magnetic field which makes water molecules within the brain tissue align, which are then stimulated and can be detected by the scanner. The patient must stay still for 45 minutes in uncomfortable head gear.
• Electroencephalogram (EEG)- involves placing electrodes onto the scalp to record activity from groups of neurons in the brain.
• An EEG relies on the fact that the electrochemical activity of neurons is detectable a short distance away from the neurons themselves (isn't sensitive enough to detect single neurons firing).
• With an EEG, the pattern of changes in electrical activity over a period of time can be recorded- we call these brain waves (alpha waves, beta waves, theta waves, delta waves).
• EEGs can be used to find out about normal or healthy brain functions, and have also been useful in detecting abnormalities such as patients with epilepsy and Alzheimer's disease (so it's a good diagnostic tool).
• Event-Related Potentials (ERPs)- measure using a number of electrodes attached to the scalp and measure brain waves in general.
• ERPs are tiny changes in the electrical activity in the brain in response to a stimulus (an event, eg a sound/ picture), but detecting this specific response is difficult because it may be mixed into all of the other brain activity.
• With ERPs, to increase the accuracy of detection, the stimulus is presented several hundred times and brain waves are measured and then 'averaged together'- allowing the ERP to stand out whilst the other random brain activity cancels itself out.
• ERPs have allowed us to develop a very detailed understanding of healthy and unhealthy brain functioning in real time.
• Post-mortem examinations Strengths:

  • Allows for a more detailed examination of anatomical & neurochemical aspects of the brain that wouldn't be possible with the sole use of non-invasive techniques such as FMRI and EEG.
  • It enables researchers to examine deeper regions of the brain such as the hypothalamus & hippocampus.
• Post-mortem examinations Weakness:

  • Doesn't give 'real time' information about how the brain responds.
• FMRI Strengths:

  • Is non-invasive and doesn't expose the brain to potentially harmful radiation.
  • Is good for functional mapping as it can pinpoint active areas, which EEG & ERPs cannot (has good spatial resolution).
• FMRI Weakness:

  • Brain activity is being inferred from blood flow rather than being directly measured, which both EEGs and & ERPs can.
• EEG Strength:

  • Provides a recording of the brain's activity in real time rather than a still image of the passive brain, meaning that the researcher can accurately measure a particular task or activity with the brain activity associated with it.
• EEG Weakness:

  • Doesn't give good spatial accuracy, ie where the activity is coming from- so it's not useful for functional mapping, which FMRI is.
• ERP Strengths:

  • Can detect changes as soon as a single millisecond, so gives excellent temporal resolution.
  • Provides a continuous measure of processing in response to a stimulus, making it possible to determine how processing is affected by a specific experimental manipulation.
• ERP Weakness:

  • ERPs are so small & difficult to pick out from other electrical activity in the brain, requiring a large number of trials to gain meaningful data. This limits the type of question that ERP readings can realistically answer.