Ways of investigating the brain

• What is spatial resolution?

  The ability of an imaging system to discriminate between two adjacent parts of the brain
• What is temporal resolution?

  • Precision of a measurement with respect to time - Is there a time delay between brain activity and seeing image on screen 
• What is an FMRI?

  • This technique measures changes in brain activity while a person performs a task. It does it through measuring the changes in blood flow and indicates therefore increased neural activity. 
  •  If a particular area requires more oxygen, more blood will transport more oxygen to that area. The more active the brain area is, the more oxygen it requires.
  • As a result of these changes in blood flow, researchers produce maps showing which areas of the brain are involved in particular mental activity.
  • Fmri images show activity about 1-4 seconds after it occurs and accurate within 2mm. 
• Positive evaluation of an FMRI regarding non-invasive insertion?

  • A strength of fmri is that it is non-invasive and does not involve the insertion of instruments.
  • It also does not expose the brain to any harmful radiation.
  • Therefore unlike PET scans, it is risk free and straightforward to use.
  • More patients will undertake a Fmri scans as a result, which allows psychologists to get further knowledge about their study. 
• Positive evaluation of FMRI regarding images of high spatial resolution?

  • Another strength is that it produces images of high spatial resolution, which have a high detail of 1-2mm.
  • It produces a clear picture of how brain activity is localised. EEG has a very low spatial resolution and it does not show any visible images like the FMRI does.
  • FMRI is therefore a useful and scientific way of investigating scientific phenomena and is more accurate than other techniques. 
• Weakness of an FMRI?

  • One weakness of fmri is that there is a 4 second time-lag between the initial firing of the neuron and the image shown by the FMRI on the screen.
  • It has, therefore, poor temporal resolution.
  • Compared to the EEG’s, the EEG’s have a temporal resolution of about a millisecond or less.
  • There are limitations to FMRI’s as psychologists cannot predict with accuracy when the brain activity has occurred.
• What is an EEG?

  • EEG’s measure electrical activity through electrodes that are fixed to the scalp using a skull cap. The electrodes detect small electrical changes from the activity of brain cells below where the electrodes are replaced.  
  • When the electrical signals from the different electrodes are graphed over a period of time, the representation is called an EEG. The scan represents the brainwave patterns that are generated from millions of neurons, providing an overall account of brain activity. 
  • EEG’s can be used to detect abnormalities such as epilepsy, tumours and Alzheimer’s disease. Those with epilepsy show a spike in activity but those with a brain injury or disease show slowing of activity. 
  • EEG’s are a general measure of brain activity.
• Positive evaluation of EEG and ERP regarding its non invasive use??

  • Both techniques are non-invasive and do not allow for any exposure to any potentially harmful radiation.
  • Unlike other scanning techniques such as PET, it is virtually risk free and straightforward to use.
  • This means EEG’s and ERP’s are often used which allow psychologists to increase knowledge about disorders like epilepsy.
  • However, it could be argued that as electrodes are attached to the scalp, the technique may be uncomfortable for the patient. 
• Positive evaluation regarding the high temporal resolution of EEG's and ERP's?

  • Unlike fmri, EEG and ERP technology has high temporal resolution,
  • Modern EEG technology can detect brain activity at a resolution of a single millisecond and measures brain activity in real time.
  • Therefore, EEG and ERP scans allow for more accurate measuring of the brain.
• One disadvantage of EEG and ERP's?

  • One disadvantage of EEG and ERP’s is that they have poor spatial resolution, having a low spatial resolution means EEG/ERP cannot discriminate between two adjacent parts of the brain.
  • This means that the EEG/ERP cannot be used for localisation of function within the brain.
  • They are far less accurate than techniques such as FMRI
• EEG's and ERP's limited depth evaluation?

  • EEG’s and ERP’s also only detect activity in superficial regions of the brain, they are unable to provide information on what is occurring in deeper regions like the hypothalamus.
  • Electrodes are implanted in non-humans to record activity in deep regions of the brain but it is not ethically possible to do this with humans, it would be too invasive.
• Specific evaluations to an EEG or an ERP?

  • One limitation of EEG’s is that they are generalised information from thousands of neurons. It is not useful for pinpointing the exact region of neural activity and makes it difficult to draw accurate conclusions
  • One strength of ERP’s is that they bring more specificity to the measurement of neural processes that could never be achieved through raw EEG data as it eliminates the extraneous neuronal activity.
  • It is a more accurate technique than EEG’s