Human Research: Brain Scanning Techniques

Magnetic Resonance Imaging (MRI), Positron Emission Tomography (PET) and Functional Magnetic Resonance Imaging (fMRI) for quick revision of brain scanning techniques as a method of human research in health psychology

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Magnetic Resonance Imaging (MRI)

Structural brain scanning technique

  • The person is placed in the scanner
  • Electromagnetism affects the positively charged particles (protons) in hydrogen atoms/molecules
  • They respond like compass needles, and align when the magnetic field is turned on, passing through the head
  • As protons return to their original positions, they emit radio waves that are detected by the scanner, and converted into an image
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Evaluation of MRI

Strengths

  • Provides objective images of brain structure
  • Highly reliable as it follows a standardised procedure
  • Scanning is essentially non-invasive (doesn't involve surgery or going physically inside of the body)
  • Ethical - informed consent is given, right to withdraw, protection from harm, no deception, painless
  • In studying drug use - structural imaging allows comparison of the brains of users and non-users

Weaknesses

  • Provides only a biological understanding of drug effect - cognitive aspects (subjective thoughts and feelings) cannot be scanned
  • Equipment is expensive, and not easily available
  • It is difficult to get humans who want to participate in drug studies
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Functional Magnetic Resonance Imaging (fMRI)

Functional brain scanning technique

  • Electromagneticism causes haemoglobin (iron) molecules in the blood to resonate
  • These molecules emit radio waves which the scanner converts to colour
  • Different colours on the scan indicate varying levels of blood flow
  • The greater the blod flow the greater the brain activity
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Evaluation of fMRI

Strengths

  • Provides objective images of brain function
  • Highly reliable as it follows a standardised procedure
  • Scanning is essentially non-invasive (doesn't involve surgery or going physically inside of the body)
  • Ethical - informed consent is given, right to withdraw, protection from harm, no deception, painless
  • Functional imaging allows researcher to understand the immediate impact of drug use on brain activity, as 'live' action

Weaknesses

  • Provides only a biological understanding of drug effect - cognitive aspects (subjective thoughts and feelings) cannot be scanned
  • Equipment is expensive, and not easily available
  • It is difficult to get humans who want to participate in drug studies
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Positron Emission Tomography (PET)

Functional brain scanning technique

  • A radioactive tracer in glucose solution is injected into the arm, reaching the brain in 1 minute
  • It decays in 10-15 minutes
  • As it decays, gamma radiation is released (decays when the brain cells start to uptake the oxygen in the glucose)
  • The greater the blood flow/brain activity, the greater the 'emission' of radiation
  • Like fMRI, this brain activity is represented by colour variation in the image
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Evaluation of PET

Strengths

  • Provides objective images of brain function
  • Highly reliable as it follows a standardised procedure
  • Scanning is essentially non-invasive (doesn't involve surgery or going physically inside of the body)
  • Ethical - informed consent is given, right to withdraw, protection from harm, no deception, painless
  • Functional imaging allows researcher to understand the immediate impact of drug use on brain activity, as 'live' action

Weaknesses

  • Provides only a biological understanding of drug effect - cognitive aspects (subjective thoughts and feelings) cannot be scanned
  • Equipment is expensive, and not easily available
  • It is difficult to get humans who want to participate in drug studies
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