Neuroimaging Notes

Neuroimaging Techniques

  • Neuroimaging captures a picture of the brain.
  • Helps overcome ethical constraints in studying the live, intact, and injured brain.
  • Relatively non-invasive.

Categories of Neuroimaging

  • Structural Neuroimaging:
    • Produces images of brain structure and anatomy.
    • Examples: CT and standard MRI.
  • Functional Neuroimaging:
    • Provides views of brain function.
    • Shows images of the brain 'at work'.
    • Examples: PET and fMRI.

Computerized Tomography (CT)

  • Uses x-ray equipment to scan the brain at different angles.
  • Creates a horizontal cross-section image of the brain.
  • Requires a contrast substance to highlight blood vessels.
  • Useful for locating and identifying brain abnormalities and injury (e.g., tumors, stroke damage).
  • Limitations:
    • Shows only brain structure.
    • Not as detailed as other scanners.

Magnetic Resonance Imaging (MRI)

  • Uses magnetic fields to vibrate atoms in the brain and generate an image.
  • More sensitive than CT, producing clearer and more detailed images.
  • Used for diagnosing structural abnormalities.
    • Can detect small changes in brain anatomy such as distinguishing between cancerous and noncancerous tissue.
    • Can reveal tissue degeneration, blood clots, and leaks.

Functional Neuroimaging

  • Overcomes the limitation of CT and MRI by revealing brain activity during mental processes.

Positron Emission Tomography (PET)

  • Produces color images showing brain structure, activity, and function.
  • Records activity levels in different brain areas during tasks.
  • Tracks a glucose solution containing a radioactive tracer injected into the bloodstream.
  • Shows brain activity, but images are less detailed than MRI.
  • Color code indicates activity levels: violet, blue, green, yellow, and red (highest).

Functional Magnetic Resonance Imaging (fMRI)

  • Detects and records brain activity by measuring oxygen consumption.
  • Does not expose participants to radioactive tracers.
  • Identifies active brain areas by detecting changes in blood oxygen levels.
  • Uses standard MRI technology but provides better images than PET.
  • Can take numerous pictures rapidly, providing detailed and precise images of brain activity averaged over seconds.

Electroencephalography (EEG)

  • Detects, amplifies, and records general patterns of electrical activity in the brain.
  • Used to study states of consciousness (e.g., awake, sleeping, dreaming) and brain disorders (e.g., epilepsy, Parkinson’s disease).
  • Identifies distinctive brainwave patterns in conditions like schizophrenia.

Other Functional Neuroimaging Techniques

  • Magnetoencephalography (MEG).
  • Single photon emission computed tomography (SPECT).
  • Diffuse optical tomography (DOT).
  • Near infra-red spectroscopy (NRIS).
  • Functional near infra-red spectroscopy (fNIRS).
  • Each has its own strengths and limitations.