PSYCH 415--Notes for Methods in Neuropsychology

1. x-rays
   1. basically, the idea behind x-rays is like shining a strong light through an envelope to see what's inside - some things are more opaque to light and to x-rays (called "radio-opaque") than other things
   2. unfortunately, brain tissue is uniformly translucent to x-rays, so very little if any anatomical detail can be seen unless a contrast is used (a radio-opaque substance)
      1. pneumoencephalography - air is used as the contrast to show the position and shape of the ventricles, which are enlarged or displaced due to certain brain abnormalities (such as a crowding mass or tumor in the brain); has been replaced by CTs and MRIs today
      2. angiography - a contrast is injected into the blood to show the blood vessels in the brain, which may be displaced by a crowding mass, or absent due to a stroke, or may have other sorts of abnormal structure (such as an aneurysm, to be discussed later)
2. scans
   1. CAT or CT scans - computed (axial) tomography
      1. a computer-assisted x-ray technique
      2. typically about 8-9 horizontal scans of the brain are obtained
      3. a moderate amount of anatomical detail is visible, and tumors and other lesions show up well
   2. MRI scans - magnetic resonance imaging (aka NMR or nuclear magnetic resonance)
      1. when subjected to a strong magnetic field, hydrogen atoms can be made to emit radiation when activated by radio waves
      2. can produce high resolution images (lots of anatomical detail visible) as well as 3D images
   3. functional MRI (fMRI) - shows oxygen uptake by cells, hence activation
      1. while CAT and MRI can show only structure, fMRI can be used to visualize functioning of the living brain
   4. diffusion tensor imaging (tractotomy) - a form of MRI that tracks the movement of water molecules along fiber pathways
   5. PET scans - positron emission tomography
      1. detects the radiation emitted by a radioactively tagged substance that is taken up by brain cells (e.g., radioactive glucose) or that binds to receptors (drugs, neurotransmitters, etc.)
      2. very low res, so shows very little anatomical detail, but once again allows function to be visualized
   6. SPECT (single photon emission computed tomorgraphy) - a variation of the PET scanning technique that is capable of producing 3D imaging

1. electroencephalography (EEG)
   1. electrodes are attached to the scalp with electrically conductive paste
   2. the summated (or averaged) activity of the underlying neurons (mostly in the cortex) is recorded
   3. patient concerns about having their thoughts read, etc., are unfounded - about the best you can do is discover the patient's general state of arousal and alertness
      

      type	approx. freq.	voltage	behavior
      beta	20 Hz	LVF	awake, aroused, alert, attentive
      alpha	10 Hz	HVS	awake, resting, drowsy, inattentive
      theta	5 Hz	HVS	light sleep, extremely bored, watching TV
      delta	2.5 Hz	HVS	deep slow-wave sleep
      Notes: LVS = low voltage fast, HVS = high voltage slow

   4. beta activity is called "desynchronized"; the others are called "synchronized"
2. event-related potentials (ERPs) - once upon a time called "evoked potentials"
   1. electrical signals related to stimuli such as sensory stimuli that can be filtered out of the background EEG by computer averaging
   2. the position or existence of various P- and N-waves can reveal if the sensory system is functioning abnormally
3. other electrical recordings
   1. electromyography (EMG) - from the muscles
   2. electrooculography (EOG) - from the eyes
   3. electrocardiography (EKG) - from the heart
   4. skin conductance (SCR or GSR) - from the skin
4. magnetoencephalography (MEG)
   1. same idea as EEG but records the magnetic field generated by brain cells rather than the electrical field - this requires considerably more expensive equipment but also yields much more information

1. craniotomy - opening the skull to expose the brain
2. stereotaxic surgery - a technique first developed for experimental work on animals that allows precise placement in the brain of a lesion, an electrode, a cannula, etc.
3. and so on: brain stapling

1. twin studies
2. adoption studies

Sources

• Carlson, Neil R. (2005). Foundations of Physiological Psychology (6th ed.). Boston: Allyn & Bacon.
• Elias, Loren J. & Saucier, Deborah M. (2006). Neuropsychology: Clinical and Experimental Foundations. Boston: Allyn & Bacon.
• Kolb, Bryan & Whishaw, Ian Q. (2003). Fundamental of Human Neuropsychology (5th ed.). New York: Worth.
• Netter, Frank H. (1962). The Ciba Collection of Medical Illustrations, Vol. 1: Nervous System. Summit, NJ: Ciba Publications.
• Pinel, John P. J. (2006). Biopsychology (6th ed.). Boston: Allyn & Bacon.

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