Term
| gold standard of neuroassessment (2) |
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Definition
| autopsy, although functional deficits i.e., due to metabolic disorders) are not apparent on these. The gold standard for behavioral effects is neuropsychological testing. |
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Term
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Definition
| Using earphones to direct sound to one ear or the other, hemispheric aysmmetry for speech can be tested, since people usually have a right ear advantage (Kimura, 1961). Sometimes this is used to assess for integrity of the corpus callosum. |
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Term
| tachistoscopic presentation |
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Definition
Stimuli are presented very briefly, for microseconds, faster than the eyes can move. Since the eye cannot fixate in another area of the picture, the input is selectively processed first in one hemisphere. Useful in assessment of individuals with severed corpus callosum to assess functions of each hemisphere (e.g., Gazzaniga and split brain patient).
Computers have replaced the old T- scopes, such as the one pictured above. |
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Term
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Definition
Electrical recording from multiple electrodes placed on the surface of the head (cortex is found directly below the surface), which reflects the entrained action of thousands of neurons directly underneath. The cumulative voltage over time is expressed in waves that are designated according to their frequency (e.g., fast waves indicative of wakefulness are beta waves, slow waves occurring during sleep or coma are theta waves). typically used to assess for epilepsy and sleep disorders.
Inexpensive and non-invasive. |
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Term
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Definition
This is a positive deflection that occurs at approximately 300 milliseconds after a sensory event, and is thought to reflect a cognitive process, a sort of “ah ha” moment of realization. It is seen as an index of information processing speed. It occurs later in older populations and in dementias.
Delayed EPs in response to sensory and motor events can indicate areas in spinal cord, midbrain and above that are affected. |
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Term
| structural imaging tests (3) |
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Definition
Computerized tomography (CT)
Structural magnetic resonance imaging (MRI)
Diffuse tensor imaging (DTI) |
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Term
| functioning imaging tests (5) |
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Definition
Functional MRI = BOLD (blood oxygenation level dependent)
Positron emission tomography (PET)
Magnetoencephalogram (MEG)
Diffusion functional MRI (DfMRI)
Functional Near-Infrared Spectroscopy (fNIRS) |
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Term
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Definition
| Technique which amplifies brain electrical signals (ionic flow in dendrites occurring due to neurotransmission) while muting environmental signals, using highly sensitive superconducting quantum interference devices, or SQUIDs. About 50,000 active neurons are required to generate a detectable signal. Due to the weakness of the signal, it is mostly the large, pyramidal cells in cortex that are recorded. |
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Term
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Definition
Computer software generates
a 3D image of the brain from a
series of 2D X-rays taken around
an axis of rotation.
The word "tomography" is derived from the Greek tomos (volume) and graphein (to write). |
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Term
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Definition
Provides a 3D image of the structure of the brain.
Does not require radioactive isotopes; relies on a strong magnet. |
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Term
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Definition
A method involving injection of a radioactive isotope (molecule that binds to a receptor) to visualize neurotransmitter binding.
Is invasive and has risks, is also quite expensive ($2-5K). |
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Term
| Diffusion Tension Imaging |
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Definition
| Technique used since 1980s to track brain white matter fibers and connectivity. Based on the fact that water molecules will move around randomly (diffuse away) unless there is a structure that limits this. |
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Term
| functional near infared spectroscopy |
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Definition
| Light is emitted from optodes attached to a band around an area of cortex in the infrared frequency spectrum and penetrates the scalp and a couple of millimeters into the cortex. Cortical activation increases the amount of oxygen in the bloodstream, which absorbs different amounts of light. The light is then reabsorbed by sensors on the head and changes correspond to different blood oxygen levels. |
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