G. Dennis Rains,
Kutztown University of Pennsylvania
| angiography | The process by which a radiopaque (X-ray-absorbing) dye is injected into the cerebral circulation to make the vasculature (veins and arteries) visible on X ray.
|
 |
|
|
| anterograde transport | Axoplasmic transport that conveys materials from the cell body of the neuron to the axon terminal.
|
|
|
|
| association | Consistent co-occurrence of impairment in two or more functions. Association suggests that the two behavioral or cognitive phenomena are manifestations of one underlying process.
|
|
|
|
| autoradiography | A technique in which radioactive tracer is injected into an area of gray matter and then moved (via axoplasmic transport) to the axon terminals. This allows the identification of the structures that are the targets of the injected neurons.
|
|
|
|
| axon terminal | The end of the axon. Also called the terminal bouton.
|
|
|
|
| axoplasmic transport | An active process whereby substances within a neuron are moved across its length.
|
|
|
|
| commissurotomy (split-brain surgery) | Surgical sectioning (cutting) of the corpus callosum.
|
|
|
|
| diaschisis | The temporary disruptive effect that a cerebral lesion may exert on neighboring or even distant neural tissue. This may take the form of swelling, bleeding, or other short-term pathological processes.
|
|
|
|
| dichotic listening | A method in which different stimuli are delivered simultaneously to the two ears, using stereophonic earphones. The accuracy of report for the two ears is then compared.
|
|
|
|
| dissociation of function | Impairment in one function without impairment in a second function. The two functions are said to be dissociable--for example, vision and hearing are dissociable. See also single dissociation and double dissociation.
|
|
|
|
| double dissociation | Two functions are said to constitute a double dissociation if in some cases impairment in function A is seen without impairment in function B and in other cases impairment in function B is seen without impairment in function A. For example, hearing and vision are doubly dissociable.
|
|
|
|
| dyseidetic dyslexia | A reading impairment in which a person is able to read words by sound (phonological reading) but not directly from the visual percept (i.e., sight reading). Compare dysphonetic dyslexia.
|
|
|
|
| dysphonetic dyslexia | A reading impairment in which a person is able to read words directly from the visual percept (sight reading) but not by sound (phonological decoding). Compare dyseidetic dyslexia.
|
|
|
|
| electrocorticography (ECo) | The stimulation during surgery of the exposed cortex of a patient (with a low-voltage electrode). The results of this stimulation make possible a functional mapping of the cortex.
|
|
|
|
| event-related potential (ERP) | A method that measures the brief change in EEG activity that occurs in a particular area of the cortex after a specific event.
|
|
|
|
| fiber tract | A large number of axons bundled together and conveying information from one region of the central nervous system to another.
|
|
|
|
| functional magnetic resonance imaging (fMRI) | An imaging method that takes advantage of the fact that increases in blood flow (and hemoglobin) change the magnetic properties of the blood. Because blood flow is a correlate of neural activity, when MRI is used to detect these changes, it becomes a method for measuring brain activity.
|
|
|
|
| laterality studies | Studies that use special techniques to investigate hemispheric specialization in normal subjects.
|
|
|
|
| magnetic resonance imaging (MRI) | An imaging process that subjects the brain to a high magnetic field, causing the hydrogen atoms in the brain to line up in parallel. When radio waves are then passed across these atoms, they assume a characteristic pattern that is a function of the number of atoms present. This imaging method is very sensitive to variations in tissue density.
|
|
|
|
| magnetoencephalography (MEG) | A technique for measuring small magnetic fields generated by the electrical currents of neurons.
|
|
|
|
| microtubules | Long tubular structures within the axon along which vesicles containing various materials move in the process of axoplasmic transport.
|
|
|
|
| pneumoencephalography | The process in which an X ray of the head is taken after the cerebrospinal fluid in the cerebral ventricles is drained and replaced with air. The resulting contrast between the density of brain tissue and the air in the ventricles allows the shape of the ventricles to be visualized on X ray.
|
|
|
|
| positron emission tomography (PET) | A functional imaging method in which a number of different radioactive tracers can be injected into the cerebral circulation and then very precisely measured by a bank of sensors positioned around the head. This makes possible high resolution measurements of relative metabolic activity in different parts of the brain.
|
|
|
|
| receptive field | The stimulus characteristics that cause an individual neuron to fire maximally or minimally.
|
|
|
|
| regional cerebral blood flow (rCBF) | An imaging method in which a radioactive isotope is inhaled or injected and its distribution is then measured using a bank of sensors arranged symmetrically around the surface of the skull. The radioactive label is a marker of blood flow, which in turn is a correlate of brain metabolic activity.
|
|
|
|
| retrograde transport | The process by which materials within the cell are moved from the axon terminal to the cell body (as distinct from anterograde transport, which is in the opposite direction).
|
|
|
|
| single-cell recording | A method that involved inserting an exceedingly small diameter electrode into an individual neuron and measuring that cell's activity (frequency of firing). Also called unit recording.
|
|
|
|
| single dissociation | Two functions are said to constitute a single dissociation if in some cases impairment in function A is seen without impair-ment in function B, but impairment in function B is never seen without impairment in function A. For example, understanding heard language and hearing sound are singly dissociable.
|
|
|
|
| single photon emission computerized tomography (SPECT) | A functional imaging method roughly analogous to positron emission tomography (PET) but with less spatial resolution.
|
|
|
|
| sodium amobarbital test | A procedure in which the barbiturate sodium amobarbital is injected into one hemisphere (via the internal carotid artery), temporarily anesthetizing the hemisphere. During the test, the function of the noninjected hemisphere can be assessed.
|
|
|
|
| subtraction method | The method in which some measure of a control task (that is postulated to differ from the task under investigation in only one critical way) is subtracted from the same measure of the task under investigation. The resulting difference between the two measures is then inferred to reflect the critical difference between the two tasks. This method is used extensively in functional imaging studies.
|
|
|
|
| suppression | The phenomenon in which patients with commissurotomy report very few words presented to the left ear in a dichotic listening task (although they are able to report normally words presented to the left ear only).
|
|
|
|
| vesicles | Membrane-bound spheres within the neuron containing various materials.
|
2002 McGraw-Hill Higher Education