EEG Terms

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EEG Terms

Postby somnonaut » Wed Nov 22, 2006 6:01 pm

Found at www.aset.org Word of the week.

SHARP WAVE
a transient with a duration of greater than 70 milliseconds but less than 200 milliseconds

COMMON MODE REJECTION
the characteristic of a differential amplifier to reject like or common signals

ASYNCHRONOUS
appearing with different timing over the hemispheres, the non-simultaneous occurrence of EEG activity over regions of the same or opposite sides of the head

MENINGES
the three membranes enveloping the brain and spinal cord. The three layers are the dura, arachnoid, and pia

HOMOLOGOUS
areas sharing common function, the same area on the opposite side, or having the same relative position. C3 and C4 are homologous electrodes

PHASE REVERSAL
the condition existing when two or more waves recorded in two or more channels of the EEG are 180 degrees out of phase. Phase reversals are the localization method of bipolar montages, indicating the location of focal abnormality

ELECTROCORTICOGRAPHY
the recording of electrical activity directly from the surface of the cerebral cortex either during surgery or post surgery using implanted electrodes

HYPSARRHYTHMIA
random high voltage slow waves and spikes interspersed with brief stretches of flattening associated with infantile spasms

INTERMITTENT
happening from time to time with no definite periodic pattern

TRANSVERSE
lying or going crosswise or at right angles to something. In EEG, a transverse montage goes across the head from left to right.

TRANSIENT ISCHEMIC ATTACK (TIA)
an acute neurological deficit of vascular origin that clears completely. A TIA can last minutes to hours but no longer than 24 hours.

BURST
a group of waves that appear and disappear abruptly and are distinguished from the background activity by difference in frequency, form, and amplitude.

BROCA'S APHASIA
expressive aphasia caused by damage to the dominant frontal lobe. The patient has an inability to express herself well with spoken words.

EPILEPTIFORM
waves often associated with epilepsy such as spikes, sharp waves, or spike and slow waves.

INPUT 1 and INPUT 2
the two inputs for each EEG channel that transmit the electrical potentials into the different amplifier.

SYNCOPE
episodic loss of consciousness, a spell, swoon, or faint

PERIODICITY
the time interval between the occurrence of a wave or pattern. A waveform is said to be periodic if it occurs at regular intervals of time.

LAMBDA
sharp transients occurring over the occipital regions of the scalp in waking patients during visual scanning of a pattern.

CORTEX
the convoluted layer of gray matter covering the surface of the cerebral hemispheres. About one-half of the cortex is hidden within the folded walls of the sulci.

SLEEP SPINDLES
12 to 15 hertz activity seen in the central areas with some spread to the frontal and parietal areas during light sleep.

PAROXYSMAL
sudden appearance of a new pattern, most often of high voltage, distinctly different from the background with an abrupt return to the previous pattern.

TINNITUS
ringing in the ears.

PARASAGITTAL
the two planes running from front to back on either side of the midline.

PHOTIC DRIVING
A normal response seen over the posterior portion of the head during photic stimulation. Photic driving can be at the same frequency as the flash rate or is a harmonic or subharmonic of the flash rate.

NEURALGIA
pain along the course of a nerve

IMPEDANCE
measurement of the opposition of the flow of alternating current (AC). Impedance is used to check the connection between the electrode, the conductive medium, and the scalp.

BIPOLAR
literally meaning having two poles. In EEG, it refers to montages that are “scalp to scalp” montages such as the longitudinal bipolar montage.

SPIKE
a transient with a duration of less than 70 milliseconds and commonly negative in polarity
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