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Encyclopedia > Evoked potential


In neurophysiology, an evoked potential (or "evoked response") is an electrical potential recorded from a human or animal subject following presentation of a stimulus, as distinct from spontaneous potentials such as electroencephalograms or electromyograms. Evoked potential amplitudes tend to be low, ranging from less than a microvolt to several microvolts, compared to tens of microvolts for EEG, millivolts for EMG, and often close to a volt for EKG. In order to resolve these low-amplitude potentials against the background of ongoing EEG, EKG, EMG and other biological signals and ambient noise, signal averaging is usually required. The signal is time-locked to the stimulus and most of the noise occurs randomly, allowing the noise to be averaged out with averaging of repeated responses. Neurophysiology is a part of physiology as a science, which is concerned with the study of the nervous system. ... Binomial name Homo sapiens Linnaeus, 1758 Subspecies Homo sapiens idaltu(extinct) Homo sapiens sapiens Homo (genus). ... Phyla Porifera (sponges) Ctenophora (comb jellies) Cnidaria (coral, jellyfish, anenomes) Placozoa (trichoplax) Subregnum Bilateria (bilateral symmetry) Acoelomorpha (basal) Orthonectida (flatworms, echinoderms, etc. ... Electroencephalography is the neurophysiologic exploration of the electrical activity of the brain by the application of electrodes to the scalp. ... Electromyography (EMG) is a medical technique for measuring muscle response to nervous stimulation. ... Amplitude is a nonnegative scalar measure of a waves magnitude of oscillation, that is, magnitude of the maximum disturbance in the medium during one wave cycle. ... The volt is the SI derived unit for electric potential and voltage (derived from the ampere and watt). ... Lead II An electrocardiogram (ECG or EKG, abbreviated from the German Elektrokardiogramm) is a graphic produced by an electrocardiograph, which records the electrical voltage in the heart in the form of a continuous strip graph. ... NOiSE is a one volume manga created by Tsutomu Nihei as a prequel to his much-acclaimed ten-volume work, Blame! It offers some rather sketchy information concerning the Megastructures origins and initial size, as well as the beginnings of silicon life ...


Signals can be recorded from cerebral cortex, brainstem, spinal cord and peripheral nerves. Usually the term "evoked potential" is reserved for responses involving either recording from, or stimulation of, central nervous system structures. Thus evoked CMAP (compound motor action potentials) or SNAP (sensory nerve action potentials) as used in NCV (nerve conduction studies) are generally not thought of as evoked potentials, though they do meet the above definition. Location of the Cerebral cortex Slice of the Cerebral cortex, ca. ... The brain stem is the stalk of the brain below the cerebral hemispheres. ... The spinal cord is a part of the vertebrate nervous system that is enclosed in and protected by the vertebral column (it passes through the spinal canal). ... The peripheral nervous system or PNS, is part of the nervous system,and I have no clue what it does. ...


Sensory evoked potentials have been widely used in clinical medicine since the 1970s, including SSEP (somatosensory), VEP (visual) and BAEP (brainstem auditory) evoked potentials. These are also abbreviated as SSER, etc., and the BAEP is known as BSER, BAER, ABR, etc. SSEP are elicited by an electrical shock to a peripheral nerve as with NCV; VEP by an alternating checkerboard stimulus (PSVEP, pattern shift visual evoked potential) or a flash (strobe light or LED), and auditory evoked potentials by a click or tone, usually presented through earphones. Gustatory, olfactory, and even nociceptive (pain-evoked) potentials also exist, as do cognitive (event-related) potentials, though none of these have found widespread clinical application. In addition, transcranial motor evoked potentials, recorded either epidurally or from muscles following electrical or magnetic transcranial stimulation of motor cortex, have become increasingly important in recent years. The 1970s in its most obvious sense refers to the decade between 1970 and 1979. ... In the field of neuropsychology, a visual evoked potential is an evoked potential caused by sensory stimulation of a subjects visual field. ... Sign warning of possible electric shock hazard An electric shock may occur upon contact with electricity. ... A strobe light (Strobe) is a device used to produces regular flashes of very intense white light and is closely related to a common camera flash. ... External links LEd Category: TeX ... In-ear headphones Headphones (also known as earphones, stereophones, headsets, or the slang term cans) is a transducer that receives an electrical signal from a media player or receiver and uses speakers placed in close proximity to the ears (hence the name earphone) to convert the signal into audible sound... Taste is one of the most common and fundamental of the senses in life on Earth. ... Olfaction, the sense of smell, is the detection of chemicals dissolved in air (or, by animals that breathe water, in water). ... According to the International Society for the Study of Pain, there are two different terms: pain and nociception. ... A top-down view of skeletal muscle Muscle is a contractile form of tissue. ... A year is the time between two recurrences of an event related to the orbit of the Earth around the Sun. ...


BAEP originally were very useful for detection of brainstem tumors and acoustic neuromas; when clinical averaging systems were first developed, the BAEP was more sensitive than early CT scanners. After several generations of progress in clinical imaging, however, this application is of marginal usefulness. BAEP is still used as a method of screening hearing in neonates, who can not be effectively tested by behavioral audiometry (though evoked oto-acoustic emissions recordings may eventually supplant BAEP in this application). BAEP is also used for intraoperative neurophysiologic monitoring in skull base surgery such as acoustic neuroma resection, where the auditory nerve is at risk. Acoustic neuroma (or Vestibular Schwannoma) is a benign tumor of the acoustic nerve (more properly the vestibulocochlear nerve) just after it has left the brainstem, in the pontine angle. ... A human infant The word Infant derives from the Latin in-fans, meaning unable to speak. ... A typical modern surgery operation For other meanings of the word, see Surgery (disambiguation) Surgery (from the Greek cheirourgia meaning hand work) is the medical specialty that treats diseases or injuries by operative manual and instrumental treatment. ...


All three of the commonly used sensory modalities are useful in clinical diagnosis and monitoring of MS (multiple sclerosis); this is the main application for PSVEP. SSEP is also useful in coma.


SSEP and MEP (motor evoked potentials), along with EEG and EMG, are extremely useful in intraoperative neurophysiologic monitoring for a wide variety of neurosurgical, otologic, spinal and other surgical procedures. See IONM (intraoperative neurophysiologic monitoring), or surgical neurophysiology.


Evoked potentials are usually done on one sensory mode at a time. Visual evoked potentials may be induced by a flashing light, auditory evoked potentials by the onset of a sound, and somatosensory evoked potentials by a solenoid pulsing against a person's skin. A visual evoked potential (VEP) is an evoked potential caused by sensory stimulation of a subjects visual field. ...


See also


  Results from FactBites:
 
Evoked potential - Wikipedia, the free encyclopedia (498 words)
In neurophysiology, an evoked potential (or "evoked response") is an electrical potential recorded from a human or animal subject following presentation of a stimulus, as distinct from spontaneous potentials such as electroencephalograms or electromyograms.
Evoked potential amplitudes tend to be low, ranging from less than a microvolt to several microvolts, compared to tens of microvolts for EEG, millivolts for EMG, and often close to a volt for EKG.
Visual evoked potentials may be induced by a flashing light, auditory evoked potentials by the onset of a sound, and somatosensory evoked potentials by a solenoid pulsing against a person's skin.
Visual evoked potential - Wikipedia, the free encyclopedia (206 words)
A visual evoked potential (VEP) is an evoked potential caused by sensory stimulation of a subject's visual field.
Visual evoked potentials are also used in the investigation of basic functions of visual perception.
Sometimes, the term "visual evoked cortical potential" (VECP) is used to distinguish the VEP from retinal or subcortical potentials.
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