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Evoked potential

An evoked potential or evoked response is an electrical potential in a specific pattern recorded from a specific part of the nervous system, especially the brain, of a human or other animals following presentation of a stimulus such as a light flash or a pure tone. Different types of potentials result from stimuli of different modalities and types.[1] Evoked potential is distinct from spontaneous potentials as detected by electroencephalography (EEG), electromyography (EMG), or other electrophysiologic recording method. Such potentials are useful for electrodiagnosis and monitoring that include detections of disease and drug-related sensory dysfunction and intraoperative monitoring of sensory pathway integrity.[2]

Evoked potential
MeSHD005071
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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 20 millivolts for ECG. To resolve these low-amplitude potentials against the background of ongoing EEG, ECG, 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.[3]

Signals can be recorded from cerebral cortex, brain stem, spinal cord, peripheral nerves and muscles. Usually the term "evoked potential" is reserved for responses involving either recording from, or stimulation of, central nervous system structures. Thus evoked compound motor action potentials (CMAP) or sensory nerve action potentials (SNAP) as used in nerve conduction studies (NCS) are generally not thought of as evoked potentials, though they do meet the above definition.

Evoked potential is different from event-related potential (ERP), although the terms are sometimes used synonymously, because ERP has higher latency, and is associated with higher cognitive processing.[1][4] Evoked potentials are mainly classified by the type of stimulus: somatosensory, auditory, visual. But they could also be classified according to stimulus frequency, wave latencies, potential origin, location, and derivation.

Steady-state evoked potential Edit

An evoked potential is the electrical response of the brain to a sensory stimulus. Regan constructed an analogue Fourier series analyzer to record harmonics of the evoked potential of flickering (sinusoidally modulated) light. Rather than integrating the sine and cosine products, Regan fed the signals to a two-pen recorder via lowpass filters.[5] This allowed him to demonstrate that the brain attained a steady-state regime in which the amplitude and phase of the harmonics (frequency components) of the response were approximately constant over time. By analogy with the steady-state response of a resonant circuit that follows the initial transient response he defined an idealized steady-state evoked potential (SSEP) as a form of response to repetitive sensory stimulation in which the constituent frequency components of the response remain constant with time in both amplitude and phase.[5][6] Although this definition implies a series of identical temporal waveforms, it is more helpful to define the SSEP in terms of the frequency components that are an alternative description of the time-domain waveform, because different frequency components can have quite different properties.[6][7] For example, the properties of the high-frequency flicker SSEP (whose peak amplitude is near 40–50 Hz) correspond to the properties of the subsequently discovered magnocellular neurons in the retina of the macaque monkey, while the properties of the medium-frequency flicker SSEP ( whose amplitude peak is near 15–20 Hz) correspond to the properties of parvocellular neurons.[8] Since a SSEP can be completely described in terms of the amplitude and phase of each frequency component it can be quantified more unequivocally than an averaged transient evoked potential.

It is sometimes said that SSEPs are elicited only by stimuli of high repetition frequency, but this is not generally correct. In principle, a sinusoidally modulated stimulus can elicit a SSEP even when its repetition frequency is low. Because of the high-frequency rolloff of the SSEP, high frequency stimulation can produce a near-sinusoidal SSEP waveform, but this is not germane to the definition of a SSEP. By using zoom-FFT to record SSEPs at the theoretical limit of spectral resolution ΔF (where ΔF in Hz is the reciprocal of the recording duration in seconds) Regan and Regan discovered that the amplitude and phase variability of the SSEP can be sufficiently small that the bandwidth of the SSEP's constituent frequency components can be at the theoretical limit of spectral resolution up to at least a 500-second recording duration (0.002 Hz in this case).[9] Repetitive sensory stimulation elicits a steady-state magnetic brain response that can be analysed in the same way as the SSEP.[7]

The "simultaneous stimulation" technique Edit

This technique allows several (e.g., four) SSEPs to be recorded simultaneously from any given location on the scalp.[10] Different sites of stimulation or different stimuli can be tagged with slightly different frequencies that are virtually identical to the brain, but easily separated by Fourier series analyzers.[10] For example, when two unpatterned lights are modulated at slightly different frequencies (F1 and F2) and superimposed, multiple nonlinear cross-modulation components of frequency (mF1 ± nF2) are created in the SSEP, where m and n are integers.[7] These components allow nonlinear processing in the brain to be investigated. By frequency-tagging two superimposed gratings, spatial frequency and orientation tuning properties of the brain mechanisms that process spatial form can be isolated and studied.[11][12] Stimuli of different sensory modalities can also be tagged. For example, a visual stimulus was flickered at Fv Hz and a simultaneously presented auditory tone was amplitude modulated at Fa Hz. The existence of a (2Fv + 2Fa) component in the evoked magnetic brain response demonstrated an audio-visual convergence area in the human brain, and the distribution of this response over the head allowed this brain area to be localized.[13] More recently, frequency tagging has been extended from studies of sensory processing to studies of selective attention[14] and of consciousness.[15]

The "sweep" technique Edit

The sweep technique is a hybrid frequency domain/time domain technique.[16] A plot of, for example, response amplitude versus the check size of a stimulus checkerboard pattern plot can be obtained in 10 seconds, far faster than when time-domain averaging is used to record an evoked potential for each of several check sizes.[16] In the original demonstration of the technique the sine and cosine products were fed through lowpass filters (as when recording a SSEP ) while viewing a pattern of fine checks whose black and white squares exchanged place six times per second. Then the size of the squares was progressively increased so as to give a plot of evoked potential amplitude versus check size (hence "sweep"). Subsequent authors have implemented the sweep technique by using computer software to increment the spatial frequency of a grating in a series of small steps and to compute a time-domain average for each discrete spatial frequency.[17][18] A single sweep may be adequate or it may be necessary to average the graphs obtained in several sweeps with the averager triggered by the sweep cycle.[19] Averaging 16 sweeps can improve the signal-to-noise ratio of the graph by a factor of four.[19] The sweep technique has proved useful in measuring rapidly adapting visual processes[20] and also for recording from babies, where recording duration is necessarily short. Norcia and Tyler have used the technique to document the development of visual acuity[17][21] and contrast sensitivity[22] through the first years of life. They have emphasized that, in diagnosing abnormal visual development, the more precise the developmental norms, the more sharply can the abnormal be distinguished from the normal, and to that end have documented normal visual development in a large group of infants.[17][21][22] For many years the sweep technique has been used in paediatric ophthalmology (electrodiagnosis) clinics worldwide.

Evoked potential feedback Edit

This technique allows the SSEP to directly control the stimulus that elicits the SSEP without the conscious intervention of the experimental subject.[5][19] For example, the running average of the SSEP can be arranged to increase the luminance of a checkerboard stimulus if the amplitude of the SSEP falls below some predetermined value, and to decrease luminance if it rises above this value. The amplitude of the SSEP then hovers about this predetermined value. Now the wavelength (colour) of the stimulus is progressively changed. The resulting plot of stimulus luminance versus wavelength is a plot of the spectral sensitivity of the visual system.[6][19]

Sensory evoked potentials Edit

Sensory evoked potentials (SEP) are recorded from the central nervous system following stimulation of sense organs, for example, visual evoked potentials elicited by a flashing light or changing pattern on a monitor,[23] auditory evoked potentials by a click or tone stimulus presented through earphones), or tactile or somatosensory evoked potential (SSEP) elicited by tactile or electrical stimulation of a sensory or mixed nerve in the periphery. Sensory evoked potentials have been widely used in clinical diagnostic medicine since the 1970s, and also in intraoperative neurophysiology monitoring (IONM), also known as surgical neurophysiology.

There are three kinds of evoked potentials in widespread clinical use: auditory evoked potentials, usually recorded from the scalp but originating at brainstem level; visual evoked potentials, and somatosensory evoked potentials, which are elicited by electrical stimulation of peripheral nerve. Examples of SEP usage include:[4]

  • SSEP can be used to locate lesions such as peripheral nerve or spinal cord.
  • VEP and BAEP can supplement neuroimaging as part of workups to diagnose diseases such as multiple sclerosis.
  • Short latency EPs such as SSEP, VEP, and BAEP can be used to indicate prognosis for traumatic and anoxic brain injury. Early after anoxic brain injury, no response indicates mortality accurately. In traumatic brain injury, abnormal responses indicates failure to recover from coma. In both types of injury, normal responses may indicate good outcome. Moreover, recovery in responses often indicates clinical recovery.

Long and Allen[24] were the first investigators to report the abnormal brainstem auditory evoked potentials (BAEPs) in an alcoholic woman who recovered from acquired central hypoventilation syndrome. These investigators hypothesized that their patient's brainstem was poisoned, but not destroyed, by her chronic alcoholism.

Visual evoked potential Edit

Visual evoked potential (VEP) is an evoked potential elicited by presenting light flash or pattern stimulus which can be used to confirm damage to visual pathway[25] including retina, optic nerve, optic chiasm, optic radiations, and occipital cortex.[26] One application is in measuring infant's visual acuity. Electrodes are placed on infant's head over visual cortex and a gray field is presented alternately with a checkerboard or grating pattern. If the checker's boxes or stripes are large enough to be detected, VEP is generated; otherwise, none is generated. It's an objective way to measure infant's visual acuity.[27]

VEP can be sensitive to visual dysfunctions that may not be found with just physical examinations or MRI, even if it cannot indicate etiologies.[26] VEP may be abnormal in optic neuritis, optic neuropathy, demyelinating disease, multiple sclerosis, Friedreich’s ataxia, vitamin B12 deficiency, neurosyphilis, migraine, ischemic disease, tumor compressing the optic nerve, ocular hypertension, glaucoma, diabetes, toxic amblyopia, aluminum neurotoxicity, manganese intoxication, retrobulbar neuritis, and brain injury.[28] It can be used to examine infant's visual impairment for abnormal visual pathways which may be due to delayed maturation.[26]

The P100 component of VEP response, which is the positive peak with the delay about 100 ms, has a major clinical importance. The visual pathway dysfunction anterior to the optic chiasm maybe where VEPs are most useful. For example, patients with acute severe optic neuritis often lose the P100 response or have highly attenuated responses. Clinical recovery and visual improvement come with P100 restoration but with an abnormal increased latency that continues indefinitely, and hence, it maybe useful as an indicator of previous or subclinical optic neuritis.[29]

In 1934, Adrian and Matthew noticed potential changes of the occipital EEG can be observed under stimulation of light. Ciganek developed the first nomenclature for occipital EEG components in 1961. During that same year, Hirsch and colleagues recorded a visual evoked potential (VEP) on the occipital lobe (externally and internally), and they discovered amplitudes recorded along the calcarine fissure were the largest. In 1965, Spehlmann used a checkerboard stimulation to describe human VEPs. An attempt to localize structures in the primary visual pathway was completed by Szikla and colleagues. Halliday and colleagues completed the first clinical investigations using VEP by recording delayed VEPs in a patient with retrobulbar neuritis in 1972. A wide variety of extensive research to improve procedures and theories has been conducted from the 1970s to today and the method has also been described in animals.[30]

VEP Stimuli Edit

The diffuse-light flash stimulus is rarely used nowadays due to the high variability within and across subjects. However, it is beneficial to use this type of stimulus when testing infants, animals or individuals with poor visual acuity. The checkerboard and grating patterns use light and dark squares and stripes, respectively. These squares and stripes are equal in size and are presented, one image at a time, via a computer screen.

VEP Electrode Placement Edit

Electrode placement is extremely important to elicit a good VEP response free of artifact. In a typical (one channel) setup, one electrode is placed 2.5 cm above the inion and a reference electrode is placed at Fz. For a more detailed response, two additional electrodes can be placed 2.5  cm to the right and left of Oz.

VEP Waves Edit

 
Normal visual evoked potential

The VEP nomenclature is determined by using capital letters stating whether the peak is positive (P) or negative (N) followed by a number which indicates the average peak latency for that particular wave. For example, P100 is a wave with a positive peak at approximately 100 ms following stimulus onset. The average amplitude for VEP waves usually falls between 5 and 20 microvolts.

Normal values are depending on used stimulation hardware (flash stimulus vs. cathode ray tube or liquid crystal display, checkerboard field size, etc.).

Types of VEP Edit

Some specific VEPs are:

  • Monocular pattern reversal (most common)
  • Sweep visual evoked potential
  • Binocular visual evoked potential
  • Chromatic visual evoked potential
  • Hemi-field visual evoked potential
  • Flash visual evoked potential
  • LED Goggle visual evoked potential
  • Motion visual evoked potential
  • Multifocal visual evoked potential
  • Multi-channel visual evoked potential
  • Multi-frequency visual evoked potential
  • Stereo-elicited visual evoked potential
  • Steady state visually evoked potential

Auditory evoked potential Edit

Auditory evoked potentials (AEP) can be used to trace the signal generated by a sound through the ascending auditory pathway. The evoked potential is generated in the cochlea, goes through the cochlear nerve, through the cochlear nucleus, superior olivary complex, lateral lemniscus, to the inferior colliculus in the midbrain, on to the medial geniculate body, and finally to the cortex.[31]

Auditory evoked potentials (AEPs) are a subclass of event-related potentials (ERPs). ERPs are brain responses that are time-locked to some "event", such as a sensory stimulus, a mental event (such as recognition of a target stimulus), or the omission of a stimulus. For AEPs, the "event" is a sound. AEPs (and ERPs) are very small electrical voltage potentials originating from the brain recorded from the scalp in response to an auditory stimulus, such as different tones, speech sounds, etc.

Brainstem auditory evoked potentials are small AEPs that are recorded in response to an auditory stimulus from electrodes placed on the scalp.

AEPs serve for assessment of the functioning of the auditory system and neuroplasticity.[32] They can be used to diagnose learning disabilities in children, aiding in the development of tailored educational programs for those with hearing and or cognition problems.[33]

Somatosensory evoked potential Edit

 
Normal somatosensory evoked potential (tibial nerve)

Somatosensory evoked potentials (SSEPs) are EP recorded from the brain or spinal cord when stimulating peripheral nerve repeatedly.[34] SSEPs are used in neuromonitoring to assess the function of a patient's spinal cord during surgery. They are recorded by stimulating peripheral nerves, most commonly the tibial nerve, median nerve or ulnar nerve, typically with an electrical stimulus. The response is then recorded from the patient's scalp.

Although stimuli such as touch, vibration, and pain can be used for SSEP, electrical stimuli are most common because of ease and reliability.[34] SSEP can be used for prognosis in patients with severe traumatic head injury.[35] Because SSEP with latency less than 50 ms is relatively independent of consciousness, if used early in comatose patient, it can predict outcome reliably and efficiently.[36] For example, comatose patients with no responses bilaterally has 95% chance of not recovering from coma.[37] But care should be taken analyzing the result. For example, increased sedation and other CNS injuries such as the spinal cord can affect SEP.[34]

Because of the low amplitude of the signal once it reaches the patient's scalp and the relatively high amount of electrical noise caused by background EEG, scalp muscle EMG or electrical devices in the room, the signal must be averaged. The use of averaging improves the signal-to-noise ratio. Typically, in the operating room, over 100 and up to 1,000 averages must be used to adequately resolve the evoked potential.

The two most looked at aspects of an SSEP are the amplitude and latency of the peaks. The most predominant peaks have been studied and named in labs. Each peak is given a letter and a number in its name. For example, N20 refers to a negative peak (N) at 20ms. This peak is recorded from the cortex when the median nerve is stimulated. It most likely corresponds to the signal reaching the somatosensory cortex. When used in intraoperative monitoring, the latency and amplitude of the peak relative to the patient's post-intubation baseline is a crucial piece of information. Dramatic increases in latency or decreases in amplitude are indicators of neurological dysfunction.

During surgery, the large amounts of anesthetic gases used can affect the amplitude and latencies of SSEPs. Any of the halogenated agents or nitrous oxide will increase latencies and decrease amplitudes of responses, sometimes to the point where a response can no longer be detected. For this reason, an anesthetic utilizing less halogenated agent and more intravenous hypnotic and narcotic is typically used.

Clinical Uses Edit

SEP findings do not by themselves lead to a specific diagnosis, and organic diseases cannot necessarily be excluded with normal SEP findings. Findings must be interpreted in the context of the patient’s clinical presentation. Evaluating the peripheral responses with SEPs could contribute to the diagnosis of peripheral nerve damage.

Furthermore, SEPs could be abnormal in different pathologies such as multiple sclerosis (MS), hereditary spinocerebellar degenerations, hereditary spastic paraplegia, AIDS and vitamin B12 or vitamin E deficiency. In patients with MS, evoked potential findings often complement findings on MRI.

In the acute stage after a traumatic spinal injury or brain trauma, the absence of SEP responses do not correlate with prognosis. However, an early return to normal or preserved cortical responses in the subacute stage correlate with a positive outcome.

SEPs can be helpful to evaluate subcortical and cortical function in comatose patients and are less sensitive to sedative drugs than EEG. SEP´s and BAEP´s together are the best tools to assist in the confirmation of brain death in comatose patients

Clinical consideration in children Edit

As in the adult, SEP findings in combination with the clinical assessment and EEG findings can contribute to the determination of prognosis in comatose children. In high risk newborns, tracking SEP findings over time can be helpful for outcome prognostication. Several neurodegenerative disorders have abnormal findings in spinal and cortical SEP components. Moreover, compressive lesions on the spine (e.g. Arnold-Chiari malformation or mucopolysaccharidosis) are associated with abnormal SEPs, which may precede abnormalities on MRI.

Laser evoked potential Edit

Conventional SSEPs monitor the functioning of the part of the somatosensory system involved in sensations such as touch and vibration. The part of the somatosensory system that transmits pain and temperature signals is monitored using laser evoked potentials (LEP). LEPs are evoked by applying finely focused, rapidly rising heat to bare skin using a laser. In the central nervous system they can detect damage to the spinothalamic tract, lateral brain stem, and fibers carrying pain and temperature signals from the thalamus to the cortex. In the peripheral nervous system pain and heat signals are carried along thin (C and A delta) fibers to the spinal cord, and LEPs can be used to determine whether a neuropathy is located in these small fibers as opposed to larger (touch, vibration) fibers.[38]

Motor evoked potentials Edit

Motor evoked potentials (MEP) are recorded from muscles following direct stimulation of exposed motor cortex, or transcranial stimulation of motor cortex, either magnetic or electrical. Transcranial magnetic MEP (TCmMEP) potentially offer clinical diagnostic applications. Transcranial electrical MEP (TCeMEP) has been in widespread use for several years for intraoperative monitoring of pyramidal tract functional integrity.

During the 1990s, there were attempts to monitor "motor evoked potentials", including "neurogenic motor evoked potentials" recorded from peripheral nerves, following direct electrical stimulation of the spinal cord. It has become clear that these "motor" potentials were almost entirely elicited by antidromic stimulation of sensory tracts—even when the recording was from muscles (antidromic sensory tract stimulation triggers myogenic responses through synapses at the root entry level).[clarification needed] TCMEP, whether electrical or magnetic, is the most practical way to ensure pure motor responses, since stimulation of sensory cortex cannot result in descending impulses beyond the first synapse (synapses cannot be backfired).

TMS-induced MEPs have been used in many experiments in cognitive neuroscience. Because MEP amplitude is correlated with motor excitability, they offer a quantitative way to test the role of various types of intervention on the motor system (pharmacological, behavioral, lesion, etc.). TMS-induced MEPs may thus serve as an index of covert motor preparation or facilitation, e.g., induced by the mirror neuron system when seeing someone's else actions.[39] In addition, MEPs are used as a reference to adjust the intensity of stimulation that needs to be delivered by TMS when targeting cortical regions whose response might not be as easily measurable, e.g., in the context of TMS-based therapy.

Intraoperative monitoring Edit

Somatosensory evoked potentials provide monitoring for the dorsal columns of the spinal cord. Sensory evoked potentials may also be used during surgeries which place brain structures at risk. They are effectively used to determine cortical ischemia during carotid endarterectomy surgeries and for mapping the sensory areas of the brain during brain surgery.

Electrical stimulation of the scalp can produce an electric current within the brain that activates the motor pathways of the pyramidal tracts. This technique is known as transcranial electrical motor potential (TcMEP) monitoring. This technique effectively evaluates the motor pathways in the central nervous system during surgeries which place these structures at risk. These motor pathways, including the lateral corticospinal tract, are located in the lateral and ventral funiculi of the spinal cord. Since the ventral and dorsal spinal cord have separate blood supply with very limited collateral flow, an anterior cord syndrome (paralysis or paresis with some preserved sensory function) is a possible surgical sequela, so it is important to have monitoring specific to the motor tracts as well as dorsal column monitoring.

Transcranial magnetic stimulation versus electrical stimulation is generally regarded as unsuitable for intraoperative monitoring because it is more sensitive to anesthesia. Electrical stimulation is too painful for clinical use in awake patients. The two modalities are thus complementary, electrical stimulation being the choice for intraoperative monitoring, and magnetic for clinical applications.

See also Edit

References Edit

  1. ^ a b VandenBos, Gary R, ed. (2015). evoked potential (EP). p. 390. doi:10.1037/14646-000. ISBN 978-1-4338-1944-5. {{cite book}}: |work= ignored (help)
  2. ^ Sugerman, Richard A (2014). "CHAPTER 15 - Structure and Function of the Neurologic System". In McCance, Kathryn L; Huether, Sue E; Brashers, Valentina L; Rote, Neal S (eds.). Evoked Potentials. ISBN 978-0-323-08854-1. {{cite book}}: |work= ignored (help)
  3. ^ Karl E. Misulis; Toufic Fakhoury (2001). Spehlmann's Evoked Potential Primer. Butterworth-heinemann. ISBN 978-0-7506-7333-4.
  4. ^ a b Kwasnica, Christina (2011). Kreutzer, Jeffrey S; DeLuca, John; Caplan, Bruce (eds.). Evoked Potentials. p. 986. doi:10.1007/978-0-387-79948-3. ISBN 978-0-387-79947-6. {{cite book}}: |work= ignored (help)
  5. ^ a b c Regan D (1966). "Some characteristics of average steady–state and transient responses evoked by modulated light". Electroencephalography and Clinical Neurophysiology. 20 (3): 238–48. doi:10.1016/0013-4694(66)90088-5. PMID 4160391.
  6. ^ a b c Regan D (1979). "Electrical responses evoked from the human brain". Scientific American. 241 (6): 134–46. Bibcode:1979SciAm.241f.134R. doi:10.1038/scientificamerican1279-134. PMID 504980.
  7. ^ a b c Regan, D. (1989). Human brain electrophysiology: Evoked potentials and evoked magnetic fields in science and medicine. New York: Elsevier, 672 pp.
  8. ^ Regan D.; Lee B.B. (1993). "A comparison of the human 40 Hz response with the properties of macaque ganglion cells". Visual Neuroscience. 10 (3): 439–445. doi:10.1017/S0952523800004661. PMID 8494797. S2CID 3132361.
  9. ^ Regan M.P.; Regan D. (1988). "A frequency domain technique for characterizing nonlinearities in biological systems". Journal of Theoretical Biology. 133 (3): 293–317. Bibcode:1988JThBi.133..293R. doi:10.1016/S0022-5193(88)80323-0.
  10. ^ a b Regan D.; Heron J.R. (1969). "Clinical investigation of lesions of the visual pathway: a new objective technique". Journal of Neurology, Neurosurgery, and Psychiatry. 32 (5): 479–83. doi:10.1136/jnnp.32.5.479. PMC 496563. PMID 5360055.
  11. ^ Regan D.; Regan M.P. (1988). "Objective evidence for phase–independent spatial frequency analysis in the human visual pathway". Vision Research. 28 (1): 187–191. doi:10.1016/S0042-6989(88)80018-X. PMID 3413995. S2CID 21369518.
  12. ^ Regan D.; Regan M.P. (1987). "Nonlinearity in human visual responses to two–dimensional patterns and a limitation of Fourier methods". Vision Research. 27 (12): 2181–3. doi:10.1016/0042-6989(87)90132-5. PMID 3447366. S2CID 3175111.
  13. ^ Regan M.P.; He P.; Regan D. (1995). "An audio–visual convergence area in human brain". Experimental Brain Research. 106 (3): 485–7. doi:10.1007/bf00231071. PMID 8983992. S2CID 27044876.
  14. ^ Morgan S. T.; Hansen J. C.; Hillyard S. A. (1996). "Selective attention to stimulus location modulates the steady-state evoked potential". Proceedings of the National Academy of Sciences USA. 93 (10): 4770–4774. doi:10.1073/pnas.93.10.4770. PMC 39354. PMID 8643478.
  15. ^ Srinivasan R, Russell DP, Edelman GM, Tononi G (1999). "Increased synchronization of neuromagnetic responses during conscious perception". Journal of Neuroscience. 19 (13): 5435–48. doi:10.1523/JNEUROSCI.19-13-05435.1999. PMC 6782339. PMID 10377353.
  16. ^ a b Regan D (1973). "Rapid objective refraction using evoked brain potentials". Investigative Ophthalmology. 12 (9): 669–79. PMID 4742063.
  17. ^ a b c Norcia A. M.; Tyler C. W. (1985). "Infant VEP acuity measurements: Analysis of individual differences and measurement error". Electroencephalography and Clinical Neurophysiology. 61 (5): 359–369. doi:10.1016/0013-4694(85)91026-0. PMID 2412787.
  18. ^ Strasburger, H.; Rentschler, I. (1986). "A digital fast sweep technique for studying steady-state visual evoked potentials" (PDF). Journal of Electrophysiological Techniques. 13 (5): 265–278.
  19. ^ a b c d Regan D (1975). "Colour coding of pattern responses in man investigated by evoked potential feedback and direct plot techniques". Vision Research. 15 (2): 175–183. doi:10.1016/0042-6989(75)90205-9. PMID 1129975. S2CID 42218073.
  20. ^ Nelson J. I.; Seiple W. H.; Kupersmith M. J.; Carr R. E. (1984). "A rapid evoked potential index of cortical adaptation". Investigative Ophthalmology & Visual Science. 59 (6): 454–464. doi:10.1016/0168-5597(84)90004-2. PMID 6209112.
  21. ^ a b Norcia A. M.; Tyler C. W. (1985). "Spatial frequency sweep VEP: Visual acuity during the first year of life". Vision Research. 25 (10): 1399–1408. doi:10.1016/0042-6989(85)90217-2. PMID 4090273. S2CID 23557430.
  22. ^ a b Norcia A. M.; Tyler C. W.; Allen D. (1986). "Electrophysiological assessment of contrast sensitivity in human infants". American Journal of Optometry and Physiological Optics. 63 (1): 12–15. doi:10.1097/00006324-198601000-00003. PMID 3942183. S2CID 19809242.
  23. ^ O'Shea, R. P., Roeber, U., & Bach, M. (2010). Evoked potentials: Vision. In E. B. Goldstein (Ed.), Encyclopedia of Perception (Vol. 1, pp. 399-400, xli). Los Angeles: Sage. ISBN 978-1-4129-4081-8
  24. ^ Long KJ, Allen N (1984). "Abnormal Brainstem Auditory Evoked Potentials Following Ondine's Curse". Arch. Neurol. 41 (10): 1109–1110. doi:10.1001/archneur.1984.04050210111028. PMID 6477223.
  25. ^ O’Toole, Marie T, ed. (2013). visual-evoked potential (VEP). p. 1880. ISBN 978-0-323-08541-0. {{cite book}}: |work= ignored (help)
  26. ^ a b c Hammond, Flora; Grafton, Lori (2011). Kreutzer, Jeffrey S; DeLuca, John; Caplan, Bruce (eds.). Visual Evoked Potentials. p. 2628. doi:10.1007/978-0-387-79948-3. ISBN 978-0-387-79947-6. {{cite book}}: |work= ignored (help)
  27. ^ Goldstein, E Bruce (2013). "Chapter 2: The Beginning of Perceptions". Sensation and Perception (9th ed.). WADSWORTH: CENGAGE Learning. Method: Peferential looking, p. 46. ISBN 978-1-133-95849-9.
  28. ^ Hammond & Grafton (2011) cited Huszar, L (2006). "Clinical utility of evoked potentials". eMedicine. Retrieved 2007-07-09.
  29. ^ Aminoff, Michael J (2001). Braunwald, Eugene; Fauci, Anthony S; Kasper, Dennis L; Hauser, Stephen L; Longo, Dan L; Jameson, J Larry (eds.). 357. ELECTROPHYSIOLOGIC STUDIES OF THE CENTRAL AND PERIPHERAL NERVOUS SYSTEMS. EVOKED POTENTIALS. ISBN 0-07-007272-8. {{cite book}}: |work= ignored (help)
  30. ^ Strain, George M.; Jackson, Rose M.; Tedford, Bruce L. (1990-07-01). "Visual Evoked Potentials in the Clinically Normal Dog". Journal of Veterinary Internal Medicine. 4 (4): 222–225. doi:10.1111/j.1939-1676.1990.tb00901.x. ISSN 1939-1676. PMID 2401969.
  31. ^ Musiek, FE & Baran, JA (2007). The Auditory system. Boston, MA: Pearson Education, Inc.
  32. ^ Sanju, Himanshu Kumar; Kumar, Prawin (2016). "Enhanced auditory evoked potentials in musicians: A review of recent findings". Journal of Otology. 11 (2): 63–72. doi:10.1016/j.joto.2016.04.002. ISSN 1672-2930. PMC 6002589. PMID 29937812.
  33. ^ Frizzo, Ana C. F. (10 June 2015). "Auditory evoked potential: a proposal for further evaluation in children with learning disabilities". Frontiers in Psychology. 6: 788. doi:10.3389/fpsyg.2015.00788. PMC 4461809. PMID 26113833.
  34. ^ a b c McElligott, Jacinta (2011). Kreutzer, Jeffrey S; DeLuca, John; Caplan, Bruce (eds.). Somatosensory Evoked Potentials. pp. 2319–2320. doi:10.1007/978-0-387-79948-3. ISBN 978-0-387-79947-6. {{cite book}}: |work= ignored (help)
  35. ^ McElligott (2011) cited Lew, HL; Lee, EH; Pan, SS L; Chiang, JYP (2007). Zasler, ND; Katz, DL; Zafonte, RD (eds.). Electrophysiological assessment techniques: Evoked potentials and electroencephalography. {{cite book}}: |work= ignored (help)
  36. ^ McElligott (2011) cited Lew, HL; Dikman, S; Slimp, J; Temkin, N; Lee, EH; Newell, D; et al. (2003). "Use of somatosensory evoked potentials and cognitive event related potentials in predicting outcome in patients with severe traumatic brain injury". American Journal of Physical Medicine & Rehabilitation. 82 (1): 53–61. doi:10.1097/00002060-200301000-00009. PMID 12510186. S2CID 45096294.
  37. ^ McElligott (2011) อ้างอิง Robinson, L. R. (2004). Kraft, GL; Lew, HL (eds.). Somatosensory evoked potentials in coma prognosis. pp. 43–61. doi:10.1016/s1047-9651(03)00102-5. PMID 15029898. {{cite book}}: |work= ignored (help)
  38. ^ Treede RD, Lorenz J, Baumgärtner U (December 2003). "Clinical usefulness of laser-evoked potentials". Neurophysiol Clin. 33 (6): 303–14. doi:10.1016/j.neucli.2003.10.009. PMID 14678844. S2CID 18486576.
  39. ^ Catmur C.; Walsh V.; Heyes C. (2007). "Sensorimotor learning configures the human mirror system". Curr. Biol. 17 (17): 1527–1531. doi:10.1016/j.cub.2007.08.006. PMID 17716898.

External links Edit

evoked, potential, evoked, potential, evoked, response, electrical, potential, specific, pattern, recorded, from, specific, part, nervous, system, especially, brain, human, other, animals, following, presentation, stimulus, such, light, flash, pure, tone, diff. An evoked potential or evoked response is an electrical potential in a specific pattern recorded from a specific part of the nervous system especially the brain of a human or other animals following presentation of a stimulus such as a light flash or a pure tone Different types of potentials result from stimuli of different modalities and types 1 Evoked potential is distinct from spontaneous potentials as detected by electroencephalography EEG electromyography EMG or other electrophysiologic recording method Such potentials are useful for electrodiagnosis and monitoring that include detections of disease and drug related sensory dysfunction and intraoperative monitoring of sensory pathway integrity 2 Evoked potentialMeSHD005071 edit on Wikidata 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 20 millivolts for ECG To resolve these low amplitude potentials against the background of ongoing EEG ECG 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 3 Signals can be recorded from cerebral cortex brain stem spinal cord peripheral nerves and muscles Usually the term evoked potential is reserved for responses involving either recording from or stimulation of central nervous system structures Thus evoked compound motor action potentials CMAP or sensory nerve action potentials SNAP as used in nerve conduction studies NCS are generally not thought of as evoked potentials though they do meet the above definition Evoked potential is different from event related potential ERP although the terms are sometimes used synonymously because ERP has higher latency and is associated with higher cognitive processing 1 4 Evoked potentials are mainly classified by the type of stimulus somatosensory auditory visual But they could also be classified according to stimulus frequency wave latencies potential origin location and derivation Contents 1 Steady state evoked potential 1 1 The simultaneous stimulation technique 1 2 The sweep technique 1 3 Evoked potential feedback 2 Sensory evoked potentials 2 1 Visual evoked potential 2 1 1 VEP Stimuli 2 1 2 VEP Electrode Placement 2 1 3 VEP Waves 2 1 4 Types of VEP 2 2 Auditory evoked potential 2 3 Somatosensory evoked potential 2 3 1 Clinical Uses 2 3 2 Clinical consideration in children 2 3 3 Laser evoked potential 3 Motor evoked potentials 4 Intraoperative monitoring 5 See also 6 References 7 External linksSteady state evoked potential EditAn evoked potential is the electrical response of the brain to a sensory stimulus Regan constructed an analogue Fourier series analyzer to record harmonics of the evoked potential of flickering sinusoidally modulated light Rather than integrating the sine and cosine products Regan fed the signals to a two pen recorder via lowpass filters 5 This allowed him to demonstrate that the brain attained a steady state regime in which the amplitude and phase of the harmonics frequency components of the response were approximately constant over time By analogy with the steady state response of a resonant circuit that follows the initial transient response he defined an idealized steady state evoked potential SSEP as a form of response to repetitive sensory stimulation in which the constituent frequency components of the response remain constant with time in both amplitude and phase 5 6 Although this definition implies a series of identical temporal waveforms it is more helpful to define the SSEP in terms of the frequency components that are an alternative description of the time domain waveform because different frequency components can have quite different properties 6 7 For example the properties of the high frequency flicker SSEP whose peak amplitude is near 40 50 Hz correspond to the properties of the subsequently discovered magnocellular neurons in the retina of the macaque monkey while the properties of the medium frequency flicker SSEP whose amplitude peak is near 15 20 Hz correspond to the properties of parvocellular neurons 8 Since a SSEP can be completely described in terms of the amplitude and phase of each frequency component it can be quantified more unequivocally than an averaged transient evoked potential It is sometimes said that SSEPs are elicited only by stimuli of high repetition frequency but this is not generally correct In principle a sinusoidally modulated stimulus can elicit a SSEP even when its repetition frequency is low Because of the high frequency rolloff of the SSEP high frequency stimulation can produce a near sinusoidal SSEP waveform but this is not germane to the definition of a SSEP By using zoom FFT to record SSEPs at the theoretical limit of spectral resolution DF where DF in Hz is the reciprocal of the recording duration in seconds Regan and Regan discovered that the amplitude and phase variability of the SSEP can be sufficiently small that the bandwidth of the SSEP s constituent frequency components can be at the theoretical limit of spectral resolution up to at least a 500 second recording duration 0 002 Hz in this case 9 Repetitive sensory stimulation elicits a steady state magnetic brain response that can be analysed in the same way as the SSEP 7 The simultaneous stimulation technique Edit This technique allows several e g four SSEPs to be recorded simultaneously from any given location on the scalp 10 Different sites of stimulation or different stimuli can be tagged with slightly different frequencies that are virtually identical to the brain but easily separated by Fourier series analyzers 10 For example when two unpatterned lights are modulated at slightly different frequencies F1 and F2 and superimposed multiple nonlinear cross modulation components of frequency mF1 nF2 are created in the SSEP where m and n are integers 7 These components allow nonlinear processing in the brain to be investigated By frequency tagging two superimposed gratings spatial frequency and orientation tuning properties of the brain mechanisms that process spatial form can be isolated and studied 11 12 Stimuli of different sensory modalities can also be tagged For example a visual stimulus was flickered at Fv Hz and a simultaneously presented auditory tone was amplitude modulated at Fa Hz The existence of a 2Fv 2Fa component in the evoked magnetic brain response demonstrated an audio visual convergence area in the human brain and the distribution of this response over the head allowed this brain area to be localized 13 More recently frequency tagging has been extended from studies of sensory processing to studies of selective attention 14 and of consciousness 15 The sweep technique Edit The sweep technique is a hybrid frequency domain time domain technique 16 A plot of for example response amplitude versus the check size of a stimulus checkerboard pattern plot can be obtained in 10 seconds far faster than when time domain averaging is used to record an evoked potential for each of several check sizes 16 In the original demonstration of the technique the sine and cosine products were fed through lowpass filters as when recording a SSEP while viewing a pattern of fine checks whose black and white squares exchanged place six times per second Then the size of the squares was progressively increased so as to give a plot of evoked potential amplitude versus check size hence sweep Subsequent authors have implemented the sweep technique by using computer software to increment the spatial frequency of a grating in a series of small steps and to compute a time domain average for each discrete spatial frequency 17 18 A single sweep may be adequate or it may be necessary to average the graphs obtained in several sweeps with the averager triggered by the sweep cycle 19 Averaging 16 sweeps can improve the signal to noise ratio of the graph by a factor of four 19 The sweep technique has proved useful in measuring rapidly adapting visual processes 20 and also for recording from babies where recording duration is necessarily short Norcia and Tyler have used the technique to document the development of visual acuity 17 21 and contrast sensitivity 22 through the first years of life They have emphasized that in diagnosing abnormal visual development the more precise the developmental norms the more sharply can the abnormal be distinguished from the normal and to that end have documented normal visual development in a large group of infants 17 21 22 For many years the sweep technique has been used in paediatric ophthalmology electrodiagnosis clinics worldwide Evoked potential feedback Edit This technique allows the SSEP to directly control the stimulus that elicits the SSEP without the conscious intervention of the experimental subject 5 19 For example the running average of the SSEP can be arranged to increase the luminance of a checkerboard stimulus if the amplitude of the SSEP falls below some predetermined value and to decrease luminance if it rises above this value The amplitude of the SSEP then hovers about this predetermined value Now the wavelength colour of the stimulus is progressively changed The resulting plot of stimulus luminance versus wavelength is a plot of the spectral sensitivity of the visual system 6 19 Sensory evoked potentials EditSensory evoked potentials SEP are recorded from the central nervous system following stimulation of sense organs for example visual evoked potentials elicited by a flashing light or changing pattern on a monitor 23 auditory evoked potentials by a click or tone stimulus presented through earphones or tactile or somatosensory evoked potential SSEP elicited by tactile or electrical stimulation of a sensory or mixed nerve in the periphery Sensory evoked potentials have been widely used in clinical diagnostic medicine since the 1970s and also in intraoperative neurophysiology monitoring IONM also known as surgical neurophysiology There are three kinds of evoked potentials in widespread clinical use auditory evoked potentials usually recorded from the scalp but originating at brainstem level visual evoked potentials and somatosensory evoked potentials which are elicited by electrical stimulation of peripheral nerve Examples of SEP usage include 4 SSEP can be used to locate lesions such as peripheral nerve or spinal cord VEP and BAEP can supplement neuroimaging as part of workups to diagnose diseases such as multiple sclerosis Short latency EPs such as SSEP VEP and BAEP can be used to indicate prognosis for traumatic and anoxic brain injury Early after anoxic brain injury no response indicates mortality accurately In traumatic brain injury abnormal responses indicates failure to recover from coma In both types of injury normal responses may indicate good outcome Moreover recovery in responses often indicates clinical recovery Long and Allen 24 were the first investigators to report the abnormal brainstem auditory evoked potentials BAEPs in an alcoholic woman who recovered from acquired central hypoventilation syndrome These investigators hypothesized that their patient s brainstem was poisoned but not destroyed by her chronic alcoholism Visual evoked potential Edit Visual evoked potential VEP is an evoked potential elicited by presenting light flash or pattern stimulus which can be used to confirm damage to visual pathway 25 including retina optic nerve optic chiasm optic radiations and occipital cortex 26 One application is in measuring infant s visual acuity Electrodes are placed on infant s head over visual cortex and a gray field is presented alternately with a checkerboard or grating pattern If the checker s boxes or stripes are large enough to be detected VEP is generated otherwise none is generated It s an objective way to measure infant s visual acuity 27 VEP can be sensitive to visual dysfunctions that may not be found with just physical examinations or MRI even if it cannot indicate etiologies 26 VEP may be abnormal in optic neuritis optic neuropathy demyelinating disease multiple sclerosis Friedreich s ataxia vitamin B12 deficiency neurosyphilis migraine ischemic disease tumor compressing the optic nerve ocular hypertension glaucoma diabetes toxic amblyopia aluminum neurotoxicity manganese intoxication retrobulbar neuritis and brain injury 28 It can be used to examine infant s visual impairment for abnormal visual pathways which may be due to delayed maturation 26 The P100 component of VEP response which is the positive peak with the delay about 100 ms has a major clinical importance The visual pathway dysfunction anterior to the optic chiasm maybe where VEPs are most useful For example patients with acute severe optic neuritis often lose the P100 response or have highly attenuated responses Clinical recovery and visual improvement come with P100 restoration but with an abnormal increased latency that continues indefinitely and hence it maybe useful as an indicator of previous or subclinical optic neuritis 29 In 1934 Adrian and Matthew noticed potential changes of the occipital EEG can be observed under stimulation of light Ciganek developed the first nomenclature for occipital EEG components in 1961 During that same year Hirsch and colleagues recorded a visual evoked potential VEP on the occipital lobe externally and internally and they discovered amplitudes recorded along the calcarine fissure were the largest In 1965 Spehlmann used a checkerboard stimulation to describe human VEPs An attempt to localize structures in the primary visual pathway was completed by Szikla and colleagues Halliday and colleagues completed the first clinical investigations using VEP by recording delayed VEPs in a patient with retrobulbar neuritis in 1972 A wide variety of extensive research to improve procedures and theories has been conducted from the 1970s to today and the method has also been described in animals 30 VEP Stimuli Edit The diffuse light flash stimulus is rarely used nowadays due to the high variability within and across subjects However it is beneficial to use this type of stimulus when testing infants animals or individuals with poor visual acuity The checkerboard and grating patterns use light and dark squares and stripes respectively These squares and stripes are equal in size and are presented one image at a time via a computer screen VEP Electrode Placement Edit Electrode placement is extremely important to elicit a good VEP response free of artifact In a typical one channel setup one electrode is placed 2 5 cm above the inion and a reference electrode is placed at Fz For a more detailed response two additional electrodes can be placed 2 5 cm to the right and left of Oz VEP Waves Edit nbsp Normal visual evoked potentialThe VEP nomenclature is determined by using capital letters stating whether the peak is positive P or negative N followed by a number which indicates the average peak latency for that particular wave For example P100 is a wave with a positive peak at approximately 100 ms following stimulus onset The average amplitude for VEP waves usually falls between 5 and 20 microvolts Normal values are depending on used stimulation hardware flash stimulus vs cathode ray tube or liquid crystal display checkerboard field size etc Types of VEP Edit Some specific VEPs are Monocular pattern reversal most common Sweep visual evoked potential Binocular visual evoked potential Chromatic visual evoked potential Hemi field visual evoked potential Flash visual evoked potential LED Goggle visual evoked potential Motion visual evoked potential Multifocal visual evoked potential Multi channel visual evoked potential Multi frequency visual evoked potential Stereo elicited visual evoked potential Steady state visually evoked potentialAuditory evoked potential Edit Auditory evoked potentials AEP can be used to trace the signal generated by a sound through the ascending auditory pathway The evoked potential is generated in the cochlea goes through the cochlear nerve through the cochlear nucleus superior olivary complex lateral lemniscus to the inferior colliculus in the midbrain on to the medial geniculate body and finally to the cortex 31 Auditory evoked potentials AEPs are a subclass of event related potentials ERPs ERPs are brain responses that are time locked to some event such as a sensory stimulus a mental event such as recognition of a target stimulus or the omission of a stimulus For AEPs the event is a sound AEPs and ERPs are very small electrical voltage potentials originating from the brain recorded from the scalp in response to an auditory stimulus such as different tones speech sounds etc Brainstem auditory evoked potentials are small AEPs that are recorded in response to an auditory stimulus from electrodes placed on the scalp AEPs serve for assessment of the functioning of the auditory system and neuroplasticity 32 They can be used to diagnose learning disabilities in children aiding in the development of tailored educational programs for those with hearing and or cognition problems 33 Somatosensory evoked potential Edit nbsp Normal somatosensory evoked potential tibial nerve Somatosensory evoked potentials SSEPs are EP recorded from the brain or spinal cord when stimulating peripheral nerve repeatedly 34 SSEPs are used in neuromonitoring to assess the function of a patient s spinal cord during surgery They are recorded by stimulating peripheral nerves most commonly the tibial nerve median nerve or ulnar nerve typically with an electrical stimulus The response is then recorded from the patient s scalp Although stimuli such as touch vibration and pain can be used for SSEP electrical stimuli are most common because of ease and reliability 34 SSEP can be used for prognosis in patients with severe traumatic head injury 35 Because SSEP with latency less than 50 ms is relatively independent of consciousness if used early in comatose patient it can predict outcome reliably and efficiently 36 For example comatose patients with no responses bilaterally has 95 chance of not recovering from coma 37 But care should be taken analyzing the result For example increased sedation and other CNS injuries such as the spinal cord can affect SEP 34 Because of the low amplitude of the signal once it reaches the patient s scalp and the relatively high amount of electrical noise caused by background EEG scalp muscle EMG or electrical devices in the room the signal must be averaged The use of averaging improves the signal to noise ratio Typically in the operating room over 100 and up to 1 000 averages must be used to adequately resolve the evoked potential The two most looked at aspects of an SSEP are the amplitude and latency of the peaks The most predominant peaks have been studied and named in labs Each peak is given a letter and a number in its name For example N20 refers to a negative peak N at 20ms This peak is recorded from the cortex when the median nerve is stimulated It most likely corresponds to the signal reaching the somatosensory cortex When used in intraoperative monitoring the latency and amplitude of the peak relative to the patient s post intubation baseline is a crucial piece of information Dramatic increases in latency or decreases in amplitude are indicators of neurological dysfunction During surgery the large amounts of anesthetic gases used can affect the amplitude and latencies of SSEPs Any of the halogenated agents or nitrous oxide will increase latencies and decrease amplitudes of responses sometimes to the point where a response can no longer be detected For this reason an anesthetic utilizing less halogenated agent and more intravenous hypnotic and narcotic is typically used Clinical Uses Edit SEP findings do not by themselves lead to a specific diagnosis and organic diseases cannot necessarily be excluded with normal SEP findings Findings must be interpreted in the context of the patient s clinical presentation Evaluating the peripheral responses with SEPs could contribute to the diagnosis of peripheral nerve damage Furthermore SEPs could be abnormal in different pathologies such as multiple sclerosis MS hereditary spinocerebellar degenerations hereditary spastic paraplegia AIDS and vitamin B12 or vitamin E deficiency In patients with MS evoked potential findings often complement findings on MRI In the acute stage after a traumatic spinal injury or brain trauma the absence of SEP responses do not correlate with prognosis However an early return to normal or preserved cortical responses in the subacute stage correlate with a positive outcome SEPs can be helpful to evaluate subcortical and cortical function in comatose patients and are less sensitive to sedative drugs than EEG SEP s and BAEP s together are the best tools to assist in the confirmation of brain death in comatose patients Clinical consideration in children Edit As in the adult SEP findings in combination with the clinical assessment and EEG findings can contribute to the determination of prognosis in comatose children In high risk newborns tracking SEP findings over time can be helpful for outcome prognostication Several neurodegenerative disorders have abnormal findings in spinal and cortical SEP components Moreover compressive lesions on the spine e g Arnold Chiari malformation or mucopolysaccharidosis are associated with abnormal SEPs which may precede abnormalities on MRI Laser evoked potential Edit Conventional SSEPs monitor the functioning of the part of the somatosensory system involved in sensations such as touch and vibration The part of the somatosensory system that transmits pain and temperature signals is monitored using laser evoked potentials LEP LEPs are evoked by applying finely focused rapidly rising heat to bare skin using a laser In the central nervous system they can detect damage to the spinothalamic tract lateral brain stem and fibers carrying pain and temperature signals from the thalamus to the cortex In the peripheral nervous system pain and heat signals are carried along thin C and A delta fibers to the spinal cord and LEPs can be used to determine whether a neuropathy is located in these small fibers as opposed to larger touch vibration fibers 38 Motor evoked potentials EditMotor evoked potentials MEP are recorded from muscles following direct stimulation of exposed motor cortex or transcranial stimulation of motor cortex either magnetic or electrical Transcranial magnetic MEP TCmMEP potentially offer clinical diagnostic applications Transcranial electrical MEP TCeMEP has been in widespread use for several years for intraoperative monitoring of pyramidal tract functional integrity During the 1990s there were attempts to monitor motor evoked potentials including neurogenic motor evoked potentials recorded from peripheral nerves following direct electrical stimulation of the spinal cord It has become clear that these motor potentials were almost entirely elicited by antidromic stimulation of sensory tracts even when the recording was from muscles antidromic sensory tract stimulation triggers myogenic responses through synapses at the root entry level clarification needed TCMEP whether electrical or magnetic is the most practical way to ensure pure motor responses since stimulation of sensory cortex cannot result in descending impulses beyond the first synapse synapses cannot be backfired TMS induced MEPs have been used in many experiments in cognitive neuroscience Because MEP amplitude is correlated with motor excitability they offer a quantitative way to test the role of various types of intervention on the motor system pharmacological behavioral lesion etc TMS induced MEPs may thus serve as an index of covert motor preparation or facilitation e g induced by the mirror neuron system when seeing someone s else actions 39 In addition MEPs are used as a reference to adjust the intensity of stimulation that needs to be delivered by TMS when targeting cortical regions whose response might not be as easily measurable e g in the context of TMS based therapy Intraoperative monitoring EditSomatosensory evoked potentials provide monitoring for the dorsal columns of the spinal cord Sensory evoked potentials may also be used during surgeries which place brain structures at risk They are effectively used to determine cortical ischemia during carotid endarterectomy surgeries and for mapping the sensory areas of the brain during brain surgery Electrical stimulation of the scalp can produce an electric current within the brain that activates the motor pathways of the pyramidal tracts This technique is known as transcranial electrical motor potential TcMEP monitoring This technique effectively evaluates the motor pathways in the central nervous system during surgeries which place these structures at risk These motor pathways including the lateral corticospinal tract are located in the lateral and ventral funiculi of the spinal cord Since the ventral and dorsal spinal cord have separate blood supply with very limited collateral flow an anterior cord syndrome paralysis or paresis with some preserved sensory function is a possible surgical sequela so it is important to have monitoring specific to the motor tracts as well as dorsal column monitoring Transcranial magnetic stimulation versus electrical stimulation is generally regarded as unsuitable for intraoperative monitoring because it is more sensitive to anesthesia Electrical stimulation is too painful for clinical use in awake patients The two modalities are thus complementary electrical stimulation being the choice for intraoperative monitoring and magnetic for clinical applications See also EditBereitschaftspotential Contingent negative variation Difference due to memory Early left anterior negativity Error related negativity Event related potential Evoked field Electroencephalography Electroretinography Slow vertex response Event related potential N100 N200 N2pc N170 N400 Visual N1 C1 and P1 P200 P300 P3a P3b P600 neuroscience International Society for Clinical Electrophysiology of Vision Late positive component Lateralized readiness potential Mismatch negativity Neural oscillation Oddball paradigm Somatosensory evoked potentialReferences Edit a b VandenBos Gary R ed 2015 evoked potential EP p 390 doi 10 1037 14646 000 ISBN 978 1 4338 1944 5 a href Template Cite book html title Template Cite book cite book a work ignored help Sugerman Richard A 2014 CHAPTER 15 Structure and Function of the Neurologic System In McCance Kathryn L Huether Sue E Brashers Valentina L Rote Neal S eds Evoked Potentials ISBN 978 0 323 08854 1 a href Template Cite book html title Template Cite book cite book a work ignored help Karl E Misulis Toufic Fakhoury 2001 Spehlmann s Evoked Potential Primer Butterworth heinemann ISBN 978 0 7506 7333 4 a b Kwasnica Christina 2011 Kreutzer Jeffrey S DeLuca John Caplan Bruce eds Evoked Potentials p 986 doi 10 1007 978 0 387 79948 3 ISBN 978 0 387 79947 6 a href Template Cite book html title Template Cite book cite book a work ignored help a b c Regan D 1966 Some characteristics of average steady state and transient responses evoked by modulated light Electroencephalography and Clinical Neurophysiology 20 3 238 48 doi 10 1016 0013 4694 66 90088 5 PMID 4160391 a b c Regan D 1979 Electrical responses evoked from the human brain Scientific American 241 6 134 46 Bibcode 1979SciAm 241f 134R doi 10 1038 scientificamerican1279 134 PMID 504980 a b c Regan D 1989 Human brain electrophysiology Evoked potentials and evoked magnetic fields in science and medicine New York Elsevier 672 pp Regan D Lee B B 1993 A comparison of the human 40 Hz response with the properties of macaque ganglion cells Visual Neuroscience 10 3 439 445 doi 10 1017 S0952523800004661 PMID 8494797 S2CID 3132361 Regan M P Regan D 1988 A frequency domain technique for characterizing nonlinearities in biological systems Journal of Theoretical Biology 133 3 293 317 Bibcode 1988JThBi 133 293R doi 10 1016 S0022 5193 88 80323 0 a b Regan D Heron J R 1969 Clinical investigation of lesions of the visual pathway a new objective technique Journal of Neurology Neurosurgery and Psychiatry 32 5 479 83 doi 10 1136 jnnp 32 5 479 PMC 496563 PMID 5360055 Regan D Regan M P 1988 Objective evidence for phase independent spatial frequency analysis in the human visual pathway Vision Research 28 1 187 191 doi 10 1016 S0042 6989 88 80018 X PMID 3413995 S2CID 21369518 Regan D Regan M P 1987 Nonlinearity in human visual responses to two dimensional patterns and a limitation of Fourier methods Vision Research 27 12 2181 3 doi 10 1016 0042 6989 87 90132 5 PMID 3447366 S2CID 3175111 Regan M P He P Regan D 1995 An audio visual convergence area in human brain Experimental Brain Research 106 3 485 7 doi 10 1007 bf00231071 PMID 8983992 S2CID 27044876 Morgan S T Hansen J C Hillyard S A 1996 Selective attention to stimulus location modulates the steady state evoked potential Proceedings of the National Academy of Sciences USA 93 10 4770 4774 doi 10 1073 pnas 93 10 4770 PMC 39354 PMID 8643478 Srinivasan R Russell DP Edelman GM Tononi G 1999 Increased synchronization of neuromagnetic responses during conscious perception Journal of Neuroscience 19 13 5435 48 doi 10 1523 JNEUROSCI 19 13 05435 1999 PMC 6782339 PMID 10377353 a b Regan D 1973 Rapid objective refraction using evoked brain potentials Investigative Ophthalmology 12 9 669 79 PMID 4742063 a b c Norcia A M Tyler C W 1985 Infant VEP acuity measurements Analysis of individual differences and measurement error Electroencephalography and Clinical Neurophysiology 61 5 359 369 doi 10 1016 0013 4694 85 91026 0 PMID 2412787 Strasburger H Rentschler I 1986 A digital fast sweep technique for studying steady state visual evoked potentials PDF Journal of Electrophysiological Techniques 13 5 265 278 a b c d Regan D 1975 Colour coding of pattern responses in man investigated by evoked potential feedback and direct plot techniques Vision Research 15 2 175 183 doi 10 1016 0042 6989 75 90205 9 PMID 1129975 S2CID 42218073 Nelson J I Seiple W H Kupersmith M J Carr R E 1984 A rapid evoked potential index of cortical adaptation Investigative Ophthalmology amp Visual Science 59 6 454 464 doi 10 1016 0168 5597 84 90004 2 PMID 6209112 a b Norcia A M Tyler C W 1985 Spatial frequency sweep VEP Visual acuity during the first year of life Vision Research 25 10 1399 1408 doi 10 1016 0042 6989 85 90217 2 PMID 4090273 S2CID 23557430 a b Norcia A M Tyler C W Allen D 1986 Electrophysiological assessment of contrast sensitivity in human infants American Journal of Optometry and Physiological Optics 63 1 12 15 doi 10 1097 00006324 198601000 00003 PMID 3942183 S2CID 19809242 O Shea R P Roeber U amp Bach M 2010 Evoked potentials Vision In E B Goldstein Ed Encyclopedia of Perception Vol 1 pp 399 400 xli Los Angeles Sage ISBN 978 1 4129 4081 8 Long KJ Allen N 1984 Abnormal Brainstem Auditory Evoked Potentials Following Ondine s Curse Arch Neurol 41 10 1109 1110 doi 10 1001 archneur 1984 04050210111028 PMID 6477223 O Toole Marie T ed 2013 visual evoked potential VEP p 1880 ISBN 978 0 323 08541 0 a href Template Cite book html title Template Cite book cite book a work ignored help a b c Hammond Flora Grafton Lori 2011 Kreutzer Jeffrey S DeLuca John Caplan Bruce eds Visual Evoked Potentials p 2628 doi 10 1007 978 0 387 79948 3 ISBN 978 0 387 79947 6 a href Template Cite book html title Template Cite book cite book a work ignored help Goldstein E Bruce 2013 Chapter 2 The Beginning of Perceptions Sensation and Perception 9th ed WADSWORTH CENGAGE Learning Method Peferential looking p 46 ISBN 978 1 133 95849 9 Hammond amp Grafton 2011 cited Huszar L 2006 Clinical utility of evoked potentials eMedicine Retrieved 2007 07 09 Aminoff Michael J 2001 Braunwald Eugene Fauci Anthony S Kasper Dennis L Hauser Stephen L Longo Dan L Jameson J Larry eds 357 ELECTROPHYSIOLOGIC STUDIES OF THE CENTRAL AND PERIPHERAL NERVOUS SYSTEMS EVOKED POTENTIALS ISBN 0 07 007272 8 a href Template Cite book html title Template Cite book cite book a work ignored help Strain George M Jackson Rose M Tedford Bruce L 1990 07 01 Visual Evoked Potentials in the Clinically Normal Dog Journal of Veterinary Internal Medicine 4 4 222 225 doi 10 1111 j 1939 1676 1990 tb00901 x ISSN 1939 1676 PMID 2401969 Musiek FE amp Baran JA 2007 The Auditory system Boston MA Pearson Education Inc Sanju Himanshu Kumar Kumar Prawin 2016 Enhanced auditory evoked potentials in musicians A review of recent findings Journal of Otology 11 2 63 72 doi 10 1016 j joto 2016 04 002 ISSN 1672 2930 PMC 6002589 PMID 29937812 Frizzo Ana C F 10 June 2015 Auditory evoked potential a proposal for further evaluation in children with learning disabilities Frontiers in Psychology 6 788 doi 10 3389 fpsyg 2015 00788 PMC 4461809 PMID 26113833 a b c McElligott Jacinta 2011 Kreutzer Jeffrey S DeLuca John Caplan Bruce eds Somatosensory Evoked Potentials pp 2319 2320 doi 10 1007 978 0 387 79948 3 ISBN 978 0 387 79947 6 a href Template Cite book html title Template Cite book cite book a work ignored help McElligott 2011 cited Lew HL Lee EH Pan SS L Chiang JYP 2007 Zasler ND Katz DL Zafonte RD eds Electrophysiological assessment techniques Evoked potentials and electroencephalography a href Template Cite book html title Template Cite book cite book a work ignored help McElligott 2011 cited Lew HL Dikman S Slimp J Temkin N Lee EH Newell D et al 2003 Use of somatosensory evoked potentials and cognitive event related potentials in predicting outcome in patients with severe traumatic brain injury American Journal of Physical Medicine amp Rehabilitation 82 1 53 61 doi 10 1097 00002060 200301000 00009 PMID 12510186 S2CID 45096294 McElligott 2011 xangxing Robinson L R 2004 Kraft GL Lew HL eds Somatosensory evoked potentials in coma prognosis pp 43 61 doi 10 1016 s1047 9651 03 00102 5 PMID 15029898 a href Template Cite book html title Template Cite book cite book a work ignored help Treede RD Lorenz J Baumgartner U December 2003 Clinical usefulness of laser evoked potentials Neurophysiol Clin 33 6 303 14 doi 10 1016 j neucli 2003 10 009 PMID 14678844 S2CID 18486576 Catmur C Walsh V Heyes C 2007 Sensorimotor learning configures the human mirror system Curr Biol 17 17 1527 1531 doi 10 1016 j cub 2007 08 006 PMID 17716898 External links Edit Evoked Potentials at the U S National Library of Medicine Medical Subject Headings MeSH Retrieved from https en wikipedia org w index php title Evoked potential amp oldid 1169991531, wikipedia, wiki, book, books, library,

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