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At least 19 recordsLinked to original sources
PubMed1987

Brainstem auditory evoked potentials evoked by clicks of different polarity in multiple sclerosis patients.

Brainstem auditory evoked potentials (BAEP) evoked by condensation, rarefaction clicks and clicks of alternating polarity were examined in 52 controls and in 95 patients with a certain or presumed diagnosis of multiple sclerosis. It was shown that the type of stimulation could influence the shape of the BAEP considerably. In multiple sclerosis patients pathological results were found in 67 ears from 44 patients. Rarefaction as well as condensation clicks independently could elicit BAEPs with increased latencies of one or more peaks, while clicks of alternating polarity failed to detect abnormalities in a great number of cases. These findings make the application of the latter type of stimulation doubtful.

Adolescent↗
PubMedDate not supplied

[Cortical and spinal evoked potentials in parkinsonism. Part I. Visual potentials evoked with a checkerboard pattern].

In 21 patients with parkinsonism and 20 healthy controls visual potentials evoked with checker pattern used as an alternating stimulus were studied. The left and right eye were examined separately recording visual cortical responses in the central occipital area. The analysed elements included the latency of the first highest positive wave P100 and the amplitude of the P100/N120 complex. Prolongation of the mean latency of P100 was found in patients with parkinsonism, but it was not significant statistically. No differences were found of the P100/N120 amplitude in the group with parkinsonism in relation to healthy controls. In the patients with parkinsonian syndrome (mainly of atherosclerotic origin) the mean latency of the visual potentials was longer and the amplitude was lower than in cases of Parkinson's disease. Attention is called to the high variability of the visual evoked potentials related to the clinical state and origin of the disease (parkinsonian syndrome and Parkinson's disease).

Aged↗
PubMedDate not supplied

[Cortical and spinal evoked potentials in parkinsonism. Part II. Somatosensory potentials evoked form the posterior tibial nerve].

In 20 patients with parkinsonism somatosensory evoked potentials were studied. The posterior tibial nerves were stimulated successively at the medial ankle. The averaged responses were recorded at the level of the L2 vertebra, C2 vertebra and in the central parietal area (Cz/Pz). The obtained data were compared with similar values in a control group. The conduction velocity in the sensory fibres of the tibial nerves was normal in both groups. No significant differences were found also between the patients and the controls in the latency of the spinal lumbar and cervical potentials, and the spinal conduction time (L2-C2) was normal. In the patients with parkinsonism the cortical evoked response N35 was significantly prolonged. Differences were noted also in the time of central conduction (C2-cortex) between the patients and the controls, but they were not significant statistically. The effects of disturbed dopamine metabolism on the electro-physiological processes in the peripheral and the central nervous system are discussed.

Aged↗
PubMed1989

Differential influence of posture and intentional movement on human somatosensory evoked potentials evoked by different stimuli.

Somatosensory evoked potentials (SEP) recorded from humans were elicited by a cutaneous shock to the index finger or with a ramp displacement of the finger that stretched the first dorsal interosseous muscle. A somatosensory stimulus was presented while a subject maintained a steady posture of the metacarpophalangeal joint or during a rapid voluntary abduction of the index finger. Both activities were performed against a constant opposing load of 0.15 Nm or without a load. SEPs were recorded over the postcentral arm area, together with the electromyogram of the first dorsal interosseous muscle. The major components of the SEPs were P56, N130, P174, N232 and P294. The amplitudes of all components were diminished substantially during active movement. A constant load opposing postural fixation or active movement did not influence the SEP amplitude. The amplitude of the P56 component was differentially affected by the shock or ramp stimuli. The findings demonstrate that active movement gates sensory input, while sustained tonic muscular activity with an opposing constant load does not, and that different somesthetic inputs may be processed differently during movement.

Adult↗
PubMedDate not supplied

Visually evoked potentials evoked by moving unidimensional noise stimuli: effects of contrast, spatial frequency, active electrode location, reference electrode location, and stimulus type.

We determined the relative importance of electrode derivation, stimulus type, spatial frequency and contrast in determining the relative size of the late negative and early positive responses of motion elicited VEPs. Seven subjects aged 22-48 years with normal vision were tested binocularly. Motion onset and motion reversal were employed as modes of stimulus presentation. For both, pseudo-random one-dimensional noise patterns whose peak power was at 5.2, 2.6, 1.3, 0.325 and 0.1625 cycles per degree (cpd) were stimuli. Contrasts were 70% and 5%. Active electrodes were placed at Oz, 5 cm to the left of Oz, 5 cm to the right of Oz and a frontal midline position (Fpz) and referenced to linked mastoids. Transient motion reversal elicited a prominent positive response present in all subjects and at low contrasts. Motion onset VEPs have a complex waveform which may be either predominantly positive or negative. The most important variables in determining whether a prominent positivity or negativity is present in the motion onset VEP are the contrast and the spatial frequencies. Data such as these are first efforts in developing recommendations for the motion VEP.

Acoustic Stimulation↗
PubMedDate not supplied

Central administration of cholecystokinin potentiates evoked potential amplitude in the hippocampal dentate gyrus.

Cholecystokinin and related ligands were injected into a lateral ventricle and recordings made of the field potential in the hippocampal dentate gyrus evoked by stimulation of the medial entorhinal cortex. With the exception of the unsulfated octapeptide, these compounds induced an increase in population action potential amplitude. The unsulfated octapeptide was found to inhibit the action of its sulfated congener, and alone induced a decrease in response amplitude. These results suggest a modulation of intracortical activation of the dentate gyrus by cholecystokinin, and that this action is probably mediated by a central-type receptor.

Animals↗
PubMed1981

Visual evoked potentials, auditory evoked potentials and EEG in shunted hydrocephalic children.

Visual evoked potentials (VEP) and auditory evoked potentials (AEP) were studied together with the EEG, in 15 hydrocephalic children who had been shunted previously, and in a control group of 10 normal children. From the control group normal VEP's, AEP's and EEG's were obtained. In all 15 hydrocephalic children the EEG was abnormal. AEP's were normal in 9 and abnormal in 6 cases. VEP's were normal in 7 and abnormal in 8 cases. Only 4 patients showed both abnormal VEP's and AEP's. No relation could be demonstrated between the severity of EEG disturbances and evoked response abnormalities.

Auditory Pathways↗
PubMedDate not supplied

Brainstem auditory evoked potential, visual evoked potential and nerve conduction velocity and their relation with HbA1c and beta 2 microglobulin in children with insulin dependent diabetes mellitus.

Brain stem auditory evoked response (BAER), visual evoked response (VER) and nerve conduction velocities (NCV) were studied in 18 insulin-dependent diabetic children between the ages of 3.5 and 16 years (mean 9.0 +/- 3.2 years). The results were compared with those of age-matched controls. The VER latencies of the diabetic children in the right eye and left eye were significantly prolonged when compared with the control group. NCV of n. peroneus and the latency of sensorial n. medianus were significantly impaired when compared with the control group. Although the latencies of waves III, IV and V of the right ear and the interpeak latencies of I-III, I-V, III-V of both ears were prolonged, the comparison with the control group was not significant. The beta 2 microglobulin levels of the diabetic patients were significantly higher than those of the control group. There was a positive correlation between the beta 2 microglobulin and the BAER interpeak latencies of wave III-V in both ears (r: 0.51 p < 0.01). There was also a positive correlation between NCVs of n. peroneus and n. medianus (motor and sensorial) with beta 2 microglobulin (r: 0.52 p < 0.01) and between VER latencies (r: 0.52 p < 0.01) of both eyes separately. In our study the prolonged latencies of VER and BAER were detected in the absence of clinical abnormalities in visual and hearing systems.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed2000

Different generators in human temporal-parasylvian cortex account for subdural laser-evoked potentials, auditory-evoked potentials, and event-related potentials.

In order to localize cortical areas mediating pain we now report subdural cortical potentials evoked by auditory stimulation (auditory-evoked potentials - AEPs) and by cutaneous stimulation with a laser (laser-evoked potentials - LEPs). Stimulation with the laser evokes a pure pain sensation by selective activation of nociceptors. LEPs were maximal over the inferior aspect of the central sulcus and had the same polarity on either side of the sylvian fissure. AEPs were maximal posterior to the LEP maximum and had opposite polarity on opposite sides of the sylvian fissure, consistent with the location of a known generator in the temporal operculum. Auditory P3 (event-related) potentials were maximal over the temporal base. These findings demonstrate that the LEP generator is not in secondary somatosensory cortex on the parietal operculum and is different from the P3 generator.

Adult↗
PubMed2002

Unified neurophysical model of EEG spectra and evoked potentials.

Evoked potentials -- the brain's transient electrical responses to discrete stimuli -- are modeled as impulse responses using a continuum model of brain electrical activity. Previous models of ongoing brain activity are refined by adding an improved model of thalamic connectivity and modulation, and by allowing for two populations of excitatory cortical neurons distinguished by their axonal ranges. Evoked potentials are shown to be modelable as an impulse response that is a sum of component responses. The component occurring about 100 ms poststimulus is attributed to sensory activation, and this, together with positive and negative feedback pathways between the cortex and thalamus, results in subsequent peaks and troughs that semiquantitatively reproduce those of observed evoked potentials. Modulation of the strengths of positive and negative feedback, in ways consistent with psychological theories of attentional focus, results in distinct responses resembling those seen in experiments involving attentional changes. The modeled impulse responses reproduce key features of typical experimental evoked response potentials: timing, relative amplitude, and number of peaks. The same model, with further modulation of feedback, also reproduces experimental spectra. Together, these results mean that a broad range of ongoing and transient electrocortical activity can be understood within a common framework, which is parameterized by values that are directly related to physiological and anatomical quantities.

Cerebral Cortex↗
PubMed1985

Facial nerve evoked potentials.

Evoked potentials representing both intracranial and extracranial activity have been recorded from the canine scalp after retrograde stimulation of peripheral facial nerve branches. A negative electrode at the vertex and a positive electrode at the ipsilateral mastoid (grounded at the contralateral mastoid) show a monophasic negative stylomastoid evoked potential that appears to be generated from the facial nerve trunk at the stylomastoid foramen. When the positive electrode is moved from the mastoid to the posterior scalp (overlying the foramen magnum), a similar potential with a latency 1.5 msec greater is obtained. This brain stem evoked potential is generated from fibers in the vicinity of the root entry zone and the initial trajectory into the brain stem. A potential of similar latency but greater magnitude is recorded with the positive electrode in the cerebrospinal fluid of the posterior fossa.

Animals↗
PubMed1991

Method for predicting an EEG waveform as an aid to the accurate recording of evoked potentials.

Evoked potentials are the brain's responses to incoming stimuli and are usually recorded under noisy circumstances. To improve the signal-to-noise ratio, signal averaging has been widely applied to the recorded data, but an improved method is required. A method of EEG waveform prediction for the accurate recording of evoked potentials is proposed, and an electroencephalographic waveform predicted by using an EEG model and a nonlinear exponentially weighted least squares method, subtracting the predicted EEG waveform from the raw data and extracting the evoked waveform. By the use of this method, we have successfully predicted the EEG waveform and detected the evoked potential with only a small number of averages.

Adult↗
PubMedDate not supplied

Intracerebral sources of human auditory-evoked potentials.

Evoked potentials to brief 1,000-Hz tones presented to either the left or the right ear were recorded from 30 electrodes arrayed over the head. These recordings were submitted to two different forms of source analysis: brain electric source analysis (BESA) and variable-resolution electromagnetic tomography (VARETA). Both analyses showed that the dominant intracerebral sources for the late auditory-evoked potentials (50-300 ms) were in the supratemporal plane and lateral temporal lobe contralateral to the ear of stimulation. The analyses also suggested the possibility of additional sources in the frontal lobes.

Auditory Cortex↗
PubMed2002

[Temporal-spatial analysis of evoked potentials].

Evoked potentials are widely used in clinical neurophysiology. The conventional analysis methods of evoked potentials are based on the waves in time domain. Analysis based on time-spatial domain will provide more information than simple time domain analysis. The existing temporal-spatial analysis methods, such as microstate, frequency domain analysis and event-related coherence, are introduced in this paper.

Evoked Potentials↗
PubMed1997

[Monitoring for spinal cord ischemia by the use of the motor evoked potentials, the evoked spinal cord potential and the segmental evoked spinal cord potential during thoracoabdominal aortic surgery--a case report].

A 55-year-old woman, who was detected an enlargement of the aorta with body CT, was admitted to our hospital. Preoperative examination revealed that the aneurysm was expanded from ascending aorta to the abdominal aorta above the celiac artery. She underwent total arch replacement using elephant trunk technique. Forty-four days after operation, she underwent thoracoabdominal aortic replacement with monitoring for spinal cord ischemia by the use of the motor evoked potentials (MEP), the evoked spinal cord potential (ESCP) and the segmental evoked spinal cord potential (S-ESCP). Under the partial cardiopulmonary bypass with femoral venous drainage and femoral arterial cannulation on normothermia, the aneurysmal part of the aorta was segmentally cross-clamped and the three lumbar arteries and the celiac artery were reconstructed one by one. During the operation, the monitor showed no remarkable change, even while the aorta was cross clamped. Her postoperative course was uneventful without any spinal cord damage. Combined use of MEP, ESCP, and S-ESCP was useful for monitoring spinal cord injury during thoracoabdominal aneurysmal repair.

Aorta, Thoracic↗
PubMed1996

Source modeling of esophageal evoked potentials.

Evoked potentials can be recorded from the scalp after stimulation of the esophagus by balloon distension. The purpose of this study was to estimate the number and localization of sources contributing to the esophageal evoked potential (EEP). The EEP was recorded from 32 scalp electrodes in 5 healthy subjects. Spatio-temporal dipole modeling was performed in the time interval from 185 msec to 525 msec after stimulation (mean values). The EEP was best explained by the combined activity of 1 dipole located relatively high in the midline and 2 lateral dipoles. Given the anatomical projection of esophageal sensory fibers and the location of these dipoles the sources were probably located in the cingulate gyri and insular cortex. There was no evidence that sources in the lower brain-stem contributed to the scalp recorded EEP.

Adult↗
PubMed1993

Method for single-trial recording of somatosensory evoked potentials.

Evoked potentials (EPs) in response to stimuli are recorded from a human scalp contaminated with noise. To improve the signal-to-noise ratio, averaging methods have been widely used for the recorded data. However, when the waveforms of EP for each stimulus are not identical, the average waveform of the EP deteriorates. Variation of the EP waveform to each stimulus itself is important information for the EP. In this paper, a recording method for single somatosensory evoked potential (SEP) waveform is proposed, in which three kinds of band-pass filters were selectively used during three specific time sectors for each interstimulus interval. For the late section of the interval, an EEG waveform prediction method was applied to eliminate contaminated alpha rhythm components. By using the proposed method, we were successful in detecting the single SEP waveform.

Adult↗