Ultra-conformal skin electrodes with synergistically enhanced conductivity for long-time and low-motion artifact epidermal electrophysiology.

Accurate and imperceptible monitoring of electrophysiological signals is of primary importance for wearable healthcare. Stiff and bulky pregelled electrodes are now commonly used in clinical diagnosis, causing severe discomfort to users for long-time using as well as artifact signals in motion. Here, we report a ~100 nm ultra-thin dry epidermal electrode that is able to conformably adhere to skin and accurately measure electrophysiological signals. It showed low sheet resistance (~24 Ω/sq, 4142 S/cm), high transparency, and mechano-electrical stability. The enhanced optoelectronic performance was due to the synergistic effect between graphene and poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), which induced a high degree of molecular ordering on PEDOT and charge transfer on graphene by strong π-π interaction. Together with ultra-thin nature, this dry epidermal electrode is able to accurately monitor electrophysiological signals such as facial skin and brain activity with low-motion artifact, enabling human-machine interfacing and long-time mental/physical health monitoring.

Nerve conductions studies in experimental models of autoimmune neuritis: A meta-analysis and guideline.

Nerve conduction studies (NCS) are essential to assess peripheral nerve fiber function in research models of immune-mediated neuritis. However, the current lack of standard protocols and reference values impedes data comparability across models and studies. We performed a systematic review and subsequent meta-analysis of the last 30 years of NCS of immune-mediated neuritis in Lewis-rats. Twenty-six papers met the inclusion criteria for meta-analysis. Extracted data showed considerable heterogeneity of recorded nerve conduction velocity (NCV) and compound muscle action potential (CMAP). Studies also significantly differed in terms of technical, methodical, and data reporting issues. The heterogeneity of the underlying studies emphasizes the need for standardization when conducting and reporting NCS in rats. We provide normative values for NCS of the sciatic nerve of Lewis rats and propose seven items that should be addressed when NCS are performed when studying immune paradigms in Lewis rats.

Recomendaciones sobre estudios neurofisiológicos en tiempos de pandemia de COVID-19 / Recommendations on neurophysiological studies during the COVID-19 pandemic

A finales de enero, la Organización Mundial de la Salud declaró el brote actual de la enfermedad por coronavirus COVID-19 como emergencia de salud pública de importancia internacional. En España, desde que el 14 de marzo de 2020 el Gobierno decretase el estado de alarma, los médicos encargados de las pruebas neurofisiológicas las hemos estado realizando sin tener un criterio consensuado ni unas pautas adecuadas de seguridad claras para los facultativos, los técnicos ni los pacientes. Las siguientes recomendaciones, basadas en el actual conocimiento de la enfermedad y, por tanto, susceptibles de variaciones en el futuro, se proponen cuando la pandemia parece que ha entrado en un proceso de disminución de la virulencia y, con ello, las medidas estrictas de confinamiento hasta ahora mantenidas; sin embargo, ante la posibilidad de una segunda oleada de rebrotes de la pandemia, parece necesario establecer unas recomendaciones básicas y de mínimos para respetar el derecho del paciente a una atención adecuada, similar a la previa a la pandemia, y mantener unos mínimos de seguridad para los propios pacientes y los médicos, técnicos y personal sanitario que realizan estas pruebas. Se trata de recomendaciones sobre el establecimiento de una prioridad basándose en el motivo de consulta, el establecimiento de llamadas de comprobación de la situación clínica del paciente antes de acudir a la consulta externa y las normas de ejecución de las pruebas neurofisiológicas, que se basan, en general, en la preservación de circuitos hospitalarios, el respeto y el cuidado de las barreras de contagio conocidas de esta enfermedad, y la utilización de material desechable. Estas recomendaciones son de especial interés, sobre todo por la incertidumbre de no saber la evolución de la infección por el SARS-CoV-2 en las próximas semanas o meses

At the end of January, the current outbreak of COVID-19 coronavirus disease was declared an important international public health emergency. In Spain, since the government declared the state of alarm on 14 March 2020, doctors responsible for carrying out neurophysiological tests have been performing them without any consensus criterion or clear safety guidelines for doctors, technicians or patients. The following recommendations, based on current knowledge of the disease and therefore liable to change in the future, are proposed when the pandemic appears to have entered a process of decreasing virulence and, with it, the strict containment measures established to date. However, in view of the possibility of a second wave of the pandemic, it seems necessary to establish basic and minimum recommendations to respect the patient's right to appropriate care, similar to that provided prior to the pandemic, and to maintain minimum safety standards for the patients themselves and for the doctors, technicians and health personnel carrying out these tests. These recommendations concern the constitution of a priority based on the reason for consultation, the establishment of calls to check the patient's clinical situation before going to the outpatient department and the rules for carrying out neurophysiological tests, which are generally based on the preservation of hospital circuits, respect for and observation of the known barriers to contagion of this disease, and the use of disposable material. These recommendations are of particular interest, especially given the uncertainty of not knowing the evolution of the SARS-CoV-2 infection in the coming weeks or months

[Recommendations on neurophysiological studies during the COVID-19 pandemic]. / Recomendaciones sobre estudios neurofisiológicos en tiempos de pandemia de COVID-19.

At the end of January, the current outbreak of COVID-19 coronavirus disease was declared an important international public health emergency. In Spain, since the government declared the state of alarm on 14 March 2020, doctors responsible for carrying out neurophysiological tests have been performing them without any consensus criterion or clear safety guidelines for doctors, technicians or patients. The following recommendations, based on current knowledge of the disease and therefore liable to change in the future, are proposed when the pandemic appears to have entered a process of decreasing virulence and, with it, the strict containment measures established to date. However, in view of the possibility of a second wave of the pandemic, it seems necessary to establish basic and minimum recommendations to respect the patient's right to appropriate care, similar to that provided prior to the pandemic, and to maintain minimum safety standards for the patients themselves and for the doctors, technicians and health personnel carrying out these tests. These recommendations concern the constitution of a priority based on the reason for consultation, the establishment of calls to check the patient's clinical situation before going to the outpatient department and the rules for carrying out neurophysiological tests, which are generally based on the preservation of hospital circuits, respect for and observation of the known barriers to contagion of this disease, and the use of disposable material. These recommendations are of particular interest, especially given the uncertainty of not knowing the evolution of the SARS-CoV-2 infection in the coming weeks or months.

TITLE: Recomendaciones sobre estudios neurofisiológicos en tiempos de pandemia de COVID-19.A finales de enero, la Organización Mundial de la Salud declaró el brote actual de la enfermedad por coronavirus COVID-19 como emergencia de salud pública de importancia internacional. En España, desde que el 14 de marzo de 2020 el Gobierno decretase el estado de alarma, los médicos encargados de las pruebas neurofisiológicas las hemos estado realizando sin tener un criterio consensuado ni unas pautas adecuadas de seguridad claras para los facultativos, los técnicos ni los pacientes. Las siguientes recomendaciones, basadas en el actual conocimiento de la enfermedad y, por tanto, susceptibles de variaciones en el futuro, se proponen cuando la pandemia parece que ha entrado en un proceso de disminución de la virulencia y, con ello, las medidas estrictas de confinamiento hasta ahora mantenidas; sin embargo, ante la posibilidad de una segunda oleada de rebrotes de la pandemia, parece necesario establecer unas recomendaciones básicas y de mínimos para respetar el derecho del paciente a una atención adecuada, similar a la previa a la pandemia, y mantener unos mínimos de seguridad para los propios pacientes y los médicos, técnicos y personal sanitario que realizan estas pruebas. Se trata de recomendaciones sobre el establecimiento de una prioridad basándose en el motivo de consulta, el establecimiento de llamadas de comprobación de la situación clínica del paciente antes de acudir a la consulta externa y las normas de ejecución de las pruebas neurofisiológicas, que se basan, en general, en la preservación de circuitos hospitalarios, el respeto y el cuidado de las barreras de contagio conocidas de esta enfermedad, y la utilización de material desechable. Estas recomendaciones son de especial interés, sobre todo por la incertidumbre de no saber la evolución de la infección por el SARS-CoV-2 en las próximas semanas o meses.

The effects of anthropometric and demographic factors on conduction parameters of the ulnar nerve: Multivariate analysis.

The objective of the study is to investigate the effects of age, height, gender, body mass index (BMI), waist-to-hip ratio (WHR), arm and elbow measures on ulnar nerve conduction. We enrolled 261 "disease-free" subjects. We analyzed motor conduction velocity (MCV) in across elbow (AE) and forearm tracts, and sensory conduction velocity in 4th, 5th digit-wrist tracts (U4, U5) and in dorsal ulnar cutaneous nerve (DUC). We calculated the amplitudes of sensory and motor potentials (CMAPa and SNAPa), % of CMAPa drop AE, MCV drop and distal motor latency (DML). Univariate and multivariate analyses were performed. We estimated the predictive equations. The median nerve was examined for comparison. Age was negatively correlated with all conduction parameters. Forearm and AE MCV, % of CMAPa drop, DML, U4 and U5 SCV also depended upon height. Females had higher U4 and U5 SNAPa than males. BMI showed inverse relationship with U4 and U5 SNAPa. DUC parameters depended upon BMI and arm length. Similar trends were observed for the median nerve. "Normative" ulnar conduction parameters should be adjusted for demographic and anthropometric measures to improve diagnostic sensitivity.

[Quality and performance in cardiac pacing and electrophysiology. An update to the 2010 Italian Association of Arrhythmology and Cardiac Pacing (AIAC) - Italian Federation of Cardiology (IFC) Document 'Structure and functional organization of Arrhythmology']. / Qualità e performance in Elettrostimolazione ed Elettrofisiologia. Aggiornamento al documento dell'Associazione Italiana di Aritmologia e Cardiostimolazione (AIAC) ­ Federazione Italiana di Cardiologia (FIC) 2010 "Struttura e organizzazione funzionale dell'Aritmologia".

In the last decade the field of cardiac pacing and electrophysiology underwent major advancements thanks to both new ways of arrhythmia management and technological innovations. At the same time, the clinical competence and the procedural qualitative level of Cardiac Rhythm Centers have increased significantly. In 2010 an ad hoc Committee of the Italian Association of Arrhythmology and Cardiac Pacing (AIAC) and the Italian Federation of Cardiology (FIC) published a consensus document on the organization of Cardiac Rhythm Centers and on the standards of professional practice in pacing and electrophysiology in Italy. In particular, this document focused on the minimal requirements of a Center to be qualified as suitable to perform first, second and third-level cardiac pacing and electrophysiology activities. However, most of these indicators have been overcome over time. Thus, an update of the previously published organizational model appeared necessary. In this document several new requirements and indicators about the organization and performance of both operators and Cardiac Arrhythmia Centers have been introduced. These include: (i) "structural and procedural requirements" (types of diagnostic and therapeutic procedures performed, logistic structures, healthcare staff and technologies), (ii) "activity indicators" (number of procedures performed); (iii) "appropriateness indicators" (adherence to guideline recommendations); (iv) "outcome indicators" (procedural success and complications); and (v) "quality of care indicators" (management and continuity of care levels). By applying these requirements and indicators, each center can optimize its procedures, increasing its performance and effectiveness. Finally, a new model for the organization of the Italian network of Cardiac Arrhythmia Centers is also suggested.

Meta-analysis of biological variables' impact on spinal motoneuron electrophysiology data.

Experimental, methodological, and biological variables must be accounted for statistically to maximize accuracy and comparability of published neuroscience data. However, accounting for all variables is nigh impossible. Thus we aimed to identify particularly influential variables within published neurological data, from cat, rat, and mouse studies, via a robust statistical process. Our goal was to develop tools to improve rigor in the collection and analysis of data. We strictly constrained experimental and methodological variables and then assessed four key biological variables within motoneuron research: species, age, sex, and cell type. We quantified intraexperimental and interexperimental variances in 11 commonly reported electrophysiological properties of spinal motoneurons. We first assessed variances without accounting for biological variables and then reassessed them while accounting for all four variables. We next assessed variances with all possible combinations of these four variables. We concluded that some motoneuron properties have low intraexperimental, but high interexperimental, variance; that individual motoneuron properties are impacted differently by biological variables; and that some unexplained variances still remain. We report here the optimal combinations of biological variables to reduce interexperimental variance for all 11 parameters. We also rank each parameter by intra- and interexperimental consistency. We expect these results to assist with design of experimental and analytical methods, and to support accuracy in simulations. Furthermore, although demonstrated on spinal motoneuron electrophysiology literature, our approach is applicable to biological data from all fields of neuroscience. This approach represents an important aid to experimental design, comparison of reported data, and reduction of unexplained variance in neuroscience data.NEW & NOTEWORTHY Our meta-analysis shows the impact of species, age, sex, and cell type on lumbosacral motoneuron electrophysiological properties by thoroughly quantifying variances across literature for the first time. We quantify the variances of 11 motoneuron properties with consideration of biological variables, thus providing specific insights for motoneuron modelers and experimenters, and providing a general methodological template for the quantification of variance in neurological data with the consideration of any experimental, methodological, or biological variables of interest.

ISCEV extended protocol for derivation and analysis of the strong flash rod-isolated ERG a-wave.

The International Society for the Clinical Electrophysiology of Vision (ISCEV) standard for full-field electroretinography (ERG) describes a minimum set of tests, but encourages the use of additional protocols for clinical ERG testing. This extended protocol describes recording methods and derivations that will allow analysis of rod-driven components of the dark-adapted (DA) strong flash ERG a-wave, more closely related to rod phototransduction than ISCEV standard DA ERGs. The method involves recording ERGs to a flash strength equivalent to 30 cd s m2 under conditions of dark adaptation and additionally to the same stimulus following light adaptation (LA) and in the presence of a standard photopic background luminance of 30 cd m-2. The isolated rod-driven ERG a-wave is derived by subtracting the LA response from the DA ERG. The method is likely to be of value in the characterization of retinal disorders which affect rod quantal catch, diseases that affect the dynamics of any component of the activation phase of rod phototransduction, or those affecting total numbers of rod photoreceptors.

ISCEV extended protocol for the S-cone ERG.

The International Society for Clinical Electrophysiology of Vision (ISCEV) standard for full-field electroretinography (ERG) describes a minimum procedure for testing generalized retinal function but encourages more extensive testing. This extended protocol describes a method of assessing the function of the short-wavelength-sensitive cone (S-cone) retinal pathway, using a short-wavelength flash superimposed on a background that saturates the rods and adapts the L/M-cones to elicit a response, known as the S-cone ERG. Stimulus parameters such as the strength and luminance of the flash and background, respectively, and their spectral and temporal characteristics are specified. As a complement to the ISCEV standard, testing the S-cone ERG enables further characterization of light-adapted retinal function and may refine diagnosis of some retinal disorders. Typical applications are described including use in the diagnosis of rod monochromacy and S-cone monochromacy, identification and investigation of cone On-bipolar cell dysfunction and use of the technique to confirm the diagnosis of enhanced S-cone syndrome.

From MEAs to MOAs: The Next Generation of Bioelectronic Interfaces for Neuronal Cultures.

Since their introduction in the early 1970s, microelectrode arrays (MEAs) have been dominating the electrophysiology market thanks to their reliability, extreme robustness, and usability. Over the past 40 years, silicon technology has also played a role in the advancement of the field, and CMOS-based in vitro and in vivo systems are now able to achieve unprecedented spatial resolutions, giving the possibility to unveil hidden behavior of cellular aggregates down to the subcellular level. However, both the MEAs and silicon-based electronic devices present unavoidable problems such as their expensiveness, the usual rigidity of the employed materials, and the need of an (usually bulky) external reference electrode. Possible interesting alternatives to these incredibly useful devices unexpectedly lie in the field of organic electronics, thanks to the fast-growing pace of improvement that this discipline has undergone in the last 10-15 years. In this chapter, a particular organic transistor called organic charge-modulated field-effect transistor (OCMFET) will be presented as a promising bio-electronic interface, and a complete description of its employment as a detector of cellular electrical activity and as an ultrasensitive pH sensor will be provided, together with the discussion about the possibility of using such a device as an innovative multisensing tool for both electrophysiology and (neuro)pharmacology.

International Multisite Study of Human-Induced Pluripotent Stem Cell-Derived Cardiomyocytes for Drug Proarrhythmic Potential Assessment.

To assess the utility of human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) as an in vitro proarrhythmia model, we evaluated the concentration dependence and sources of variability of electrophysiologic responses to 28 drugs linked to low, intermediate, and high torsades de pointes (TdP) risk categories using two commercial cell lines and standardized protocols in a blinded multisite study using multielectrode array or voltage-sensing optical approaches. Logistical and ordinal linear regression models were constructed using drug responses as predictors and TdP risk categories as outcomes. Three of seven predictors (drug-induced arrhythmia-like events and prolongation of repolarization at either maximum tested or maximal clinical exposures) categorized drugs with reasonable accuracy (area under the curve values of receiver operator curves ∼0.8). hiPSC-CM line, test site, and platform had minimal influence on drug categorization. These results demonstrate the utility of hiPSC-CMs to detect drug-induced proarrhythmic effects as part of the evolving Comprehensive In Vitro Proarrhythmia Assay paradigm.

Ultrasound-guided, open-source microneurography: Approaches to improve recordings from peripheral nerves in man.

OBJECTIVE: Microneurography is the only method for recording from single neurons in intact human nerves. It is challenging - requiring technical expertise, investment in specialised equipment and has sparse data yields. METHODS: We assessed whether ultrasound guidance in combination with an 'open access' amplifier and data capture system (Open-Ephys) would simplify and expand the scope of microneurographic recordings in humans. RESULTS: In 32 healthy consenting volunteers, ultrasound-guidance improved success rates for obtaining cutaneous C-fibres and reduced "Skin to Nerve" times from 28.5 min to 4.5 min for recordings of the peroneal nerve (P < 0.0001). We illustrate the potential utility of ultrasound-guided microneurography for difficult to access nerves with phrenic nerve recording during a Valsalva manoeuvre. We show that Open Ephys is a viable alternative to commercially available recording systems and offers advantages in terms of cost and software customisability. CONCLUSIONS: Ultrasound guidance for microneurography with Open Ephys facilitates cutaneous C nociceptor recordings and allows recordings to be made from nerves previously considered inaccessible. SIGNIFICANCE: We anticipate that the adoption of these techniques will improve microneurography experimental efficiency, adds an important visual learning aid and increases the generalisability of the approach.

ISCEV extended protocol for the dark-adapted red flash ERG.

The International Society for Clinical Electrophysiology of Vision (ISCEV) standard for full-field electroretinography (ERG) describes a minimum procedure, but encourages more extensive testing. This ISCEV extended protocol describes an extension to the ERG standard, namely the dark-adapted (DA) red flash ERG. The DA red flash ERG can be incorporated conveniently within the ISCEV standard ERG protocol after a minimum of 20-min DA and recorded after the DA 0.01 ERG to a flash strength of 0.3 phot cd s m-2, eliciting a waveform with two positive peaks in healthy individuals. The first positive component is the cone-mediated x-wave with a peak at 30-50 ms; the second is a rod-mediated b-wave with a peak time of approximately 100 ms. Shorter DA times may be desirable to shorten the recording time or to alter the prominence of the early cone-mediated x-wave relative to the rod-mediated b-wave. The DA red flash ERG is used to aid the diagnosis of achromatopsia (rod monochromacy), cone dystrophy and other forms of cone system dysfunction, including "Bradyopsia" (RGS9/R9AP-retinopathy), when the DA red flash ERG x-wave is preserved in the absence of ISCEV standard LA ERGs. The DA red flash ERG can also help determine the origin of residual DA ERGs in cases of severe rod dysfunction, for example in disorders such as vitamin A deficiency, fundus albipunctatus (RDH5-retinopathy), Oguchi disease (SAG- or GRK1-retinopathy) and some rod-cone dystrophies. To shorter DA periods, the x-wave may be elicited without the following rod b-wave, shown to be helpful in abbreviated protocols for children.

ISCEV extended protocol for the photopic On-Off ERG.

The International Society for Clinical Electrophysiology of Vision (ISCEV) standard for full-field electroretinography (ERG) describes a minimum procedure, but encourages more extensive testing. This ISCEV extended protocol describes an extension to the ERG standard, namely the photopic On-Off ERG, and outlines common clinical applications. A light stimulus duration of 150-200 ms is used in the presence of a rod-suppressing background to elicit cone-driven On- and Off-system ERG components. The On-response occurs after the stimulus onset and has a negative a-wave and positive b-wave. The Off d-wave is a positive component evoked by stimulus offset. Common diagnoses that may benefit from additional photopic On-Off ERG testing include retinal dystrophies and retinal disorders that cause dysfunction at a level that is post-phototransduction or post-receptoral. On-Off ERGs assess the relative involvement of On- and Off-systems and may be of use in the diagnosis of disorders such as complete and incomplete congenital stationary night blindness (complete and incomplete CSNB), melanoma-associated retinopathy, and some forms of autoimmune retinopathy. The photopic On-Off ERGs may also be useful in X-linked retinoschisis, Batten disease, Duchenne muscular dystrophy, spinocerebellar degeneration, quinine toxicity, and other retinal disorders.

ElVisML: an open data format for the exchange and storage of electrophysiological data in ophthalmology.

PURPOSE: The ISCEV standards and recommendations for electrophysiological recordings in ophthalmology define a set of protocols with stimulus parameters, acquisition settings, and recording conditions, to unify the data and enable comparability of results across centers. Up to now, however, there are no standards to define the storage and exchange of such electrophysiological recordings. The aim of this study was to develop an open standard data format for the exchange and storage of visual electrophysiological data (ElVisML). METHODS: We first surveyed existing data formats for biomedical signals and examined their suitability for electrophysiological data in ophthalmology. We then compared the suitability of text-based and binary formats, as well as encoding in Extensible Markup Language (XML) and character/comma-separated values. RESULTS: The results of the methodological consideration led to the development of ElVisML with an XML-encoded text-based format. This allows referential integrity, extensibility, the storing of accompanying units, as well as ensuring confidentiality and integrity of the data. A visualization of ElVisML documents (ElVisWeb) has additionally been developed, which facilitates the exchange of recordings on mailing lists and allows open access to data along with published articles. CONCLUSIONS: The open data format ElVisML ensures the quality, validity, and integrity of electrophysiological data transmission and storage as well as providing manufacturer-independent access and long-term archiving in a future-proof format. Standardization of the format of such neurophysiology data would promote the development of new techniques and open software for the use of neurophysiological data in both clinic and research.

Methodological standards and functional correlates of depth in vivo electrophysiological recordings in control rodents. A TASK1-WG3 report of the AES/ILAE Translational Task Force of the ILAE.

This paper is a result of work of the AES/ILAE Translational Task Force of the International League Against Epilepsy. The aim is to provide acceptable standards and interpretation of results of electrophysiological depth recordings in vivo in control rodents.

Nerve Conduction Studies as a Measure of Disease Progression: Objectivity or Illusion?

BACKGROUND: Clinical nerve conduction studies (NCS) are often used as a secondary outcome measure in therapeutic trials, but show a high degree of inter-trial variability even when technical factors known to affect the recorded responses are minimised. This raises the intriguing possibility that some of the observed variability may reflect true changes in nerve activity. OBJECTIVES: Our aim was determine how much variability these factors might produce, and how this might affect the results of commonly used neuropathy rating scales. METHODS: A standardised protocol was repeated over forty consecutive trials by the same operators in two healthy subjects. The protocol included recordings that shared either a stimulating or a recording electrode position, such that changes due to electrode position could be excluded, and hand temperature was closely controlled. RESULTS: Despite controlling for inter-operator differences, electrode position, and hand temperature, the variability in sensory nerve action potential (SNAP) amplitude was extremely high (Range 23 µV, CoV = 10.7-18.8). This variability was greater than the change in amplitude needed to move a subject from point 0 to point 4 on the CMT neuropathy rating scale. Neither temperature or electrode position accounted for all of this variability, suggesting that additional as yet unidentified factors are responsible. CONCLUSION: Even under closely controlled conditions and sophisticated laboratory methods, test-to-test variability can be significant. The factors responsible for this variability may be difficult to control, limiting the utility of single nerve recordings as a trial outcome measure.

The changing shape of the ISCEV standard pattern onset VEP.

PURPOSE: Pattern onset VEPs do not always show distinct C1-C2-C3 peaks and troughs. Our purpose was to study changes in pattern onset VEP with age to determine when the illustrated ISCEV standard onset VEP waveform can be reliably recorded. METHODS: We recorded pattern onset VEPs from an Oz electrode referred to mid-frontal electrode according to ISCEV standards by presenting checks of 60' and 15' side length in a 15° field. Twenty-four adults aged 20-63 years participated. Amplitudes and latencies were collated. Pattern onset adult VEP shapes were compared to the waveform published in the ISCEV VEP standard and to paediatric pattern onset VEP waveforms recorded from 16 infants aged 7 months. RESULTS: The shape of the pattern onset VEP changed gradually with age. The C1-C2-C3 morphology of the ISCEV standard pattern onset VEP becomes apparent consistently after 40 years to 60' check stimulation. As age increases a negative trough, C2 is more frequently seen; however, the broad positive peak which characterises infant onset VEPs may still be recorded at 20 years. The group median measurements of onset VEPs to 60' were C1 7 µV@ 88 ms (range 67-110 ms), C2 9 µV@109 ms (range 89-158 ms) and C3 13 µV@121-246 ms. To smaller 15' checks, peak latencies were earlier and C2 became more obvious. The group median measures of onset VEPs to 15' were C1 2 µV@69 ms (55-108 ms), C2 10 µV@90 ms (77-145 ms) and C3 14 µV@122 ms (99-200 ms). CONCLUSION: The ISCEV standard onset VEP best describes the waveform configuration and latency of the onset VEP produced by 60' checks in adults of more than 40 years of age. The onset VEP waveform produced by 15' checks is distinguished by more prominent negative C2 and earlier C1 and C2 latencies.