Modified nomenclature for the "10%" electrode system

A modified nomenclature for designating the auxiliary electrodes of the 10% system is described.     

CMAP variability as a function of electrode site and size

The site of the recording electrode influences the amplitude of the compound muscle action potential (CMAP) and its variation over a length of nerve. The effects of large electrodes on this source of intra-individual variability were assessed. Right median nerves of 20 healthy subjects were studied, and recordings made at three sites (at 1-cm intervals) using five electrode sizes (0.01, 1, 2, 4, and 10 cm²). Site-induced variability was defined as the standard deviation (SD_i) and coefficient of variation (CV_i) of the measurements of the three sites. Site induced variability of all parameters (latency, duration, amplitude, area, MNCV, and the percentile changes of duration, amplitude, and area over the forearm) decreased significantly with electrode size. Decreases were most pronounced for amplitude and area: CV_i fell from 29% and 30% (0.01-cm² electrode) to 10% and 8% (10 cm²). It is argued that large electrodes record activity of more motor units than small electrodes, and that their measurement fields overlap to a greater extent. The use of large electrodes is recommended in order to reduce site-induced CMAP variability.© 1995 John Wiley &Sons, Inc.     

Influence of electrode site and size on variability of magnetic evoked potentials

Successive magnetic evoked potentials (MEPs) concern varying motor neurons. We investigated whether this MEP-specific source of variability depends on electrode site and size. Amplitude variability (standard deviation) was largest over the center of the hypothenar muscles. Latencies were longer at distal and proximal sites than at the center site. Large electrodes (10 cm²) did not decrease this source of amplitude variability compared with EEG electrodes, in contrast to other sources of variability. © 1998 John Wiley & Sons, Inc. Muscle Nerve 21: 1779–1782, 1998     

Recording from defined populations of retinal ganglion cells using a high-density CMOS-integrated microelectrode array with real-time switchable electrode selection

In order to understand how retinal circuits encode visual scenes, the neural activity of defined populations of retinal ganglion cells (RGCs) has to be investigated. Here we report on a method for stimulating, detecting, and subsequently targeting defined populations of RGCs. The possibility to select a distinct population of RGCs for extracellular recording enables the design of experiments that can increase our understanding of how these neurons extract precise spatio-temporal features from the visual scene, and how the brain interprets retinal signals. We used light stimulation to elicit a response from physiologically distinct types of RGCs and then utilized the dynamic-configurability capabilities of a microelectronics-based high-density microelectrode array (MEA) to record their synchronous action potentials. The layout characteristics of the MEA made it possible to stimulate and record from multiple, highly overlapping RGCs simultaneously without light-induced artifacts. The high-density of electrodes and the high signal-to-noise ratio of the MEA circuitry allowed for recording of the activity of each RGC on 14±7 electrodes. The spatial features of the electrical activity of each RGC greatly facilitated spike sorting. We were thus able to localize, identify and record from defined RGCs within a region of mouse retina. In addition, we stimulated and recorded from genetically modified RGCs to demonstrate the applicability of optogenetic methods, which introduces an additional feature to target a defined cell type. The developed methodologies can likewise be applied to other neuronal preparations including brain slices or cultured neurons.     

A note on nomenclature

Psychiatric Quarterly -     

Transcranial electrical stimulation nomenclature

Transcranial electrical stimulation (tES) aims to alter brain function non-invasively by applying current to electrodes on the scalp. Decades of research and technological advancement are associated with a growing diversity of tES methods and the associated nomenclature for describing these methods. Whether intended to produce a specific response so the brain can be studied or lead to a more enduring change in behavior (e.g. for treatment), the motivations for using tES have themselves influenced the evolution of nomenclature, leading to some scientific, clinical, and public confusion. This ambiguity arises from (i) the infinite parameter space available in designing tES methods of application and (ii) varied naming conventions based upon the intended effects and/or methods of application. Here, we compile a cohesive nomenclature for contemporary tES technologies that respects existing and historical norms, while incorporating insight and classifications based on state-of-the-art findings. We consolidate and clarify existing terminology conventions, but do not aim to create new nomenclature. The presented nomenclature aims to balance adopting broad definitions that encourage flexibility and innovation in research approaches, against classification specificity that minimizes ambiguity about protocols but can hinder progress. Constructive research around tES classification, such as transcranial direct current stimulation (tDCS), should allow some variations in protocol but also distinguish from approaches that bear so little resemblance that their safety and efficacy should not be compared directly. The proposed framework includes terms in contemporary use across peer-reviewed publications, including relatively new nomenclature introduced in the past decade, such as transcranial alternating current stimulation (tACS) and transcranial pulsed current stimulation (tPCS), as well as terms with long historical use such as electroconvulsive therapy (ECT). We also define commonly used terms-of-the-trade including electrode, lead, anode, and cathode, whose prior use, in varied contexts, can also be a source of confusion. This comprehensive clarification of nomenclature and associated preliminary proposals for standardized terminology can support the development of consensus on efficacy, safety, and regulatory standards.     

Pattern ERG: effects of reference electrode site, stimulus mode and check size

We studied monocular pattern ERG (PERG) in 10 normal subjects and a patient with optic neuritis. No clinically significant PERG could be recorded from the occluded eye with any reference (ipsilateral ear or temple, or midfrontal), indicating that cross-contamination is not present with binocular testing. Ipsilateral temple reference minimized VEP (P100/N100) contribution to the PERG N95 which occurred with ipsilateral ear or midfrontal reference. The conclusions were confirmed by results from the patient, who had marked monocular delay of a normal amplitude P100. Twenty-four subjects were tested with monocular and binocular stimulation using an ipsilateral temple reference. There were differences in PERG latencies and amplitudes although the interside amplitude ratio showed smaller differences with binocular stimulation. Increasing check size (17, 35 and 70 min) decreased P50 and N95 latencies and increased P50 amplitude.     

Recording electrophysiological signals from small moving animals: electrode fixation and low torque swivel for recording a weakly electric fish in a group

A silicone rubber ring maintains an electrode on the electric organ of a mormyrid fish. The electrode is connected with a novel swivel, which allows free motion of the wire around its axis. The principle of the rotating contact is based on magnetic contact between a steel pin (moving) and a steel ball (fixed). Using this apparatus, a single fish within a group is recorded. The general electric activity of the group is recorded by means of two sets of fixed differential electrodes. These devices may be adapted for neuroethological studies of other small animals.     

Scalp-EEG Recording via Methohexital Narcosis

This study sought to compare the localization of methohexital induced activation in the epileptogenic zone between scalp derived and subdural electrode ECoG recordings and to correlate with seizure outcome after epilepsy surgery. Electroencephalogram (EEG) and ECoG recordings of 15 patients (15–53 years of age, mean: 34 years) with a preoperative methohexital narcosis (low dose 40–50 mg and high dose 80–100 mg) were postoperatively analyzed. Six out of eight patients with both scalp recordings and ECoG recordings showed congruous epileptogenic zone activation (temporal/frontal) in noninvasive and invasive recordings. All improved postoperatively 1, 2. Five postoperatively improved patients (two with ECoG and three with EEG) had an additional temporal spike induction opposite the operated hemisphere 1, 3. One postoperatively seizure-free patient had no temporal activation in EEG but did in ECoG 1, 4. In none of the postoperatively improved patients was EEG falsely localizing [2]. Five of seven patients with scalp-EEG recording showed exclusive activation, one patient predominant activation of the temporal epileptogenic zone. All of these patients improved postoperatively [3]. Postoperatively, all but one patient were seizure-free or had > 75% improvement. One patient with an EEG activation incongruous with the side of operation had no postoperative improvement. Methohexital induced activation of epileptogenic foci is congruent in EEG and ECoG and is a reliable method for lateralization and localization of the epileptogenic zone.     

The influence of the reference electrode on CMAP configuration: Leg nerve observations and an alternative reference site

Peroneal and tibial compound motor action potentials (CMAP) recorded using the standard belly-tendon montage have different configurations. The peroneal CMAP is a smooth dome shape, while the tibial CMAP has a slow-rising initial component followed by a higher amplitude negative peak. To evaluate possible causes of these differences, we investigated the individual activity recordable at the belly and tendon electrodes by using a referential montage with the opposite foot as the reference. This type recording shows that the peroneal belly site produces most of the nerve CMAP, whereas the tendon site generates most of the high tibial CMAP. Some features and technical problems of referential CMAP recording using an opposite limb reference are shown. An alternative method using an ipsilateral distal leg reference site is described. A montage which separately records the activity at the belly or tendon electrodes may provide new insight into mechanisms of commonly observed nerve conduction phenomena. © 1996 John Wiley & Sons, Inc.