Modular multipin electrodes for comfortable dry EEG.

Electrode and cap concepts for continuous and ubiquitous monitoring of brain activity will open up new fields of application and contribute to increased use of electroencephalography (EEG) in clinical routine, neurosciences, brain-computer-interfacing and out-of-the-lab monitoring. However, mobile and unobtrusive applications are currently hindered by the lack of applicable convenient and reliable electrode and cap systems. We propose a novel modular electrode concept based on a flexible polymer substrate, coated with electrically conductive metallic films. The overall concept enables design adaptation to different head regions and cap designs. We describe the single modules of the system and investigate the influence of electrode pin number, coating material and adduction force on electrode-skin impedance and perceived wearing comfort. Our results contribute to rapid and comfortable multichannel dry EEG.

Novel Multipin Electrode Cap System for Dry Electroencephalography.

Current usage of electroencephalography (EEG) is limited to laboratory environments. Self-application of a multichannel wet EEG caps is practically impossible, since the application of state-of-the-art wet EEG sensors requires trained laboratory staff. We propose a novel EEG cap system with multipin dry electrodes overcoming this problem. We describe the design of a novel 24-pin dry electrode made from polyurethane and coated with Ag/AgCl. A textile cap system holds 97 of these dry electrodes. An EEG study with 20 volunteers compares the 97-channel dry EEG cap with a conventional 128-channel wet EEG cap for resting state EEG, alpha activity, eye blink artifacts and checkerboard pattern reversal visual evoked potentials. All volunteers report a good cap fit and good wearing comfort. Average impedances are below 150 kΩ for 92 out of 97 dry electrodes, enabling recording with standard EEG amplifiers. No significant differences are observed between wet and dry power spectral densities for all EEG bands. No significant differences are observed between the wet and dry global field power time courses of visual evoked potentials. The 2D interpolated topographic maps show significant differences of 3.52 and 0.44% of the map areas for the N75 and N145 VEP components, respectively. For the P100 component, no significant differences are observed. Dry multipin electrodes integrated in a textile EEG cap overcome the principle limitations of wet electrodes, allow rapid application of EEG multichannel caps by non-trained persons, and thus enable new fields of application for multichannel EEG acquisition.

Novel flexible Dry multipin electrodes for EEG: Signal quality and interfacial impedance of Ti and TiN coatings.

Conventional Silver/Silver-Chloride electrodes are inappropriate for routine high-density EEG and emerging new fields of application like brain computer interfaces. A novel multipin electrode design is proposed. It enables rapid and easy application while maintaining signal quality and patient comfort. The electrode design is described and impedance and EEG tests are performed with Titanium and Titanium Nitride coated electrodes. The results are compared to conventional reference electrodes in a multi-volunteer study. The calculated signal parameters prove the multipin electrode concept to reproducibly acquire EEG signal quality comparable to Ag/AgCl electrodes. The promising results encourage further investigation and can provide a technological base for future preparation-free multichannel EEG systems.

Impedance pneumography using textile electrodes.

The acquisition of physiological parameters using textile and textile-integrated sensors has become an important alternative for mobile and long-term monitoring. We analyzed to different commercially available electrically conductive textiles concerning their applicability for textile-based impedance pneumography. We immersed the textiles to four corroding solutions and observed no considerable changes in the absolute value as well as the phase shift of the material impedances. Subsequently, we performed impedance pneumography tests with different current amplitudes and frequencies. Using silver coated synthetic textile electrodes it was possible to detect the correct respiration frequency during normal, flat as well as slow, deep respiration.

Novel flexible dry PU/TiN-multipin electrodes: first application in EEG measurements.

Dry biosignal electrodes for electro-encephalography (EEG) are an essential step for realization of ubiquitous EEG monitoring and brain computer interface technologies. We propose a novel electrode design with a specific shape for hair layer interfusion and reliable skin contact. An electrically conductive Titanium-Nitride (TiN) thin layer is deposited on a polyurethane substrate using a multiphase DC magnetron sputtering technique. In the current paper we describe the development and manufacturing of the electrode. Furthermore, we perform comparative EEG measurements with conventional Ag/AgCl electrodes in a 6-channel setup. Our results are promising, as the primary shape of the EEG is preserved in the signals of both electrodes sets, according to recordings of spontaneous EEG and visual evoked potentials. The variance of both signals is in the same order of magnitude. The Wilcoxon-Mann-Whitney two-sample rank-sum test revealed no significant differences for 25 of the 28 compared signal episodes. Hence, our novel electrodes show equivalent signal quality compared to conventional Ag/AgCl electrodes.

Choroidal folds associated with increased intracranial pressure.

PURPOSE: To determine whether a relationship exists between increased intracranial pressure and the presence of idiopathic choroidal folds. METHODS: A prospective study in which 12 consecutive patients presenting with choroidal folds were evaluated by imaging studies (ultrasonography, magnetic resonance imaging, and/or computed tomography) to rule out known causes of choroidal folds, such as orbital disease, choroidal tumor, posterior scleritis, hypotony, and choroidal neovascular membrane. A lumbar puncture was performed on each of these patients, and measurement of opening pressure of cerebrospinal fluid was obtained. RESULTS: Twelve patients with choroidal folds included nine men and three women. Six patients (50%) presented with papilledema in the eye with choroidal folds. The other six patients (50%) presented with only choroidal folds. In this study, 10 (83%) of 12 patients had an opening pressure greater than 230 mm H(2)O. In patients presenting with only choroidal folds, five (83%) of six patients had an opening pressure greater than 230 mm H(2)O, with an average opening pressure of 290 mm H(2)O. CONCLUSION: Depending on the timing of the evaluation, papilledema may or may not be present, and only choroidal folds may be seen as a reflection of increased intracranial pressure. We believe that increased intracranial pressure from any source (that is, pseudotumor cerebri, sinus thrombosis, or intracranial mass) can present with only choroidal folds; therefore, these patients should have an appropriate work-up that should probably include a lumbar puncture before the title of "idiopathic" is given to their finding.

Vertical fusional amplitudes in patients wearing vertical anisometropic correction.

OBJECTIVE: To examine the relationship between vertical anisometropic spectacle correction and vertical fusional amplitudes in patients. DESIGN: Comparative observational case series. PARTICIPANTS: Twenty-one patients exposed to greater than 0.5 diopters of vertical anisometropic spectacle correction were compared with 46 patients not exposed to anisometropic correction. METHODS: Vertical fusional amplitudes were recorded in all patients using a prism bar. MAIN OUTCOME MEASURES: Vertical fusional amplitudes and vertical anisometropia. RESULTS: In patients exposed to greater than 0.5 diopters of vertical anisometropic spectacle correction, vertical fusional amplitudes measured 5.2+/-1.4 prism diopters. Patients not exposed to anisometropic correction had vertical fusional amplitudes of 2.7+/-1.2 prism diopters (P < 0.0001). CONCLUSION: Patients with vertical anisometropic correction have increased vertical fusional amplitudes. This finding is relevant when evaluating patients with ocular motility disorders, especially with regard to distinguishing acquired versus longstanding deviations.

Field-programmable smart-pixel arrays: design, VLSI implementation, and applications.

A smart-pixel array is a two-dimensional array of optoelectronic devices that combine optical inputs and outputs with electronic processing circuitry. A field-programmable smart-pixel array (FP-SPA) is a smart-pixel array capable of having its electronic functionality dynamically programmed in the field. Such devices could be used in a diverse range of applications, including optical switching, optical digital signal processing, and optical image processing. We describe the design, VLSI implementation, and applications of a first-generation FP-SPA implemented with the 0.8-microm complementary metal-oxide semiconductor-self-electro-optic effect device technology made available through the Lucent Technologies-Advanced Research Projects Agency Cooperative (Lucent/ARPA/COOP) program. We report spice simulations and experimental results of two sample applications: In the first application, we configure this FP-SPA as an array of free-space optical binary switches that can be used in optical multistage networks. In the second, we configure the device as an optoelectronic transceiver for a dynamically reconfigurable free-space intelligent optical backplane called the hyperplane. We also describe the testing setup and the electrical and the optical tests that demonstrate the correct functionality of the fabricated device. Such devices have the potential to reduce significantly the need for custom design and fabrication of application-specific optoelectronic devices in the same manner that field-programmable gate arrays have largely eliminated the need for custom design and fabrication of application-specific gate arrays, except in the most demanding applications.