Subretinal Stimulation Chip Set with 3025 Electrodes, Spatial Peaking Filter, Illumination Adaptation and Implant Lifetime Optimization.

A subretinal stimulator chip has been designed and tested, which combines high pixel number with highest simulation voltages, lowest power consumption, spatial peaking and illumination adaptation. A supporting ASIC completes the implantable device electronics. Blind mouse retina has successfully been stimulated in vitro.

PEDOT-CNT coated electrodes stimulate retinal neurons at low voltage amplitudes and low charge densities.

OBJECTIVE: The aim of this study was to compare two different microelectrode materials--the conductive polymer composite poly-3,4-ethylenedioxythiophene (PEDOT)-carbon nanotube(CNT) and titanium nitride (TiN)--at activating spikes in retinal ganglion cells in whole mount rat retina through stimulation of the local retinal network. Stimulation efficacy of the microelectrodes was analyzed by comparing voltage, current and transferred charge at stimulation threshold. APPROACH: Retinal ganglion cell spikes were recorded by a central electrode (30 µm diameter) in the planar grid of an electrode array. Extracellular stimulation (monophasic, cathodic, 0.1-1.0 ms) of the retinal network was performed using constant voltage pulses applied to the eight surrounding electrodes. The stimulation electrodes were equally spaced on the four sides of a square (400 × 400 µm). Threshold voltage was determined as the pulse amplitude required to evoke network-mediated ganglion cell spiking in a defined post stimulus time window in 50% of identical stimulus repetitions. For the two electrode materials threshold voltage, transferred charge at threshold, maximum current and the residual current at the end of the pulse were compared. MAIN RESULTS: Stimulation of retinal interneurons using PEDOT-CNT electrodes is achieved with lower stimulation voltage and requires lower charge transfer as compared to TiN. The key parameter for effective stimulation is a constant current over at least 0.5 ms, which is obtained by PEDOT-CNT electrodes at lower stimulation voltage due to its faradaic charge transfer mechanism. SIGNIFICANCE: In neuroprosthetic implants, PEDOT-CNT may allow for smaller electrodes, effective stimulation in a safe voltage regime and lower energy-consumption. Our study also indicates, that the charge transferred at threshold or the charge injection capacity per se does not determine stimulation efficacy.

[Management of the pandemic influenza (H1N1) 2009 in Germany - results from an evaluation of the public health authorities]. / Das Management der Influenza A/H1N1-Pandemie durch die Gesundheitsämter in Deutschland - Ergebnisse einer bundesweiten Befragung.

In 2009, the health-care system was faced with numerous challenges resulting from the emergence and the worldwide spread of a new influenza virus. Public health authorities played a fundamental role in the management of the pandemic. The Advisory Committee for Infectious Disease Protection of the German Medical Association for Public Health Authorities (BVÖGD e.V.) requested the local public health authorities in Germany to take part in a written evaluation of the management of the new influenza pandemic in February 2010, before the official end of the influenza pandemic. The purpose of this timely analysis was to identify areas in need of improvement in preparation for similar incidents that may occur in the future. The survey showed that the communication between the various parties involved, the prompt and appropriate transmission of information, as well as the control over the overwhelming onslaught of information need to be optimised. The participants also found the practicability of the official recommendations to be lacking. The wide scale increase in workload, as seen on a national basis, required to deal with the pandemic indicates that the public health services have only very limited resources for handling crisis situations, and this must be taken into consideration when planning for coping with such matters in the future. The findings of the study participants for the national management of a pandemic coincide in most aspects with the results of other evaluations. Distinct differences in the assessment of policies were noticeable when comparing the experiences in the various German states (Bundesländer). A detailed analysis of the points at issue is necessary before possible best practice models can be developed.

Spatially resolved electronic detection of biopolymers.

An integrated array of field-effect transistor structures is used to detect two oppositely charged biopolymers: poly(L-lysine) and DNA. Local deposition of polymer solutions on part of the array induces sizeable variations in the dc current-voltage characteristics of the transistors exposed to the molecular charge. The whole transistor array is measured in the presence of a common electrolyte. Differential signals are studied as a function of electrolyte salt and polymer concentrations. The measurements provide information on the interface electrostatic potentials of the (semiconductor/biopolymer/electrolyte) system and the experimental data are compared to an analytical model which accounts for screening of the adsorbed charge by mobile ions.

Noninvasive neuroelectronic interfacing with synaptically connected snail neurons immobilized on a semiconductor chip.

A hybrid circuit of a semiconductor chip and synaptically connected neurons was implemented and characterized. Individual nerve cells from the snail Lymnaea stagnalis were immobilized on a silicon chip by microscopic picket fences of polyimide. The cells formed a network with electrical synapses after outgrowth in brain conditioned medium. Pairs of neurons were electronically interfaced for noninvasive stimulation and recording. Voltage pulses were applied to a capacitive stimulator on the chip to excite the attached neuron. Signals were transmitted in the neuronal net and elicited an action potential in a second neuron. The postsynaptic excitation modulated the current of a transistor on the chip. The implementation of the silicon-neuron-neuron-silicon circuit constitutes a proof-of-principle experiment for the development of neuroelectronic systems to be used in studies on neuronal signal processing, neurocomputation, and neuroprosthetics.