Electrical properties of light-addressed sub-µm electrodes fabricated by use of nanostencil-technology

A wide range of applications in neurotechnological research rely on planar microelectrode arrays (MEA) but the disadvantage of these systems is the low density of electrodes caused by the problem of wiring a great number of electrodes. In turn this results in a low number of good cell to electrode contacts. To overcome this drawback, a great number of laterally isolated sub-um electrodes is placed on a photoconductor layer (amorphous silicon a-Si:H). By use of a laser beam, only those sub-um electrodes lying under the cell can be selected to form an electrical contact to one of the underlying indium tin oxide (ITO) leads providing a high seal resistance at the cell / electrodes interface. A biocompatible and biostable composite layer of electrodes (100–500 nm) and insulator is formed using nanostencil-technology. Dark to bright ratio D of the photoconductor is determined to 10^5 – 10^6 . The impedance of Au and TiN sub-um electrodes in physiological solution is measured. Spatial resolution of the system is limited by light-scattering inside the supporting glass substrate; the effective diameter of the conductive region illuminated by the laser spot with intrinsic diameter 1.6 um is 6–7 ~um

Coherence Potentials: Loss-Less, All-or-None Network Events in the Cortex

Transient associations among neurons are thought to underlie memory and behavior. However, little is known about how such associations occur or how they can be identified. Here we recorded ongoing local field potential (LFP) activity at multiple sites within the cortex of awake monkeys and organotypic cultures of cortex. We show that when the composite activity of a local neuronal group exceeds a threshold, its activity pattern, as reflected in the LFP, occurs without distortion at other cortex sites via fast synaptic transmission. These large-amplitude LFPs, which we call coherence potentials, extend up to hundreds of milliseconds and mark periods of loss-less spread of temporal and amplitude information much like action potentials at the single-cell level. However, coherence potentials have an additional degree of freedom in the diversity of their waveforms, which provides a high-dimensional parameter for encoding information and allows identification of particular associations. Such nonlinear behavior is analogous to the spread of ideas and behaviors in social networks

Untersuchung des Elektronenemissionsmechanismus von MIM (Metall-Isolator-Metall)-Duennschichtkathoden und der Anwendbarkeit als Vielstrahlelektronenquelle zum Aufbau eines elektronenoptischen Flachbildschirms

SIGLETIB: DR 1483 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman