18,711 research outputs found
Endoneural selective stimulating using wire-microelectrode arrays
In acute experiments eight 5- to 24-wire-microelectrode arrays were inserted into the common peroneal nerve of the rat, to investigate whether the electrodes could selectively stimulate motor units of the extensor digitorum longus (EDL) muscle. Twitch-force-recruitment curves were measured from the EDL for each array electrode. The curves were plotted on a double-logarithmic scale and parameterized by the low-force slope (which represents the power p in the power-law relationship of force F versus stimulus current I, or F~Ip) and the threshold current. The slopes and threshold currents measured with array electrodes did not differ significantly from those obtained with randomly inserted single wire-microelectrodes. This indicates that, although involving a more invasive insertion procedure, electrode arrays provide neural contacts with low-force recruitment properties similar to those of single wires. Array results revealed partial blocking of neural conduction, similar to that reported with microneurographic insertion with single needles. The efficiency of the array was defined as the fraction of array electrodes selectively contacting a motor unit and evoking the corresponding threshold force. Efficiency thus expresses the practical value of the used electrode array in terms of the total number of distinct threshold forces that can be stimulated by selecting the appropriate electrodes. The eight arrays were capable of evoking threshold forces selectively with an average efficiency of 0.81 (or 81%
A versatile all-channel stimulator for electrode arrays, with real-time control
Over the last few decades, technology to record through ever increasing numbers of electrodes has become available to electrophysiologists. For the study of distributed neural processing, however, the ability to stimulate through equal numbers of electrodes, and thus to attain bidirectional communication, is of paramount importance. Here, we present a stimulation system for multi-electrode arrays which interfaces with existing commercial recording hardware, and allows stimulation through any electrode in the array, with rapid switching between channels. The system is controlled through real-time Linux, making it extremely flexible: stimulation sequences can be constructed on-the-fly, and arbitrary stimulus waveforms can be used if desired. A key feature of this design is that it can be readily and inexpensively reproduced in other labs, since it interfaces to standard PC parallel ports and uses only off-the-shelf components. Moreover, adaptation for use with in vivo multi-electrode probes would be straightforward. In combination with our freely available data-acquisition software, MeaBench, this system can provide feedback stimulation in response to recorded action potentials within 15 ms
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A Wireless Implantable System for Facilitating Gastrointestinal Motility.
Gastrointestinal (GI) electrical stimulation has been shown in several studies to be a potential treatment option for GI motility disorders. Despite the promising preliminary research progress, however, its clinical applicability and usability are still unknown and limited due to the lack of a miniaturized versatile implantable stimulator supporting the investigation of effective stimulation patterns for facilitating GI dysmotility. In this paper, we present a wireless implantable GI modulation system to fill this technology gap. The system consists of a wireless extraluminal gastrointestinal modulation device (EGMD) performing GI electrical stimulation, and a rendezvous device (RD) and a custom-made graphical user interface (GUI) outside the body to wirelessly power and configure the EGMD to provide the desired stimuli for modulating GI smooth muscle activities. The system prototype was validated in bench-top and in vivo tests. The GI modulation system demonstrated its potential for facilitating intestinal transit in the preliminary in vivo chronic study using porcine models
Neuroelectronic interfacing with cultured multielectrode arrays toward a cultured probe
Efficient and selective electrical stimulation and recording of neural activity in peripheral, spinal, or central pathways requires multielectrode arrays at micrometer scale. ¿Cultured probe¿ devices are being developed, i.e., cell-cultured planar multielectrode arrays (MEAs). They may enhance efficiency and selectivity because neural cells have been grown over and around each electrode site as electrode-specific local networks. If, after implantation, collateral sprouts branch from a motor fiber (ventral horn area) and if they can be guided and contacted to each ¿host¿ network, a very selective and efficient interface will result. Four basic aspects of the design and development of a cultured probe, coated with rat cortical or dorsal root ganglion neurons, are described. First, the importance of optimization of the cell-electrode contact is presented. It turns out that impedance spectroscopy, and detailed modeling of the electrode-cell interface, is a very helpful technique, which shows whether a cell is covering an electrode and how strong the sealing is. Second, the dielectrophoretic trapping method directs cells efficiently to desired spots on the substrate, and cells remain viable after the treatment. The number of cells trapped is dependent on the electric field parameters and the occurrence of a secondary force, a fluid flow (as a result of field-induced heating). It was found that the viability of trapped cortical cells was not influenced by the electric field. Third, cells must adhere to the surface of the substrate and form networks, which are locally confined, to one electrode site. For that, chemical modification of the substrate and electrode areas with various coatings, such as polyethyleneimine (PEI) and fluorocarbon monolayers promotes or inhibits adhesion of cells. Finally, it is shown how PEI patterning, by a stamping technique, successfully guides outgrowth of collaterals from a neonatal rat lumbar spinal cord explant, after six days in cultur
Microelectrode arrays of diamond-insulated graphitic channels for real time detection of exocytotic events from cultured chromaffin cells and slices of adrenal glands
A microstructured graphitic 4x4 multielectrode array was embedded in a single
crystal diamond substrate (4x4 {uG-SCD MEA) for real-time monitoring of
exocytotic events from cultured chromaffin cells and adrenal slices. The
current approach relies on the development of a parallel ion beam lithographic
technique, which assures the time effective fabrication of extended arrays with
reproducible electrode dimensions. The reported device is suitable for
performing amperometric and voltammetric recordings with high sensitivity and
temporal resolution, by simultaneously acquiring data from 16 rectangularly
shaped microelectrodes (20x3.5 um^2) separated by 200 um gaps. Taking advantage
of the array geometry we addressed the following specific issues: i) detect
both the spontaneous and KCl-evoked secretion simultaneously from several
chromaffin cells directly cultured on the device surface, ii) resolve the
waveform of different subsets of exocytotic events, iii) monitoring quantal
secretory events from thin slices of the adrenal gland. The frequency of
spontaneous release was low (0.12 Hz and 0.3 Hz respectively for adrenal slices
and cultured cells) and increased up to 0.9 Hz after stimulation with 30 mM KCl
in cultured cells. The spike amplitude as well as rise and decay time were
comparable with those measured by carbon fiber microelectrodes and allowed to
identify three different subsets of secretory events associated to "full
fusion" events, "kiss and-run" and "kiss-and-stay" exocytosis, confirming that
the device has adequate sensitivity and time resolution for real-time
recordings. The device offers the significant advantage of shortening the time
to collect data by allowing simultaneous recordings from cell populations
either in primary cell cultures or in intact tissues
Simultaneous multi-patch-clamp and extracellular-array recordings: Single neuron reflects network activity
The increasing number of recording electrodes enhances the capability of
capturing the network's cooperative activity, however, using too many monitors
might alter the properties of the measured neural network and induce noise.
Using a technique that merges simultaneous multi-patch-clamp and
multi-electrode array recordings of neural networks in-vitro, we show that the
membrane potential of a single neuron is a reliable and super-sensitive probe
for monitoring such cooperative activities and their detailed rhythms.
Specifically, the membrane potential and the spiking activity of a single
neuron are either highly correlated or highly anti-correlated with the
time-dependent macroscopic activity of the entire network. This surprising
observation also sheds light on the cooperative origin of neuronal burst in
cultured networks. Our findings present an alternative flexible approach to the
technique based on a massive tiling of networks by large-scale arrays of
electrodes to monitor their activity.Comment: 36 pages, 9 figure
All-carbon multi-electrode array for real-time in vitro measurements of oxidizable neurotransmitters
We report on the ion beam fabrication of all-carbon multi electrode arrays
(MEAs) based on 16 graphitic micro-channels embedded in single-crystal diamond
(SCD) substrates. The fabricated SCD-MEAs are systematically employed for the
in vitro simultaneous amperometric detection of the secretory activity from
populations of chromaffin cells, demonstrating a new sensing approach with
respect to standard techniques. The biochemical stability and biocompatibility
of the SCD-based device combined with the parallel recording of
multi-electrodes array allow: i) a significant time saving in data collection
during drug screening and/or pharmacological tests over a large number of
cells, ii) the possibility of comparing altered cell functionality among cell
populations, and iii) the repeatition of acquisition runs over many cycles with
a fully non-toxic and chemically robust bio-sensitive substrate.Comment: 24 pages, 5 figure
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