IEEE transactions on neural systems and rehabilitation engineering : a publication of the IEEE Engineering in Medicine and Biology Society
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IEEE Trans Neural Syst Rehabil Eng · Oct 2009
Automated stimulus-response mapping of high-electrode-count neural implants.
Over the past decade, research in the field of functional electrical stimulation (FES) has led to a new generation of high-electrode-count (HEC) devices that offer increasingly selective access to neural populations. Incorporation of these devices into research and clinical applications, however, has been hampered by the lack of hardware and software platforms capable of taking full advantage of them. In this paper, we present the first generation of a closed-loop FES platform built specifically for HEC neural interface devices. ⋯ Mean time to map perithreshold stimulus level was 16.4 s for electrodes that evoked responses (n = 3200), and 3.6 s for electrodes that did not evoke responses (n = 1800). Mean time to locate recruitment curve asymptote for an electrode (n = 155) was 9.6 s , and each point in the recruitment curve required 0.87 s. These results demonstrate the utility of our FES platform by showing that it can be used to completely automate a typically time- and effort-intensive procedure associated with using HEC devices.
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IEEE Trans Neural Syst Rehabil Eng · Oct 2009
Long micro-channel electrode arrays: a novel type of regenerative peripheral nerve interface.
We have demonstrated that micro-channel electrode arrays with 100 microm x 100 microm cross-section channels support axon regeneration well, and that micro-channels of similar calibre and up to 5 mm long can support axon regeneration and vascularisation. They may be microfabricated using silicon, silicone, or polyimide and thin metal films to form 3-D bundles of long micro-channels. Arrays of "mini-nerves," i.e., miniature nerve fascicles with their own blood vessels, successfully grew through implants 0.5-5 mm long. Furthermore, guiding the regenerating nerve fibres into the small insulating channels allows for a significant increase of the extracellular (recordable) amplitude of action potentials, which promises considerable improvement for in vivo electrophysiology.
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IEEE Trans Neural Syst Rehabil Eng · Oct 2009
Thresholds for transverse stimulation: fiber bundles in a uniform field.
Cable theory is used to model fibers (neural or muscular) subjected to an extracellular stimulus or activating function along the fiber (longitudinal stimulation). There are cases however, in which activation from fields across a fiber (transverse stimulation) is dominant and the activating function is insufficient to predict the relative stimulus thresholds for cells in a bundle. This work proposes a general method of quantifying transverse extracellular stimulation using ideal cases of long fibers oriented perpendicular to a uniform field (circular cells in a 2-D extracellular domain). ⋯ They also show that approximating cells as holes can accurately predict firing order and Phi(pact) of cells in bundles. Potential profiles from this hole model can also be applied to single cell models to account for time-dependent transmembrane voltage responses and more accurately predict Phi(pact). The approaches used herein apply to other examples of transverse cell stimulation where cable theory is inapplicable and coupled model simulation is too costly to compute.
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IEEE Trans Neural Syst Rehabil Eng · Aug 2009
A 128-channel 6 mW wireless neural recording IC with spike feature extraction and UWB transmitter.
This paper reports a 128-channel neural recording integrated circuit (IC) with on-the-fly spike feature extraction and wireless telemetry. The chip consists of eight 16-channel front-end recording blocks, spike detection and feature extraction digital signal processor (DSP), ultra wideband (UWB) transmitter, and on-chip bias generators. Each recording channel has amplifiers with programmable gain and bandwidth to accommodate different types of biological signals. ⋯ UWB telemetry is designed to wirelessly transfer raw data from 128 recording channels at a data rate of 90 Mbit/s. The chip is realized in 0.35 mum complementary metal-oxide-semiconductor (CMOS) process with an area of 8.8 x 7.2 mm(2) and consumes 6 mW by employing a sequential turn-on architecture that selectively powers off idle analog circuit blocks. The chip has been tested for electrical specifications and verified in an ex vivo biological environment.