David J. Anderson - US grants

The major thrust of this Center proposal is to enable research investigators in systems neurobiology, neuroprosthesis designers and other electrophysiologists to communicate with excitable tissue using multichannel thin-film devices constructed on silicon substrates. One, two and three dimensional arrays with tens to hundreds of recording or stimulation sites can be custom designed to fit the needs of specific tissue communication applications. There is a significant service and technology transfer component to this center. The Center educates investigators on the technology and its use through a number of media. New users are first given stock devices found in a catalog published by the Center and proceed to working with the Center staff to design new probes and matching an interconnect technology to their application. The service component and the research projects of the Center are designed to move the technology in three major directions over the next five years: 1) make the design of probes more rational by developing a data base and models will quantitatively guide researchers and designers, 2) broaden the distribution offerings of the Center include fluid delivery probes, probes with active circuits, probes coated with bioactive materials and three dimensional probes and 3) move the fabrication from University Laboratories to commercial fabrication facilities. Three internal research projects drive these thrusts. These projects cover extensions of the device technology, through experimentation and modeling, understand more fully the recording and stimulation characteristics of the devices, and development of methods by which exact geometrical relationships between tissue and devices can be confirmed postmortem. In addition to these projects there are several collaborative projects with investigators in universities and industry involving all of our major application areas.

technology /technique development; animal tissue; nervous system; hearing; ear; biomedical resource; biomedical equipment development; bioengineering /biomedical engineering; Mammalia;

health care; technology /technique development; urinary tract; nervous system; hearing; biomedical resource; biomaterials; Mammalia; bioengineering /biomedical engineering; ear; eye; prosthesis; behavioral /social science research tag;

This project addresses biological neural networks (NNs) in the auditory system in the context of high-channel count electrodes. We propose to extend our past work on recording in the cochlear nuclei (CN) and inferior colliculus (IC) using thin-film electrode technology to address technical, biological, and theoretical questions about data collection and analysis and neural circuit identification. Both acute and chronic multiunit recording at CN, IC, and auditory cortex (AC) of guinea pig will be used to address these questions. The general aims of this project are to apply the enhanced data gathering made possible by the thin-film, multicontact electrode technologies which concern this Resource Center to advance network estimation for NNs in general, and to obtain a better understanding of neural processing in the networks of the auditory system. The areas of work include 1) the study of waveforms recorded with multicontact electrodes including field potentials and the detection of discharges and their parsing into valid spike trains; 2) the collection and analysis of multiple spike train data from CN, IC, and AC using sound stimuli and local chemical and electrical stimuli in acute and chronic guinea pig preparations; 3) the study of NN identification problems using simulations of classes of networks and experimental data from thin-film electrodes.

9812525
Jenkins
Implantable antitachycardia devices (ICDs) have achieved overwhelming success in salvaging thousands of lives by providing immediate electrical therapy for the treatment of potentially lethal arrhythmias, i.e., ventricular tachycardia and ventricular fibrillation. These rhythms are believed responsible for over 80% of cases of sudden cardiac death, which claims 400,000 victims per year. The number of implants of ICDs is exceptional, over 100,000 implants to date, despite its relative infancy in the medical field. A large remaining problem to be solved in ICD technology is refinement of detection criteria such that the device no longer offers a simple brute force solution (if in question, shock). This is a three-fold problem: false shocks are an unnecessary patient distress; false shocks deplete battery power rendering the device less capable of addressing true urgencies and forcing premature explantation; and false shocks (or antitachycardia pacing) can initiate ventricular tachycardia (VT) or ventricular fibrillation (VF) when none previously existed. The specific aims of this proposal are: 1) to develop new signal processing techniques and pattern recognition schemes for accurate arrhythmia detection which exploit the present state of technology in ICDs; 2) to design improved diagnostic distinction between ventricular tachycardia and ventricular fibrillation which capitalize on the unique therapeutic choices for conversion of these arrhythmias; and 3) to refine methods of dual-chamber analysis for application to ICD arrhythmia diagnosis. Improved detection schemes comprise an engineering problem which must be addressed by modern digital signal processing techniques and imaginative engineering solutions employing concepts of lead-field theory and novel pattern recognition ideas.
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This project addresses biological neural networks (NNs) in the auditory system in the context of high-channel count electrodes. We propose to extend our past work on recording in the cochlear nuclei (CN) and inferior colliculus (IC) using thin-film electrode technology to address technical, biological, and theoretical questions about data collection and analysis and neural circuit identification. Both acute and chronic multiunit recording at CN, IC, and auditory cortex (AC) of guinea pig will be used to address these questions. The general aims of this project are to apply the enhanced data gathering made possible by the thin-film, multicontact electrode technologies which concern this Resource Center to advance network estimation for NNs in general, and to obtain a better understanding of neural processing in the networks of the auditory system. The areas of work include 1) the study of waveforms recorded with multicontact electrodes including field potentials and the detection of discharges and their parsing into valid spike trains; 2) the collection and analysis of multiple spike train data from CN, IC, and AC using sound stimuli and local chemical and electrical stimuli in acute and chronic guinea pig preparations; 3) the study of NN identification problems using simulations of classes of networks and experimental data from thin-film electrodes.

The placement of microprobes into deep brain structures such as hippocampus, Scarpa's ganglion, inferior colliculus, cochlear nucleus and deep cortical layers continues to be a growing area of interest for our external collaborators. Dr. Buzsaki's presentations at national meetings as well as his publications have stirred a great deal of interest from those recording in hippocampus. Challenges in using the probes for these preparations include holding the probe and maintaining a straight trajectory during insertion, accurate site placement in small regions well below the brain surface, and stabilization after insertion. We are working with the listed group of collaborative researchers to solve these problems. Probes with long shanks tend to bend during insertion. Several investigators are using cannular preparations to insert probes into deep structures. Others are exploring the coatings to enhance rigidity, or attachment of small, more rigid structures to the back of the substrate. New methods for insertion are also being evaluated for their ability to enhance the straightness of insertions. Custom probes have been designed by the above investigators and have been fabricated and provided by the Center mounted and bonded to desired connectors. The work done within this scientific sub-project benefits many investigators with new placement techniques, not only in deep brain structures but in other areas as well.

Observation of multichannel activity or stimulation with probes in the periphery is particularly challenging. First, simple penetration of a nerve track is much more difficult than brain tissue. We have solved this problem by fabricating probes with very sharp tips formed using shallow boron diffusion. These probes have been shown to penetrate much more readily than those with standard deep diffused tips. "Sieve" electrodes can also be used when to record from regenerated nerve fibers (Highstein and Bradley). This type of probe has holes through which the fibers can regenerate, and recording sites which surround the holes. The second challenge involves motion with respect to surrounding fixation points is larger then in the cortex or brainstem. The device must somehow be fixed within the nerve track and a cable or transmission system which allows large motions relative to the interconnect area must be provided. We have included barbs and suture loops/holes on several of the custom designs to enhance positional stability. Cables on these designs have been slotted to increase flexibility. Third, in many peripheral situations signals must be transmitted a relatively long distance to reach (or be sent from) the external world. We continue to work with PI Medical in Portland, Oregon to develop a combined system for Dr. Highstein (see collaborative project on Post-processing and Packaging).