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An Implantable Brain-Computer Interface for Investigation of Novel Closed-Loop Therapies

Martin Schüttler1, Fabian Kohler1, Christian Stolle1, Jörg Fischer1, Thomas Stieglitz2, 3, Alexis Gkogkidis3, 4, Xi Wang3, 4, Mortimer Gierthmuehlen4, Christian Scheiwe4, Jörn Rickert1, 2* and Tonio Ball2, 4
  • 1 CorTec GmbH, Germany
  • 2 BrainLinks BrainTools, Exzellenzcluster, Albert Ludwigs Universität Freiburg, Germany
  • 3 Professur für Biomedizinische Mikrotechnik, Institut für Mikrosystemtechnik, Albert Ludwigs Universität Freiburg, Department of Microsystems Engineering, Germany
  • 4 Klinik für Neurochirurgie, Universitätsklinikum Freiburg, Faculty of Medicine, Germany

INTRODUCTION In 1997, deep brain stimulation (DBS) was approved by the FDA for clinical treatment of essential tremor. In the following two decades neuromodulation of the central nervous system became a very active field and was applied for treating many different conditions. Similar to the technological progression of cardiac pacmakers, concepts were developed to adapt the stimulation pattern to the patient's need, making the devices responsive. Today, only two of these closed-loop devices are approved for clinical use, the Medtronic Activa PC+S and the Neuropace RNS. Both devices work with eight electrode contacts on the surface of or deep inside the brain and permit delivery of electrical stimuli initiated, or modified in intensity, based on neural signal recordings. Here, we present the development of a closed-loop device that overcomes current application limitation by increasing the electrode contact number, minimizing the closed-loop response time and transferring the closed-loop control algorithms to a device outside the body, allowing maximum freedom for clinical research. MATERIALS AND METHODS The system design is inspired by today's cochlear implants: The implant is wirelessly powered by a body-external transceiver. Cortical electrode arrays are and DBS electrodes can be connected to the hermetically packaged implanted electronics. The device records synchronously from 32 electrode contacts at 1kS/s (16bit) at a pass band of 0.5 to 450Hz. These data are wirelessly streamed to the body-external transceiver, which is connected to a laptop-PC, running the control software. The software can send instructions to the implant to generate electrical stimuli of up to 6mA on each of the 32 electrode contacts. Typically, it takes some 10ms for closing the loop of recording and recording-based stimulation, strongly depended on the signal analysis and decision-taking algorithms used. RESULTS The system (Figure 1) was implanted in sheep (approved by the Regierungspraesidium Freiburg, Germany and the Animal Ethics Committee of the University of Freiburg) to investigate functionality and biological acceptance. Excellent robustness of the implanted hardware was proven over 5 months in the current / over 15 months in the previous implant generation as well as good biological-acceptance. Signal quality was evaluated in auditory evoked potential experiments using electrode-grids (1mm diameter PtIr contacts): The signal-to-noise ratio did not significantly change over time (Figure 2). ACKNOWLEDGEMENT Funding was supplied within the German Cluster of Excellence BrainLinks-BrainTools (EXC 1086), by the Federal Ministry for Education and Research (13GW0053A-E) and by the Federal Ministry Economic Affairs and Energy (16KN022122). Figure 1: Photograph of brain-computer interface implant consisting of electronic unit, a short counter electrode lead, two grid electrodes and two connectors for DBS leads. Figure 2: Development of signal-to-noise ratio (SNR) of responses in the frequency domain recorded from sheep auditory cortex as response to an auditory stimulus of 3 s length and 8 kHz frequency. Individual tracks show SNRs from individual electrode contacts, the bold line shows the average.

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Keywords: Brain machine interface (BMI), Central Nervous System, closed-loop system, Implantable devices, Deep Brain Stimulation

Conference: MEA Meeting 2018 | 11th International Meeting on Substrate Integrated Microelectrode Arrays, Reutlingen, Germany, 4 Jul - 6 Jul, 2018.

Presentation Type: Poster Presentation

Topic: In vivo applications of MEAs

Citation: Schüttler M, Kohler F, Stolle C, Fischer J, Stieglitz T, Gkogkidis A, Wang X, Gierthmuehlen M, Scheiwe C, Rickert J and Ball T (2019). An Implantable Brain-Computer Interface for Investigation of Novel Closed-Loop Therapies. Conference Abstract: MEA Meeting 2018 | 11th International Meeting on Substrate Integrated Microelectrode Arrays. doi: 10.3389/conf.fncel.2018.38.00080

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Received: 15 Mar 2018; Published Online: 17 Jan 2019.

* Correspondence: Dr. Jörn Rickert, CorTec GmbH, Freiburg, BW, 79110, Germany, sales@cortec-neuro.com