New Perspectives on Neuroengineering and Neurotechnologies: NSF-DFG Workshop Report

This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/TBME.2016.2543662, IEEE Transactions on Biomedical Engineering TBME-00086-2016.R1 New Perspectives on Neuroengineering and Neurotechnologies: NSF-DFG Workshop Report Chet T. Moritz*, Patrick Ruther, Sara Goering, Alfred Stett, Tonio Ball, Wolfram Burgard, Eric H. Chudler, Rajesh P. N. Rao Abstract- Goal: To identify and overcome barriers to creating new Index Terms- Brain-Computer Interface, Brain-Machine neurotechnologies capable of restoring both motor and sensory Interface, Computational Neuroscience, Neuroengineering, function in individuals with neurological conditions. Methods: Neuroethics, Neurostimulation, Neuromodulation, This report builds upon the outcomes of a joint workshop between Neurotechnology the US National Science Foundation (NSF) and the German Research Foundation (DFG) on New Perspectives in I. INTRODUCTION Neuroengineering and Neurotechnology convened in Arlington, VA, November 13-14, 2014. Results: The participants identified Rapid advances in neuroscience, engineering, and computing key technological challenges for recording and manipulating neural activity, decoding and interpreting brain data in the are opening the door to radically new approaches to treating presence of plasticity, and early considerations of ethical and neurological and mental disorders and understanding brain social issues pertinent to the adoption of neurotechnologies. function. These new approaches are based on the ability to Conclusions: The envisaged progress in neuroengineering record and stimulate neural activity with increasing precision. requires tightly integrated hardware and signal processing efforts, This precision is leading to the rapid expansion of neural advances in understanding of physiological adaptations to closed- interfaces, devices that interact with the nervous system to loop interactions with neural devices, and an open dialog with stakeholders and potential end-users of neurotechnology. restore or enable sensory and/or motor function. Examples of Significance: The development of new neurotechnologies (e.g., bi- successful neural interfaces include cochlear implants for the directional brain-computer interfaces) could significantly improve deaf [1], retinal implants for the blind [2] and devices for deep the quality of life of people living with the effects of brain or brain stimulation (DBS) for Parkinson’s patients and spinal cord injury, or other neurodegenerative diseases. Focused individuals with essential tremor and other motor symptoms efforts aimed at overcoming the remaining barriers at the [3]. electrode tissue interface, developing implantable hardware with on-board computation, and refining stimulation methods to This report focuses on a type of neural interfaces termed precisely activate neural tissue will advance both our brain-computer interfaces (BCIs; also known as brain-machine understanding of brain function and our ability to treat currently interfaces (BMIs)). We use the term BCIs to describe devices intractable disorders of the nervous system. that interface directly with the brain via recording and/or stimulation hardware. The origins of BCIs can be traced back several decades to seminal experiments by Eberhard Fetz who Partial support for accommodations and travel for workshop used BCIs to study operant conditioning of single neurons in participants was provided by NSF grant no. 1441422 and EEC- 1028725, and the DFG grant no. EXC 1086. monkeys [4, 5] and Jose Delgado who pioneered neurostimulation techniques [6]. Shortly thereafter, Vidal Chet T. Moritz ([email protected]), Departments of Rehabilitation Medicine and Physiology & Biophysics, Center for Sensorimotor proposed the idea of non-invasive BCIs based on Neural Engineering (CSNE), and UW Institute for Neuroengineering, electroencephalography (EEG) [7]. The past two decades have University of Washington, Seattle, WA, USA, Patrick Ruther, seen a tremendous surge in BCI research [8, 9]. Department of Microsystems Engineering (IMTEK) and BrainLinks- BCIs are classified according to several factors including the BrainTools, University of Freiburg, Freiburg, Germany, Sara Goering, degree of invasiveness, and whether the BCI only records from Department of Philosophy, and Center for Sensorimotor Neural the brain, stimulates brain regions, or does both (“bi- Engineering, University of Washington, Seattle WA, USA, Alfred Stett, NMI Natural and Medical Sciences Institute at the University of directional” BCI). Invasive BCIs can record from neurons Tubingen, Reutlingen, Germany, Tonio Ball, BrainLinks-BrainTools, inside the brain, for example from the motor cortex using University of Freiburg, Freiburg, Germany, Wolfram Burgard, intracortical arrays of electrodes. Such BCIs have yielded the BrainLinks-BrainTools, University of Freiburg, Freiburg, Germany, highest information transfer rates and the best decoding Eric H. Chudler, Departments of Bioengineering and Anesthesiology performance to date, allowing human subjects to, for example, & Pain Medicine, and Center for Sensorimotor Neural Engineering, control robotic arm-and-gripper systems for self-feeding under University of Washington, Seattle, WA, USA, Rajesh P. N. Rao, Department of Computer Science and Engineering, and Center for laboratory conditions [10-12]. Noninvasive BCIs based on Sensorimotor Neural Engineering, University of Washington, Seattle, techniques such as EEG for recording from the scalp have WA, USA typically been used for controlling cursors or selecting items 0018-9294 (c) 2015 IEEE. Translations and content mining are permitted for academic research only. Personal use is also permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information. This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/TBME.2016.2543662, IEEE Transactions on Biomedical Engineering from a menu for communication purposes for completely function, and 4) bio-tolerability: the electrode-array should paralyzed patients. Such methods have been used effectively have the ability to reside in the brain for long periods of time. by people with extreme cases of amyotrophic lateral sclerosis All of these features are closely linked to the mechanical, (ALS; also known as Lou Gehrig’s disease). Advances in non- electrochemical, biochemical and metabolic interactions of the invasive BCIs were recently summarized in [13] and include hardware and biological materials at the electrode-tissue- control in up to three dimensions [14]. interface. The functionality and longevity of intracranial BCIs based on recording from the brain-surface using probes, including both intracortical microelectrode arrays and electrocorticography (ECoG) provide a middle-ground in ECoG electrode grids, are mostly affected by uncontrolled achieving higher signal-to-noise ratio than EEG and therefore events at the material-tissue interface and by a mismatch potentially higher accuracy in decoding; ECoG is typically between the properties of the biological and non-biological used for epilepsy diagnosis [15], but also provides the materials. Therefore, research efforts in materials science, opportunity for testing ECoG BCI techniques for controlling production technologies as well as immunobiology are clearly cursors [16], decoding individual finger movements [17], and justified. studying plasticity in the brain [18]. Despite these advances in Generally, after implantation, an ideal electrode array should BCI research, there are few examples where BCIs have made it establish a stable mechanical and electrical contact with the out of the laboratory to clinical devices for in-home use, tissue and should not provoke any host response. When a probe following the landmark successes of the cochlear implant and with metallic contacts is implanted, however, two responses deep brain stimulator. occur: an electrical double layer is set up at the Previous workshops on understanding brain function [19] metal/electrolyte interface and a foreign body response with an and interfacing engineering with life sciences and medicine activation of molecular and cellular cascades is triggered in the [20] have outlined ambitious plans of action in areas of brain adjacent tissue [22, 23]. In combination with the material and imaging and implanted neural interfaces such as customized geometry of the electrode, the double-layer determines the electronics, devices and models to influence and understand charge injection capacity and the impedance of the contacts, brain function, and alternative interfacing methods. The NSF- which are generally thought to be most relevant to stimulation DFG workshop focused on the challenges preventing the and sensing, respectively. In case of chronic stimulation, the successful development and translation of BCIs to clinically- electrochemistry at the interface, in conjunction with the relevant, ethically-justified, FDA-approved devices. In the charge transfer across the double-layer, may lead to corrosion, following sections, we review these challenges as identified electrode delamination, and tissue irritation which lower the and discussed by speakers and participants at the workshop. effect

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