Electrochemical Roughening and Carbon Nanotube Coating of Tetrodes for Chronic Single-Unit Recording

Abstract

Recording from single neurons in the brain for long periods of time has been a central goal in both basic neuroscience and translational neurology, in order to understand mechanisms underlying brain processes such as learning and to understand the pathogenesis of neurodynamic disease states 1 . Recent advances in materials engineering, digital signal acquisition, and analysis algorithms have brought us closer to achieving this goal, and the possibility has gathered much public attention 2,3 . However, it remains a challenge to record from the same units for weeks to months. Here, we record many high-quality tetrode neuronal signals reliably over long periods of time in both deep and superficial areas of the brain. We achieve this by combining electrochemical roughening and carbon nanotube coating of a flexible platinum/iridium substrate, with materials, packaging, and insertion optimized to minimize tip movement with brain pulsation. This "Magdeburger" probe enables recordings with long-term signal stability and high signal-to-noise ratio at a reasonable cost in both rodent brains and in substantially larger primate brains. Robust tetrode tracking of identified neurons over longer time periods, in multiple independently targeted areas of the brain, will allow fundamental advances in the study of cognitive learning, aging, and pathogenesis, and opens new possibilities for brain interfaces in humans.Currently, four main classes of electrodes are standard for chronic in vivo recordings of neural activity: microwire arrays, Utah arrays, silicon probes, and flexible thin polyimide-based electrodes 4 . These electrodes were designed to record from as many units (neurons) as possible-however, long-term stable recordings from tetrode-identified single units and juxtacellular recordings are rarely reported.Microwire arrays are made of insulated sharpened metals, packaged in brush-or comb-like arrays 5,6,7 . In selected cases, these electrodes demonstrate stable single unit recordings over months 6,7 . Recently, solidstate-based versions of such a thin-wire brush approach have been proposed 8,9,10 . The small diameter of

Electrochemical and Nanostructural Characterization of Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) Films as Coatings for Neural Electrodes

“…A preferred coating time of 60 s was established. To further test the performance of electrodes fabricated in this manner, a narrow CV scan was carried out to obtain capacitive data relevant to the recordings made when monitoring in vivo neuronal activity where the detected potential is usually tiny and within the range of −1.5 and +1.5 mV. , …”

“…To further test the performance of electrodes fabricated in this manner, a narrow CV scan was carried out to obtain capacitive data relevant to the recordings made when monitoring in vivo neuronal activity where the detected potential is usually tiny and within the range of −1.5 and +1.5 mV. 37,38 To ensure complete coverage of the full range of likely potentials to be encountered in vivo, a CV scan was carried out between −100 and + 100 mV versus SCE and tested with various scan rates of 25, 50, 100, and 200 mV s −1 for continuous five cycles. The resulting voltammograms are shown in Figure 6a, revealing capacitive behavior within this potential window with a nearly rectangle-shaped cyclic voltammogram without any discernible redox peaks.…”

Double Electrode Experiments Reveal the Processes Occurring at PEDOT-Coated Neural Electrode Arrays

“…The mechanical mismatch between the tetrode's body and the brain tissue can be mitigated by using more bendable materials, such as platinum−iridium instead of tungsten wires. 22 However, at the tetrode tip, the interface between the rigid electrode metal and the soft brain tissue remains biologically incompatible, limiting the ability to monitor neural activity over extended periods. 1,19 To maintain the benefits of controllable measurement, one solution is to coat the tetrode interface with a material that is soft, biocompatible, and conductive.…”