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

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. 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. 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. The material properties of this coating were characterized, and packaging and insertion techniques were 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 and primate brains. Robust 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.