Adaptive Movable Neural Interfaces for Monitoring Single Neurons in the Brain

Abstract

Implantable microelectrodes that are currently used to monitor neuronal activity in the brain in vivo have serious limitations both in acute and chronic experiments. Movable microelectrodes that adapt their position in the brain to maximize the quality of neuronal recording have been suggested and tried as a potential solution to overcome the challenges with the current fixed implantable microelectrodes. While the results so far suggest that movable microelectrodes improve the quality and stability of neuronal recordings from the brain in vivo, the bulky nature of the technologies involved in making these movable microelectrodes limits the throughput (number of neurons that can be recorded from at any given time) of these implantable devices. Emerging technologies involving the use of microscale motors and electrodes promise to overcome this limitation. This review summarizes some of the most recent efforts in developing movable neural interfaces using microscale technologies that adapt their position in response to changes in the quality of the neuronal recordings. Key gaps in our understanding of the brain–electrode interface are highlighted. Emerging discoveries in these areas will lead to success in the development of a reliable and stable interface with single neurons that will impact basic neurophysiological studies and emerging cortical prosthetic technologies.

A system for recording neural activity chronically and simultaneously from multiple cortical and subcortical regions in nonhuman primates

“…In implants using the ChIME system, by contrast, a substantial proportion of the recorded activity was due to new unit activity, which continued to arise for several months. The most likely reason for this is that the electrodes were moved, as others have shown using short-term implants of small numbers of movable electrodes (Cham et al 2005;Muthuswamy et al 2011). We therefore assessed the effect of manipulating the depths of the implanted electrodes on the yield.…”

“…1). Improving upon the concept of the widely used (Pasupathy and Miller 2005) methods of Crist, Wurtz, and colleagues (Crist et al 1988;Nichols et al 1998) for acute, single-electrode recordings, the ChIME microdrives employ a novel mechanism that maximizes the density of independently movable electrodes. The grid can be inserted into a plastic chamber fixed to the skull to deliver electrodes to the underlying brain.…”

“…We defined the yield in each recording session as the fraction of electrodes that recorded single-unit activity Muthuswamy et al 2011;Ward et al 2009). The average yield over all sessions was 31% (mean yield, Table 1), but the yield varied from implant to implant, ranging from 18 to 65%.…”

“…A pair of stainless steel pins on the bottom of the microdrive frame fit into grid holes and was used to secure the microdrive to the grid inside the chamber rigidly. Unlike conventional screw-based microdrive designs (Nichols et al 1998), no additional pins were used above the surface of the grid to fix each microdrive in place. This novel design reduced the size of the footprint of the microdrive on the grid, thereby increasing the density of the recording tracks.…”

State-of-the-art MEMS and microsystem tools for brain research

“…Important components of the adverse response have been studied, including insertion trauma [87][88][89] , the intrinsic foreign body response 90,91 , and straininduced damage from mechanical mismatch [92][93][94] . Long-term reliability is clearly more of a challenge in clinical applications than for neuroscience; nonetheless, tools for brain mapping should be designed to minimize disruption to the circuits being investigated.…”