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Review
, 27 (6), 453-471

Implantable Neural Probes for Brain-Machine Interfaces - Current Developments and Future Prospects

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Review

Implantable Neural Probes for Brain-Machine Interfaces - Current Developments and Future Prospects

Jong-Ryul Choi et al. Exp Neurobiol.

Abstract

A Brain-Machine interface (BMI) allows for direct communication between the brain and machines. Neural probes for recording neural signals are among the essential components of a BMI system. In this report, we review research regarding implantable neural probes and their applications to BMIs. We first discuss conventional neural probes such as the tetrode, Utah array, Michigan probe, and electroencephalography (ECoG), following which we cover advancements in next-generation neural probes. These next-generation probes are associated with improvements in electrical properties, mechanical durability, biocompatibility, and offer a high degree of freedom in practical settings. Specifically, we focus on three key topics: (1) novel implantable neural probes that decrease the level of invasiveness without sacrificing performance, (2) multi-modal neural probes that measure both electrical and optical signals, (3) and neural probes developed using advanced materials. Because safety and precision are critical for practical applications of BMI systems, future studies should aim to enhance these properties when developing next-generation neural probes.

Keywords: Brain-machine interface; Implantable neural probes; Multi-channel electrodes; Neural probes with advanced materials.

Figures

Fig. 1
Fig. 1. A schematic of a bidirectional brain-machine interface. As the figure illustrated, the system of brain-machine interface consists of three components. First one is the system that acquires neural signal, for example, neural recording systems with a neural probe. Second one is decoding component to translate neural activities into machine operational languages. Third one is encoding component that analyze feedback data from sensors and stimulate the specific regions in the brain. A fundamental concept in the bidirectional interface is referred to [8] with a permission of Frontiers Media S.A. under the terms of the Creative Commons Attribution License (CC BY).
Fig. 2
Fig. 2. (A) A schematic to represent detectable areas of neural activities by a tetrode. By improved clustering and spike sorting methods, the tetrode can detect neural activities in areas of neural assembles with 280 µm diameters. The reprint of this figure in [26] was permitted by Nature Publishing Group (Springer Nature). (B) A schematic of an experimental setup to study the control of a robot by neural signals recorded by multiple tetrodes, which were implanted in the cortex of the rat. This figure published in [34] is reprinted with a permission of Society for Neuroscience.
Fig. 3
Fig. 3. (A) A figure of implanted two 96-channel Utah arrays on a motor and posterior cortex of a non-human primate to record neural signals for an investigation of a brain-machine interfacing platform under approve of Institutional Animal Care and Use Committee at Daegu-Gyeongbuk Medical Innovation Foundation, Korea. (B) A schematic of a brain-spine interface to produce the signal of the spinal cord for walking based on neural activities of the motor cortex. To be specific, neural activities of the motor cortex were recorded by a 96-channel Utah array and decoded information from the acquired neural activities was transmitted to an electrical pulse generator inserted in the spine. The pulse generator produced electrical stimulations for walking of a spine-injured non-human primate. The re-use of this figure published in [41] was permitted by Nature Publishing Group (Springer Nature). (C) Experimental procedures, a technological setup, and a map of implanted Utah and floating electrode arrays for generating contacting senses in an artificial hand with targeted neuro-stimulations in the somatosensory cortex. This figure in [42] is re-used with a permission of National Academy of Sciences. (D) A schematic of a paralyzed patient assistant platform based on on-site available neural cursor adjustments from neural signals, which were measured by implanted Utah array. A right figure illustrates radial-8 cursor trajectories of three participants (S3, T6, and T7). The re-use of this figure published in [47] was approved by Nature Publishing Group (Springer Nature).
Fig. 4
Fig. 4. A theoretical model of a neural interfacing system to recover neural functions after brain injuries by neuro-prosthetic treatments. A schematic of a preclinical test with an implanted Michigan probe was shown. The plot in the lower right corner shows transient neural signals and artifact due to an electrical stimulation from the premotor cortex. The reprint published in [60] was approved by National Academy of Sciences.
Fig. 5
Fig. 5. (A) A flex-rigid 124-channel ECoG electrode array to measure neural activities. This neural probe was manufactured with advanced and high-resolution microscale fabrication techniques. This figure in [75] is reprinted with a permission of MDPI, Basel, Switzerland under the terms and conditions of the Creative Commons Attribution License. (B) Implant procedures, in vivo insertion and single-unit neural recording of an injectable neural probe. The re-use of this figure published in [81] was approved by Nature Publishing Group (Springer Nature). (C) A stent electrode array (middle) with 8 electrodes to acquire neural signals in the brain vessel and pre- and post-implant images in a delivery of the stent electrode array by X-ray venography. This figure published in [90] is reprinted with a permission of Nature Publishing Group (Springer Nature). (D) An implantable wireless implantable recording and stimulating probe for bidirectional BMI instruments. The reprint of this figure in [96] was permitted by MDPI, Basel, Switzerland under the terms and conditions of the Creative Commons Attribution License.
Fig. 6
Fig. 6. (A) A multimodal microprobe with optical and electrical measurements of neural activities. The multimodal probe consisted of a dual-core optical fiber, which excited fluorescent indicators and collected emitted signals, and an electrical wire to record electrical activities in neurons. This figure in [123] is reprinted with a permission of Nature Publishing Group (Springer Nature). (B) A schematic of an optetrode, which consisted of a single optical fiber with 200 µm core diameters for optogenetic stimulations and a tetrode to record neural activities and changes when the optical stimulation occurs. The re-use of this figure published in [124] was approved by Nature Publishing Group (Springer Nature).
Fig. 7
Fig. 7. (A) Carbon nanotubes coated microelectrode arrays to improve electrical property in recording neural activities. Left plots illustrates local field potential and power spectral density with frequencies in ranging from 1 to 300 Hz comparing microelectrodes coated with carbon nanotube to ones without coating. The reprint of this figure in [142] was permitted by Nature Publishing Group (Springer Nature). (B) A schematic of in vivo experimental setup in a study recording neural activities and electrochemical changes during photo-thrombosis. The neural probes used in this setup consist of graphene-oxide and gold-oxide combined electrodes. The figure published in [149] is reprinted with a permission of American Chemical Society.

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