Selective Electrical Interfaces with the Nervous System

Abstract

To achieve selective electrical interfacing to the neural system it is necessary to approach neuronal elements on a scale of micrometers. This necessitates microtechnology fabrication and introduces the interdisciplinary field of neurotechnology, lying at the juncture of neuroscience with microtechnology. The neuroelectronic interface occurs where the membrane of a cell soma or axon meets a metal microelectrode surface. The seal between these may be narrow or may be leaky. In the latter case the surrounding volume conductor becomes part of the interface. Electrode design for successful interfacing, either for stimulation or recording, requires good understanding of membrane phenomena, natural and evoked action potential generation, volume conduction, and electrode behavior. Penetrating multimicroelectrodes have been produced as one-, two-, and three-dimensional arrays, mainly in silicon, glass, and metal microtechnology. Cuff electrodes circumvent a nerve; their selectivity aims at fascicles more than at nerve fibers. Other types of electrodes are regenerating sieves and cone-ingrowth electrodes. The latter may play a role in brain-computer interfaces. Planar substrate-embedded electrode arrays with cultured neural cells on top are used to study the activity and plasticity of developing neural networks. They also serve as substrates for future so-called cultured probes.

Frequency-dependent signal transfer at the interface between electrogenic cells and nanocavity electrodes

“…Extracellular electrophysiological methods, on the other hand, yield weaker signals but allow long-term and multisite recordings of cellular networks due to reduced interference with cell viability. A well-established method for extracellular measurements relies on microelectrode arrays (MEAs) [3][4][5][6]. Fields of application for in vitro MEA systems include pharmacological highthroughput screening, cell-based biosensors, and research on information processing in neuronal networks [7][8][9][10][11][12][13].…”

Amplitude modulation based readout for very dense active microelectrode arrays

“…Two different values of the noise spectral density generated in the cell-electrode environment, corresponding to the expected most favorable and typical cases encountered during electrophysiological experiments, are taken into account. The most favorable and typical cases correspond to the cases where a large neural cell having a diameter of 20 µm and a typical neural cell size of 10 µm are considered, respectively [6]. The SNR value of the recorded signals is approximately equal to 35 dB and 25 dB for the most favorable and typical case, respectively.…”

Development of a Neural Interface for PNS Motor Control

“…The intention to perform an action is born in the cortex of the brain, is processed through multiple regions of the brain and spinal cord, and is transmitted along the axons of the PNS, finally arriving at the neuromuscular junction (NMJ) where it triggers the depolarization and contraction of the specific muscle cells required to perform the desired action. There is continual debate on where in this chain of transmission is the best location from which to derive a useful motor signal, and therefore, to target with a neural interface [8,20,22,[38][39][40].…”

“…Historically, neural interfaces have been designed with the intention of communicating directly with cortical tissue [41]. Most of these efforts use penetrating MEAs to record the depolarization of cell bodies [11,[20][21][22]. With these designs, electrodes located at the end of micron scale spikes are inserted directly into the CNS, such as in the primary motor cortex or spinal cord [12].…”