Chronic Neural Recording Using Silicon-Substrate Microelectrode Arrays Implanted in Cerebral Cortex

Abstract

An important aspect of the development of cortical prostheses is the enhancement of suitable implantable microelectrode arrays for chronic neural recording. The objective of this study was to investigate the recording performance of silicon-substrate micromachined probes in terms of reliability and signal quality. These probes were found to consistently and reliably provide high-quality spike recordings over extended periods of time lasting up to 127 days. In a consecutive series of ten rodents involving 14 implanted probes, 13/14 (93%) of the devices remained functional throughout the assessment period. More than 90% of the probe sites consistently recorded spike activity with signal-to-noise ratios sufficient for amplitudes and waveform-based discrimination. Histological analysis of the tissue surrounding the probes generally indicated the development of a stable interface sufficient for sustained electrical contact. The results of this study demonstrate that these planar silicon probes are suitable for long-term recording in the cerebral cortex and provide an effective platform technology foundation for microscale intracortical neural interfaces for use in humans.

Using a Common Average Reference to Improve Cortical Neuron Recordings From Microelectrode Arrays

“…Twenty-one male Sprague-Dawley rats were implanted with 26 16-channel chronic silicon "Michigan" microelectrode arrays, using experimental procedures outlined previously (Ludwig et al 2006;Vetter et al 2004). Arrays consisted of four shanks, each with four evenly spaced iridium electrodes.…”

“…Typically either an additional microelectrode, or a large electrode such as a stainless-steel bone screw, or stripped wire, is placed in a location with minimal cortical activity and used as a reference to subtract out correlated sources of noise (Blanche et al 2005;Henze et al 2000;Ludwig et al 2006;Nelson et al 2008;Vetter et al 2004;Webster 1998;Williams et al 1999). Both microelectrode and large electrode references have their own specific advantages and disadvantages.…”

“…Because of the sheer size of the large electrode, the reference is typically placed on top of the dural surface, as opposed to implantation in cortical tissue (Ludwig et al 2006;Vetter et al 2004). By placing the reference in a location distal from the microelectrode sites, the difference between the voltage representation of correlated sources of noise at the reference and the microelectrode sites is increased (Horsch and Dhillon 2004;Webster 1998).…”

“…Although microelectrode ref-erences match recording sites on the array in terms of geometry and impedance, they have greater impedance than their large electrode counterparts and therefore "subtract in" more thermal noise to the recordings (Horsch and Dhillon 2004;Kovacs 1994;Ludwig et al 2006;Schmidt and Humphrey 1990;Shoham and Nagarajan 2003). This problem is exacerbated in chronic applications, where the microelectrode reference becomes encapsulated in fibrous tissue, further increasing its impedance (Hochberg et al 2006;Ludwig et al 2006;Nicolelis et al 2003;Otto et al 2006;Polikov et al 2005;Rennaker et al 2007;Seymour and Kipke 2007;Spataro et al 2005;Suner et al 2005;Szarowski et al 2003;Turner et al 1999;Vetter et al 2004).…”

The Development of Brain-Machine Interface Neuroprosthetic Devices

“…16 Silicon arrays may be configured as shanks, each with a number of recording sites along each shank. 17 To produce such an array, guided boron diffusion into a silicon wafer is performed to define the shape and thickness of the device. After this step, layers of insulating material, conductive interconnects, and additional surface insulation are applied.…”