Theoretical analysis of intracortical microelectrode recordings

Abstract

Advanced fabrication techniques have now made it possible to produce microelectrode arrays for recording the electrical activity of a large number of neurons in the intact brain for both clinical and basic science applications. However, the long-term recording performance desired for these applications is hindered by a number of factors that lead to device failure or a poor signal-to-noise ratio (SNR). The goal of this study was to identify factors that can affect recording quality using theoretical analysis of intracortical microelectrode recordings of single-unit activity. Extracellular microelectrode recordings were simulated with a detailed multi-compartment cable model of a pyramidal neuron coupled to a finite element volume conductor head model containing an implanted recording microelectrode. Recording noise sources were also incorporated into the overall modeling infrastructure. The analyses of this study would be very difficult to perform experimentally; however, our model-based approach enabled a systematic investigation of the effects of a large number of variables on recording quality. Our results demonstrate that recording amplitude and noise are relatively independent of microelectrode size, but instead are primarily affected by the selected recording bandwidth, impedance of the electrode-tissue interface, and the density and firing rates of neurons surrounding the recording electrode. This study provides the theoretical groundwork that allows for the design of the microelectrode and recording electronics such that the SNR is maximized. Such advances could help enable the long-term functionality required for chronic neural recording applications.

Conducting polymer coated neural recording electrodes

“…The minimum impedance and SNR with impedance [48,49]. This should also result in a larger peak-to-peak amplitude [50], however measurement outside the stimulation period showed no correlation with impedance, and suggests that few spikes occurred during this time period.…”

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

“…Lempka et al modeled the effect of electrode size on signal amplitude and showed that site diameters ranging from 7.5 to 20 μm produced nearly identical amplitudes; however, large pyramidal cells were assumed as current dipoles 138 . The results may be very different when recording near apical dendrites or smaller cell types.…”

Impedance detection of the electrical resistivity of the wound tissue around deep brain stimulation electrodes permits registration of the encapsulation process in a rat model

“…Without a stimulating signal, the intensity of the reaction depends on the electrode material [38]. Adventitia formation is also influenced by the presence of the stimulating signal [41] likely because electrochemical reactions at the surface of stimulated electrodes alter their effective properties as "foreign bodies".…”

“…This stabilization process has been demonstrated to be perturbed by electrical stimulation in DBS [39] and intra-cochlear electrodes [37,40]. For an optimal adjustment of DBS signals, the kinetics of the resulting electrode-impedance changes by the adventitia formation must be taken into account [41].…”