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

Abstract

An animal model of deep brain stimulation (DBS) was used in in vivo studies of the encapsulation process of custom-made platinum/iridium microelectrodes in the subthalamic nucleus of hemiparkinsonian rats via electrical impedance spectroscopy. Two electrode types with 100-µm bared tips were used: i) a unipolar electrode with a 200-µm diameter and a subcutaneous gold wire counter electrode and ii) a bipolar electrode with two parallelshifted 125-µm wires. Miniaturized current-controlled pulse generators (130 Hz, 200 µA, 60 µs) enabled chronic DBS of the freely moving animals. A phenomenological electrical model enabled recalculation of the resistivity of the wound tissue around the electrodes from daily in vivo recordings of the electrode impedance over two weeks. In contrast to the commonly used 1 kHz impedance, the resistivity is independent of frequency, electrode properties, and current density. It represents the ionic DC properties of the tissue. Significant resistivity changes were detected with a characteristic decrease at approximately the 2nd day after implantation. The maximum resistivity was reached before electrical stimulation was initiated on the 8th day, which resulted in a decrease in resistivity. Compared with the unipolar electrodes, the bipolar electrodes exhibited an increased sensitivity for the tissue resistivity.

Deep Brain Stimulation of Hemiparkinsonian Rats with Unipolar and Bipolar Electrodes for up to 6 Weeks: Behavioral Testing of Freely Moving Animals

“…One possible reason for these differences may be the development of an insensitivity toward DBS, reflecting changes in the basal ganglia network [ 22 ]. In addition, readjustment of the stimulation parameters may be necessary in chronic DBS, as is common in clinical practice, to compensate for the increasing impedance caused by the development of adventitia tissue at the electrode-tissue interface [ 69 ].…”

Polarization Effect of MoO3 Increases the Thermoelectric Properties Based on the PbS Quantum-Dots Doped P3HT Devices

“…Usually, the C–F curve is divided into a low-frequency area and a high-frequency area according to the frequency range . Since the interface charges of the material respond to the low-frequency AC signal, the capacitance signal in the low-frequency area reflects the interfacial information on the device, and the capacitance signal in the high-frequency area reflects the material internal information …”

Development of a miniature device for emerging deep brain stimulation paradigms

“…To accomplish this, the device was connected to a variety of resistive loads ranging from 10 to 20 kΩ. These values were selected as they imitate the range of resistance values found by Ewing, Porr [36] and Badstuebner, Stubbe [37] when testing the impedance of small animal DBS electrodes. For any DBS experiment to be successful, the device must output the expected stimulation despite changes in the electrode or brain impedance.…”