The Thomas RECORDING offers a novel wireless microstimulation system for deep brain stimulation (wDBS) tailored for rodents. In our paper published in Nature Parkinson’s Disease (npj) [1] we demonstrate the efficacy of this device for the restoration of behavioral impairments in hemiparkinsonian mice through unilateral wDBS of the subthalamic nucleus.

Our IMS is a standardized, wearable microstimulation system suitable for translational DBS research in freely moving animal models. Recognizing that DBS systems in human patients offer programmable options for key stimulation settings such as current amplitude, stimulation frequency, and pulse width, we integrated similar programmability into our wDBS microstimulation system.

The wDBS microstimulation system consists of the microstimulator, which can be connected to an implanted stimulation microelectrode (Fig. 7). This design provides flexibility in using various types of microelectrodes, differing for instance, in length, in combination with the microstimulator.

Additionally to the implantable microstimulator we offer our quartz-glass insulated platinum–tungsten fiber microelectrodes for stimulation (Fig. 7). The shaft of the microelectrodes is just 100 μm in diameter and carries a small tip, causing minimal tissue damage and allow a high spatial resolution and stimulation selectivity for the DBS process. To ensure the reproducibility of wDBS experiments, we have standardized the stimulation microelectrodes with respect to dimensions and electrical properties.

[1] A. Grotemeyer, T. Petschner, R. Peach, D. Hoehl, T. Knauer, U. Thomas, H. Endres, R. Blum, M. Sendtner, J. Volkmann, C.W. Ip, Standardized wireless deep brain stimulation system for mice, npj Parkinson’s Disease 10(1) (2024) 153.

DOI:  https://doi.org/10.1038/s41531-024-00767-2

Device description

For behavioral studies in rodents, methods are necessary allowing animals to move freely and to remain undisturbed over extended observation periods. Such methods for long-term stimulation are necessary so that they do not intervene with the study design by restricting free movements. Furthermore, despite that fact that functional outcomes are well-documented in animal models under DBS treatment, behavioral side effects which are needed to judge psychiatric side effects and other long-term behavioral effects of high-frequency stimulation still need more research. Thus, optimized stimulation methods are required to conduct such experiments. Several possibilities exist for such experimental stimulation setups in animal models. Here we introduce a fully implantable stimulator for rat and mouse models, which is freely programmable and has a battery running time of app. 30 days with DBS typical stimulating parameters. Pulses are delivered monophasic in constant-current mode. This device is specially designed for freely moving mice or rats in behavioral tests to assess behavior that could help to understand potential side effects of DBS in neurological diseases and explore the possibilities of electrical stimulation in models of psychiatric illness. The working principle of the TREC Implantable Microstimulator System (IMS) is shown in Figure 7. The IMS consists of a battery powered implantable microstimulator and an implantable stimulation microelectrode. The implanted microstimulator is reprogrammable via a programming interface.

Figure 7: TREC IMS principle. This figure shows the working principle of the TREC IMS. The electrode/stimulator connection and the programming interface connector must be embedded in cement!

We offer two sizes of the implantable microstimulator:

Figure 8: Implantable microstimulator with a battery capacity of Q=28mAh.

Figure 9: Implantable microstimulator with a battery capacity of Q=60mAh.

The basic structure of the implantable stimulation microelectrode is shown in Figure 10 (with external ground wire) and Figure 11 (with internal ground wire). The implantable microelectrode consists of a quartz glass insulated platinum/tungsten fiber with a conical tip (tip shape D). The tip is coated with iridium oxide to increase the charge transfer capacity of the electrode and to lower the electrode tissue impedance.

Figure 10: Implantable stimulation microelectrode.
1=Quartz glass insulated platinum/tungsten electrode fiber with iridium-oxide coated tip.
2=External ground wire.
3=Connection cable.
4=Connector.

Figure 11: Implantable stimulation microelectrode.
1=Quartz glass insulated platinum/tungsten electrode fiber with iridium-oxide coated tip.
2=Internal ground wire.
3=Connection cable.
4=Connector.

The stimulation microelectrode is a quartz glass insulated platinum/tungsten microelectrode fiber with an outer diameter of 100µm and a metal core diameter of 30µm. The fiber has an iridium oxide coated conical tip. Although the microelectrode has a very small tip dimension the electrode impedance is below 80kΩ.

Figure 12: Implantable stimulation microelectrode with internal reference contact does not require to implant a ground screw!

Figure 13: Implantable stimulation microelectrode with external ground wire requires a ground screw in the skull.