Semi-automatic micro-drive system for positioning electrodes during electrophysiological recordings from rat brain

Piotr Dąbrowski(1), Ewa Kublik(2), Jakub Możaryn(1)
(1) Institute of Automatic Control and Robotics, Faculty of Mechatronics, Warsaw University of Technology, (2) Department of Neurophysiology, Nencki Institute of Experimental Biology

Electrophysiological recording of neuronal action potentials from behaving animals requires portable, precise and reliable devices for positioning of multiple microelectrodes in the brain. We propose a semi-automatic microdrive system for independent positioning of up to 8 electrodes (or tetrodes) in a rat (or larger animals). Device is intended to be used in chronic long term recording applications with freely moving animals. In such applications micro drives are used to move the electrodes vertically to achieve the best quality of a signal from isolated brain cells. Our design is based on independent stepper motors with lead screws which will offer single steps of ~10 µm semi-automatically controlled from the computer. . Micro-drive system prototype for 1 electrode was developed and tested. For experimental evaluation of proposed solution, magnetic linear and rotary encoders that provide information about electrode displacement and motor shaft movement were designed.
Because of the lack of the systematic test procedures dedicated to such applications, we propose the evaluation method similar to ISO norm for industrial robots. Repeatability, accuracy and backlash of the drive are estimated basing on results from measurements. According to the given assumptions and preliminary tests, the device should provide greater repeatability and positioning accuracy than hand-controlled manipulators, that are available on the market. Automatic positioning will also shorten the course of the experiment and improve the acquisition of signals from nerve cells. Presented solution is a prototype. Before the final micro drive system will be constructed, we plan to carry out experimental trials of the device during recording of electrophysiological signals in acute experiments.