An ergonomic rodent head fixation apparatus for closed-loop cursor control

Control of cursor on a PC monitor using a joystick is a common paradigm to elucidate the neural mechanisms of visuomotor skill learning and performance in human and non-human primates. However, this paradigm, even for reaching targets in one-dimensional space, has not been available for rodents yet. In this work, we present an ergonomic head fixation apparatus for Wistar rats to control a cursor on a PC monitor by operating two levers for acquiring stationary targets. All six axes of the apparatus, composed of V-slot aluminum profiles and 3D-printed parts, are easily adjustable according to the varying sizes of rats while allowing timely and consistent lever operations. The control of the apparatus and cursor are performed using MATLAB and Arduino. The goal of the rat in the present paradigm is to find out the correct lever which directs the cursor toward the target. In order to test the practicality of the system, we chronically implanted three rats with a head fixation bar and trained them to perform lever choice tasks to direct the cursor toward the target. Using the present system, all rats were enabled to reveal and continuously press the correct lever which moves the cursor toward the target. Our results indicate that the rats were able to detect the movements of the cursor toward the target based on the visual feedback provided. We believe the present head fixation apparatus can be used in studying the neural mechanisms underlying the closed-loop control of a cursor.