Miniature carrier with six independently moveable electrodes for recordingof multiple single-units in the cerebellar cortex of awake rats

Ensemble recording in cerebellar cortex of awake rats presents unique metho dological challenges not encountered when recording from the cerebral corte x or from deep brain structures with more homogeneous cell populations. Com pared to the cerebral cortex, removal of dura over the cerebellum evokes pr onounced swelling, and insertion of multiple closely spaced electrodes in t he cerebellar cortex causes considerable dimpling (Welsh JP, Schwartz C. Mu ltielectrode recording from the cerebellum. In: Nicolelis MAL, editor. Meth ods for Neural Ensemble Recordings, CRC Methods in Neuroscience Series. Boc a Raton, FL: CRC Press LLC, 1999, pp. 79-100). Also, a repetitious and well -defined neural circuit characterizes the cerebellar cortex across its enti re surface. With conventional multi-electrode methods, such as chronically implanted bundles or arrays of microwires, the risk of disrupting the cereb ellar cytoarchitecture is high. In most conventional multi-electrode system s, electrodes have rather low impedance and cannot be moved independently a fter implantation. These limitations make proper unit isolation, necessary to identify each of the recorded cerebellar units, very difficult. We desig ned a lightweight (14 g), miniature (base plate: 19 x 23 mm; total height: 16 mm) multi-electrode system to allow for the chronic implantation of six independently moveable sharp electrodes with high impedance, in the cerebel lar cortex. The six electrodes are arranged in a 2 x 3 matrix (inter-electr ode distance: 0.6 mm). At any time after the implantation the vertical posi tion of each individual electrode can be adjusted by screwing spring-loaded electrode heads up or down. The system preserves the integrity of the cere bellar cytoarchitecture, and enables easy isolation and identification of i ndividual cerebellar units in awake, freely moving rats. (C) 1999 Elsevier Science B.V. All rights reserved.