A multi-channel, implantable microdrive system for use with sharp, ultra-fine "Reitboeck" microelectrodes

Arrays of closely spaced quartz-insulated, platinum-tungsten microelectrodes are widely used to obtain acute recordings from chronically prepared subjects. These electrodes have excellent recording characteristics and can be fabricated to a wide variety of tip specifications. Typically, in such experiments, electrodes are introduced into, and removed from, the brain on a daily basis and, over many months of study, hundreds of penetrations may be made through an intact dura. This procedure has benefits as well as problems and risks. For some experimental aims, it might be desirable to leave the microelectrodes within the brain so that the penetrations could be continued on subsequent days. This would allow a more thorough and systematic exploration of the neurons that lie along the trajectory of each of the closely aligned electrodes and would minimize risks and preparation time associated with daily electrode insertions. Here we present a means for achieving this aim using arrays of sharp, flexible Reitboeck electrodes of extremely fine diameter (40-microm shaft diameter, pulled and ground to a fine tip). We show that these electrodes retain their excellent recording characteristics and can remain under microdrive control within the brain for periods of many months and, in one remarkable case, for >4 years.