Compensation for cross-talk and high frequency attenuation of bipolar microelectrodes

Bipolar glass microelectrodes have a capacitance between the two recording channels and each channel has a capacitance to ground. These capacitances cause respectively cross-talk and high frequency attenuation. A new and general method for compensation of both distortions is developed. In this "inverse filter' method, the compensation circuit is derived from the equivalent circuit of the electrode. The method is applicable to all kinds of bi-and multipolar electrodes. The performance of the new method is compared with the existing "feedback' method (Freygang and Frank, 1959; Tomita, 1962) for glass microelectrodes. Detailed analysis shows that methods perform well for frequencies below 500 Hz, but the inverse filter method has good characteristics to at least 5 kHz. The poor high frequency behaviour of the feedback method is caused by preamplifier phase lag.