Preamplifiers

Plexon's new line of PBX3 (complete preamp boxes including power/control boards) and PRA3 (component 16-ch boards) preamplifiers deliver improved signal-to-noise, common-mode rejection, and jumperable analog low-cut filter selection. The new preamplifiers, while they look similar to the older PBX/PRA and PBX2/PRA2 designs, have been completely redesigned for improved performance.

Each preamplifier box can accomodate up to four 16-channel preamp boards to process spike, field potential, wide band signals from depth electrodes in the brain or periferal neurvous system, or EMG signals.

The following is a PBX3 preamplifier box with 16 spike (top board) and 16 LFP (bottom board) channels.

Signal processing:

Plexon preamplifier boards come in three main varieties:

• Spike boards, for isolating the spike action potential signals
• Field potential boards, for isolating the low-frequency field potential signals, and
• Wide-band boards

The most common configuration of Plexon preamp boards when used in conjuntion with the MAP system is to combine spike, lfp, and/or wide-band boards in one preamplifier box, with electrode signals routed into multiple boards via jumpers. For RECORDER systems, the most common configuration are preamps with wide-band boards.

Filter settings:

Although customizable at the time of order, the standard filter and bandpass settings are listed below.

Gain:

Depending on the gain in the headstage (typically 1x or 20x), the preamp will be configured such that the overall fixed gain is 1000x (e.g. 1x in headstage and 1000x in preamp, or 20x in headstage and 50x in preamp).

Additional features:

• Analog Programmable Referencing

Plexon PBX3 and PRA3 preamplifiers have excellent common mode rejection capability of both fixed reference electrodes and up to five recording electrodes selected within software to be used as reference electrodes. The programmable referencing feature on the PRA and PBX 3 boards are selected within the REF2 program within the RASPUTIN suite of control programs for the MAP system.

Analog Programmable Referencing is a particularly valueable feature for recordings from freely moving animals. Artifacts caused by sudden movements, chewing, grooming, etc., can be effectively eliminated by selecting a recording electrode with artifacts (but no spike signals) to be the reference electrode for a subset of other electrodes nearby. In this way, the common artifact signal on both the reference and recording electrode is removed in analog circuitry before A/D conversion.

• Power board

Each PBX3 preamplifier has a power board located at the very top position of the box. By default the the power board provides +/- 2.5V power to the headstage amplifiers, although a modification to the board will increase the voltage to +/- 5.0V. All plexon headstages will operate with +/- 2.5V power. It is important that the power supplied to the headstage does not exceed the headstage maximum power.

Colored LEDs extend out of the power board at the top of the input-side of the preamplifier box. Red LEDs indicate a +/- 5.0V power supply. Green LEDs indicate a +/- 2.5V power supply.