Setup for combined freely moving Echem/Ephys experiments. The behavioral chamber (B) is located inside grounded Faraday cage (A). Headstage (D) is fixed on rat's head and connected through a rotating swivel (C) with the UEI potentiostat (E). The UEI is interfaced with breakout box (F) though front panel BNC connectors. The voltammetric part of the experiment is controlled by a PC (G) with NI cards that are connected to the breakout box. The electrophysiological signal is high-pass filtered (M) and sampled with NI card on the separate PC (H). The interface of the behavioral chamber components (levers, lights and tones, K) is controlled with Med Associates control module (L) that is connected to a third computer (not shown).
Block diagram of UEI potentiostat and headstage schematic. Left portion is the headstage that is connected via a DB-25 connector to the UEI chassis (right panel). The reference electrode (REF) is connected to ground. The output from the working electrode (WE) alternates between FSCV (Echem) and electrophysiology (Ephys) preamplifiers with the switch (SW1). Afterwards, signals are sent to a switching module where in Echem mode SW2 is used to connect the headstage to the Echem Amplifier. Switch SW3 grounds input to the Ephys amplifier and switch SW4 grounds the output from the Ephys amplifier to prevent overload. SW5 is used to ground the non-inverting input of the I/E converter when the system operates in Ephys mode. Headstage is connected to UEI via DB-25 cable.
Schematic circuitries for headstages with iontophoresis, analog background subtraction and multiple electrode recording. For the iontophoretic setup, an additional current source for drug ejection is added to the circuitry (A). For analog-background subtraction, an additional input through the gain resistor is added to the summing point of the amplifier (B). Recordings with multiple independent microelectrodes can be performed by using a separate amplifier for each microelectrode (C).
Photo of miniaturized headstage used for combined Echem/Ephys freely moving experiments adjacent to a U.S dime. The orange and yellow connecting wires are for reference and working electrodes. The copper connectors on the right are for bipolar stimulating electrode. One of the SO chips is the analog switch and the other is the op amps. The cable on the left of the printed circuit board leads to a DB-25 connector.
Circuitry for headstage used for combined Echem/Ephys freely moving experiments. The operational amplifiers, switch, resistors and capacitors are all on a single printed circuit board (Fig. 4). The outputs and inputs on the right hand side of the diagram are interfaced through a DB-25 connector.
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