Headfixed Configurations Basic Configuration Main Control Unit (MCU) Environmental Control Unit (ECU) Horizontal Headstage 128 Channel without Processor (HH128 np) Stimulation Main Control Unit (MCU) Environmental Control Unit (ECU) 32-Channel Electrode Interface Board (EIB) 32 Channel Stimulation Headstage (UH32stim) Stim Capable Headstage Combiner Unit (SHCU) 2stim Adapter