The “closed-loop” of the hybrid (neural-artificial) system takes the following path: (1) neural signals from multiple extracellular electrodes are amplified and filtered by analog hardware; (2) signals are digitized and processed by software, e. g., to detect action potentials or LFPs; (3) electrical stimulation hardware is triggered by detected events; and (4) stimuli are delivered to the neural tissue by the same (or different) electrodes (Figure 1). To adapt RACS hardware for use by freely moving animals, head-mounted components had to be light and sturdy enough for temporary attachment to a rodent's head.