Continuous monitoring of electrical brain activity with implanted depth electrodes is essential for understanding the neural substrates of many physiological and pathological brain functions. Such recordings are extremely difficult in freely moving experimental animals, particularly in small rodents. The wires attached to the implanted electrodes can restrain and interfere with the natural behavior of the animal. Consequently it has been impossible, up until now, to correlate truly normal behavior with neuronal activity.;This dissertation described the design, fabrication, and use of an inductively powered, novel, integrated circuit (IC) to measure, amplify, modulate, and transmit electrophysiological activity to a receiver located far from the subject, where the data is processed in real-time. A large external coil, surrounding the animal environment, generates a magnetic field sufficient to drive the miniature transceiver implanted in the test-subject. An IC, designed and fabricated in a 0.35-mum-CMOS analog-IC foundry process, amplifies, modulates, and transmits, neural signals from within the skull to a remote receiver located outside the environment of the animal. The modulated, and transmitted, neural signal is picked up by an off-the-shelf receiver controlled by novel data acquisition software. In addition to controlling the hardware, the program obtains, filters and displays the neural data in real-time. The inductive powering circuitry, together with the implantable transceiver, and data acquisition hardware and software, make up the complete neural recording system. The device is implanted in vivo and used to record neural signals from the hippocampus of un-tethered rats.
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