A radio-telemetry system for navigation and recording neuronal activity in free-roaming rats

A radio-telemetry recording system is presented which is applied to stimulate specific brain areas and record neuronal activity in a free-roaming rat. The system consists of two major parts: stationary section and mobile section. The stationary section contains a laptop, a Micro Control Unit (MCU), an FM transmitter and a receiver. The mobile section is composed of the headstage and the backpack (which includes the mainboard, FM transmitter, and receiver), which can generate biphasic microcurrent pulses and simultaneously acquire neuronal activity. Prior to performing experiments, electrodes are implanted in the Ventral Posterolateral (VPL) thalamic nucleus, primary motor area (M1) and Medial Forebrain Bundle (MFB) of the rat. The stationary section modulates commands from the laptop for stimulation and demodulates signals for neuronal activity recording. The backpack is strapped on the back of the rat and executes commands from the stationary section, acquires neuronal activity, and transmits the neuronal activity singles of the waking rat to the stationary section. All components in the proposed system are commercially available and are fabricated from Surface Mount Devices (SMD) in order to reduce the size (25 mm × 15 mm × 2 mm) and weight (10 g with battery). During actual experiments, the backpack, which is powered by a rechargeable Lithium battery (4 g), can generate biphasic microcurrent pulse stimuli and can also record neuronal activity via the FM link with a maximum transmission rate of 1 kbps for more than one hour within a 200 m range in an open field or in a neighboring chamber. The test results show that the system is able to remotely navigate and control the rat without any prior training, and acquire neuronal activity with desirable features such as small size, low power consumption and high precision when compared with a commercial 4-channel bio-signal acquisition and processing system.