With the development of neuroscience, engineering and computing, the possibilities of interpreting brain activities and restoring functions for various disabilities seem endless.Extracellular recording of the cortical activity with electrophysiological signals provides complementary information about the neural activity.While passive recording provides useful data, active electrical microstimulation is required in further research and applications.Electrical microstimulation could serve as artificial input to the neural network or serve to modulate neural activity, particularly in the relief of Parkinsonian symptoms by deep brain stimulation (DBS) of subthalamic nucleus.We are developing a bi-directional neural interface system that combines recording and stimulation in one system.Microprobe with multiple channels can be designed with various geometrical shapes for placement in different locations, regions and layers in the brain.The recording hardware is composed of a recording headstage, which amplifies signals from the microprobe, a recording interface board is capable of further signal amplifying and filtering.A data acquisition card is connected to the system controller.The stimulation hardware contains a stimulation interface board, which generates micro current/voltage.A stimulation headstage is used to generate stimulation patterns by switching channels.The software of the system controller consists of graphical user interface (GUI), algorithms of signal processing and stimulation patterns generator.The channel capacity of this system can be expanded as needed.This makes recording high frequency neural activity possible.Spikes activity of individual neurons and local field potentials in the vicinity of the probe can be recorded.This recording technique is designed with the highest spatial resolution.The potential applications of this bidirectional system are broad.As a research tool, we will use it to provide stimulus to subthalamic nucleus and record the neural activities in any parts of the cerebro-basal ganglia-thalamus circuits.With this system, we can study the mechanism of deep brain stimulation (DBS) to further understand the motor behaviors of the cerebobasal ganglia-thalamus system under normal, pathological and neuromodulation conditions.