An implantable device for the acquisition and monitoring of brain bioelectric signals is described. The implantable device has a plurality of active electrodes configured to detect brain bioelectric signals, the active electrodes being arranged on a grid connected to an electronic module of the implantable device according to a predefined pattern. The active electrodes are connected to a microprocessor of the electronic module through respective paths formed on the grid and connected to at least one analog input unit arranged in the electronic module, the at least one analog input unit being in turn connected to at least one passive electrode and to the microprocessor through a data bus. The at least one analog input unit has an analog-to-digital converter for each active electrode connected thereto. A data acquisition and processing system, which includes the implantable device is also described.