Ultra Dense EEG Network of Active Electrodes

The electroencephalogram (EEG), created in 1929 by the German psychiatrist Hans Berger, is used to record the electrical activity generated by the brain, which originates from the ion exchange between the intra and extracellular media. Signals taken by electrodes on the cranial surface, typically between 10μV and 100μV, are usually taken to the recording equipment for amplification and eventual processing, and subsequent analysis by researchers and medical staff.

However, the hospital environment is subject to electromagnetic interferences caused by electro-medical equipments, cell phones, radios and others. Those interferences can alter and even mask the EEG signals. Thus, to minimize these interferences, amplification, filtering and AD conversion circuits should be implemented in the form of an integrated circuit placed directly over the electrode, thus forming an active electrode.

At the same time, ultra-dense EEG networks require the installation of 256 or even 512 electrodes, which is impractical to manually/individually place the electrodes. Those networks are used to conduct temporal and spatial analyzes of the brain, as well as the mapping and studies of brain networks, and home-machine interface (including prosthesis activation). In addition, those networks can be used in association with other exams such as Functional Magnetic Resonance Imaging - fMRI, Transcranial Direct Current Stimulation - tDCS, Transcranial Magnetic Stimulation - TMS and Magnetoencephalography - MEG.

An EEG system of low susceptibility to electromagnetic interference is under development, compatible to ultra-dense networks of up to 512 electrodes. This integrated system will consist of:
  • Flexible cap that serves as physical support for all electrodes, previously positioned. The headgear shall support the power supply battery.
  • Integrated circuit responsible for amplification, filtering and AD conversion, to be positioned directly over the electrode, thus forming an active electrode.
  • Wireless interconnection between the active electrodes and a hub.

The integrated circuits of the active electrode and concentrator are under design in low voltage and low power CMOS technology.

ECG System with Dry Flexible Electrodes

Electrocardiogram (ECG) with Dry Flexible Electrodes.