DRA, in collaboration with Wright State University Applied Research Center (WSARC), designed and developed a mock human brain encased in a model of a human skull. The skull cavity was then filled with a conductive fluid that emulated the electrical properties of brain tissue. The purpose of the model was to develop a method of measuring the electrical current induced in the brain when exposed to low levels of Pulsed Electromagnetic Frequency (PMEF) devices and to an electric voltage applied directly to the skull to study the effect of transcranial Direct-Current Stimulation (tDCS).
DRA developed a collapsible/expandable sensor head assembly that could be folded, inserted into an empty skull through an incision made at the base, then expanded to fill the entire brain cavity with equally spaced analog sensors. The sensor head assembly was comprised of a set of five encapsulated (moisture resistant) Printed Circuit Boards (PCBs) populated with equally spaced analog sensors that are interconnected to the main processing board using a compact flexible cable system. The PCBs contained within the skull brain cavity will only contain sensors. The supporting circuitry needed to power the sensors, collect the sampled electrical data (Interrogator and Data Packetizer) and send it to a host computer system for processing (USB Interface) were fabricated on a portion of the main board located outside the skull and away from the sensors. The spacing of the interrogator and power circuits from the sensors minimized the chance of electrical circuit noise from coupling into the sensitive analog circuitry. Isolating the power, interrogator and USB interface circuits outside the skull also provided the added benefit of not being part of the system that was encapsulated to protect it from fluids used to fill the brain cavity to emulate brain tissue. Easy access to the processing system for firmware updates was an added plus for this type of architecture.
When a PMEF field or tDCS voltage was applied the sensors in the brain cavity detected the ensuing electrical currents that were read out through the USB connector. The resulting data were input into a Matlab model that created a 3-D image of the induced currents.