Epileptic seizures, occasionally referred to as fits, is defined as a transient symptom of “abnormal excessive or synchronous neuronal activity in the brain”. The outward effect can be as dramatic as a wild thrashing movement (tonic-clonic seizure) or as mild as a brief loss of awareness (absence seizure). It can manifest as an alteration in mental state, tonic or clonic movements, convulsions, and various other psychic symptoms. Sometimes it is not accompanied by convulsions but a full body “slump”, where the person simply will lose control of their body and slump to the ground. The medical syndrome of recurrent, unprovoked seizures is termed epilepsy, but seizures can also occur in people who do not have epilepsy.

Tapping into the human brain to understand its functions in daily life — as well as its malfunctions in illness — has long been a challenge for researchers. Mapping brain activity requires unwieldy, invasive arrays of electrodes and sensors that can damage tissue while only reading activity in a limited area.

Implantable Brain Sensor Electrode Array

Implantable Brain Sensor Electrode Array capable of sampling large areas of the brain with minimal wiring

Jonathan Viventi, assistant professor at the Polytechnic Institute of New York University (NYU-Poly) and New York University (NYU), co-led a team of researchers to devise a streamlined, minimally invasive brain interface that may yield new insights into the causes of brain diseases like epilepsy, as well as usher in a new generation of implantable neuroprosthetic and diagnostic devices.

At the core of the research is a novel, implantable electrode array integrating ultrathin, flexible silicon transistors capable of sampling large areas of the brain with minimal wiring for Brain Testing Interface Sensors.

Current brain sensor technologies to record or stimulate brain activity are limited by the need to wire each individual sensor at the electrode-tissue interface. The resulting mass of leads is cumbersome and renders a high-resolution map of large areas logistically impossible.

This new approach enables dense arrays of thousands of multiplexed sensors that provide unprecedented spatial resolution — more than 400 times the current level — with a fraction of the wires. In experiments, just 39 wires were required for 360 electrodes. The design can be readily scaled to thousands of electrodes, while maintaining a small number of wires. The arrays are also non-penetrating and, unlike current techniques, cause little or no damage to fragile brain tissue. The use of flexible silicon also allows active circuitry to be built right at the brain surface.

In experiments, the research team deployed their system to record various types of brain activity in animals, including sleep and visual responses and observation of the brain during an epileptic seizure. Their techniques may improve understanding of what causes epilepsy and lead to implantable technologies to stop or prevent seizures in patients.

The researchers believe this is the first reported use of ultrathin, flexible silicon in a brain interface device. The research also holds promise for other medical applications, including dramatic improvements of existing implantable devices such as cardiac pacemakers and defibrillators, cochlear and retinal implants and motor prosthetic systems. The longer-term goal is to configure these implantable arrays for use anywhere in the body, equipped with wirelessly controlled sensors capable of multiple functions such as recording, stimulating and ablating.