closed-loop stimulation

Closing the loop
for neurotechnology

Conditions such as pain and stress do not only reside in people’s minds. They manifest themselves through physiological signals. Using wearable technologies, we can leverage these signals not only to make people aware but also to improve treatments by adequate neural stimulation.
Technology explained

An electroencephalography, or EEG, no longer needs to be a complicated affair of patches and wires. Imec at Holst Centre has developed a number of EEG headset prototypes that combine user comfort with low-power technology, which opens doors to new therapeutic possibilities. This platform ensures excellent signal properties, because it uses the in-house developed DAE (digital active electrode) technology – where each dry EEG electrode is accompanied by an integrated circuit that immediately digitises the signal.

The DAE concept enables us to make a modular and expandable system that facilitates not only capturing electrical activity of the brain but also blood oxygenation level-dependent (BOLD) using optical sensors. This was demonstrated convincingly with the EU-funded ASTONISH project, where a multimodal brain-monitoring platform was developed that combines EEG and functional near-infrared spectroscopy (fNIRS).

From sensing to stimulation

Being able to monitor brain activity with a smart and compact device enables the assessment of a relevant mental state and its evolution; hence it opens the door for altering or modulating this state. As a result, closed-loop monitoring and actuation systems can be designed to actively stimulate specific neural tissue to target undesirable conditions, such as pain and stress.

Imec at Holst Centre is working on a flexible framework for vagus nerve stimulation in a closed-loop framework that combines wearable sensors for physiological monitoring and implantable or non-invasive stimulation modules. Given the role of the vagus nerve in the body, such a closed loop can be used to ensure the body maintains the homeostatic state. Signals acquired by the EEG headset and a wearable device, such as a wristband, can be interpreted by complex algorithms to sense the condition of a person. When it detects pain or discomfort the system triggers the stimulation through low-power implanted stimulation nodes. This closed-loop platform offers endless possibilities in the drug-free treatment of a wide variety of conditions, from epilepsy and depression to Parkinson’s disease and other movement disorders.

Societal benefits

Through improvements in neuroscience technology, imec at Holst Centre is developing platforms for wearable brain monitoring and closed-loop stimulation devices that are affordable, convenient and relevant for clinical applications.

Whilst still in the prototype phase, these platforms are a major step towards personalised medicine and offer great potential for proactive stress management, drug-free pain treatment for a wide variety of chronic conditions.