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Invasive and non-invasive neurotechnologies

The most fundamental difference between neurotechnologies for the purpose of this report is between invasive and non-invasive devices:

  • Invasive (implantable) neurotechnologies are surgically implanted to directly contact the brain and provide the most accurate and detailed information on a person’s brain patterns. They risk invasive surgery and long-term scarring, that may reduce device effectiveness.7 Continued access to laboratory conditions is also required, further limiting their uses on the near horizon.
  • Semi-invasive neurotechnologies focus on epidural or subdural placement near the cortex. This reduces, although does not eliminate surgical risks, as surgery to open the skull is still required. An example of an exception to this is Synchron’s stentrode which is threaded through the jugular vein to the brain. The area of minimally invasive technology is one of dynamic growth and will likely see many new developments in the intermediate future.
  • Non-invasive (wearable) neurotechnologies are placed on or outside the body, such as through a patch or headband device. They can gather both non-medical and medical data across a variety of sectors. There is often less risk associated than with surgery through the skull or spine and relatively lower equipment costs. Due to this, it’s anticipated this form of neurotechnology will be the most prominent in increased market deployment in the near term. However, it is also possible that that data gathered through these devices will be less detailed than that gathered by invasive devices, allowing fewer complex inferences.

Read and write neurotechnologies

The distinction between non-invasive and invasive neurotechnologies is an important one, both technically and medically. However, it is also critical to note that so-called ‘non-invasive’ devices can still interact in quite intimate ways in the brain. Another way to distinguish between devices is through their capabilities to record and analyse neurodata received and those that stimulate or modulate neuropatterns. Essentially, we can consider both invasive and non-invasive technologies under the following divisions:

  • Read devices such as a medical fMRI scanner, designed to image the brain activation patterns or electroencephalography (EEG) which can detect electrical activity of the brain.
  • Read-write devices such as headsets designed to assist with mental health. We can further split the write aspect of these devices; neuromodulation and neurostimulation. Neuromodulation relates to processes seeking longer-term change in brain activity, such as with the treatment of a neurodegenerative condition. Neurostimulation aims to provide a shorter-term effect.

The ability to modulate brain activity can apply to both invasive and non-invasive technologies and may significantly increase the risk of processing personal information, which we will consider in this report.

Additional definitions

There are a variety of ways to differentiate neurotechnologies that may influence the way data can be processed and the level of involvement given to a person using a technology. Active devices require a deliberate task or stimulus to generate a neural response, such as finger movement, mental arithmetic or music imagery. Reactive devices require an external cue to record a specific response, such as music, imagery, pain or even a question. Passive devices record subconscious, unprompted and more generalised responses from a person, such as fatigue levels, attention span or arousal.

Synchronous and asynchronous devices are also different; synchronous devices read on a predefined schedule while asynchronous devices allow the users of a device to interact and communicate. Linked to this definition are closed loop and open loop systems. Closed loop neurotechnologies operate on an autonomous basis, reacting or inputting on the strength of their programming and algorithmic processing. Open loop systems are ‘open’ in the sense that the people wearing or implanted with the device can choose when to make an intervention of action via a device.

See examples of technologies deploying these various approaches in Annex D.

7 Although this issue will reduce with improved miniaturisation.