Locked-in syndrome is a condition of complete paralysis of the musculature that can result from degenerative diseases such as ALS or from infarcts of the brain stem and which prevent any form of communication with the outside world, even if the sensory and cognitive functions are preserved. The current systems of brain-computer interface (neural interface) do not yet give satisfactory results.
ALS incidence in Europe is about 2/100000 per year; the prevalence is 6-8/100000. In Italy there are about 5000 ALS patients. Only a small percentage of these may reach the advanced stage (about 20% survives longer than 5 yr) and even less approach the CLIS condition.
However addressing communication in CLIS patients has a high social and emotional impact.
In addition, hands free and voice-less communication may be of interest for other application fields such as gaming, automotive, aerospace.
Several pathological conditions such as the amyotrophic lateral sclerosis (ALS) in the advanced stage, the brain stem stroke and certain types of poisoning may result in complete muscle paralysis, which deprives the patient of the possibility to communicate with the outside world (complete locked-in state – CLIS), even though sensory functions may be preserved.
This is a dramatic condition for the affected patients. Their thoughts may not be known but they are believed to undergo a rapid cognitive decline because of this condition. In spite of the big research and technological efforts in the field of brain-computer interfaces, the problem of re-establishing communication with CLIS patients is still open.
We here present an original approach whereby communication is achieved by voluntary controlling the pupil size.
Current Technology Limitations
Brain-computer interfaces have been developed based on different approaches and technologies, with different limitations:
- Invasive technologies (e.g. implanted electrode arrays): Invasive procedures, high cost, long training is necessary
- Electroencephalographic (EEG) signals: signals are very weak and noisy, specialized personnel needed, training is necessary.
- Brain near infrared spectroscopy: very expensive equipment, specialized personnel needed.
A first implementation of the present technology should be in the form of an add-on feature to existing eye-tracking-based AAC devices. In this way ALS patients will be already familiar with the device and may familiarize with the new communication mode before actually entering the complete locked-in state.
In parallel, the team is also developing a stand-alone processing unit based on the Raspberry PC-board, in order to implement the video recording and processing for detection of the pupil constriction.
Our Technology and Solution
The present solution is intrinsically simple: when voluntary switching the focus from a far to a near visual target the pupil undergoes a marked and robust constriction, which can be easily detected and used to establish a binary communication (e.g. to answer Yes/No to a given question).
On this basis Alternative and Augmentative Communication (AAC) devices can be devised in which the binary information may be used to drive more complex visual/audio interfaces, including spellers.
In particular the possibility to detect the pupil size may be implemented as an additional feature to existing AAC devices based on eye-tracking.
Different device arrangements are possible: 1) the pupil can be monitored by an eye-glasses-mounted micro camera or by a remote camera; the visual targets may be objects already present in the room (previously aligned with the gaze of the dominant eye); the pupil constriction detected by a processing unit may be used to operate a multiple selection over a displayed scanning interface or to vocalize a Yes/No answer.
No training is required: switching the focus from a far to a near target is an innate capability. This is a relevant aspect as these patients may fatigue very easily.
No specialized personnel is required: Caregivers are easily instructed to properly adjust the orientation of the camera.
No electrodes need to be attached to the skin (with associated risk of loosing proper contact in the long term).
The required technology is low-cost: mini camera, processing unit, display, loud speakers.
In order to achieve the first implementation of the solution we look for partners already active in the field of development and installation of AAC devices oriented in particular to ALS patients.
The development of a AAC device will allow to extend the clinical tests in a larger group of patients approaching the complete locked-in state, possibly through multi-center studies, also involving other research and clinical groups in Italy and abroad.
In addition, we aim to investigate possible application of this methodology in other more commercially-relevant areas such as gaming, automotive and aerospace whereby hands free and voiceless communicative possibility may be of interest