Researchers have developed a non-invasive brain-computer interface (BCI) for completely locked-in patients. This is the first time that these patients, with complete motor paralysis but an intact cognitive state, have been able to reliably communicate. A completely locked-in state involves the loss of all motor control, including that of the eye muscles, and until now some researchers suspected that such patients were unable to communicate.
The study, published in PLoS Biology, detailed the researchers’ efforts in developing a non-invasive method to allow four completely locked-in patients to answer “yes or no” questions. The technique involves patients wearing a cap that uses infrared light to measure blood flow in different areas of the brain when they think about responding “yes” or “no” to a question. The researchers trained the patients by asking them control test questions to make sure the system could accurately record their answers, before asking questions about their current lives.
Brain-computer interfaces involving implantable electrodes have previously been successfully used in patients with less severe forms of locked-in paralysis. However, these methods involved direct implantation of electrodes in the brain. The current method is non- invasive, along with being the first approach that has reliably worked for patients who are completely locked-in.
Medgadget asked lead author on the research, Dr. Ujwal Chaudhary of the University of Tübingen in Germany, some questions about the development and the next steps for the technique.
Conn Hastings, Medgadget: Previous studies have demonstrated successful brain-computer interfaces for patients with less severe forms of paralysis (such as this one). Why hasn’t it been possible to communicate with completely locked-in patients to date?
Ujwal Chaudhary, University of Tübingen: In a meta-analysis of the scientific literature of all ALS patients in CLIS, it was found that none of the existing techniques such as the P300 event-related brain potential (ERP), slow cortical potential (SCP), frequency analyses of various frequency bands of the EEG, and invasive ECoG (electrocorticogram) recordings allowed reliable and meaningful communication using a brain-computer interface (BCI). All the BCI-procedures mentioned above are based on effortful and explicit (conscious) voluntary control of a neuroelectric brain response such as learning with feedback and reward. Using such techniques patients learned to increase or decrease amplitudes of the SCP to produce event–related desynchronization (ERD) of the central alpha-rhythm to focus attention on a visually or auditorily presented sequence of letters in order to select a desired letter with the brain response. P300 is also used in a similar manner to visually select a desired letter. The required activation of explicit-voluntary (controlled) attention in these BCI-tasks means that none of them resulted in stable learning of brain-based communication. This prompted us to propose the theoretical psychophysiological notion of “extinction of goal directed cognition and thought” in complete paralysis with otherwise intact cognitive processing.
Medgadget: Prior to this study some researchers had theorized that completely locked-in patients were incapable of communication. Was it a shock when the first patient began communicating?
Ujwal Chaudhary: The extinction of goal directed thinking was certainly highly speculative in light of the complete lack of data about cognition and inner speech and motivational processing in CLIS.
When the patients began to communicate, it meant they were coming out of silence and we were unlocking the completely locked-in. The families were ecstatic. It was an overwhelming feeling of joy and happiness.
Medgadget: In simple terms, how does the technology work? How does it compare with other methods to achieve a brain-computer interface?
Ujwal Chaudhary: Functional near infrared spectroscopy (fNIRS) is a non-invasive neuro imaging modality which uses near infrared light to provide information on metabolic activity in the cortical region of the brain under investigation. In our study, fNIRS was used to measure and classify fronto-central cortical region oxygenation and deoxygenation following the “yes” and “no” thinking of CLIS patients in response to true or false questions, respectively. The “yes” and “no” signal was then used to build a model of their answer, which later on was used to predict their answers in real-time.
Medgadget: Was it difficult for the patients to master the technique and how much training was required?
Ujwal Chaudhary: The training required to use this system is very subjective and varies from one patient to another.
Medgadget: On the face of it, a completely locked-in state sounds like it would cause a significant decline in quality of life. However, all four patients indicated that they were happy. Is this something you intend to investigate further?
Ujwal Chaudhary: From past psychological assessments and other BCIs that are applicable in locked-in states we already knew that before entering CLIS these patients mostly reported good quality of life. When we started our study, we started with an open mind to get a glimpse of their thought process, so when these patients reported good quality of life using our BCI it confirmed our thinking and efforts that it is worth developing BCIs for communication in these kinds of patients. Yes, we plan to continue with our study and investigation.
Medgadget: What are the next steps for the technology? Are there any plans to develop the system to allow for more pro-active communication, so that patients can communicate at will and not just as a simple response to questions?
Ujwal Chaudhary: Our goal is to first develop the current system in such a way that it can be used by patients’ family members for daily communication and work towards a system through which the patients can formulate sentences in real-time.
Study in PLoS Biology: Brain–Computer Interface–Based Communication in the Completely Locked-In State…
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