Brain-computer interfaces (BCIs) are one of the few alternatives to enable locked-in syndrome (LIS) patients to communicate with the external world, while they are the only solution for complete locked-in syndrome (CLIS) patients, who lost the ability to control eye movements. However, successful usage of endogenous electroencephalogram(EEG)-based BCI applications is often not trivial, due to EEG variations between and within sessions and long user training required. In this work we suggest an approach to deal with this two main limitations of EEG-BCIs by inserting a progressive and expandable neurofeedback training program, able to continuously tailor the classifier to the specific user, into a multimodal BCI paradigm. We propose indeed the integration of EEG with a non-brain signal: the pupillary accommodative response (PAR). The PAR is a change in pupil size associated with gaze shifts from far to close targets; it is not governed by the somatic nervous system and is thus potentially preserved after the evolution from LIS to CLIS, which often occurs in neurodegenerative diseases, such as amyotrophic lateral sclerosis. Multimodal BCIs have been broadly investigated in literature, due to their ability to yield better overall control performances, but this would be the first attempt combining EEG and PAR. In the context of the BciPar4Sla, we are exploiting these two signals, with the aim of developing a more reliable BCI, adaptive to the extent of evolving together with the user's ability to elicit the brain phenomena needed for optimal control, and providing support even in the transition from LIS to CLIS.

翻译：脑机接口是为闭锁综合征患者提供与外界交流的少数替代方案之一，同时也是完全闭锁综合征患者的唯一解决方案——这类患者已丧失控制眼球运动的能力。然而，由于脑电图信号在会话间和会话内存在变异性，且用户训练周期较长，基于内源性脑电图的应用往往难以实现稳定使用。本研究提出了一种方法，通过将渐进可扩展的神经反馈训练程序（该程序能持续调整分类器以适配特定用户）融入多模态脑机接口范式，来解决脑电图-脑机接口的这两大核心局限。我们创新性地将脑电图与非脑信号——瞳孔调节反应进行融合。瞳孔调节反应是注视点从远距目标切换至近距目标时伴随的瞳孔尺寸变化，其不受躯体神经系统调控，因此在神经退行性疾病（如肌萎缩侧索硬化症）患者从闭锁综合征向完全闭锁综合征演变的过程中可能得以保留。多模态脑机接口因其能提升整体控制性能而受到广泛研究，但本研究首次尝试结合脑电图与瞳孔调节反应。在BciPar4Sla项目背景下，我们正运用这两种信号，旨在开发更可靠的脑机接口系统：该系统既能自适应适配，随用户诱发最佳控制所需脑现象的能力共同进化，又能在患者从闭锁综合征向完全闭锁综合征过渡阶段提供持续支持。