Toward Assessment of Sound Localization in Disorders of Consciousness Using a Hybrid Audiovisual Brain–Computer Interface

Abstract

Behavioral assessment of sound localization in the Coma Recovery Scale-Revised (CRS-R) poses a significant challenge due to motor disability in patients with disorders of consciousness (DOC). Brain-computer interfaces (BCIs), which can directly detect brain activities related to external stimuli, may thus provide an approach to assess DOC patients without the need for any physical behavior. In this study, a novel audiovisual BCI system was developed to simulate sound localization evaluation in CRS-R. Specifically, there were two alternatively flashed buttons on the left and right sides of the graphical user interface, one of which was randomly chosen as the target. The auditory stimuli of bell sounds were simultaneously presented by the ipsilateral loudspeaker during the flashing of the target button, which prompted patients to selectively attend to the target button. The recorded electroencephalography data were analyzed in real time to detect event-related potentials evoked by the target and further to determine whether the target was attended to or not. A significant BCI accuracy for a patient implied that he/she had sound localization. Among eighteen patients, eleven and four showed sound localization in the BCI and CRS-R, respectively. Furthermore, all patients showing sound localization in the CRS-R were among those detected by our BCI. The other seven patients who had no sound localization behavior in CRS-R were identified by the BCI assessment, and three of them showed improvements in the second CRS-R assessment after the BCI experiment. Thus, the proposed BCI system is promising for assisting the assessment of sound localization and improving the clinical diagnosis of DOC patients.Index Terms-Hybrid brain-computer interface (hBCI), eventrelated potential (ERP), disorders of consciousness (DOC), sound localization, behavioral assessment. I. INTRODUCTIOND ISORDERS of consciousness (DOC), including coma, vegetative state (VS, also known as unresponsive wakefulness syndrome) and minimally conscious state (MCS), usually result from a variety of acute brain injuries. DOC patients

EEG-based Brain-Computer Interfaces for people with Disorders of Consciousness: Features and applications. A systematic review

“…In Xiao et al ( 2016 , 2022 ), the Mismatch Negativity (MMN) was considered in addition to the P300. The MMN is a negative component generated in response to the violation of a rule.…”

“…Six studies aimed at evaluating the ability of patients to accomplish tasks from the CRS-R with a BCI. The items transposed in a BCI interface were the following: the visual fixation item (Xiao et al, 2018a ), the visual pursuit item (Xiao et al, 2018b ), the object recognition item (Wang et al, 2019 ), the auditory startle item (Xiao et al, 2016 ), the sound localization item (Xiao et al, 2022 ) and the communication item (Wang et al, 2017 ). All these studies implemented a BCI relying on the P300.…”

“…Xiao et al ( 2016 ) detected the auditory startle response with a BCI in a passive mode in 14 (9 VS/UWS, 4 MCS, 1 EMCS; 73.7%) of the 19 patients tested; three of them, diagnosed as VS/UWS, did not show such response in the behavioral assessment. In a successive study, Xiao et al ( 2022 ) investigated the “sound localization” item. They found that 11 patients (5 VS/UWS, 6 MCS; 61.1%) had a significant classification accuracy in the BCI assessment: 4 MCS patients reached the score corresponding to the “sound localization” item in the CRS-based assessment, while 7 patients did not reach the sound localization score in the behavioral assessment.…”

“…Xiao et al (2016) detected the auditory startle response with a BCI in a passive mode in 14 (9 VS/UWS, 4 MCS, 1 EMCS; 73.7%) of the 19 patients tested; three of them, diagnosed as VS/UWS, did not show such response in the behavioral assessment. In a successive study, Xiao et al (2022) investigated the "sound FIGURE General representation of a BCI paradigm. The figure illustrates a general pipeline of a BCI paradigm which could be adapted to each study included in the review.…”

A Behavioral Approach to Treatment and Assessment of People with Disorders of Consciousness: The Response-contingent Stimulation Strategy

“…New research will need to extend the evidence so far available with regard to the strategy through systematic replication studies entailing new patients and new technology as well as the direct involvement of new research groups [117,118]. Positive outcomes of the studies and involvement of different groups of researchers (professionals) in carrying out the studies would be critical (a) to further substantiate the strategy's impact and refine its setup and implementation process, and (b) to help the strategy become a practical tool within rehabilitation and care contexts where the need for supplementary treatment and assessment means is still apparently high [111,114,[119][120][121][122].…”