The End Of Knowledge - Vault 3 - G.TEC BCI & Neurotechnology Spring School 2024 - Day 9

graph LR classDef diagnosis fill:#f9d4d4, font-weight:bold, font-size:14px; classDef imaging fill:#d4f9d4, font-weight:bold, font-size:14px; classDef prognosis fill:#d4d4f9, font-weight:bold, font-size:14px; classDef bci fill:#f9f9d4, font-weight:bold, font-size:14px; classDef applications fill:#f9d4f9, font-weight:bold, font-size:14px; A[Haibo Di] --> B[DOC diagnosis challenging,
misdiagnosis common 1] A --> C[PET, fMRI differentiate
UWS, MCS 2] B --> D[UWS, MCS prognosis,
management differ 3] A --> E[BCIs enable locked-in
communication 4] E --> F[BCI: signal acquisition,
processing, control 5] E --> G[P300, motor imagery,
SSVEP common 6] G --> H[P300: attended targets,
auditory responses 7] G --> I[SSVEP: visual stimuli
frequency, SNR 8] C --> J[fMRI: UWS motor,
navigation activation 9] C --> K[BCI responses prognostic
of consciousness 10] E --> L[Motor, SSVEP paradigms
screen DOCs 11] L --> M[Motor imagery provides
cues, EEG 12] L --> N[SSVEP: 8-12.5Hz, MCS
outperforms UWS 13] E --> O[DOC eye tracking
limitations remain 14] E --> P[BCIs: locked-in needs,
world connection 15] P --> Q[Brain switch: on-demand
need expression 16] Q --> R[Model-based switch improves
intuitive control 17] P --> S[BCI wheelchairs: safety,
shared control 18] S --> T[Leader algorithms, obstacle
maps, trajectories 19] E --> U[Invasive BCIs may
restore movement 20] U --> V[Motor BCI controls
arm, tests 21] U --> W[Long-term motor representations
persist post-injury 22] G --> X[SSVEP easier control,
visual dependence 23] D --> Y[Locked-in progression
prediction difficult 24] E --> Z[ALS patient declined
despite BCI 25] G --> AA[SSVEP requires focused
stimulus attention 26] E --> AB[BCI barriers: identification,
tech limitations 27] AB --> AC[Non-invasive focus, invasive
future promise 28] D --> AD[Locked-in end-of-life
decisions complex 29] E --> AE[Group collaborations advance
locked-in BCIs 30] class A,B,C,D,Y,AD diagnosis; class E,F,G,H,I,L,M,N,O,P,Q,R,S,T,U,V,W,X,Z,AA,AB,AC,AE bci; class J,K imaging; class A,B,C,D,Y,AD diagnosis; class E,F,G,H,I,L,M,N,O,P,Q,R,S,T,U,V,W,X,Z,AA,AB,AC,AE bci; class J,K imaging;

Resume:

1.- Diagnosis of disorders of consciousness (DOC) and locked-in syndrome is challenging. Misdiagnosis rates can be high without proper behavioral assessments and neuroimaging.

2.- PET and fMRI scans can help differentiate between unresponsive wakefulness syndrome (UWS) and minimally conscious state (MCS) by detecting brain activity patterns.

3.- Prognosis and management options differ for UWS vs MCS patients. MCS patients may benefit from active interventions to promote consciousness.

4.- Brain-computer interfaces (BCIs) can potentially help locked-in patients communicate. BCIs can be invasive or noninvasive (EEG, fNIRS, fMRI).

5.- Typical BCI systems include signal acquisition, processing, feature extraction, classification and application to control devices or for rehabilitation. Requires subject training.

6.- P300, motor imagery, and steady-state visually evoked potentials (SSVEP) are common EEG signals used for BCIs in locked-in patients.

7.- P300 occurs when subjects attend to target stimuli. Useful for detecting auditory responses. Motor imagery changes sensorimotor rhythms for mental limb movements.

8.- SSVEP generates signals at the visual stimulation frequency over occipital cortex. Requires basic visual function and eye movement control. Higher SNR than MI.

9.- fMRI shows activation of supplementary motor area during motor imagery and parahippocampal gyrus during spatial navigation imagery in UWS patients who can follow commands.

10.- Positive BCI responses to motor imagery and visual paradigms in UWS/MCS patients is prognostic of regaining consciousness. Especially high in MCS.

11.- The research group developed motor imagery and SSVEP paradigms to screen DOC patients' ability to use different BCIs for communication.

12.- A hand raising motor imagery task was tested, providing simultaneous visual and auditory cues. Time-frequency EEG analysis showed task-related changes.

13.- An SSVEP paradigm was tested with stimuli at 8, 9.5, 11 and 12.5 Hz. MCS patients had higher accuracy than UWS.

14.- Challenges remain in using eye tracking in DOC patients who often cannot keep eyes open. Complex bedside environment also makes pupil detection difficult.

15.- Beyond diagnosis, BCIs can help locked-in patients communicate basic needs and connect with the outside world by bypassing impaired motor pathways.

16.- A brain switch can allow locked-in patients to express needs on-demand, like calling for care. False triggering is an issue with low SNR.

17.- A model-based brain switch using motor imagery was developed to improve reliability and enable intuitive asynchronous control in a 1-hour video playing task.

18.- BCIs can potentially control wheelchairs for locked-in patients, but safety is a concern with limited control dimensions. Shared control methods are promising.

19.- Leader algorithms and obstacle avoidance systems can make BCI wheelchairs safer by building maps of the environment and planning trajectories.

20.- Some locked-in patients may regain motor function with invasive BCIs. Testing motor behavior can provide more details about their state of consciousness.

21.- A motor imagery BCI was used to control a robotic arm in increasing difficulty tasks in healthy subjects. Group accuracy was >60%.

22.- Long-term (20-30 years) post-injury, motor imagery still activates expected regions in spinal cord injury patients, suggesting these representations persist.

23.- SSVEP may be easier than P300 for BCI control in locked-in patients, but requires visual ability. Patients should be tested to determine optimal paradigm.

24.- Predicting progression in locked-in patients is difficult. Traumatic cases may have better natural recovery than progressive diseases like ALS.

25.- Preliminary data from 1 ALS patient showed continued decline with BCI rehabilitation. Larger studies are needed to determine potential benefits in ALS.

26.- SSVEP requires focused attention directly on the stimulus. Users cannot attend elsewhere while controlling an SSVEP BCI.

27.- Barriers to BCI use in locked-in patients include difficulty identifying patients who could benefit, limited technologies, and invasiveness of some promising systems.

28.- Non-invasive BCIs like SSVEP and motor imagery are the current research focus, but invasive chips may enable more effective future systems.

29.- End-of-life decision making for locked-in patients is complex and should balance quality of life considerations as treatment options expand.

30.- The research group has ongoing collaborations to advance non-invasive BCI technologies and applications for locked-in and DOC patients.

Knowledge Vault built byDavid Vivancos 2024