The End Of Knowledge - Vault 3 - G.TEC BCI & Neurotechnology Spring School 2024 - Day 2

graph LR classDef stimulation fill:#f9d4d4, font-weight:bold, font-size:14px; classDef mapping fill:#d4f9d4, font-weight:bold, font-size:14px; classDef ccep fill:#d4d4f9, font-weight:bold, font-size:14px; classDef caseStudy fill:#f9f9d4, font-weight:bold, font-size:14px; classDef future fill:#f9d4f9, font-weight:bold, font-size:14px; A[Christoph Kapeller] --> B[Brain stimulation methods for
functional mapping explained. 1] A --> C[Brain stimulation identifies functions
by inhibiting/activating regions. 2] C --> D[50 Hz disrupts speech,
causes movements. 2] C --> E[1 Hz elicits CCEPs,
reveals connected networks. 3] A --> F[Functional mapping techniques:
ECOG, 50 Hz, motor. 4] A --> G[50 Hz crucial for
surgical decision-making. 5] A --> H[Charge density, parameters
control tissue damage. 6] A --> I[Cortical stimulation software
sets parameters, monitors impedance. 7] A --> J[Examples: 50 Hz disrupts
speech, causes visual illusions. 8] A --> K[Complex stimulation protocol,
patient interaction. 9] A --> L[Meta-analysis: stimulation improves
resection, reduces deficits. 10] A --> M[Seizures in 10% during
stimulation mapping. 11] A --> N[1 Hz CCEPs show
N1, N2 responses. 12] N --> O[CCEP uses monophasic
alternating polarity. 13] N --> P[CCEP responses recorded,
visualized on cortex. 14] N --> Q[CCEP connectivity matches
task-related high gamma. 15] N --> R[Epilepsy case: CCEP identified
transcallosal epileptogenic connection. 16] R --> S[Diffusion tractography visualizes
transcallosal CCEP fibers. 17] R --> T[Intraoperative CCEP abolished
after complete callosotomy. 18] R --> U[ECOG, CCEP, tractography approach:
13/14 favorable outcomes. 19] N --> V[Automated CCEP mapping
with switching unit. 20] V --> W[Simulink model controls
stimulator, switcher, amplifier. 21] A --> X[Future: compare tractography methods,
investigate white matter stimulation. 22] X --> Y[Tractography needs validation
against CCEPs, functions. 23] A --> Z[Visual system: face regions,
CCEPs, tractography correspond. 24] Z --> AA[Reliable tractography explaining
CCEPs, functions needed. 25] A --> AB[Sensory CCEP mapping,
Kalman filter: investigate further. 26] A --> AC[Brain.io hackathon registration
open for projects. 27] AC --> AD[Hackathon teams formed
based on interests. 28] AC --> AE[Team registration through
Brain.io website. 29] AC --> AF[Large registrations require
careful team formation. 30] class A,B,C,D,E,F,G,H,I,J,K,L,M stimulation; class A,F,N,O,P,Q,R,S,T,U,V,W,X,Y,Z,AA,AB ccep; class A,F mapping; class R,S,T,U caseStudy; class X,Y,Z,AA,AB future;

Resume:

1.-Christoph Kapeller explains brain stimulation methods for functional mapping, including 50 Hz for behavioral responses and 1 Hz for evoked potentials.

2.-Brain stimulation identifies functions by inhibiting or activating brain regions. Stimulation at 50 Hz can disrupt speech or cause movements.

3.-1 Hz stimulation elicits corticocortical evoked potentials (CCEPs) without behavioral effects, revealing connected networks with lower seizure risk than 50 Hz.

4.-Functional mapping techniques include electrocorticography for observational biomarkers, 50 Hz stimulation for inhibitory mapping, and excitatory methods like motor mapping.

5.-Inhibitory mapping with 50 Hz stimulation is crucial for surgical decision-making to identify eloquent cortex before resection.

6.-Charge density and stimulation parameters must be carefully controlled to avoid tissue damage. Electrode size affects safe current limits.

7.-Cortical stimulation software allows setting stimulation parameters, monitoring impedance, and visualizing responses. Current is gradually increased while observing effects.

8.-Examples demonstrate 50 Hz stimulation disrupting speech during naming tasks and causing transient visual illusions when stimulating specific regions.

9.-Stimulation protocol and patient interaction are complex, requiring systematic mapping and clear explanations from patients about perceived sensations.

10.-Meta-analysis shows cortical stimulation improves gross total resection rates and reduces severe deficits compared to surgeries without mapping.

11.-Seizures can occur in 10% of cases during stimulation mapping, requiring preparedness to abort stimulation and manage seizures.

12.-CCEPs with 1 Hz stimulation show N1 and N2 responses in anatomically connected regions, as demonstrated in language networks.

13.-CCEP mapping uses monophasic alternating polarity to avoid charge buildup and distinguish artifacts from physiological responses.

14.-CCEP responses are recorded and visualized on the cortical surface to identify network connectivity patterns.

15.-CCEP connectivity corresponds well with regions showing task-related high gamma activity, indicating functionally connected networks.

16.-In an epilepsy case study, CCEP mapping identified a transcallosal connection between bilateral frontal epileptogenic zones.

17.-Diffusion tractography, especially multi-tensor methods, can visualize transcallosal fibers corresponding to CCEP connectivity.

18.-Intraoperative CCEP monitoring during callosotomy showed abolishment of contralateral potentials after complete disconnection, confirming removal of seizure propagation pathway.

19.-Combined ECOG, CCEP, and tractography approach in 14 patients resulted in 13 favorable outcomes, with poor outcome when CCEPs persisted.

20.-Automated CCEP mapping with a switching unit enables efficient screening of connectivity between multiple electrode pairs.

21.-Simulink model allows integrated control of cortical stimulator, switching unit, and amplifier for online CCEP processing and visualization.

22.-Future work includes comparing tractography methods for reliable network mapping and investigating white matter stimulation effects.

23.-Tractography techniques need validation against functional measures like CCEPs to establish generalizability across different functional networks and pathologies.

24.-Visual system example shows correspondence between face perception regions, CCEP connectivity, and tractography, supporting network mapping approach.

25.-Establishing reliable tractography methods that explain CCEP and functional mapping results remains an important research goal.

26.-Sensory input mapping with CCEPs and Kalman filter sensor fusion requires further investigation and synchronization with other modalities.

27.-Brain.io hackathon registration is open for projects spanning gaming, programming, data analysis, and artistic domains.

28.-Hackathon teams are formed based on project interests, with Discord facilitating networking and collaboration among participants.

29.-Team registration process involves applying through Brain.io website, with organizers assisting in forming complete teams.

30.-Large number of registrations requires patience and careful management to accommodate project preferences and team formation logistics.

Knowledge Vault built byDavid Vivancos 2024