Knowledge Vault 3/23 - G.TEC BCI & Neurotechnology Spring School 2024 - Day 2
Tractography, brain stimulation and mapping for white matter navigation
Christoph Kapeller, g.tec medical engineering GmbH (AT)
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Concept Graph & Resume using Claude 3 Opus | Chat GPT4 | Llama 3:

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[ hackathon registration
open for projects. 27] AC --> AD[Hackathon teams formed
based on interests. 28] AC --> AE[Team registration through 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;


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. 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 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