Knowledge Vault 3/20 - G.TEC BCI & Neurotechnology Spring School 2024 - Day 2
Rhythmic entertainment in cortical dynamics
Kai Miller, Mayo Clinic (USA)
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Concept Graph & Resume using Claude 3 Opus | Chat GPT4 | Llama 3:

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cortical dynamics with ECoG. 1] A --> C[Workshop: 71K attendees,
17K peak, huge. 2] A --> D[Miller's funding, interactions,
G-Tech use. 3] A --> E[ECoG grids: Pt-Ir, 500K neurons,
1cm spacing, 5% coverage. 4] E --> F[Rest vs movement:
low freq down, broadband up. 5] F --> G[High freq focal, modality-specific.
Low freq widespread. 6] E --> H[Simple tasks: fast sensorimotor
activation, 2D BCI in 10min. 7] F --> I[Broadband reflects cortical
charge density differences. 8] I --> J[PCA: flat broadband component,
not oscillatory. 9] I --> K['High gamma', 'broadband'
mean broadband changes. 10] I --> L[Broadband increases in
motor, speech, visual, auditory. 11] F --> M[Low freq mask broadband.
High freq noise-limited. 12] F --> N[Spatially widespread low freq
beta suppresses inactive motor. 13] N --> O[Broadband coupled to low freq
phase at rest, decreases in movement. 14] N --> P[Thalamic input may synchronize,
suppress inactive areas. 15] N --> Q[Parkinson's: abnormal subthalamic
synchronization. DBS reduces it. 16] Q --> R[Closed-loop DBS senses, reduces
abnormal entrainment. 17] A --> S[ECoG transitioning to stereo EEG
for deeper recordings. 18] S --> T[Stereo EEG: deep structures, circuits.
Tissue affects amplitudes. 19] S --> U[Stereo EEG: similar motor broadband
up, low freq down as ECoG. 20] S --> V[Stereo EEG speech mapping:
rare right language dominance case. 21] S --> W[Central sulcus depths:
non-somatotopic motor association. 22] W --> X[Motor association active for
both body sides, differs from somatotopic. 23] W --> Y[Motor association precedes movement,
differs in timing from primary motor. 24] S --> Z[Stereo EEG BCI:
1D cursor control example. 25] Z --> AA[Motor imagery: premotor more than
primary motor. Parietal if feedback. 26] A --> AB[Miller lab: rich data,
seeks members. Key collaborators. 27] A --> AC[Open datasets:
16 ECoG, 1 stereo EEG. 28] A --> AD[Key references, review of
intracranial monitoring in epilepsy. 29] A --> AE[Open questions: entrainment roles,
changes in movement disorders. 30] class A,B,C,D miller; class E,F,G,H,I,J,K,L,M,N,O,P,Q,R ecog; class S,T,U,V,W,X,Y,Z,AA stereo; class AB,AC future;


1.-Kai Miller discusses rhythmic entrainment and cortical dynamics using electrocorticography (ECoG) and stereo EEG recordings from the brain surface.

2.-The workshop has over 71,000 attendees, with the peak lecture having over 17,000 people watching simultaneously, bigger than the Society for Neuroscience meeting.

3.-Kai is funded by NIH and foundation awards, interacts with companies but isn't paid by them, and uses G-Tech amplifiers without compensation.

4.-ECoG grids have platinum iridium pads averaging over ~500,000 neurons, spaced 1 cm apart, covering 5% of the cortical surface.

5.-Comparing power spectra at rest vs. during hand movement shows decreases in low frequencies and broadband increases in high frequencies.

6.-High frequency increases are spatially focal and specific to cortical function modality, while low frequency decreases are more widespread oscillations.

7.-Simple tasks immediately show hand sensorimotor area activation on ECoG. Patients achieved 2D cursor control via motor imagery within 10 minutes.

8.-Broadband spectral changes reflect differences in charge density between superficial and deep cortical layers, indicating aggregate neural population activity.

9.-Principal component analysis extracts a flat component across all frequencies, indicating broadband changes rather than oscillatory activity.

10.-The "high gamma" and "broadband" phrases refer to these broadband power changes seen across all frequencies, not rhythmic oscillations.

11.-Broadband power increases and low frequency oscillatory decreases occur with motor, speech, visual and auditory tasks. Broadband correlates with BOLD fMRI.

12.-At low frequencies, oscillations mask broadband changes. At high frequencies, amplifier noise limits detection. There are no "gamma oscillations."

13.-Spatially widespread low frequency (beta, 12-20 Hz) oscillations in motor cortex seem to have a suppressive role when not actively moving.

14.-Broadband power is tightly coupled to the phase of low frequency oscillations at rest. This entrainment decreases during movement.

15.-The hypothesis is that weak but widespread thalamic input synchronizes and suppresses inactive cortical areas - "suppression through synchronization."

16.-In Parkinson's disease, this suppressive synchronization from the subthalamic nucleus is abnormally strong. Deep brain stimulation reduces it, alleviating symptoms.

17.-Closed-loop deep brain stimulation is being developed to sense abnormal entrainment and stimulate to reduce it, as a Parkinson's therapy.

18.-ECoG is transitioning to stereo EEG - depth electrodes that record from the full brain volume, albeit more sparsely than ECoG.

19.-Stereo EEG allows research into deep structures and circuitry between brain areas. Tissue heterogeneity affects signal amplitudes between regions.

20.-Stereo EEG shows similar motor-related broadband power increases and low frequency decreases as ECoG, and can map somatotopic hand/foot/tongue representations.

21.-Speech mapping with stereo EEG identified right-dominant language in a rare patient, correlating with fMRI. It helps map eloquent areas pre-surgically.

22.-An unexpected finding was that in the central sulcus depths, there are non-somatotopic motor association areas, challenging classical views.

23.-This deep motor association area is active for movements of either side of the body, differing from somatotopic regions.

24.-The motor association area activity precedes movement onset, but with a different timing than the somatotopic primary motor activity.

25.-Stereo EEG can be used for brain-computer interfaces. An example showed 1D cursor control via primary motor cortex activity.

26.-With motor imagery, premotor cortex is more engaged than primary motor. Parietal areas activate specifically when feedback is provided.

27.-The lab provides a rich environment for data and seeks new members. Key collaborators include Drs. Brinkmann, Hermes and others.

28.-Multiple datasets are available open-access for others to analyze, including 16 ECoG datasets and a stereo EEG dataset.

29.-Key references are provided to the published work discussed as well as a review explaining the clinical context of epilepsy monitoring with intracranial electrodes.

30.-Important open questions remain about the functional role of entrainment in different states and its changes in movement disorders.

Knowledge Vault built byDavid Vivancos 2024