Intracranial EEG (iEEG/ECoG)
Analyze intracranial recordings from depth electrodes and subdural grids with shaft-aware bipolar referencing, high-gamma band power, and event-related high-gamma mapping — the intracranial signal that scalp EEG cannot resolve.
Research question
Which intracranial contacts show task- or event-related high-gamma activation, once the data are bipolar-referenced and quality-checked?
How this differs from scalp EEG
EEG connectivity works with scalp electrodes, an average/REST reference, and conventional bands. Intracranial recordings need bipolar referencing along each electrode shaft (to remove the shared reference and volume-conduction artifact) and emphasize high gamma (70–150 Hz), the focal marker of local cortical activation that scalp EEG attenuates. This use case targets that intracranial workflow specifically.
Who this is for
- Epilepsy monitoring and neurosurgery research teams mapping functional and event-related activity
- Neurotechnology and BCI groups decoding high-gamma responses
- Systems and cognitive neuroscience labs working with depth/grid electrodes
Data requirements
| Data | Required | Purpose |
|---|---|---|
| Intracranial recording (EDF, FIF, BrainVision) | Yes | Depth/grid electrode timeseries |
Shaft-indexed contact names (e.g. LAH1, LAH2) | Recommended | Enables automatic bipolar pairing along shafts |
Task events .tsv (onset, duration, trial_type) | For peri-event mapping | Defines events for high-gamma response |
Channels named with a shaft prefix and contact index pair automatically into sequential bipolar derivations; unindexed channels are left monopolar.
Workflow
Upload intracranial recording → (optional) artifact review → iEEG analysis (bipolar + high gamma) → upload events → peri-event high-gamma → interpret
Step 1 — Upload the recording
Create a study and upload the intracranial dataset with modality iEEG or ECoG. The same readers used for scalp EEG ingest EDF/FIF/BrainVision intracranial data.
Step 2 — Review artifacts (optional)
Use the artifact review panel to inspect per-channel quality and flag noisy contacts before analysis.
Step 3 — Run iEEG analysis
Open the dataset and the iEEG / ECoG analysis panel:
- Choose bipolar referencing (sequential pairs along each shaft) or keep monopolar.
- The pipeline computes per-channel band power including high gamma (70–150 Hz) and ranks contacts by high-gamma power.
Step 4 — Peri-event high-gamma mapping
Upload a task events file. The pipeline computes a baseline-normalized high-gamma response per contact and condition, identifying which contacts activate for each event type.
Step 5 — Connectivity and interpretation (optional)
Run advanced connectivity on the bipolar montage to relate active contacts, and use Interpret for a grounded narrative over the computed metrics.
Expected outputs
- Bipolar montage with shaft-paired derivations and a channel-count summary
- Per-channel band power including a high-gamma ranking of contacts
- Peri-event high-gamma response per contact and condition
- Run record with parameters and pipeline version for reproducibility
Example insight
After bipolar referencing, three contacts on the left anterior hippocampal shaft show a 40–60% high-gamma increase locked to stimulus onset, while neighbouring contacts are unchanged — a focal task-related activation.
Typical analyses
| Analysis | Question |
|---|---|
| Functional mapping | Which contacts activate (high gamma) during a task condition? |
| Reference comparison | How does bipolar referencing change the high-gamma map vs monopolar? |
| Event-related dynamics | Which contacts respond to one condition but not another? |
| Spectral profiling | Which contacts carry the most high-gamma power at rest? |