Update README.md

README.md

@@ -69,6 +69,14 @@ Each `Sherlock{i}` directory contains:
 - `Sherlock{i}/sub-0/ses-1/meg/*.fif` — raw MEG recordings
 - `Sherlock{i}/sub-0/ses-1/meg/*.tsv` — BIDS events files (recommended going forward)
 
+### Shared metadata
+
+The repository also includes a top-level `metadata/` directory containing information shared across all `Sherlock{i}` datasets:
+
+- `metadata/channels.tsv` — BIDS-style channel metadata table (name, type, units, filter settings, sampling frequency, and status) used consistently across datasets
+- `metadata/sensor_xyz.json` — sensor position array of shape `(n_channels, 3)` giving XYZ coordinates for each channel. Please refer to the raw FIF (`*_meg.fif`) for coordinate frame and transforms. Provided as a lightweight convenience for visualisation / sanity checks.
+- `metadata/neo/ct_sparse.fif` and `metadata/neo/sss_cal.dat` — site-specific MaxFilter/SSS calibration files for the NEO scanner. These are required if you want to run Signal Space Separation / Maxwell filtering (e.g. via `mne.preprocessing.maxwell_filter`) on the raw FIF files. If you are only using the provided serialised `.h5` competition derivatives, you should not need these files.
+
 ## Stimulus audio (LibriVox)
 
 The spoken-audio stimuli are derived from **LibriVox** public-domain recordings of the first seven Sherlock Holmes books (recording versions linked below). The stimuli are provided in this repository as WAV files converted from the LibriVox downloads.