Atlas: Connectomics Reference

A working reference for the technical track: landmark datasets with specifications and access routes, the software landscape by workflow stage, benchmarks, and the curation schema for adding entries.

Stylized vector art: a reference table with one row highlighted and a bookmark tab.

How to use this page

This is a lookup table, not a lesson. Come here when you need to answer one of:

Specifications below are as published and are approximate where releases have been revised. Always confirm current figures and access terms against the primary source before citing them — dataset sizes in particular change as proofreading continues (Unit 04 §2).


1. Landmark datasets

Invertebrate

Dataset Scale Modality / resolution What it is good for Access
C. elegans (White et al. 1986; Cook et al. 2019; Witvliet et al. 2021) 302 neurons; whole animal; a developmental series across maturation ssTEM The complete-nervous-system reference case. Witvliet’s series is the best available data on how connectivity changes with development WormWiring, WormAtlas
Larval Drosophila brain (Winding et al. 2023) ~3,000 neurons; ~550,000 synapses; whole brain ssTEM A whole brain small enough for exhaustive graph analysis; bilateral matching studies CATMAID instances; published supplements
Drosophila hemibrain (Scheffer et al. 2020) ~25,000 neurons; ~20 million synapses; central brain FIB-SEM, near-isotropic 8 nm Cell-type census; the cleanest large connectome for analysis teaching, because isotropy makes tracing quality high neuPrint
FAFB / FlyWire (Zheng et al. 2018; Dorkenwald et al. 2024) Whole adult brain; ~139,000 neurons; ~54.5 million synapses ssTEM, 4 × 4 × 40 nm The first whole-brain connectome of a behaviorally complex animal; community-proofread FlyWire (registration required); CAVE
Drosophila male adult nerve cord (MANC) ~23,000 neurons FIB-SEM Motor circuits; connecting brain to periphery neuPrint

Vertebrate

Dataset Scale Modality / resolution What it is good for Access
Mouse retina (e2198 and relatives) (Briggman, Helmstaedter, Denk) ~10⁵–10⁶ µm³ SBEM Structure-function in a well-characterized circuit; direction selectivity Published; some via community portals
Kasthuri saturated reconstruction (Kasthuri et al. 2015) ~1,500 µm³ mouse neocortex, densely reconstructed ssSEM (ATUM) The reference for what dense, saturated reconstruction means and costs Open Connectome / BossDB
Hippocampal CA1 resource (Harris et al. 2015) Dense neuropil volume ssTEM Spine and synapse ultrastructure; a standard teaching set for Units 05–06 Published resource
MICrONS (Allen Institute, Baylor, Princeton; 2025 release) ~1 mm³ mouse visual cortex; ~200,000 cells; ~500 million synapses ssTEM, 4 × 4 × 40 nm, co-registered with in-vivo two-photon calcium imaging The reference functional-connectomics dataset. The co-registration is what makes it unique CAVE / caveclient; MicronsBinder notebooks
H01 human cortex (Shapson-Coe et al. 2024) ~1 mm³ human temporal cortex; ~57,000 cells; ~150 million synapses; ~1.4 PB ssTEM, ~4 × 4 × 30 nm Human tissue at synapse resolution; species comparison Google/Lichtman lab public release; Neuroglancer
Larval zebrafish whole brain (Hildebrand et al. 2017) Whole brain, larval ssEM Whole-vertebrate-brain scale in a tractable organism Published resource
MouseConnects / HI-MC (NIH BRAIN CONNECTS) Scaling toward whole mouse brain Volume EM The current flagship scaling effort; see the case study Program resources

Choosing among them

If your question is about… Start with
Whole-brain graph structure in a behaving animal FlyWire, or larval Drosophila for exhaustive analysis
Cell types and their connectivity, with clean tracing Hemibrain
Structure–function relationships MICrONS
Human-specific features H01
Development of connectivity C. elegans developmental series
What dense reconstruction actually requires Kasthuri 2015
Teaching ultrastructure reading Harris CA1 resource; any of the above in Neuroglancer

Before proposing new acquisition, check this table. A large fraction of good connectomics questions can be answered by re-analysis of existing public data. The cost difference is not marginal: acquiring a new mm-scale volume is a multi-year, multi-million-dollar program, while re-analyzing one is a compute bill and your time. Work the comparison out for your own question with Unit 03’s cost arithmetic before assuming you need new data. See Unit 02’s common errors.


2. Software, by workflow stage

Stage Tool What it does
Viewing Neuroglancer The standard browser-based viewer for petascale volumes, meshes, and annotations
  webKnossos Viewing, annotation, and proofreading with collaborative features
Data access CloudVolume Python access to precomputed/chunked volumes
  caveclient Client for CAVE — segmentation, synapse tables, materialization versions
  neuprint-python Client for neuPrint (hemibrain, MANC)
  intern Client for BossDB-hosted volumes
Storage formats Precomputed, N5, Zarr / OME-Zarr Chunked, multiresolution array formats (Unit 04 §3)
Annotation / proofreading CATMAID Collaborative skeleton tracing; the system behind FAFB-era tracing
  VAST Manual volume annotation
  CAVE / ChunkedGraph Versioned, concurrent proofreading over immutable supervoxels
Segmentation Flood-filling networks Iterative single-object growth
  Affinity + agglomeration stacks (e.g. gunpowder-based pipelines, PyTorch Connectomics) The dominant production family
  Ilastik Interactive pixel classification for smaller volumes and prototyping
Morphology navis, natverse Neuron morphology analysis in Python and R
  meshparty Meshes and skeletons from segmentations
Graph analysis networkx General graph analysis, triad census
  graspologic Statistical graph analysis: embeddings, graph matching, two-sample testing
  DotMotif Declarative subgraph/motif queries over connectomes
Hosting BossDB Community archive for volumetric neuroscience data

3. Benchmarks and evaluation

Benchmark What it evaluates Notes
SNEMI3D 3D neurite segmentation Long-standing reference challenge; small volume
CREMI Neuron segmentation and synaptic partner identification in Drosophila EM Includes synaptic partner assignment, which most benchmarks omit
ISBI 2012 2D membrane segmentation Historical; useful for teaching, not representative of current difficulty

Caution when reading benchmark results. Scores on small, well-prepared benchmark volumes systematically overstate performance on production data, which contains artifacts (Unit 03), rare morphologies, and volume boundaries that benchmarks exclude. When evaluating a method for your project, the question is not its leaderboard position but its error rate on your tissue — which means running it on a representative sub-volume of your own data (Unit 03 §3, the pilot reconstruction rule).

Report metrics as described in Unit 08 §3: at minimum VI decomposed into split and merge components, plus one tracing-oriented metric such as ERL, plus the effect on your endpoint.


4. Contributing an entry

Required metadata

Every atlas entry carries:

The known_limits field is the one most often left blank and the one most worth filling. An atlas of tools without limits is advertising.

Curation policy

  1. Add only resources with a clear technical contribution or benchmark value.
  2. Mark superseded methods as historical rather than deleting them, when they remain pedagogically useful — the history of a method often explains its assumptions.
  3. Prefer resources with reproducible artifacts: data, code, or an explicit protocol.
  4. Re-review on schedule; retire stale links.
  5. Every entry links to at least one unit, so the atlas stays connected to teaching rather than becoming an orphaned bibliography.

Quality-control checks


Visual context set

This page is a lookup table and this panel is deck context, not reference material — nothing here should be cited. Use it instead to rehearse the habit §1 asks for: confirm every specification against the primary source, because dataset sizes and cell counts change as proofreading continues.

Atlas references opener visual

Module14 L3 S03-02: The opening of the source deck’s reference stream. Treat any figure it carries as provisional — volume sizes, cell counts, and synapse counts in this field are release-dependent, so check them against the primary source before citing (Unit 04 §2).

Atlas mid-reference stream visual

Module14 L3 S10: Mid-stream references. Use it to test the curation standard in §4: for each resource named, ask whether you could write its known_limits sentence. That field is the one most often left blank, and an atlas of tools without limits is advertising.

Atlas closing references visual

Module14 L3 S19: Closing references. Check them against the choosing table in §1 before proposing new acquisition — a large share of good connectomics questions can be answered by re-analysis of existing public data, at a small fraction of the cost.

Developmental motifs reference context visual

Techtalk S44: Developmental motif comparison, cross-referenced here from Unit 09. Use it as the pointer into the C. elegans developmental series in §1 — the dataset to reach for when the question is how connectivity changes with maturation rather than what it is in one adult.

Attribution: module14 lesson3 and neuroAI source decks (historical/context visuals).


Mini-lab: curate one entry (30 minutes)

Add one resource to the atlas. Produce:

  1. All required metadata fields, complete.
  2. One sentence on the technical contribution — what can you now do that you could not?
  3. One sentence on the limitation or failure context — when does this not work?
  4. The unit or units it supports, with a sentence on how.

Rubric. Proficient: all fields present and accurate. Strong: the limitation sentence is specific enough that a reader could predict a failure case from it, and the unit mapping identifies where in that unit’s workflow the resource fits.


References

§4 of this page requires every contributed entry to carry “a standardized citation string, with DOI”. This section is that rule applied to the page itself. Every dataset named in §1 is here, with the published reference rather than its preprint — several of these circulated as bioRxiv preprints for years and are still cited that way.

Invertebrate

Vertebrate

MouseConnects / HI-MC is an in-progress BRAIN CONNECTS program rather than a released dataset; see the case study for its current state. Tool entries in §2 link to their own documentation, which is the citable source for a version.

Evidence pack: papers and datasets

This unit is anchored to canonical papers and datasets used in connectomics practice. Use these as required preparation before activities.

Key papers

Key datasets

Competency checks

  • Curate an entry with complete metadata and explicit limitations.
  • Assign evidence maturity and review cadence for each resource.

Capability development brief

Capability target: Curate a trustworthy connectomics reference atlas with transparent metadata and evidence quality signals.

Required expertise

  • Information scientist (taxonomy and metadata schemas)
  • Domain editor (method and dataset quality review)
  • Reproducibility lead (citation and versioning standards)

Core concepts to teach

  • Metadata completeness: Minimum descriptive fields required for responsible reuse.
  • Evidence grading: Explicit quality and maturity signals for methods, datasets, and tools.
  • Reference maintenance: Scheduled review and change tracking to keep entries current.

Studio activity

Atlas Entry Sprint - Produce publishable reference entries with complete metadata and quality notes. The unit's own lab above is the graded version of this exercise; do that one.

Assessment artifacts

  • Atlas entry template and quality checklist.
  • Curated starter index with versioned citations.

Related concepts

Reproducibility and Reference Curation

Curate methods, datasets, and tools with metadata completeness and explicit limitations.

Open in Concept Explorer

finding reliable resources maintaining citation hygiene