06 Axons and Dendrites

Technical Training: Nanoscale Connectomics

Session outcomes (60 minutes)

• Classify neurites using a reproducible multi-cue protocol.
• Document uncertainty and escalation rationale for edge cases.
• Quantify classification quality with confusion-style summaries.

Pedagogical arc

• Model: expert classifies one neurite live.
• Practice: pair annotation on mixed-evidence panels.
• Consensus: adjudication and policy revision.
• Check: justified final call and uncertainty note.

Why this unit is high leverage

• Axon/dendrite identity errors distort connectivity statistics.
• Misclassification propagates into motif analysis and model priors.
• Reproducible identity policy is a prerequisite for trustworthy graphs.

Visual context: morphology baseline

Visual context: dendritic cue panel

Visual context: axonal cue panel

Side-by-side discrimination

• Ask learners to justify which cue would survive lower image quality.

Ambiguous process case

• Train weighted-evidence reasoning, not binary heuristics.

Continuity check case

• Require short-path continuity inspection before final call.

High-complexity edge case

• Escalate unresolved ambiguity to adjudication queue.

Operational classification protocol

1. Initial morphology read.
2. Synaptic/organellar context check.
3. Continuity check in adjacent slices.
4. Confidence assignment.
5. Escalation if evidence conflict persists.

Misconceptions to correct

• “Thin process = axon”.
• “One bouton-like feature determines identity”.
• “Ambiguous means annotator failed”.

Activity

Classify three ambiguous neurites and submit:

• primary label,
• cue table,
• confidence,
• alternate label and why rejected.

Rubric checkpoint

• Pass: label plus two independent cues.
• Strong: includes continuity evidence and uncertainty logic.
• Flag: unsupported hard labels.

External paper figure integration

• Kasthuri et al. 2015: process morphology examples in dense reconstructions.
• MICrONS/FlyWire morphology figures for large-scale context.
• Optional neuroanatomy atlas figure for compartment-level validation.

External inserted figure (open license)

• Source URL: https://commons.wikimedia.org/wiki/Special:FilePath/Complete_neuron_cell_diagram_en.svg
• License: Public domain (Wikimedia Commons file metadata).

References and attribution

• Internal visuals: Pat Rivlin axon/dendrite training set.
• Journal-club tie-in: https://doi.org/10.1016/j.cell.2015.06.054