Skip to content

Back to the catalog

Axonal delay dispersion decides whether a neuron detects an event or a sequence, and predicts cortical column diameter
arxiv.orgpaper

Axonal delay dispersion decides whether a neuron detects an event or a sequence, and predicts cortical column diameter

This arXiv preprint proposes a "delay-signature" framework where the dispersion of axonal conduction delays converging on a dendritic branch determines whether a neuron acts as an event detector (coincidence) or an order-selective sequence detector, using simulations of an integrator-neuron model. The authors find a single scalar (delay dispersion) governs this computational transition, sets a millisecond-scale timing tolerance, and together with conduction velocity predicts cortical column diameter — linking myelination to what a neuron computes, not just how fast it signals.

TL;DR Axonal delay dispersion is proposed as the physical parameter that switches a neuron between event detection and sequence detection, and it predicts cortical column diameter.
Open original ↗
Document

What it claims

The paper puts a mechanism and three quantitative claims behind the "delay dispersion sets computation" idea the summary states. The premise: cortical neurons fire sparsely — often fewer than one spike per sensory window — so rate coding is insufficient and temporal coding necessary. The delays converging on a dendritic branch act as a "physical key": only input sequences whose spike-time differences the delays compensate arrive synchronously, and coincidence detection (via calcium plateau thresholds) converts that synchrony into an all-or-none output.

Evidence

Three results, as the abstract states them:

  • Transition is emergent, and the slope is one. Under random delays and connectivity, sequence detectors do not exist at narrow dispersion; the dispersion at which they overtake event detectors tracks the inter-event interval with a slope statistically indistinguishable from one. This is what maps the computational distinction onto the anatomical myelinated/unmyelinated split.
  • The code's limits, with an asymmetry. The same dispersion bounds the longest codable interval and fixes an absolute timing tolerance of ~1 ms — and the tolerance is asymmetric: slowing is better tolerated than speeding.
  • Column-diameter prediction validated on two areas. The millisecond window and horizontal conduction velocity together predict cortical column diameter, and the two areas with direct measurements fall where the relation puts them.

Limits

This is an abstract-only page; the mechanism, the neuron model, and the two validation areas are asserted, not shown here — the reader must open the PDF for the integrator-model details, the identity of the two cortical areas, and whether the slope-one and 1-ms figures survive parameter variation. All results are from simulations of a single integrator-neuron model, not physiological recordings; the myelination-as-computational-switch claim is an inference from the delay/dispersion mapping, not a measured neural switch. Note there is a v2 (21 Sep 2026) superseding this v1 — and the PDF size dropped from 1,119 KB to 355 KB between versions, so figures or content may have changed; check v2 before citing.

Organisations named here

  • Jipeng Sun

Related in research