Precise and stable edge orientation signaling by human first-order tactile neurons

  1. Vaishnavi Sukumar
  2. Roland S Johansson
  3. J Andrew Pruszynski  Is a corresponding author
  1. Western University, Canada
  2. Umeå University, Sweden


Fast-adapting type 1 (FA-1) and slow-adapting type 1 (SA-1) first-order neurons in the human tactile system have distal axons that branch in the skin and form many transduction sites, yielding receptive fields with many highly sensitive zones or 'subfields'. We previously demonstrated that this arrangement allows FA-1 and SA-1 neurons to signal the geometric features of touched objects, specifically the orientation of raised edges scanned with the fingertips. Here we show that such signaling operates for fine edge orientation differences (5-20°) and is stable across a broad range of scanning speeds (15-180 mm/s); that is, under conditions relevant for real-world hand use. We found that both FA-1 and SA-1 neurons weakly signal fine edge orientation differences via the intensity of their spiking responses and only when considering a single scanning speed. Both neuron types showed much stronger edge orientation signaling in the sequential structure of the evoked spike trains and FA-1 neurons performed better than SA-1 neurons. Represented in the spatial domain, the sequential structure was strikingly invariant across scanning speeds, especially those naturally used in tactile spatial discrimination tasks. This speed invariance suggests that neurons' responses are structured via sequential stimulation of their subfields and thus links this capacity to their terminal organization in the skin. Indeed, the spatial precision of elicited action potentials rationally matched spatial acuity of subfield arrangements, which corresponds to a spatial period similar to the dimensions of individual fingertip ridges.

Data availability

Al the raw data generated as part of this study are publicly available.

The following data sets were generated

Article and author information

Author details

  1. Vaishnavi Sukumar

    Neuroscience Graduate Program, Western University, London, Canada
    Competing interests
    No competing interests declared.
  2. Roland S Johansson

    Department of Integrative Medical Biology, Umeå University, Umeå, Sweden
    Competing interests
    No competing interests declared.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-3288-8326
  3. J Andrew Pruszynski

    Department of Physiology and Pharmacology, Western University, London, Canada
    For correspondence
    Competing interests
    J Andrew Pruszynski, Reviewing editor, eLife.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-0786-0081


Vetenskapsrådet (22209)

  • J Andrew Pruszynski

Canadian Institutes of Health Research (Foundation Grant)

  • J Andrew Pruszynski

Canada Research Chairs (Tier 2)

  • J Andrew Pruszynski

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.


Human subjects: All participants provided written informed consent in accordance with the Declaration of Helsinki. The Umeå University ethics committee approved the study (PI: Johansson).

Reviewing Editor

  1. Hannes P Saal, University of Sheffield, United Kingdom

Publication history

  1. Preprint posted: June 3, 2022 (view preprint)
  2. Received: June 29, 2022
  3. Accepted: October 27, 2022
  4. Accepted Manuscript published: October 31, 2022 (version 1)
  5. Version of Record published: November 8, 2022 (version 2)


© 2022, Sukumar et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.


  • 370
    Page views
  • 76
  • 0

Article citation count generated by polling the highest count across the following sources: Crossref, PubMed Central, Scopus.

Download links

A two-part list of links to download the article, or parts of the article, in various formats.

Downloads (link to download the article as PDF)

Open citations (links to open the citations from this article in various online reference manager services)

Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)

  1. Vaishnavi Sukumar
  2. Roland S Johansson
  3. J Andrew Pruszynski
Precise and stable edge orientation signaling by human first-order tactile neurons
eLife 11:e81476.

Further reading

    1. Neuroscience
    2. Physics of Living Systems
    Sabrina A Jones, Jacob H Barfield ... Woodrow L Shew
    Research Article

    Naturally occurring body movements and collective neural activity both exhibit complex dynamics, often with scale-free, fractal spatiotemporal structure. Scale-free dynamics of both brain and behavior are important because each is associated with functional benefits to the organism. Despite their similarities, scale-free brain activity and scale-free behavior have been studied separately, without a unified explanation. Here we show that scale-free dynamics of mouse behavior and neurons in visual cortex are strongly related. Surprisingly, the scale-free neural activity is limited to specific subsets of neurons, and these scale-free subsets exhibit stochastic winner-take-all competition with other neural subsets. This observation is inconsistent with prevailing theories of scale-free dynamics in neural systems, which stem from the criticality hypothesis. We develop a computational model which incorporates known cell-type-specific circuit structure, explaining our findings with a new type of critical dynamics. Our results establish neural underpinnings of scale-free behavior and clear behavioral relevance of scale-free neural activity.

    1. Neuroscience
    Barna Zajzon, David Dahmen ... Renato Duarte
    Research Article

    Information from the sensory periphery is conveyed to the cortex via structured projection pathways that spatially segregate stimulus features, providing a robust and efficient encoding strategy. Beyond sensory encoding, this prominent anatomical feature extends throughout the neocortex. However, the extent to which it influences cortical processing is unclear. In this study, we combine cortical circuit modeling with network theory to demonstrate that the sharpness of topographic projections acts as a bifurcation parameter, controlling the macroscopic dynamics and representational precision across a modular network. By shifting the balance of excitation and inhibition, topographic modularity gradually increases task performance and improves the signal-to-noise ratio across the system. We demonstrate that in biologically constrained networks, such a denoising behavior is contingent on recurrent inhibition. We show that this is a robust and generic structural feature that enables a broad range of behaviorally-relevant operating regimes, and provide an in-depth theoretical analysis unravelling the dynamical principles underlying the mechanism.