Method at a glance
- Modality: multimodal (C-tactile/affective touch, sympathetic outflow, vagal — the last only recently)
- Measures: Multiunit activity in peripheral nerves lying close to the skin surface in awake, unanesthetized humans — the only direct readout of human peripheral afferent (and efferent sympathetic) traffic.
- Procedure: A very-small-diameter needle with a small exposed tip is inserted percutaneously to impale a nerve underlying the skin; multiunit neural activity is recorded without anesthesia, in the awake participant, typically while a stimulus (e.g. controlled skin stroking) is delivered to the receptive field.
- Also called: percutaneous nerve recording, in vivo human nerve recording
Strengths
- Direct measurement of peripheral neural traffic in awake humans — no anesthesia, no inference from a downstream proxy.
- The only human method that can record from C-tactile afferents, and therefore the technical basis of the Affective touch (C-tactile afferents) proposal to make interoceptive signalling experimentally manipulable.
- Recently extended to the human vagus nerve using ultrasound guidance (Ottaviani et al. 2020) — the nerve that carries most of the wiki’s interoceptive claims, recorded directly for the first time.
Limitations
- Only reaches nerves lying close to the skin surface. Most interoceptive afferents are visceral, thin, unmyelinated and diffusely arrayed — precisely the population it cannot reach, which is why affective touch is interesting as an accessible proxy.
- Invasive and technically demanding: an impaled nerve in an awake person, yielding multiunit rather than single-unit clarity.
- Small samples and specialist labs; nothing in the wiki’s evidence base is built on it.
Connections
- Key studies: Quigley et al. (2021), Chen et al. (2021)
- Related methods: Heartbeat detection task, Skin conductance response (SCR), Event-related potentials
Enters the wiki through Quigley et al. (2021), and it is worth a page for one reason: it is the wiki’s only method that measures human interoceptive signalling at the nerve.
Everything else here is a proxy at some remove. Heartbeat counting measures a judgment about a signal. Skin conductance measures one sympathetic effector. ERPs measure cortex. Microneurography measures the traffic.
Why it matters, and why it doesn’t (yet)
The catch is anatomical and is the same catch that shapes the entire literature. The method reaches “peripheral nerves that lie close to the skin’s surface.” Interoceptive afferents are mostly visceral, thin, unmyelinated and diffusely arrayed — deep and inaccessible. So the method that could in principle settle the field’s measurement problem is, for most interoceptive modalities, unusable.
Two developments make it relevant anyway:
C-tactile afferents. CT fibres share the morphology of interoceptive afferents but live in hairy skin, and can be recorded microneurographically in humans (Ackerley et al. 2014; McGlone et al. 2014). This is the technical half of the Affective touch (C-tactile afferents) proposal: if CT afferents are functionally interoceptive, then microneurography plus a controlled brush gives an interoceptive channel that can be both recorded and stimulated in healthy awake people — converting a correlational literature into an experimental one.
The human vagus. Quigley et al.’s closing paragraph names “recording from the vagus nerve in humans” (Ottaviani et al. 2020, ultrasound-guided microneurography) alongside VNS and affective-touch manipulation as the techniques that may open interoceptive processes to human study. The wiki’s vagal material — immune-to-brain signalling, the microbiota interface, gut-hippocampal priming, VNS as therapy, and Polyvagal theory’s contested claims — is entirely inferential about what the human vagus is actually carrying. This is the method that could stop it being inferential.
Status in the wiki
Recorded as a capability, not as an evidence base. No study in raw/ uses it. It is here because the wiki’s standing complaint is that interoception cannot be manipulated in humans, and this is the one entry on the short list of things that might change that.
Nominated twice in one journal issue. Quigley et al. proposed it as the way to convert a correlational literature into an experimental one, via CT afferents in the skin. Chen et al. — the NIH framing paper for the same issue — independently name it as the recent addition to a human toolkit they describe as otherwise “largely limited to a handful of approaches and remain mostly correlational” (heartbeat measures, skin conductance, self-report accuracy and awareness scales), citing Ackerley & Watkins (2018) on single C-fibre recording and Park et al. (2012) on sympathetic reactivity.
Two of the six papers in the issue pointing at the same underused technique, one of them the funder, is worth treating as a signal about where the field is being steered rather than as two independent endorsements. It does not change the caution above: the anatomical warrant for the affective-touch application is still a single patient, and no study here has used the method for anything.