Von Economo neurons (VENs)

Large spindle-shaped projection neurons (also called spindle neurons or, with fork cells, a distinctive frontoinsular morphology) clustered among layer-5 pyramidal cells at the anterior insula / frontal-operculum junction and in the anterior-cingulate-cortex. Featured prominently in Craig (2009) and referenced in Seth (2013). See insular-cortex, ad-craig.

Why they matter

• Phylogeny tracks self-awareness. VENs are present in humans, progressively fewer in great apes, absent in macaques; also reported in elephants and whales. This distribution parallels the mirror test for self-recognition, and Craig ties it to the human expansion of the AIC and the emergence of the global-emotional-moment.
• Proposed function: fast, long-range interconnections between the physically separated limbic sensory (AIC) and motor (ACC) cortices — analogous to the U-fibres linking somatosensory and motor cortex — enabling the highly integrated “emotional moments” that Craig’s model requires. Their actual connections remain largely unmapped (a stated limitation).
• Clinical anchor: in behavioural-variant frontotemporal dementia, selective VEN degeneration correlates with loss of self-conscious behaviour and emotional awareness (Seeley et al.) — the strongest evidence linking VENs to awareness, and cited in both Craig 2009 and Seth 2013.

Correction: VENs are present in macaques (Evrard et al. 2012)

The phylogeny claim above is out of date, and the wiki inherited the out-of-date version. Craig (2009) reports VENs as absent in macaques, which is what makes the distribution look like a clean ladder tracking self-awareness. Chen et al. (2021) instead describe VENs and fork neurons as found “primarily in the AIC and ACC of macaques, great apes, and humans, as well as in several other large and highly social mammalian species such as elephants and whales,” citing Evrard, Forro & Logothetis (2012), Von Economo neurons in the anterior insula of the macaque monkey, Neuron 74:482-489 — published three years after Craig’s review.

This is a supersession rather than a live disagreement: Craig wrote before the macaque result existed, and nobody in the wiki’s sources defends the absence claim after 2012. But it matters for what the phylogeny was being used to argue. Craig’s ladder — present in humans, fewer in great apes, absent in macaques — parallels mirror-test self-recognition, and that parallel is load-bearing for the inference from VEN distribution to the global-emotional-moment and human-specific awareness. If macaques have them, the correlation with mirror self-recognition weakens considerably, and VEN presence stops being a marker of the specific capacity Craig invoked it for.

The wiki holds the correction and does not rewrite craig-2009-anterior-insula, which reports its literature accurately for 2009. The dependent inference on that page should be read with this attached. See also insular-cortex on species differences, and note that Chen et al. add a transcriptomic handle the older literature lacked (Yang et al. 2019, microdissected-cell RNA sequencing of VENs in human ACC; Cobos & Seeley 2015 on layer V subcerebral projection transcription factors) — a route to the “language” the caveat below says is unknown.

Caveats

The connectivity and “language” of VENs are unknown; their proposed role in awareness is inferential (morphology + phylogenetic + lesion correlation), not demonstrated by tracing their circuits. The phylogenetic leg of that inference is now weaker than the section above it originally implied.