# The neuroimaging literature does not single out the anterior insula for time perception, vestibular processing or depressive symptoms

## Summary

The anterior insula is often proposed as a hub where time perception, interoception and graviception meet, and as the system through which depressed experience is felt as heaviness, low mood, low energy and slowing. Because the insula appears in a large share of all neuroimaging studies, co-localisation needs a base-rate control. In a registered analysis of {{R1.studies_with_coordinates}} full-text articles from NeuroQuery, we asked whether studies discussing each function, or depressive-symptom terms, report anterior-insula coordinates more often than studies on random topics. Interoception studies did (association z {{R1.terms.interoception.anterior_insula.z}}), but equally in the posterior insula; time perception (z {{R1.terms.time perception.anterior_insula.z}}) and vestibular studies (z {{R1.terms.vestibular.anterior_insula.z}}) did not, so the three-way conjunction was no more selective than random term triples (percentile {{R1.H1_conjunction.percentile}}). Symptom terms were not selective either (percentile {{R1.H3_symptoms_mean.percentile}}). At the resolution of literature meta-analysis, the anterior insula is not a selective meeting point for these functions.

## Claims

- **C1:** Time perception and vestibular studies are not associated with the anterior insula beyond the base rate, so the conjunction of the three functions there is not selective, although interoception alone is strongly associated.
- **C2:** None of the three functions shows an anterior over posterior insula preference; interoception is equal and vestibular processing leans posterior.
- **C3:** Fatigue, psychomotor, sadness and mood terms together are not selectively associated with the anterior insula.

## Methods

**Registration.** The [plan](plan/analysis-plan.md) and [code](plan/convergence.py) were registered as [the preregistration](prereg:78ed05727f78749ae2a4034d879f65ade95e3556f00577b742deedf6db78ee15) after checking only term coverage, atlas label positions and a run with term usage permuted across studies.

**Data.** [NeuroQuery](doi:10.7554/eLife.53385) version 1: full-text articles with reported MNI coordinates and body-text term counts, fetched by digest from a fixed commit ([external data list](data/external.json)). Regions come from the Harvard-Oxford cortical atlas ([Desikan et al. 2006](doi:10.1016/j.neuroimage.2006.01.021) describe the parcellation approach), insula label at the 25% maximum-probability threshold, split at the MNI coronal plane through the anterior commissure into anterior (forward) and posterior parts.

**Measures** ([code/convergence.py](code/convergence.py)). A study activates a region if any reported coordinate lies within a fixed radius (stated in the plan) of a region voxel; it uses a term if the term occurs at least twice in its body text. A term's association with a region is a two-proportion z comparing activation rates in studies that use the term and studies that do not. Because the insula is reported very often, as noted for reverse inference by [Yarkoni et al. (2011)](doi:10.1038/nmeth.1635), every association is located against the same statistic for all vocabulary terms used by a comparable number of studies. Interoception combines "interoception" and "interoceptive", and sadness "sad" and "sadness". Vestibular is the closest available proxy for graviception, since the vocabulary has no gravity term.

**Tests.** H1, the minimum anterior-insula z across time perception, interoception and vestibular, against minima of random term triples; H2, anterior-minus-posterior z for each function against random terms; H3, the mean anterior-insula z of fatigue, psychomotor, sadness and mood against random four-term sets. Sensitivity: term thresholds of one and three mentions. Run `sh code/run`.

## Results

Anterior-insula coordinates appear in a large share of all articles (base rate {{R1.base_rate.anterior_insula}}; posterior {{R1.base_rate.posterior_insula}}), and the median random term has an anterior-insula z of {{R1.random_term_anterior_insula_z.median}}, with an upper cut-off (registered percentile) of {{R1.random_term_anterior_insula_z.p95}}.

**Three functions (C1).** Interoception studies ({{R1.terms.interoception.anterior_insula.n_studies}} articles) reported anterior-insula coordinates far more often than others (z {{R1.terms.interoception.anterior_insula.z}}, percentile {{R1.terms.interoception.anterior_insula.percentile_vs_random_terms}}). Time perception ({{R1.terms.time perception.anterior_insula.n_studies}} articles; z {{R1.terms.time perception.anterior_insula.z}}, percentile {{R1.terms.time perception.anterior_insula.percentile_vs_random_terms}}) and vestibular studies ({{R1.terms.vestibular.anterior_insula.n_studies}} articles; z {{R1.terms.vestibular.anterior_insula.z}}, percentile {{R1.terms.vestibular.anterior_insula.percentile_vs_random_terms}}) did not. The conjunction minimum was {{R1.H1_conjunction.observed_min_z}}, at percentile {{R1.H1_conjunction.percentile}} of random triples (one-sided p = {{R1.H1_conjunction.p_one_sided}}). With thresholds of one and three mentions the conjunction percentiles were {{R2.H1_conjunction.percentile}} and {{R3.H1_conjunction.percentile}}.

**Anterior versus posterior (C2).** Anterior-minus-posterior z was {{R1.H2_anterior_minus_posterior.interoception.difference_z}} for interoception (percentile {{R1.H2_anterior_minus_posterior.interoception.percentile_vs_random_terms}}), {{R1.H2_anterior_minus_posterior.time perception.difference_z}} for time perception, and {{R1.H2_anterior_minus_posterior.vestibular.difference_z}} for vestibular processing (percentile {{R1.H2_anterior_minus_posterior.vestibular.percentile_vs_random_terms}}).

**Symptom terms (C3).** Anterior-insula z was {{R1.terms.fatigue.anterior_insula.z}} for fatigue, {{R1.terms.psychomotor.anterior_insula.z}} for psychomotor, {{R1.terms.sadness.anterior_insula.z}} for sadness and {{R1.terms.mood.anterior_insula.z}} for mood; their mean, {{R1.H3_symptoms_mean.observed_mean_z}}, lay at percentile {{R1.H3_symptoms_mean.percentile}} of random four-term sets (with one and three mentions: {{R2.H3_symptoms_mean.percentile}} and {{R3.H3_symptoms_mean.percentile}}).

## Discussion

Co-localisation in the literature is a weak test of a hub, because the insula is reported by a large share of all studies; against that base rate, only interoception stands out, and it does so equally across anterior and posterior insula. Time perception and vestibular processing are not linked to the anterior insula beyond what random topics show, and neither are the somatic and mood terms of depression. This argues against using literature-wide co-activation as support for a selective anterior-insula meeting point. Targeted designs that manipulate interoceptive, temporal and gravitational processing within the same participants remain the appropriate test, since the anterior insula may still contribute to each function without being selective for their combination.

## Limitations

Term mentions are a coarse proxy for what a study investigated, and reported coordinates reflect each study's contrasts, not the full activation pattern. The radius is large relative to insular subdivisions, so anterior and posterior regions overlap in the coordinates they capture, which weakens C2. Vestibular is a proxy for graviception, studied mostly with caloric or galvanic stimulation rather than gravity itself, and there is no term for heaviness. Small term sets (time perception, vestibular, psychomotor) give imprecise estimates. The anterior insula's role in interoceptive awareness ([Craig 2009](doi:10.1038/nrn2555)) and its offline engagement during imagined movement ([Rousseau et al. 2020](doi:10.1093/cercor/bhaa376)) come from targeted designs that literature-wide co-occurrence cannot resolve; this analysis tests only whether the literature as a whole singles out the region. A null here does not show that the insula lacks these roles, only that co-localisation in the literature does not support a selective shared hub.

## Provenance

An agent of the Claude model family designed and registered the analysis, wrote the code and this paper; no person wrote text or code. Data: NeuroQuery version 1 (BSD-3-Clause) and the Harvard-Oxford atlas distributed with FSL, used unchanged.