Summary: In 1856, Göttingen anatomist Rudolf Wagner described a striking anatomical curiosity after examining a brain that was later misidentified as belonging to the mathematician Carl Friedrich Gauss: a tissue connection spanning the central fissure (central sulcus), the deep groove separating the frontal and parietal lobes. This rare “bridged” central sulcus resurfaced in anatomical literature two decades later and has now been confirmed using modern MRI methods.
In 1876, Viennese anatomist Richard Heschl carried out an ambitious post-mortem survey of 1,087 brains to search for this bridge. He reported finding it in six cases (about 0.6%) and proposed that the surface bridge represents an extreme expression of a normal, deep-lying fold (the pli de passage fronto-pariétal moyen) that sometimes grows high enough to reach the brain surface. Nearly 150 years later, researchers reproduced Heschl’s observations using ultra-high-resolution magnetic resonance imaging (MRI), validating his anatomical insight with contemporary techniques.
An international team analyzed MRI scans from 1,112 healthy adults in the Human Connectome Project Young Adult dataset. Their work not only replicated Heschl’s structural findings with enhanced precision but also revealed a twin-based clue suggesting prenatal environmental influences shape this rare cortical feature rather than heredity alone.
Key Facts
- The 2013 Gauss/Fuchs discovery: The distinctive bridged central sulcus that first drew attention belonged to physician C. H. Fuchs. The brain of Fuchs had been mistakenly catalogued as Gauss’s during 19th-century museum work; that error was recognized in 2013 because Fuchs’s brain carried the uncommon bridge, a clear identifying landmark.
- Heschl’s large-scale anatomical audit: In 1876, Richard Heschl applied an early statistical approach to neuroanatomy, inspecting over a thousand post-mortem brains in a single year to quantify rare versus typical structural variations.
- MRI confirmation of historical findings: Using modern 3D surface reconstructions from MRI scans, the replication team identified nine bridged central sulci among 1,112 subjects (0.8%), closely matching Heschl’s original prevalence estimate.
- Twin findings and prenatal environment: The sample included many twins. The bridge was more frequent among twin participants (1.8% of dizygotic and 1.1% of monozygotic twins), yet when present it usually affected only one twin in a pair—pointing to in-womb environmental factors rather than a clear genetic cause.
- No detectable functional effect: Researchers emphasize that the bridged central sulcus is an anatomical variation without known consequences for cognition, behavior, or motor function.
Source: DPZ
Historical origins and the Gauss–Fuchs mix-up
Rudolf Wagner’s mid-19th-century report noted an unusual tissue bridge crossing the central fissure. Later research traced the specimen to physician C. H. Fuchs, whose brain had been misfiled as the brain of C. F. Gauss. Neuroscientist Renate Schweizer rediscovered this historical trail in 2013 while reviewing archival material; the rare bridged sulcus provided the key anatomical fingerprint that exposed the 150-year-old mix-up and led her to Richard Heschl’s 1877 publication.
Linking the surface bridge to a deep convolution
Heschl’s pioneering study did two things: it established how rare the bridged central sulcus is, and it quantified the height distribution of the common deep winding (the pli de passage fronto-pariétal moyen) at the same location. From his large post-mortem sample, Heschl concluded that when the deep winding reaches an unusually large height it can break through to become the visible surface bridge.
Renate Schweizer and colleagues revisited these hypotheses with MRI. They generated cortical surface reconstructions and visually inspected complete brain surfaces, mirroring Heschl’s original observational approach but with modern imaging. Their detection of nine bridged central sulci among 1,112 scans (0.8%) closely aligns with Heschl’s 0.6% estimate, supporting the historical interpretation.
New computational measures of the deep folding
Doctoral researcher Anna M. Müllen developed a computational method to measure the height distribution of the deep convolution in MRI-derived hemispheric depth profiles. The resulting distribution, while measured more precisely and thus wider in absolute terms, showed the same skew toward larger heights that Heschl reported: a pattern consistent with the idea that the bridged central sulcus represents an extreme form of a normally present deep fold.
Twin data point to prenatal environmental influences
Because the modern dataset included many twin participants, the team could assess whether the bridged central sulcus has a genetic basis. The bridge was found more often in twins overall, but within twin pairs it usually affected only one sibling. This lack of concordance in monozygotic pairs argues against a simple genetic cause and suggests that micro-environmental conditions in the womb—such as local mechanical forces or spatial constraints during cortical folding—play a major role.
Conclusions and scientific recognition
The replication confirms Heschl’s two core observations and extends them by identifying potential prenatal environmental contributors. The study highlights Heschl’s early adoption of large-sample reasoning and demonstrates how modern MRI can validate and refine historical anatomical findings. For this work, Renate Schweizer, Anna M. Müllen, and Julius Stropel received the Replication Prize from the Organization for Human Brain Mapping.
Key Questions Answered:
A: A rare bridged central sulcus served as a distinctive anatomical marker. Rudolf Wagner had drawn this unusual feature when studying C. H. Fuchs’s brain in 1856. That specimen was later miscatalogued as Gauss’s. When Renate Schweizer reviewed historical records in 2013, she used the unique bridge to identify the brain as Fuchs’s, revealing the century-old mislabeling.
A: The central sulcus separates primary motor and somatosensory cortex. Most people have a clear open sulcus at the surface, while everyone has a small deep fold at the sulcus floor. In fewer than 1% of individuals that deep fold can extend high enough to appear at the surface as a visible bridge. Researchers consider this a benign anatomical variant with no known effects on thinking or motor skills.
A: The increased frequency of the bridge in twins likely reflects prenatal environmental influences. Because the bridge usually appears in only one twin of a pair—even in identical twins—the trait does not follow a simple genetic pattern. Local differences in uterine space, pressure, or fluid dynamics during cortical folding are plausible drivers.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- The journal paper was reviewed in full for accuracy.
- Additional context was added by editorial staff.
About this neuroscience research news
Author: Susanne Diederich
Source: DPZ (German Primate Center – Leibniz Institute for Primate Research)
Contact: Susanne Diederich – DPZ
Image: The image is credited to Neuroscience News
Original Research: Open access. “The deep winding at the brain surface: replicating a historical report associating the ‘bridged’ central sulcus with the pli de passage fronto-pariétal moyen” by Renate Schweizer, Anna Marie Müllen & Julius Stropel. Brain Structure and Function. DOI: 10.1007/s00429-025-02947-z
Abstract
The deep winding at the brain surface: replicating a historical report associating the ‘bridged’ central sulcus with the pli de passage fronto-pariétal moyen
In 1876 Heschl examined 1,087 brains and reported six unilateral cases of a bridged central sulcus at the brain surface, alongside measurements of a normal deep winding at the same location that showed a skewed distribution toward larger heights. The historical data supported the hypothesis that a bridged central sulcus represents an extreme manifestation of an otherwise common deep convolution.
This replication analyzed structural MRI from 1,112 participants of the Human Connectome Project Young Adult dataset. Visual inspection identified nine bridged central sulci, confirming a prevalence below 1%. Computational extraction of deep-winding heights from 1,983 hemispheric depth profiles reproduced a similarly skewed height distribution, consistent with Heschl’s observations. Twin analyses suggested a modestly increased prevalence among twins but no concordance in monozygotic pairs, supporting a role for prenatal environmental factors. Overall, the study validates and refines historical anatomical insights into the central sulcus.