The Mystery of the Claustrum, the Front Wall of the Brain: From Early Anatomic Discovery to Modern Insights.

The claustrum, a thin sheet of gray matter between the insular cortex and putamen, has been studied for centuries. Its first known depiction appeared in Vicq d'Azyr's work (1786), and it was formally named vormauer (claustrum) by Burdach (1822). Later terms included N. taeniaeformis (Arnold, 1838) and avant-mur (Dejerine, 1895). Genetic evidence from Puelles (2017, 2022) distinguishes it from adjacent structures. Crick and Koch (2005) proposed it integrates sensory information for consciousness, but Yaşargil's neurosurgical observations show that tumor invasion or damage to the claustrum during insular glioma surgery does not impair consciousness, challenging that role. The review synthesizes historical and contemporary perspectives, highlighting the claustrum's debated function and relevance in neuroscience and neurosurgery.

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Abstract

The claustrum, a thin layer of gray matter between the insular cortex and putamen, has been a subject of anatomical and functional curiosity for centuries. Although early anatomical descriptions provide some insights, modern neuroimaging and neurosurgical studies have reignited interest in its structure and function. This study examines the historical evolution of the claustrum's terminology and clinical significance. A comprehensive review was conducted, analyzing neuroanatomical texts from the 15th to 20th centuries and contemporary academic publications on the claustrum. The investigation focused on anatomical descriptions, variations in nomenclature, and the claustrum's neurosurgical significance. The first known depiction of the claustrum appeared in the work of Vicq d'Azyr (1786), followed by formal naming as the vormauer (claustrum) by Burdach (1822). Subsequent terminology included N. taeniaeformis (Arnold, 1838) and avant-mur (Dejerine, 1895). Neurodevelopmental research by Puelles (2017, 2022) provided genetic evidence distinguishing it from adjacent structures. Functionally, Crick and Koch (2005) proposed its role in consciousness as a sensory integrator. Still, Yaşargil's neurosurgical observations indicate that tumor invasion or iatrogenic damage of the claustrum in cases of insular glioma does not result in impaired consciousness, prompting a reassessment of its functional role. This review synthesizes historical and contemporary perspectives to highlight the claustrum's relevance in neuroscience and neurosurgery. Although its exact function remains debated, ongoing research continues to shed light on its role in brain connectivity and integration. Understanding the claustrum's structure and function may lead to novel insights into sensory processing, cognition, and potential neurosurgical applications.