Historical controversies about the thalamus: from etymology to function

Abstract

<jats:p>The authors report on and discuss the historical evolution of the 3 intellectual and scientific domains essential for the current understanding of the function of the human thalamus: 1) the identification of the thalamus as a distinct anatomical and functional entity, 2) the subdivision of thalamic gray matter into functionally homogeneous units (the thalamic nuclei) and relative disputes about nuclei nomenclature, and 3) experimental physiology and its limitations.</jats:p><jats:p>Galen was allegedly the first to identify the thalamus. The etymology of the term remains unknown although it is hypothesized that Galen may have wanted to recall the thalamus of Odysseus. Burdach was the first to clearly and systematically define the thalamus and its macroscopic anatomy, which paved the way to understanding its internal microarchitecture. This structure in turn was studied in both nonhuman primates (Friedemann) and humans (Vogt and Vogt), leading to several discrepancies in the findings because of interspecies differences. As a consequence, two main nomenclatures developed, generating sometimes inconsistent (or nonreproducible) anatomo-functional correlations. Recently, considerable effort has been aimed at producing a unified nomenclature, based mainly on functional data, which is indispensable for future developments. The development of knowledge about macro- and microscopic anatomy has allowed a shift from the first galenic speculations about thalamic function (the “thalamus opticorum nervorum”) to more detailed insights into the sensory and motor function of the thalamus in the 19th and 20th centuries. This progress is mostly the result of lesion and tracing studies. Direct evidence of the in vivo function of the human thalamus, however, originates from awake stereotactic procedures only.</jats:p><jats:p>Our current knowledge about the function of the human thalamus is the result of a long process that occurred over several centuries and has been inextricably intermingled with the increasing accumulation of data about thalamic macro- and microscopic anatomy. Although the thalamic anatomy can currently be considered well understood, further studies are still needed to gain a deeper insight into the function of the human thalamus in vivo.</jats:p>

The Predictive Potential of Altered Voxel-Based Morphometry in Severely Obese Patients With Meibomian Gland Dysfunction

“…The thalamus occupies an important position in the deep brain and contributes to sensory cognition, motor function, as well as emotional processing ( Serra et al, 2019 ). Recent investigations on structural and functional alterations of the thalamus have uncovered their relationships with the severity of cognitive impairment.…”

Routes of the thalamus through the history of neuroanatomy

“…Hence, Galen's thalamus was a storeroom for the vital spirit. Burdach (see below) was even convinced that Galen had never seen the thalamus, as he stated in 1822 (Serra et al, 2019).…”

“…In fact the name Galen gave to this structure was 'thalamus nervorum opticorum'. 'Thalamus' means inner chamber or anteroom in a given semantic context and, in another one, bridal bed or bridal chamber (Gailloud et al, 2003;Jones, 1985;Serra et al, 2019). According to Gailloud et al (2003) and Jones (1985), 'thalamos' may originate in the even older word 'thalam', which designates the first of the three chambers of an Egyptian temple (see Figure 1.2.…”

Microneurosurgical removal of thalamic lesions: surgical results and considerations from a large, single-surgeon consecutive series

“…T he deep location of the thalamus and its proximity to vital neural and vascular structures pose a formidable challenge to surgeons willing to pursue thalamic surgery, [1][2][3][4] and a conservative attitude toward such lesions dominates the literature. A biopsy followed by adjuvant therapy is the favored approach for thalamic tumors, 5 whereas thalamic cavernous malformations are removed at only highly selected centers.…”

“…1). 2 Most lesions within the thalamus can be safely reached through one of these surfaces. And each of these surfaces can in turn be reached by one or more of the following TCTV or TCi approaches (Fig.…”