Despite a large amount of information obtained during the last 50 plus years, the human thalamus still remains for the most part terra incognita. Refinement of imaging techniques has led to an impressive leap in understanding of cortical functioning in human and interaction between different parts of the cortex during performance of specific tasks. A sort of functional brain anatomy has been unfolding in front of our eyes. At the same time the thalamus, which is intricately interconnected with the entire cortex and plays a pivotal role in its functioning, has somehow faded from the attention focus. The fact that thalamic neuronal circuits, especially in the nuclei connected with the frontal lobe are species-specific and their complexity is the highest in primates points to evolutionary importance of this brain entity. Yet, due to its deep position in the brain, complex anatomical organization, and quite importantly, the lack of easily graspable maps to enable interpretation of imaging data, thalamus has rarely been considered in the analysis of functional circuits.
Over several decades our studies concentrated on so-called motor-related thalamic nuclei in primate and non-primate species that process information from the basal ganglia and cerebellum before forwarding it to the neocortex. We have been able to outline these nuclei also in the human thalamus using immunocytochemical techniques in a study with monoclonal antibody to isoform 65 of glutamic acid decarboxylase (GAD65). This technique allowed to identify the territories of three major subcortical afferents, pallidal, nigral and cerebellar, in the human thalamus and demarcate their extent and topographical relationships. Using these data and continuous series of Nissl-stained sagittal sections we constructed the nuclear maps of the human thalamus within a system of coordinates basically the same as in the atlas of Schaltenbrand and Bailey (1959), which is used in neurosurgery, but with a simplified and functionally relevant nomenclature for motor thalamic nuclei (Ilinsky et al. 2018)
Demonstrated at this site are digitized images of Nissl-stained sections and series of color-coded maps in sagittal, coronal and horizontal planes within the stereotactic coordinates, as well as a series of sagittal MRI cuts (reconstructed from coronal images), all from the same tissue block.. The 3D volume was co-registered with MNI space by Andreas Horn (Charité University, Berlin, Germany) and is available in Lead-DBS website (www.lead-dbs.org). Just download Lead-DBS and you’ll find it installed in there. The nifti files can be found in: /templates/space/MNI_ICBM_009b_NLIN_ASYM/atlases/Human Motor Thalamus (Ilinsky 2017).
Comparison of proposed nomenclature of motor-related nuclei with Hassler’s nomenclature, which is used in Schaltenbrand and Bailey atlas (1959), is provided on the page IMAGES of this site entitled ‘Comments on nuclear delineations and nomenclature’. For discussion on identification of motor thalamic nuclei in the MRIs during contemporary neurosurgery see ‘Surgical thalamic targets in the light of proposed outlines and nomenclature’ at the bottom of the same IMAGES page.
Feedback in form of constructive criticism, suggestions, and/or proposals is welcome.