> Percellation and naming the motor thalamic nuclei is a mess because conventions were derived from either studying cell and myelin architecture in humans (e.g. Hassler) or connectomics in primates (e.g. Olszewski, Jones) ![[Pasted image 20250202164312.png]] Fig 1. Rough translation of nomenclature among authors, though, they don't cover the same anatomical borders. ^[Macchi G, Jones EG. Toward an agreement on terminology of nuclear and subnuclear divisions of the motor thalamus. _Journal of Neurosurgery_. 1997;86(4):670-685. doi:[10.3171/jns.1997.86.4.0670](https://doi.org/10.3171/jns.1997.86.4.0670)] → The motor thalamus locates in the lateral and ventral third of the thalamus, where it receives subcortical afferents from the basal ganglia (nigral and pallidal afferents) plus the cerebellum, and subsequently projects to the primary motor area, supplementary motor area, and premotor cortex. - It is limited medially by the internal medullary lamina, posteriorly by somatosensory nuclei, and laterally by the internal capsule. - The dorsal and lateral thalamus (superior border) receives intrathalamic fibres without external afferents ⇒ integration nuclei. ![[Pasted image 20250202172227.png]] Fig. 2 Typical microelectrode mapping of the Vim nucleus (Hassler's nomenclature) to implant DBS for [[Essential Tremor (ET)]] treatment, where 2-3 electrodes tracks are used to define the location of Vim and Vc prior to positioning the DBS electrode.^[Gross RE, Krack P, Rodriguez-Oroz MC, Rezai AR, Benabid AL. Electrophysiological mapping for the implantation of deep brain stimulators for Parkinson’s disease and tremor. _Movement Disorders_. 2006;21(S14):S259-S283. doi:[10.1002/mds.20960](https://doi.org/10.1002/mds.20960)] - Study of the thalamus has shifted toward defining the thalamic nuclei based on subcortical afferents (Jones and colleagues' nomenclature, Fig 3), though, conventions in functional neurosurgery largely remains grounded on the Schaltenbrand atlas (Hassler's nomenclature, Fig. 2). Despite their differences, they share the following patterns: ^[Krack P, Dostrovsky J, Ilinsky I, Kultas-Ilinsky K, Lenz F, Lozano A, Vitek J. Surgery of the motor thalamus: Problems with the present nomenclatures. _Movement Disorders_. 2002;17(S3):S2-S8. doi:[10.1002/mds.10136](https://doi.org/10.1002/mds.10136)] 1. anterior-posterior topographic organization of the ventral-lateral nuclei: nigral and pallidal afferent (ant, responding to active movement), cerebellar afferent (mid, responding to passive movement), sensory medial lemniscus afferent (post, responding to sensory) 1. There's further but non conclusive evidence suggesting the following connections nigral and pallidal afferent (Vop), cerebellar afferent (Vim), sensory medial lemniscus afferent (Vc) ^[Macchi G, Jones EG. Toward an agreement on terminology of nuclear and subnuclear divisions of the motor thalamus. _Journal of Neurosurgery_. 1997;86(4):670-685. doi:[10.3171/jns.1997.86.4.0670](https://doi.org/10.3171/jns.1997.86.4.0670)] 2. ![[Pasted image 20250204234705.png | 600]]^[Parras O, Domínguez P, Tomás-Biosca A, Guridi J. The role of tractography in the localisation of the Vim nucleus of the thalamus and the dentatorubrothalamic tract for the treatment of tremor. _Neurologia_. 2022;37(8):691-699. doi:[10.1016/j.nrleng.2019.09.008](https://doi.org/10.1016/j.nrleng.2019.09.008)] 2. the pathways of 3 territories do not share intersecting neuronal nodes ("overlapping"), but there are significant interdigitations ⇒ borders are not well demarcated 1. interdigitations is less for cerebellar and somatosensory inputs ![[Pasted image 20250202185153.png]] Fig 3. Morel's model, more common in current neuroimaging and basic science literature ^[Kumar VJ, Scheffler K, Grodd W. The structural connectivity mapping of the intralaminar thalamic nuclei. _Sci Rep_. 2023;13(1):11938. doi:[10.1038/s41598-023-38967-0](https://doi.org/10.1038/s41598-023-38967-0)] - Medial group: MD, Mediodorsal nucleus; MDmc, Magnocellular part; MDpc, Parvocellular part; MV, Medioventral nucleus; Pv, Paraventricular nucleus; Hb, Habenular nucleus - Intralaminar group: CL, Central lateral nucleus; CeM, Central medial nucleus; CM, Centre médian nucleus; Pf, Parafascicular nucleus; sPf, Subparafascicular nucleus - Posterior group: PuM, Medial pulvinar; PuI, Inferior pulvinar; PuL, Lateral pulvinar; PuA, Anterior pulvinar; LP, Lateral posterior nucleus; MGN, Medial geniculate nucleus; SG, Suprageniculate nucleus; Li, Limitans nucleus; Po, Posterior nucleus; LGN, Lateral geniculate nucleus