Short official Latin term

Libelle of note

For the updated TNA, the following subdivision of the long fibre tracts has been adopted, based on Swanson and Bota’s proposal (Swanson LW, Bota M 2010 Foundation model of structural connectivity in the nervous system with a schema for wiring diagrams, connectome, and basic plan architecture. Proc Natl Aad Sci USA 107:20610-20617). In essence, this system includes: (1) Radices centrales (Central roots) for the cranial nerve roots within the brain stem, including the genu of the facial nerve, the decussation of the trochlear nerves, the solitary tract, the spinal and mesencephalic tracts of the trigeminal nerve, and the gracile and uneate fasciculi. The tractus opticus may also be viewed as a central root for the diencephalon and hypothalamus. (2) Tractus proprii (Intrinsic tracts), remaing to one part of the brain or within the spinal cord. The Tractus associationis cerebri (Association tracts of cerebrum), intrinsic to the cerebrum, are listed under their usual name. (3) Tractus commissurales (Commissural tracts) for the corpus callosum and the commissures (anterior, habenular, posterior); the term Transverse tracts will not be applied, some 'transverse tracts' are contralateral branches of a long tract. (4) Tractus longi (Longitudinal tracts) to be divided into: (a) Ascending tracts; (b) Cerebellar efferent tracts; and (c) Descending tracts. The problem of redundancy/repitition of terms has been solved by adding a topographical description where appropriate (pars spinalis/spinal part, pars rhombencephalica caudalis/caudal rhombencephalic or pars bulbaris/bubar part), pars rhombencephalica rostralis/rostral rhombencephalic part, pars pontina/pontine part, where appropriate and related to the real pons, pars mesencephalica/mesencephalic part, pars cerebellaris/cerebellar part, pars diencephalica/diencephalic part, par hypothalamica/hypothalamic part, Pars capsularis/capsular part)

For the Reticulospinal tracts various terms are used in the literature. Following the study on human reticulospinal fibres by Nathan PW, Smith MC, Deacon P (1996 Vestibulospinal, reticulospinal and descending propriospinal nerve fibres in man. Brain 119:1809-1833), here, a simplified subdivision into a Lateral (from The Myelencephalon) and a Medial reticulospinal tract (from the Pons) is advocated.

Nathan and Smith described the Propriospinal fasciculi as Posterior or Dorsal, Lateral, and Anterior or Ventral Ground bundles (Nathan PW, Smith MC 1959 Fasciculi proprii of the spinal cord in man. Brain 82:610-668). The term Fasciculus septomarginalis (Septomarginal fasciculus) is used for: 1) the Oval bundle of Flechsig, present at lumbar levels; and 2) the Triangle of Philippe-Gombault, present at sacral levels (see Schoenen J, Grant G 2004 The spinal cord: Connections. In: Paxinos G, Mai JK, eds: The Human Nervous System, 2nd ed. Elsevier, Amsterdam, pp 236-265). The term Fasciculus interfascicularis is also known as the Comma tract of Schultze, present at cervical and high thoracic levels. According to Nathan and Smith (1959), the Comma tract consists of descending divisions of the cervical and upper thoracic dorsal roots. The Fasciculus cornucommissuralis is present throughout the cord, best developed at lumbar levels; situated along the medial side of the posterior grey column abutting the posterior commissure. It consists of ipsilaterally running propriospinal fibres (see Schoenen and Grant 2004).

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For the Tractus spinoolivaris (Spino-olivary tract) as eponym Helweg tract is used. Smith and Deacon (Smith MC, Deacon P 1981 Helweg's triangular tract in man. Brain 104:249-277) denied that Helweg's tract contains spino-olivary fibres; more likely reticulospinal; Helweg's tract can be identified in Weigert-stained sections, but hardly in Luxol-Fast-Blue-stained sections. The term Fibrae olivospinales is deleted (non-existent); they are probably reticulospinal fibres; see Brodal A 1969 Neurological Anatomy in Relation to Clinical Medicine, 2nd ed. Oxford University Press, New York).

(Tractus anterolateralis): A Tract may be defined as a projection (a set of fibres with one main source and one main site of termination) which manifests itself as a fibre concentration over at least part of its course (Nieuwenhuys R 1998 Structure and organisation of fibre systems. In: Nieuwenhuys R, ten Donkelaar HJ, Nicholson C: The Central Nervous System of Vertebrates. Springer, Berlin-Heidelberg-New York, pp 113-157). For fibre systems with a more diffuse organization, the term Fibrae is advocated.

The Capsula extrema (Extreme capsule) forms one of the Long association systems involved in language processing (see Catani M, Thiebaut de Schotten M 2012 Atlas of Human Brain Connections. Oxford University Press, Oxford).

Although in the Fasciculus arcuatus (Arcuate fasciculus) three segments (anterior, long and posterior) were distinguished (Cayani M, Jones DK, ffytche DH 2005 Perisylvian language pathways. Ann Neurol 57:8-16), more recent research showed that the anterior segment belongs to the superior longitudinal fasciculus and the posterior segment is in reality separate and was renamed Fasciculus temporoparietalis verticalis (temporoparietal vertical or aslant tract), leaving the long segment as the true arcuate fasciculus (Fernandez-Miranda JC, Wang Y, Pathak S, et al. 2015 Asymmetry, connectivity, and segmentation of the arcuate fascicle in the human brain. Brain Struct Funct 220:3665-3680)

The Fasciculus longitudinalis superior (Superior longitudinal fasciculus) appears to be composed of three bundles (SLFI-III or Superior, Middle and Inferior; Makris N, Kennedy DN, McInerney S, et al. 2005 Segmentation of subcomponents within the superior longitudinal fascicle in humans: A quantitative, in vivo, DT-MRI study. Cereb Cortex 15:854-869) as in monkeys (Schmahmann JD, Pandya DN 2006 Fiber Pathways of the Brain. Oxford University Press, New York; Thiebaut de Schotten M, Dell'Acqua F, Valabreque R, Catani M 2012 Monkey to human comparative anatomy of the frontal lobe association tracts. Cortex 48:82-96).

Here, the new nomenclature for the long association fibres of the cerebrum is advocated as proposed by Mandonnet E, Sarubbo S, Petit L (2018 The nomenclature of human white matter association pathways: Proposal for a systematic taxonomic anatomical classification. Front Neuroanat 12:94).

The Fibrae U-figuratae (U-shaped fibres) were first described by Meynert (1872), and replaced the term Fibrae arcuatae cerebri (Arnold 1838) that became obsolete.

Recently, the Fasciculus temporoparietalis verticalis (Temporoparietal aslant tract) was demonstrated, replacing the vertical segment of the arcuate fasciculus (Panesar SS, Belo JT, Yeh F-C, Fernandez-Miranda JC 2019 Structure, asymmetry, and connectivity of the human temporo-parietal asland and vertical occipital fasciculi. Brain Struct Funct 224:907-923; see also 6273).

(Commissura hippocampi): The old term Psalterium has been added; much in use by clinicians; for a study on the cells of origin of commissural connections of the monkey hippocampal formation, see Amaral DG, Insausti R, Cowan WM (1984) The commissural connections of the monkey hippocampal formation. J Comp Neurol 224:307-336.

The Tractus vestibulomesencephalici include (Büttner-Ennever JA, Gerrits NM 2004 Vestibular system. In: Paxinos G, Mai JK, eds. The Human Nervous System, 2nd ed. Elsevier, Amsterdam, pp 1213-1240): the Tractus vestibulomesencephalicus medialis, containing fibres from Vestibular nuclei to Oculomotor nuclei, passing via the MLF; the Tractus vestibulomesencephalicus lateralis, with fibres from the Lateral vestibular nucleus to Oculomotor nuclei, passing just lateral to the MLF (eponym: Ascending tract of Deiters; the Tractus vestibulomesencephalicus ventralis, with fibres from the Y group and the Superior vestibular nucleus crossing in the Ventral tegmentum either within or below the Brachium conjunctivum.

A Tractus spinohypothalamicus (Spinohypothalamic tract) has been characterized functionally in monkeys (Zhang X, Wenk HN, Gokin AP, et al. 1999 Physiological studies of spinohypothalamic tract neurons in the lumbar enlargement of monkeys. J Neurophysiol 82:1054-1058; see also Westlund KN, Willis WD Jr 2012 Pain system. IN: Mai JK, Paxinos G, eds: The Human Nervous System, 3rd ed. Elsevier, Amsterdam, pp 1144-1186).

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(Tractus trigeminothalamici): The Tractus trigeminothalamicus anterior arises in the Spinal trigeminal nucleus and joins the Medial lemniscus, whereas the Tractus trigeminothalamicus lateralis arises in the Caudal part of the Spinal trigeminal nucleus and joins the Anterolateral tract.

(Tractus vestibulothalamicus): In monkeys, Vestibulothalamic projections pass via both the FLM and the Ascending tract of Deiters (Lang W, Büttner-Ennever JA, Büttner U 1979 Vestibular projections to the monkey thalamus: An autoradiographic study. Brain Res 177:3-17). Zwergal et al. (2008) demonstrated a Vestibulothalamic tract adjacent to the Medial lemniscus in humans (Zwergal A, Büttner-Ennever JA, Brandt T, Strupp M 2008 An ipsilateral vestibulothalamic tract adjacent to the medial lemniscus in humans. Brain 131:2928-2935).

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The Via endofolialis (Endfolial pathway) is composed of Hilar Schaffer collaterals from CA3h (see Lim C, Mufson EJ, Kordower JH, et al. 1997 Connections of the hippocampal formation in humans. II. The endfolial pathway. J Comp Neurol 385:352-371).

The Pedunculus temporalis (Temporal peduncle) forms the connection between the temporal and frontal lobes and contains: (1) the Fasciculus occipitofrontalis inferior (Inferior occipitofrontal fasciculus); and (2) the Fasciculus uncinatus cerebri (Uncinate fasciculus).

The Fasciculus subcallosus (Subcallosal fasciculus or Bundle of Muratoff; Muratoff W 1893 Secundäre Degenerationen nach Durchschneidung des Balkens. Neurol Centralbl 12:714-729) forms a separate bundle of Corticostriatal fibres (see Schmahmann JD, Pandya DN 2007 The complex history of the fronto-occipital fasciculus. J Hist Med 16:362-377).

The Fasciculus frontalis obliquus (Frontal aslant tract or Frontal oblique tract) connects the SMA and pre-SMA with the opercular part of the Inferior frontal gyrus (Catani M, Dell'Acqua F, Vergani F, et al. 2012 Short frontal lobe connections of the human brain. Cortex 48:273-291).