Projections from the medial septum and diagonal band of Broca to the dorsal and central superior raphe nuclei: a non-cholinergic pathway

Summary The anatomical organization of projections from the medial septal nucleus (MS), and the vertical (VDB) and horizontal limb (HDB) of the diagonal band of Broca to the dorsal raphe nucleus (NRD) and the central superior raphe nucleus (RCS) of the rat were studied by anterograde [³H]-leucine, and True Blue and Fluoro Gold fluorescent retrograde tracing. Projections from the MS were found to enter the basal mesencephalon at the rostro-medial aspect of the pontine nuclei, curve dorsally and terminate throughout the RCS and in the caudal portion of the NRD. Fibers from the VDB were found to enter these raphe nuclei by two separate routes; some fibers reached the basal mesencephalon, curved dorsally and terminated in the RCS and NRD. Other fibers entered the pedunculopontine nucleus, curved medially and reached the NRD. Presumed terminal labelling was found overlaying the RCS and NRD throughout their rostro-caudal extensions. The brain stem projections from HDB entered the mesencephalon by the same routes as those from VDB, but the labelling over RCS was sparse, and the NRD labelling was preferentially distributed to the rostral portion of the nucleus. The present data indicate a crude topographic organization of the projections from the septal region to the NRD and RCS. In general, the distribution of presumed terminal labelling appeared to be more closely associated with the distribution of NRD and RCS 5-HT immunoreactive cell bodies, than with the cytoarchitectonically defined extensions of these raphe nuclei. By sequential evaluation of the distribution of retrogradely labelled and acetylcholine esterase-stained cells on the same section, and by selective tracing with radiolabelled choline, it appears that the vast majority, if not all, of the neurons in MS and diagonal band which project to the rostral raphe are non-cholinergic.Abbreviations CLi caudal linear raphe nucleus - DTg dorsal tegmental nucleus - flm medial longitudinal fasciculus - HDB horizontal limb of the diagonal band of Broca - IP interpeduncular nucleus - MS medial septal nucleus - NRD dorsal raphe nucleus - PAG periaqueductal gray - Pn pontine nucleus - R red nucleus - RCS central superior raphe nucleus - RMg raphe magnus nucleus - RPn pontine raphe nucleus - SN substantia nigra - VDB vertical limb of the diagonal band of Broca - VTg ventral tegmental nucleus - 5 trigeminal motor nucleus     

Retrograde labeling of neurons in the brain stem following injections of [3H]choline into the forebrain of the rat

Summary In an attempt to identify cholinergic neurons of the brain stem which project to the forebrain, retrograde labeling of neurons in the brain stem was examined by autoradiography following injections of 20 Ci [³H]choline into the thalamus, hypothalamus, basal forebrain and frontal cortex. After injections into the thalamus, retrogradely labeled neurons were evident within the lateral caudal mesencephalic and dorsolateral oral pontine tegmentum (particularly in the laterodorsal and pedunculopontine tegmental nuclei) and in smaller number within the latero-medial caudal pontine (Reticularis pontis caudalis, Rpc) and medullary (Reticularis gigantocellularis, Rgc) reticular formation. Following [³H]choline injections into the lateral hypothalamus and into the basal forebrain, retrogradely labeled neurons were localized in the dorsolateral caudal midbrain and oral pontine tegmentum and in smaller number in the medial medullary reticular formation (Rgc), as well as in the midbrain, pontine and medullary raphe nuclei. After injections into the anterior medial frontal cortex, a small number of retrogradely labeled cells were found in the brain stem within the laterodorsal tegmental nucleus and the dorsal raphe nucleus. In a parallel immunohistochemical study, choline acetyltransferase (ChAT)-positive neurons were found to be located in most of the regions of the reticular formation where cells were retrogradely labeled from the forebrain following [³H]choline injections. These results suggest that multiple cholinergic neurons within the lateral caudal midbrain and dorsolateral oral pontine tegmentum and a few within the caudal pontine and medullary reticular formation project to the thalamus, hypothalamus and basal forebrain and that a limited number of pontine cholinergic neurons project to the frontal cortex.Abbreviations of Neuroanatomical Terms 3 oculomotor nuc - 4 trochlear nuc - 4V fourth ventricle - 6 abducens nuc - 7 facial nuc - 7n facial nerve - 8n vestibulocochlear nerve - 10 dorsal motor nuc vagus - 12 hypoglossal nuc - 12n hypoglossal nerve - Amb ambiguus nuc - Aq cerebral aqueduct - bic brachium inf colliculus - CB cerebellum - CG central gray - CLi caudal linear nuc raphe - Cnf cuneiform nuc - cp cerebral peduncle - Cu cuneate nuc - D nuc Darkschewitsch - DCo dorsal cochlear nuc - DLL dorsal nuc lateral lemniscus - DPB dorsal parabrachial nuc - DR dorsal raphe nuc - dsc dorsal spinocerebellar tract - DTg dorsal tegmental nuc - dtgx dorsal tegmental decussation - ECu external cuneate nuc - Fl flocculus - IC inferior colliculus - icp inferior cerebellar peduncle - IF interfascicular nuc - InC interstitial nuc Cajal - IO inferior olive - IP interpeduncular nuc - KF Kolliker-Fuse nuc - LC locus coeruleus - Ldt laterodorsal tegmental nuc - Ifp longitudinal fasciculus pons - ll lateral lemniscus - LRt lateral reticular nuc - LRtS5 lateral reticular nucsubtrigeminal - LSO lateral superior olive - LTz lateral nuctrapezoid body - LVe lateral vestibular nuc - mcp middle cerebellar peduncle - Me5 mesencephalic trigeminal nuc - MGD medial geniculate nuc, dorsal - ml medial lemniscus - mlf medial longitudinal fasciculus - MnR median raphe nuc - Mo5 motor trigeminal nuc - MSO medial superior olive - MTz medial nuc trapezoid bbody - MVe medial vestibular nuc - PBg parabigeminal nuc - Pgl nuc paragigantocellularis lateralis - Pn pontine nuc - PPTg pedunculopontine tegmental nuc - Pr5 principal sensory trigeminal - PrH prepositive hypoglossal nuc - py pyramidal tract - Rgc reticularis gigantocellularis - Rgca reticularis gigantocellularis pars alpha - Rmes reticularis mesencephali - RMg raphe magnus nuc - RN red nuc - Ro nuc Roller - ROb raphe obscurus nuc - Rp reticularis parvicellularis - RPa raphe pallidus nuc - Rpc reticularis ponds caudalis - RPn raphe pontis nuc - Rpo reticularis pontis oralis - RR retrorubral nuc - rs rubrospinal tract - RtTg reticulotegmental nuc pons - s5 sensory root trigeminal nerve - SC superior colliculus - SCD superior colliculus,deep layer - SCI superior colliculus, intermediate layer - scp superior cerebellar peduncle - SCS superior colliculus, superficial layer - SGe suprageniculate nuc pons - SNC substantia nigra compact - SNL substantia nigra,lateral - SNR substantia nigra, reticular - SolL solitary tract nuc,lateral - SolM solitary tract nuc, medial - sp5 spinal tract trigeminal nerve - sp5I spinal trigeminal nuc, interpositus - Sp5O spinal trigeminal nuc, oral - spth spinothalamic tract - SpVe spinal vestibular nuc - SuVe superior vestibular nuc - tp tectopontine - ts tectospinal tract - tz trapezoid body - VCo ventral cochlear nuc - VLL ventral nuc lateral lemniscus - VPB ventral parabrachial nuc - vsc ventral spinocerebellar tract - VTA ventral tegmental area - VTg ventral tegmental nuc - vtgx ventral tegmental decussation - xscp decussation superior cerebellar peduncle This investigation was supported by grants from the Medical Research Council (MRC) of Canada (MT-6464: BEJ and MT 7376: AB). B.E. Jones holds a Chercheur Boursier Senior Award from the Fonds de la Recherche en Santé du Quebec (FRSQ), and A. Beaudet a Scientist Award from MRC     

Neuroanatomical study of afferent projections to the supramammillary nucleus of the rat

We examined the regions projecting to the supramammillary nucleus of the rat with retrograde transport of WGA-HRP and WGA, and anterograde transport of Phaseolus vulgaris leucoagglutinin. The supramammillary nucleus receives major descending afferents from the infralimbic cortex, the dorsal peduncular cortex, the nucleus of the diagonal band of Broca, the medial and lateral preoptic nuclei, bilaterally. The major ascending afferents come from the pars compacta of the nucleus centralis superior, the ventral tegmental nucleus, and the laterodorsal tegmental nucleus. The supramammillary nucleus also receives a few (but distinct) fibers from the anterior and lateral hypothalamic nuclei, the ventral premammillary nucleus, the interpeduncular nucleus, the cuneiform nucleus, the dorsal raphe nucleus, the incertus nucleus, and the C3 region including the prepositus hypoglossi nucleus. All descending fibers run through the medial forebrain bundle. Almost all ascending fibers from the pars compacta of the nucleus centralis superior and the laterodorsal tegmental nucleus run through the mammillary peduncle, and terminate throughout the supramammillary nucleus. A few fibers from the laterodorsal tegmental nucleus and the C3 region run through the fasciculus longitudinalis dorsalis and terminate in the dorsal part of the supramammillary nucleus including the supramammillary decussation.Abbreviations a anterior commissure - AC accumbens nucleus - AR arcuate nucleus - BS bed nucleus of the stria terminalis - C3 C3 adrenergic region - CA interstitial nucleus of Cajal - CC pars compacta of the nucleus centralis superior - CS nucleus centralis superior - CU cuneiform nucleus - CX cingulate cortex - DB nucleus of the diagonal band of Broca - DH dorsomedial hypothalamic nucleus - ds decussation of the superior cerebellar peduncle - DX dorsal peduncular cortex - f fornix - fld fasciculus longitudinalis dorsalis - flm fasciculus longitudinalis medialis - IN incertus nucleus - IX infralimbic cortex - LC nucleus of the locus ceruleus - le lemniscus medialis - LH lateral hypothalamic nucleus - LM lateral mammillary nucleus - LO lateral preoptic nucleus - LS lateral septal nucleus - LT laterodorsal tegmental nucleus - mfb medial forebrain bundle - MM medial mammillary nucleus - MO medial preoptic nucleus - mp mammillary peduncle - mt mammillothalamic tract - MV medial vestibular nucleus - PD dorsal premammillary nucleus - PH prepositus hypoglossi nucleus - PV ventral premammillary nucleus - RD dorsal raphe nucleus - rf fasciculus retroflexus - SUM supramammillary nucleus - sx supramammillary decussation - T tenia tecta - TD dorsal tegmental nucleus - TM tuberomammillary nucleus - TV ventral tegmental nucleus - VT ventral tegmental area of Tsai     

Ascending projections from the nucleus of the brachium of the inferior colliculus in the cat

Summary Ascending projections from the nucleus of the brachium of the inferior colliculus (NBIC) in the cat were studied by the autoradiographic tracing method. Many fibers from the NBIC ascend ipsilaterally in the lateral tegmentum along the medial border of the brachium of the inferior colliculus. At midbrain levels, fibers from the NBIC end in the superior colliculus, the pretectum, the central gray and the peripeduncular tegmental region bilaterally with ipsilateral predominance. NBIC fibers to the superior colliculus are distributed densely to laminae VI an III throughout the whole rostrocaudal extent of the colliculus. In the pretectum, NBIC fibers terminate in the anterior and medial nuclei and the nucleus of the posterior commissure. NBIC fibers to the dorsal thalamus are distributed largely ipsilaterally. Many NBIC fibers end in the dorsal and medial divisions of the medial geniculate body, but few in the ventral division. The NBIC also sends fibers to the suprageniculate, limitans and lateralis posterior nuclei and the lateral portion of the posterior nuclear complex; these regions of termination of NBIC fibers constitute, as a whole, a single NBIC recipient sector. Additionally, the NBIC sends fibers to the centralis lateralis, medialis dorsalis, paraventricular and subparafascicular nuclei of the thalamus.Abbreviations APtC Pars compacta of anterior pretectal nucleus - APtR Pars reticulata of anterior pretectal nucleus - BIC Brachium of infertior colliculus - CG Central gray - CL Nucleus centralis lateralis - CP Cerebral peduncle - D Dorsal division of medial geniculate body - IC Inferior colliculus - LG Lateral geniculate body - LP Nucleus lateralis posterior - Lim Nucleus limitans - M Medial division of medial geniculate body - MD Nucleus medialis dorsalis - ML Medial lemniscus - NBIC Nucleus of brachium of inferior colliculus - NPC Nucleus of posterior commissure - PN Pontine nuclei - Ppr Peripeduncular region - Pt Pretectum - Pbg Parabigeminal nucleus - Pol Lateral portion of posterior nuclear complex - Pom Medial portion of posterior nuclear complex - Pul Pulvinar - Pv Nucleus paraventricularis - R Red nucleus - SC Superior colliculus - Sg Nucleus suprageniculatus - Spf Nucleus subparafascicularis - V Ventral division of medial geniculate body - VPL Nucleus ventralis posterolateralis - VPM Nucleus ventralis posteromedialis - II,III,IV,VI Tectal laminae     

A horseradish peroxidase study of afferent connections of the globus pallidus in Macaca mulatta

Summary The high tonic discharge rates of globus pallidus neurons in awake monkeys suggest that these neurons may receive some potent excitatory input. Because most current electrophysiological evidence suggests that the major described pallidal afferent systems from the neostriatum are primarily inhibitory, we used retrograde transport of horseradish peroxidase (HRP) to identify possible additional sources of pallidal afferent fibers. The appropriate location was determined before HRP injection by mapping the characteristic high frequency discharge of single pallidal units in awake animals. In animals with injections confined to the internal pallidal segment, retrograde label was seen in neurons of the pedunculopontine nucleus, dorsal raphe nucleus, substantia nigra, caudate, putamen, subthalamic nucleus, parafascicular nucleus, zona incerta, medial and lateral subthalamic tegmentum, parabrachial nuclei, and locus coeruleus. An injection involving the external pallidal segment and the putamen as well resulted in additional labeling of cells in centromedian nucleus, pulvinar, and the ventromedial thalamus.Abbreviations AC anterior commissure - CG central grey - CM centromedian nucleus - CN caudate nucleus - DM dorsomedial nucleus - DR dorsal raphe nucleus - DSCP decussation of superior cerebellar peduncle - GPe globus pallidus, external segment - GPi globus pallidus, internal segment - LC locus coeruleus - LL lateral lemniscus - MG medial geniculate nucleus - ML medial lemniscus - NVI abducens nucleus - OT optic tract - Pbl lateral parabrachial nucleus - Pbm medial parabrachial nucleus - Pf parafascicular nucleus - PPN pedunculopontine nucleus - PuO oral pulvinar nucleus - RN red nucleus - SCP superior cerebellar peduncle - SI substantia innominata - SNc substantia nigra, pars compacta - SNr substantia nigra, pars reticulata - STN subthalamic nucleus - TMT mamillothalamic tract - VA ventral anterior nucleus - VLc ventral lateral nucleus, pars caudalis - VLm ventral lateral nucleus, pars medialis - VLo ventral lateral nucleus, pars oralis - VPI ventral posterior inferior nucleus - VPM ventral posterior medial nucleus - VPLc ventral posterior lateral nucleus, pars caudalis - ZI zona incerta     

Afferents to the basal forebrain cholinergic cell area from pontomesencephalic--catecholamine, serotonin, and acetylcholine--neurons

The afferent input to the basal forebrain cholinergic neurons from the pontomesencephalic tegmentum was examined by retrograde transport of wheatgerm agglutinin-horseradish peroxidase in combination with immunohistochemistry. Multiple tyrosine hydroxylase-, dopamine-beta-hydroxylase-, serotonin- and choline acetyltransferase-immunoreactive fibres were observed in the vicinity of the choline acetyltransferase-immunoreactive cell bodies within the globus pallidus, substantia innominata and magnocellular preoptic nucleus. Micro-injections of horseradish peroxidase-conjugated wheatgerm agglutinin into this area of cholinergic perikarya led to retrograde labelling of a large population of neurons within the pontomesencephalic tegmentum, which included cells in the ventral tegmental area, substantia nigra, retrorubral field, raphe nuclei, reticular formation, pedunculopontine tegmental nucleus, laterodorsal tegmental nucleus, parabrachial nuclei and locus coeruleus nucleus. Of the total population of retrogradely labelled neurons, a significant (approximately 25%) proportion were tyrosine hydroxylase-immunoreactive and found in the ventral tegmental area (A10), the substantia nigra (A9), the retrorubral field (A8), the raphe nuclei (dorsalis, linearis and interfascicularis) and the locus coeruleus nucleus (A6), Another important contingent (approximately 10%) was represented by serotonin neurons of the dorsal raphe nucleus (B7), the central superior nucleus (B8) and ventral tegmentum (B9). A small proportion (less than 1%) was represented by cholinergic neurons of the pedunculopontine (Ch5) and laterodorsal (Ch6) tegmental nuclei. These results demonstrate that pontomesencephalic monoamine neurons project in large numbers up to the basal forebrain cholinergic neurons and may represent a major component of the ventral tegmental pathway that forms the extra-thalamic relay from the brainstem through the basal forebrain to the cerebral cortex.     

Mesopontine rostromedial tegmental nucleus neurons projecting to the dorsal raphe and pedunculopontine tegmental nucleus: psychostimulant-elicited Fos expression and collateralization

The mesopontine rostromedial tegmental nucleus (RMTg) is a GABAergic structure in the ventral midbrain and rostral pons that, when activated, inhibits dopaminergic neurons in the ventral tegmental area and substantia nigra compacta. Additional strong outputs from the RMTg to the pedunculopontine tegmental nucleus pars dissipata, dorsal raphe nucleus, and the pontomedullary gigantocellular reticular formation were identified by anterograde tracing. RMTg neurons projecting to the ventral tegmental area express the immediate early gene Fos upon psychostimulant administration. The present study was undertaken to determine if neurons in the RMTg that project to the additional structures listed above also express Fos upon psychostimulant administration and, if so, whether single neurons in the RMTg project to more than one of these structures. We found that about 50% of RMTg neurons exhibiting retrograde labeling after injections of retrograde tracer in the dorsal raphe or pars dissipata of the pedunculopontine tegmental nucleus express Fos after acute methamphetamine exposure. Also, we observed that a significant number of RMTg neurons project both to the ventral tegmental area and one of these structures. In contrast, methamphetamine-elicited Fos expression was not observed in RMTg neurons labeled with retrograde tracer following injections into the pontomedullary reticular formation. The findings suggest that the RMTg is an integrative modulator of multiple rostrally projecting structures.     

Projections of the substantia nigra, ventral tegmental area and amygdala to the pallidum in dog brain

Using the method based on HRP retrograde axonal transport organization of projections of substantia nigra, tegmental ventral field and amygdala on pallidum was studied. Neuronal fibres from all dopaminergic portions of substantia nigra and tegmental ventral field were found to project on both structures of dog dorsal pallidum (globus pallidus and entopeduncular nucleus). Ventral pallidum receives projectional axons only from neurons of basal nucleus of amygdala and tegmental ventral field.     

Topography and functional role of dopaminergic projections from the ventral mesencephalic tegmentum to the ventral pallidum.

A dopaminergic projection from the ventral tegmental area to the ventral pallidum was identified in the rat using anterograde tract tracing and combined retrograde tracing-immunocytochemistry. The projection was found to be topographically organized such that fibers innervating the ventromedial ventral pallidum arose from neurons located along the midline nuclei of the ventral mesencephalon, including the nucleus interfascicularis and nucleus linearis caudalis. Ventral tegmental neurons situated more laterally, in the nucleus parabrachialis pigmentosus and nucleus paranigralis, projected to the ventromedial and dorsolateral ventral pallidum. The substantia nigra did not supply a major contribution to this projection. The proportion of ventral tegmental area dopaminergic neurons projecting to the ventral pallidum ranged from approximately 30% to 60%. The functional significance of the projection is indicated since intra-ventral pallidum microinjections of dopamine elicited a dose-dependent increase in locomotor activity. Furthermore, whereas pretreatment of the ventral pallidum with the GABAA agonist muscimol has been shown to attenuate opioid-induced locomotor activity elicited from the ventral pallidum, it did not attenuate the dopamine-induced motor response. Thus, while mu-opioids in the ventral pallidum may presynaptically regulate GABAergic efferents from the nucleus accumbens, it appears that the dopaminergic input directly influences the ventral pallidal output neuron which is involved in locomotion.     

The cerebellar projection from the raphe nuclei in the cat as studied with the method of retrograde transport of horseradish peroxidase

Summary Following injections of horseradish peroxidase (HRP) in the cerebellar cortex and nuclei of the cat, the distribution of labeled cells in the raphe nuclei was mapped. The findings confirm those made previously in studies of retrograde cell degeneration following cerebellar ablations (Brodal et al., 1960a), and in addition reveal new details in the projection of the raphe nuclei onto the cerebellar cortex and nuclei.All the raphe nuclei except nucleus linearis intermedius and nucleus linearis rostralis project onto the cerebellar cortex. The nuclei raphe obscurus and pontis contribute the greatest number of afferents to the cerebellum.With the exception of lobule VI which probably is the recipient of a weak projection, all parts of the cerebellar cortex receive afferents from the raphe nuclei. The heaviest projection is to the vermis of lobules VIIA and X, and to crus II. The afferents to the cerebellar nuclei are few in number (Tables 2–6).The observations indicate that each raphe neuron probably projects to more than one terminal site in the cerebellum.The findings are discussed with reference to other efferent and afferent studies of the raphe nuclei. All these studies indicate that the raphe nuclei have widespread efferent and afferent connections, making them capable to participate in a variety of regulatory functions.List of abbreviations f.apm. Ansoparamedian fissure - f.icul. Intraculminate fissure - f.in.cr. Intercrural fissure - fl. Flocculus - f.pc. Preculminate fissure - f.pfl. parafloccular fissure - f.ppd. Prepyramidal fissure - f.pr. Fissura prima - f.prc. Precentral fissure - f.prc.a Precentral fissure a - f.p.l. Posterolateral fissure - f.p.s. Posterior superior fissure - f.sec. Fissura secunda - HII–HX Hemispheral lobules II–X - HVIIA cr.I, cr. II Crus I and II of lobule HVIIA - HVIIIA,B Sublobules A and B of lobule HVIII - Li Nucleus linearis intermedius - Lr Nucleus linearis rostralis - l.ans. Ansiform lobule - N.f. Nucleus fastigii - N.i.a. Nucleus interpositus anterior - N.i.p. Nucleus interpositus posterior - N.l. Nucleus lateralis - pfl.d. Dorsal paraflocculus - pfl.v. Ventral paraflocculus - Rd Nucleus raphe dorsalis - Rm Nucleus raphe magnus - Rob Nucleus raphe obscurus - Rpa Nucleus raphe pallidus - Rpo Nucleus raphe pontis - Sc Nucleus raphe centralis superior - s.int.cr.1 Intracrural sulcus 1 - s.int.cr.2 Intracrural sulcus 2 - I–VI Vermian lobules I–VI - VIIA,B Anterior and posterior sublobule of lobule VII - VIIIA,B Anterior and posterior sublobule of lobule VIII     

大鼠脑干到前额叶皮质的传入投射——WGA-HRP法研究

用WGA-HRP法研究了25只大鼠前额叶皮质的脑干传入投射。在前扣带回背部、前边缘区及岛叶无颗粒皮质背部注射WGA-HRP后,脑干中的逆行标记细胞大致可分为三类。第一类为单胺类神经元集中的核团,其中蓝斑、腹侧被盖区、黑质致密部、中缝背核、中央上核及尾侧线形核等广泛投射到前额叶皮质各部,而外侧网状核、连合核、中缝大核、A_4、A_5、臂旁核、黑质网状部及颅侧线形核投射到前额叶皮质各部的数量不同。外侧网状核、连合核、中缝大核、A_4、A_5到前额叶皮质的投射文献上尚未见报道。第二类为与眼肌运动有关的核团,如E-W核、导水管周灰质、中脑网状结构及脑桥吻侧网状核。第三类为与感觉有关的核团,如臂旁核、三叉神经感觉主核及连合核。     

GABAergic neurons comprise a major cell type in rodent visual relay nuclei: an immunocytochemical study of pretectal and accessory optic nuclei

Summary The enzyme glutamic acid decarboxylase (GAD) has been localized in sections of rodent brains (gerbil, rat) using conventional immunocytochemical techniques. Our findings demonstrate that large numbers of GAD-positive neurons and axon terminals (puncta) are present in the visual relay nuclei of the pretectum and the accessory optic system. The areas of highest density of these neurons are in the nucleus of the optic tract (NOT) of the pretectum, the dorsal and lateral terminal accessory optic nuclei (DTN, LTN), the ventral and dorsal subdivisions of the medial terminal accessory optic nucleus (MTNv, MTNd), and the interstitial nucleus of the posterior fibers of the superior fasciculus (inSFp). The findings indicate that 27% of the NOT neurons are GAD-positive and that these neurons are distributed over all of the NOT except the most superficial portion of the NOT caudally. The GAD-positive neurons of the NOT are statistically smaller (65.9 m²) than the total population of neurons of the NOT (84.3 [j,m2) but are otherwise indistinguishable in shape from the total neuron population. The other visual relay nuclei that have been analyzed (DTN, LTN, MTNv, MTNd, inSFp) are similar in that from 21% to 31% of their neurons are GAD-positive; these neurons are smaller in diameter and are more spherical than the total populations of neurons. The data further show that a large proportion of the neurons in these visual relay nuclei are contacted by GAD-positive axon terminals. It is estimated that approximately one-half of the neurons of the NOT and the terminal accessory optic nuclei receive a strong GABAergic input and have been called GAD-recipient neurons. Further, the morphology of the GAD-positive neurons combined with their similar distribution to the GAD-recipient neurons suggest that many of these neurons are acting as GABAergic, local circuit neurons. On the other hand, the large number of GAD-positive neurons in the NOT and MTN (20–30%) in relation to estimates of projection neurons (75%) presents the possibility that some may in fact be projection neurons. The overall findings provide morphological evidence which supports the general conclusion that GABAergic neurons play a significant role in modulating the output of the visually related NOT and terminal accessory optic nuclei.Abbreviations to Figures A Cerebral aqueduct - CP Posterior commissure - DK Nucleus of Darkschewitsch - DMN Deep mesencephalic nucleus - DTN Dorsal terminal nucleus, accessory optic system - HITr Habenulointerpeduncular tract - IGL Intergeniculate leaflet - INC Interstitial nucleus of Cajal - inSFp Interstitial nucleus, superior fasciculus, posterior fibers - LGNd Dorsal lateral geniculate nucleus - LGNv Ventral posterior nucleus - LP Lateral posterior nucleus - LTN Lateral terminal nucleus, accessory optic system - MB Mammillary body - MGN Medial geniculate nucleus - ML Medial lemniscus - MTNd Medial terminal nucleus, dorsal subdivision, accessory optic system - MTNv Medial terminal nucleus, ventral subdivision, accessory optic system - NOT Nucleus of the optic tract - NPC Nucleus of posterior commissure - OT Optic tract - PA Anterior pretectal nucleus - PAG Periaqueductal gray - pbp Nucleus parabrachialis pigmentosus - pC Cerebral peduncle - PM Medial pretectal nucleus - pn Nucleus paranigralis - PO Pretectal olivary nucleus - pp Posterior pretectal nucleus - PPN Peripeduncular nucleus - RNm Magnocellular division, red nucleus - RNp Parvocellular division, red nucleus - SC Superior colliculus - SGP Stratum griseum profundus, superior colliculus - SGS Stratum griseum superficiale, superior colliculus - SGM Stratum griseum medium, superior colliculus - SNc Substantia nigra, pars compacta - SNr Substantia nigra, pars reticulata - SO Stratum opticum, superior colliculus - VB Ventrobasal complex - ZI Zona incerta - 3N Oculomotor nerve, root fibers - 3V Third ventricle Supported by USPHS grants EY03642, NS15669, NS20228, EY03018, and NS15321. C.E.R. is the recipient of a Klingenstein Fellowship in the Neurosciences; R.H.I.B. is a Research Career Development Fellow of the National Eye Institute; and J.H.F. is a Research Career Development Fellow of the National Institutes of Health     

Tachykinin immunoreactivity in terminals of trigeminal afferent fibers in adult and fetal monkey thalamus

Summary Immunocytochemistry of fetal and adult monkey thalamus reveals a dense concentration of tachykinin immunoreactive fibers and terminals in the dorsolateral part of the VPM nucleus in which the contralateral side of the head, face and mouth is represented. The immunoreactive fibers enter the VPM nucleus from the thalamic fasciculus and electron microscopy reveals that they form large terminals resembling those of lemniscal axons and terminating in VPM on dendrites of relay neurons and on presynaptic dendrites of interneurons. Double labeling strategies involving immunostaining for tachykinins after retrograde labeling of brainstem neurons projecting to the VPM failed to reveal the origin of the fibers. The brainstem trigeminal nuclei, however, are regarded as the most likely sources of the VPM-projecting, tachykinin positive fibers.Abbreviations AB ambiguus nucleus - AN abducens nucleus - C cuneate nucleus - CD dorsal cochlear nucleus - CL central lateral nucleus - CM centre médian nucleus - D dendrite - DR dorsal raphe - DV dorsal vagal nucleus - EC external cuneate nucleus - FM medial longitudinal fasciculus - FN facial nucleus - G gracile nucleus - Gc gigantocellular reticular formation - HN hypoglossal nucleus - ICP inferior cerebellar peduncle - IO inferior olivary complex - LC locus coeruleus - LL lateral lemniscus - LM medial lemniscus - M5 motor trigeminal nucleus - NS solitary nucleus - OS superior olivary complex - P dendritic protrusion - Pb parabrachial nucleus - Pc parvocellular reticular formation - PLa anterior pulvinar nucleus - Pp prepositus hypoglossi nucleus - Ps presynaptic region - Py pyramidal tract - P5 principal sensory trigeminal nucleus - R reticular nucleus - RF reticular formation - RL lateral reticular nucleus - S5 spinal trigeminal nucleus - T terminal - T5 spinal trigeminal tract - VL lateral vestibular nucleus - VM medial vestibular nucleus - VMb basal ventral medial nucleus - VPI ventral posterior inferior nucleus - VPL ventral posterior lateral nucleus - VPM ventral posterior medial nucleus - VR ventral raphe - VS superior vestibular nucleus - VSp spinal vestibular nucleus - ZI zona incerta - 5 trigeminal nerve - 6 abducens nerve - 7 facial nerve     

Projections to the rostral reticular thalamic nucleus in the rat

Summary Afferent pathways to the rostral reticular thalamic nucleus (Rt) in the rat were studied using anterograde and retrograde lectin tracing techniques, with sensitive immunocytochemical methods. The analysis was carried out to further investigate previously described subregions of the reticular thalamic nucleus, which are related to subdivisions of the dorsal thalamus, in the paraventricular and midline nuclei and three segments of the mediodorsal thalamic nucleus. Cortical inputs to the rostral reticular nucleus were found from lamina VI of cingulate, orbital and infralimbic cortex. These projected with a clear topography to lateral, intermediate and medial reticular nucleus respectively. Thalamic inputs were found from lateral and central segments of the mediodorsal nucleus to the lateral and intermediate rostral reticular nucleus respectively and heavy paraventricular thalamic inputs were found to the medial reticular nucleus. In the basal forebrain, afferents were found from the vertical and horizontal limbs of the diagonal band, substantia innominata, ventral pallidum and medial globus pallidus. Brainstem projections were identified from ventrolateral periaqueductal grey and adjacent sites in the mesencephalic reticular formation, laterodorsal tegmental nucleus, pedunculopontine nucleus, medial pretectum and ventral tegmental area. The results suggest a general similarity in the organisation of some brainstem Rt afferents in rat and cat, but also show previously unsuspected inputs. Furthermore, there appear to be at least two functional subdivisions of rostral Rt which is reflected by their connections with cortex and thalamus. The studies also extend recent findings that the ventral striatum, via inputs from the paraventricular thalamic nucleus, is included in the circuitry of the rostral Rt, providing further evidence that basal ganglia may function in concert with Rt. Evidence is also outlined with regard to the possibility that rostral Rt plays a significant role in visuomotor functions.Abbreviations ac anterior commissure - aca anterior commissure, anterior - Acb accumbens nucleus - AI agranular insular cortex - AM anteromedial thalamic nucleus - AV anteroventral thalamic nucleus - BST bed nucleus of stria terminalis - Cg cingulate cortex - CG central gray - CL centrolateral thalamic nucleus - CM central medial thalamic nucleus - CPu caudate putamen - DR dorsal raphe nucleus - DTg dorsal tegmental nucleus - EP entopeduncular nucleus - f fornix - Fr2 Frontal cortex, area 2 - G gelatinosus thalamic nucleus - GP globus pallidus - Hb habenula - HDB horizontal limb of diagonal band - IAM interanterodorsal thalamic nucleus - ic internal capsule - INC interstitial nucleus of Cajal - IF interfascicular nucleus - IL infralimbic cortex - IP interpeduncular nucleus - LC locus coeruleus - LDTg laterodorsal tegmental nucleus - LH lateral hypothalamus - LHb lateral habenular nucleus - ll lateral lemniscus - LO lateral orbital cortex - LPB lateral parabrachial nucleus - MD mediodorsal thalamic nucleus - MDL mediodorsal thalamic nucleus, lateral segment - Me5 mesencephalic trigeminal nucleus - MHb medial habenular nucleus - mlf medial longitudinal fasciculus - MnR median raphe nucleus - MO medial orbital cortex - mt mammillothalamic tract - OPT olivary pretectal nucleus - pc posterior commissure - PC paracentral thalamic nucleus - PF parafascicular thalamic nucleus - PPTg pedunculopontine tegmental nucleus - PrC precommissural nucleus - PT paratenial thalamic nucleus - PV paraventricular thalamic nucleus - PVA paraventricular thalamic nucleus, anterior - R red nucleus - Re reuniens thalamic nucleus - RRF retrorubral field - Rt reticular thalamic nucleus - Scp superior cerebellar peduncle - SI substantia innominata - sm stria medullaris - SNR substantia nigra, reticular - st stria terminalis - TT tenia tecta - VL ventrolateral thalamic nucleus - VO ventral orbital cortex - VP ventral pallidum - VPL ventral posterolateral thalamic nucleus - VTA ventral tegmental area - 3 oculomotor nucleus - 3V 3rd ventricle - 4 trochlear nucleus     

Descending projections from brainstem and sensorimotor cortex to spinal enlargements in the cat

Summary Single and double retrograde tracer techniques were employed in cats to investigate: (1) the topographical relationships between supraspinal neurons projecting to either the brachial or lumbosacral enlargement, (2) the distribution and relative frequency of single supraspinal neurons which project to both enlargements by means of axonal branching.In one group of cats large injections of horseradish peroxidase (HRP) were made throughout either the brachial or lumbosacral enlargement. The results from these experiments support recent observations on the multiplicity of brainstem centers giving origin to descending spinal pathways and provide evidence for a population of corticospinal neurons in area 6.In a second set of experiments, HRP was injected in one enlargement, and ³H-apo-HRP (enzymatically inactive) was injected in the other enlargement. Relatively large numbers of neurons with collateral projections to both enlargements (double-labeled) were observed in the medullary and pontine reticular formation, the medial and inferior vestibular nuclei bilaterally, the ipsilateral lateral vestibular nucleus, Edinger-Westphal nucleus, caudal midline raphe nuclei and nuclear regions surrounding the brachium conjunctivum. By contrast, double-labeled neurons were infrequently observed in the red nucleus and sensorimotor cortex, contralateral to the injections.In the red nucleus, lateral vestibular nucleus and sensorimotor cortex, neurons projecting to the brachial enlargement were largely segregated topographically from neurons projecting to the lumbosacral enlargement. However, there was some overlap, and double-labeled neurons were consistently observed within the region of overlap. In the sensorimotor cortex, the overlap between brachial- and lumbar-projecting neurons was most prominent in areas 4 and 3a, along the cruciate sulcus, but also involved other cytoarchitectonic regions in the medial aspect of the hemisphere.Abbreviations AM nucleus ambiguus - ap area postrema - aq aqueduct - BC brachium conjunctivum - ci central inferior nucleus of the raphe - cs central superior nucleus of the raphe - Cun cuneate nucleus - EC external cuneate nucleus - EW Edinger-Westphal nucleus - ETC central tegmental field - FTG gigantocellular tegmental field - FTL lateral tegmental field - FTM magnocellular tegmental field - FTP paralemniscal tegmental field - Gr gracile nucleus - IO inferior olive - K-F Kölliker-Fuse nucleus - LC nucleus locus coeruleus - li rostral linear nucleus of the raphe - LR lateral reticular nucleus - mlf medial longitudinal fasciculus - PAG periaqueductal gray - PbL lateral parabrachial nucleus - PG pontine gray - PON preolivary nucleus - ppr post-pyramidal nucleus of the raphe - RB restiform body - RNm red nucleus, magnocellular division - RNp red nucleus, parvocellular division - SC superior colliculus - SN substantia nigra - SOl lateral nucleus of the superior olive - SOm medial nucleus of the superior olive - Spin V spinal trigeminal nucleus - SubC nucleus subcoeruleus - TB trapezoid body - tb nucleus of the trapezoid body - trm tegmental reticular nucleus - VInf inferior vestibular nucleus - VLd lateral vestibular nucleus, dorsal division - VLv lateral vestibular nucleus, ventral division - VM medial vestibular nucleus - VSm superior vestibular nucleus, medial division Cranial Nerves and their Nuclei III oculomotor nucleus or nerve - V sensory nucleus of the trigeminal nerve - VI abducens nucleus - VII I facial nucleus, lateral part - VII m facial nucleus, medial part - X vagus nucleus - XII hypoglossal nucleus The research was supported by USPHS grants NS 12440 and MH 14277. ³H-apo-HRP was generously provided by New England Nuclear     

Projections of the bed nucleus of the stria terminalis to the mesencephalon,pons, and medulla oblongata in the cat

Summary Injections of HRP in the nucleus raphe magnus and adjoining medial reticular formation in the cat resulted in many labeled neurons in the lateral part of the bed nucleus of the stria terminalis (BNST) but not in the medial part of this nucleus. HRP injections in the nucleus raphe pallidus and in the C2 segment of the spinal cord did not result in labeled neurons in the BNST. Injections of ³H-leucine in the BNST resulted in many labeled fibers in the brain stem. Labeled fiber bundles descended by way of the medial forebrain bundle and the central tegmental field to the lateral tegmental field of pons and medulla. Dense BNST projections could be observed to the substantia nigra pars compacta, the ventral tegmental area, the nucleus of the posterior commissure, the PAG (except its dorsolateral part), the cuneiform nucleus, the nucleus raphe dorsalis, the locus coeruleus, the nucleus subcoeruleus, the medial and lateral parabrachial nuclei, the lateral tegmental field of caudal pons and medulla and the nucleus raphe magnus and adjoining medial reticular formation. Furthermore many labeled fibers were present in the solitary nucleus, and in especially the peripheral parts of the dorsal vagal nucleus. Finally some fibers could be traced in the marginal layer of the rostral part of the caudal spinal trigeminal nucleus. These projections appear to be virtually identical to the ones derived from the medial part of the central nucleus of the amygdala (Hopkins and Holstege 1978). The possibility that the BNST and the medial and central amygdaloid nuclei must be considered as one anatomical entity is discussed.Abbreviations AA anterior amygdaloid nucleus - AC anterior commissure - ACN nucleus of the anterior commissure - ACO cortical amygdaloid nucleus - AL lateral amygdaloid nucleus - AM medial amygdaloid nucleus - APN anterior paraventricular thalamic nucleus - AQ cerebral aqueduct - BC brachium conjunctivum - BIC brachium of the inferior colliculus - BL basolateral amygdaloid nucleus - BNSTL lateral part of the bed nucleus of the stria terminalis - BNSTM medial part of the bed nucleus of the stria terminalis - BP brachium pontis - CA central nucleus of the amygdala - Cd caudate nucleus - CI inferior colliculus - CL claustrum - CN cochlear nucleus - CP posterior commissure - CR corpus restiforme - CSN superior central nucleus - CTF central tegmental field - CU cuneate nucleus - D nucleus of Darkschewitsch - EC external cuneate nucleus - F fornix - G gracile nucleus - GP globus pallidus - HL lateral habenular nucleus - IC interstitial nucleus of Cajal - ICA internal capsule - IO inferior olive - IP interpeduncular nucleus - LC locus coeruleus - LGN lateral geniculate nucleus - LP lateral posterior complex - LRN lateral reticular nucleus - MGN medial geniculate nucleus - MLF medial longitudinal fascicle - NAdg dorsal group of nucleus ambiguus - NPC nucleus of the posterior commissure - nV trigeminal nerve - nVII facial nerve - OC optic chiasm - OR optic radiation - OT optic tract - P pyramidal tract - PAG periaqueductal grey - PC cerebral peduncle - PO posterior complex of the thalamus - POA preoptic area - prV principal trigeminal nucleus - PTA pretectal area - Pu putamen - PUL pulvinar nucleus - R red nucleus - RF reticular formation - RM nucleus raphe magnus - RP nucleus raphe pallidus - RST rubrospinal tract - S solitary nucleus - SC suprachiasmatic nucleus - SCN nucleus subcoeruleus - SI substantia innominata - SM stria medullaris - SN substantia nigra - SO superior olive - SOL solitary nucleus - SON supraoptic nucleus - spV spinal trigeminal nucleus - spVcd spinal trigeminal nucleus pars caudalis - ST stria terminalis - TRF retroflex tract - VC vestibular complex - VTA ventral tegmental area of Tsai - III oculomotor nucleus - Vm motor trigeminal nucleus - VI abducens nucleus - VII facial nucleus - Xd dorsal vagal nucleus - XII hypoglossal nucleus     

Projections from the medial agranular cortex to brain stem visuomotor centers in rats

Summary Projections from medial agranular cortex to brain stem in rat were determined by use of the anterograde tracers Phaseolus vulgaris leucoagglutinin, or wheat germ agglutinin conjugated horseradish peroxidase. Axonal trajectories were also followed by means of the Wiitanen modification of the Fink-Heimer degeneration technique. AGm was identified on the basis of its cytoarchitectonics. AGm projected to the anterior pretectal nucleus, the rostral interstitial nucleus of the medial longitudinal fasciculus, the medial accessory oculomotor nucleus of Bechterew, the interstitial nucleus of Cajal, the nucleus of Darkschewitsch, the nucleus cuneiformis and subcuneiformis, intermediate and deep superior collicular layers, the paramedian pontine reticular formation (reticularis pontis oralis and caudalis, and reticularis gigantocellularis), and raphe centralis superior. Differences in connections between rostral and caudal injections were observed: pontine and medullary projections were lighter from the rostral portion of AGm than from the more caudal portions of AGm. The heaviest projections to the anterior pretectal nucleus were from the caudal portion of AGm. The subcortical projections were very similar to those described for the frontal eye field in monkeys, and the majority of them targeted areas thought to be involved in coordination of gaze with head and neck movements. Thus AGm in rats may contain the homologue of the primate frontal eye fields.Abbreviations 3 main oculomotor nucleus - 7 facial motor nucleus; - I, II–IV, V, and VI cortical layers - III third ventricle - 7n facial nerve - AC Anterior commissure - AGm medial agranular cortex - Bec Nucleus of Bechterew - cc corpus callosum - Dark Nucleus of Darkschewitsch - Dc dorsal cochlear nucleus - DLG dorsal lateral geniculate nucleus - F fornix - fr fasciculus retroflexus - ic inferior colliculus - Me5 mesencephalic trigeminal nucleus - ml medial lemniscus - mlf medial longitudinal fasciculus - Mo5 trigeminal motor nucleus - nV trigeminal nerve - pc posterior commissure - pn pons - Po posterior thalamic nucleus - PPo pedunculo-pontine nucleus - PPRF paramedian pontine reticular formation - py pyramidal tract - R red nucleus - RaCs raphe centralis superior - RaD dorsal raphe nucleus - RCf reticularis cuneiformis - RiMLF rostral interstitial nucleus of the medial longitudinal fasciculus - RMc reticularis magnocellularis - RPc reticularis parvocellularis - RPoCa reticularis pontis caudalis pars alpha - RPoCb reticularis pontis caudalis pars beta - RPoO reticularis pontis oralis - RPoOm reticularis pontis oralis pars medialis - RScf reticularis subcuneiformis - sc superior colliculus - SCP superior cerebellar peduncle - so superior olive - Sp5 spinal trigeminal nucleus - Tz trapezoid nucleus - WGA-HRP wheat germ agglutinin- horseradish peroxidase     

The early development of subcortical projections to presumptive somatic sensory-motor areas of neocortex in the North American opossum

Summary We have studied the early development of subcortical projections to presumptive somatic sensory-motor areas of neocortex in the North American opossumDidelphis virginiana. The opossum is born in a very immature state, 12–13 days after conception, and climbs into an external pouch where it is available for experimental manipulation. Using the retrograde transport of wheat germ agglutinin conjugated to horseradish peroxidase, we have obtained evidence that axons from the dorsal raphe and superior central nuclei, the substantia nigra, the locus coeruleus and the parabrachial nuclei reach presumptive somatic sensory-motor areas of neocortex by at least postnatal day (PND) 10. Axons showing serotonin-like immunoreactivity, presumably from the dorsal raphe and/or superior central nuclei, and axons containing tyrosine hydroxylase immunoreactivity, presumably from the substantia nigra and/or locus coeruleus, are present in the same areas at birth or shortly thereafter. Thalamic axons do not grow into comparable areas of neocortex until after PND 10. Such axons reach the subplate region of ventrolateral neocortex first and then proceed dorsomedially; by estimated PD (EPND) 21, they are present in presumptive layers I, V and VI, but they do not innervate an identified layer IV until EPND 48. The developmental sequences suggested by our study are compared with those reported for other species and are discussed in light of their importance in the formation of major sensory and motor circuits.Abbreviations qq cerebral aqueduct - ca anterior commissure - Cb cerebellum - CcD dorsal cochlear nucleus - Cd caudate nucleus - CeS superior central nucleus - CI interior colliculus - Coe locus coeruleus - CP cortical plate - CS superior colliculus - CxA cortex ammonis - DB nucleus of the diagonal band - Dien diencephalon - Dor dorsal - EP ependyma - Fac facial nucleus - GLD dorsal lateral geniculate nucleus - GM medial geniculate body - HVM ventromedial hypothalamic nucleus - IC internal capsule - Lat lateral - Med medial - ML medial lemniscus - mlf medial longitudinal fasciculus - OSL superior olivary nucleus - PB parabrachial complex - ped cerebral peduncle - PFP parafascicular nuclei - Pu putamen - RaD dorsal raphe nucleus - rfl fasciculus retroflexus - RN red nucleus - SN substantia nigra - SNc substantia nigra, pars compacta - SNr substantia nigra, pars reticulata - STh subthalamic nucleus - Tect tectum - TgV ventral tegmental area - TrMo motor trigeminal nucleus - xVB ventrobasal nucleus of thalamus     

Axonal branching of ventral tegmental and raphe projections to the frontal cortex in the rat

Axonal collateralization of neurons whose divergent branches innervate the medial prefrontal cortex (MFC) and the sulcal cortex was studied in the rat by using the retrograde double-labeling technique. Injections of bisbenzimide and propidium iodide into the MFC and sulcal cortex resulted in double-labeling of a small population of cells within the ventral tegmental area (VTA) and pars compacta of the substantia nigra (SNC). More extensive double-labeling was evident in the midbrain raphe nuclei. Collateralization++ therefore does not appear to be an important property of the dopamine innervation of the prefrontal cortex.     

Nigrotectal projections in the primate Galago crassicaudatus

Summary The pattern of the nigrotectal projection in Galago crassicaudatus was determined using retrograde and anterograde transport methods. These experiments revealed that pars reticulata and pars lateralis of the substantia nigra project to all layers of the ipsilateral and contralateral superior colliculus, except to layer I. The nigrotectal projection is not homogeneous, but is concentrated in particular collicular layers and sublayers, and the intensity and laminar distribution of the projection varies along the rostral-caudal dimension of the superior colliculus. The ipsilateral and contralateral nigrotectal projections are generally similar, except that a tier of dense label which is prominent in the ventral part of much of the ipsilateral layer IV is not obvious contralaterally; moreover, the contralateral projection is much sparser than the ipsilateral. Deposits of tracers at different medial-lateral locations within the substantia nigra did not result in different laminar patterns of anterogradely transported label in the superior colliculus. Based on the known connections and functions of the collicular layers and sublayers, the pattern and distribution of the nigrotectal projection suggests that the substantia nigra may use this pathway to gain access to particular components of vision- and visuomotor-related networks.Abbreviations Cd Caudate - CG Central gray - CP Cerebral peduncle - D Dorsal - FEF Frontal eye field - IC Internal capsule - ICo Inferior colliculus - IP Interpeduncular nucleus - L Lateral - LG Lateral geniculate - MDmf Medial dorsal nucleus, pars multiformis - MG Medial geniculate - MI Mammillary body, lateral nucleus - Mm Mammillary body, medial nucleus - MRF Mesencephalic reticular formation - nIII Oculomotor nerve - OT Optic tract - PG Pontine gray - Pg Pregeniculate nucleus - Pt Pretectal complex - Pulv Pulvinar nuclei - Put Putamen - R Red nucleus rostral - SCi,d Superior colliculus, intermediate and deep layers - SCs Superior colliculus, superficial layers - SEF Supplementary eye field - SNc Substantia nigra, pars compacta - SNr Substantia nigra, pars reticulata - SNr, 1 Substantia nigra, pars reticulata and pars lateralis - St Subthalamic nucleus - VAmc Ventral anterior nucleus, pars magnocellularis - V Cort Visual cortical areas - ZI Zona incerta - II Layer II of the superior colliculus - III Layer III of the superior colliculus - IV Layer IV of the superior colliculus - V Layer V of the superior colliculus - VI Layer VI of the superior colliculus