大鼠间脑和皮质下端脑到前额叶皮质的传入投射——WGA-HRP法研究

本研究将 WGA-HRP 注射于25只大鼠前额叶皮质的前扣带回背部、前边缘区及岛叶无颗粒皮质背部,观察其间脑和皮质下端脑的传入联系。间脑的传入主要来自丘脑背内侧核,并有一定的局部定位。此外,丘脑的板内核群(中央外侧核、旁中央核、中央内侧核及束旁核)、腹侧核群(腹外侧核、腹内侧核、腹前核及腹后核)、中线核群(菱形核、连合核、带旁核及室旁核)、前内侧核、外侧缰核、后核及外侧核亦有到前额叶皮质的传入投射,且投射到前额叶皮质不同部位的数量不同。丘脑下部的传入主要来自外侧区、外侧视前区、尾侧大细胞核及乳头体上核,少量传入也可见于丘脑下部后区、背内侧核、腹内侧核及未定带。皮质下端脑的传入主要来自苍白球,其次为斜角带核、隔核、杏仁核及屏状核。在隔核中,除内侧隔核外还观察到外侧隔核,繖隔核及三角隔核亦投射到前额叶皮质。杏仁核中除杏仁外侧核、杏仁基底核外侧部及内侧部外,还观察到杏仁内侧核及杏仁皮质核亦有少量到前额叶皮质的传入。     

Afferent connections of dorsal and ventral agranular insular cortex in the hamsterMesocricetus auratus

The agranular insular cortex is transitional in location and structure between the ventrally adjacent olfactory allocortex primutivus and dorsally adjacent sensory-motor isocortex. Its ventral anterior division receives major afferent projections from olfactory areas of the limbic system (posterior primary olfactory cortex, posterolateral cortical amygdaloid nucleus and lateral entorhinal cortex) while its dorsal anterior division does so from non-olfactory limbic areas (lateral and basolateral amygdaloid nuclei).The medial segment of the mediodorsal thalamic nucleus projects to both the ventral and dorsal divisions of the agranular insular cortex, to the former from its anterior portion and to the latter from its posterior portion. Other thalamic inputs to the two divisions arise from the gelatinosus, central medial, rhomboid and parafascicular nuclei. The dorsal division, but not the ventral division, receives input from neurons in the lateral hypothalamus and posterior hypothalamus.The medial frontal cortex projects topographically and bilaterally upon both ventral and dorsal anterior insular cortex, to the former from the ventrally located medial orbital and infralimbic areas, to the latter from the dorsally-located anterior cingulate and medial precentral areas, and to both from the intermediately located prelimbic area. Similarly, the ipsilateral posterior agranular insular cortex and perirhinal cortex project in a topographic manner upon the two divisions of the agranular insular cortex.Commissural input to both divisions originates from pyramidal neurons in the respective contralateral homotopical cortical area. In each case, pyramidal neurons in layer V contribute 90% of this projection and 10% arises from layer III pyramidals.In the brainstem, the dorsal raphe nucleus projects to the ventral and dorsal divisions of the agranular insular cortex and the parabrachial nucleus projects to the dorsal division.Based on their cytoarchitecture, pattern of afferent connections and known functional properties, we consider the ventral and dorsal divisions of the agranular insular cortex to be, respectively, periallocortical and proisocortical portions of the limbic cortex.     

Efferent connections of the medial prefrontal cortex in the rabbit

The different cytoarchitectonic regions of the medial prefrontal cortex (mPFC) have recently been shown to play divergent roles in associative learning in rabbits. To determine if these subareas of the mPFC, including areas 24 (anterior cingulate cortex), 25 (infralimbic cortex), and 32 (prelimbic cortex) have differential efferent connections with other cortical and subcortical areas in the rabbit, anterograde and retrograde tracing experiments were performed using thePhaseolus vulgaris leukoagglutinin (PHA-L), and horseradish peroxidase (HRP) techniques. All three areas showed local dorsal-ventral projections into each of the other areas, and a contralateral projection to the homologous area on the other side of the brain. All three also revealed a trajectory through the striatum, resulting in heavy innervation of the caudate nucleus, the claustrum, and a lighter projection to the agranular insular cortex. The thalamic projections of areas 24 and 32 were similar, but not identical, with projections to the mediodorsal nucleus (MD) and all of the midline nuclei. However, the primary thalamic projections from area 25 were to the intralaminar and midline nuclei. All three areas also projected to the ventromedial and to a lesser extent to the ventral posterior thalamic nuclei. Projections were also observed in the lateral hypothalamus, in an area just lateral to the descending limb of the fornix. Amygdala projections from areas 32 and 24 were primarily to the lateral, basolateral and basomedial nuclei, but area 25 also projected to the central nucleus. All three areas also showed projections to the midbrain periaqueductal central gray, median raphe nucleus, ventral tegmental area, substantia nigra, locus coeruleus and pontine nuclei. However, only areas 24 and the more dorsal portions of area 32 projected to the superior colliculus. Area 25 and the ventral portions of area 32 also showed a bilateral projection to the parabrachial nuclei and dorsal and ventral medulla. The dorsal portions of area 32, and all of area 24 were, however, devoid of these projections. It is suggested that these differential projections are responsible for the diverse roles that the cytoarchitectonic subfields of the mPFC have been demonstrated to play in associative learning.     

Efferent connections of dorsal and ventral agranular insular cortex in the hamster, Mesocricetus auratus

The anterior portion of rodent agranular insular cortex consists of a ventral periallocortical region (AIv) and a dorsal proisocortical region (AId). Each of these two cortical areas has distinct efferent connections, but in certain brain areas their projection fields are partially or wholly overlapping. Bilateral projections to layers I, III and VI of medial frontal cortex originate in the dorsal agranular insular cortex and terminate in the prelimbic, anterior cingulate and medial precentral areas; those originating in ventral agranular insular cortex terminate in the medial orbital, infralimbic and prelimbic areas. The dorsal and ventral regions of the agranular insular cortex project topographically to the ipsilateral cortex bordering the rhinal fissure, which includes the posterior primary olfactory, posterior agranular insular, perirhinal and lateral entorhinal areas. Fibers to these lateral cortical areas were found to travel in a cell-free zone, between cortical layer VI and the claustrum, which corresponds to the extreme capsule. The dorsal and ventral regions send commissural projections to layer I, lamina dissecans and outer layer V, and layer VI of the contralateral homotopical cortex, via the corpus callosum. Projections from the ventral and dorsal regions of the agranular insular cortex to the caudatoputamen are topographically arranged and terminate in finger-like patches. The ventral, but not the dorsal region, projects to the ventral striatum and ventral pallidum. The thalamic projections of the ventral and dorsal regions are largely overlapping, with projections from both to the ipsilateral reticular nucleus and bilaterally to the rhomboid, mediodorsal, gelatinosus and ventromedial nuclei. The heaviest projection is that to the full anteroposterior extent of the medial segment of the mediodorsal nucleus. Brainstem areas receiving projections from the ventral and dorsal regions include the lateral hypothalamus, substantia nigra pars compacta, ventral tegmental area and dorsal raphe nucleus. In addition, the ventral region projects to the periaqueductal gray and the dorsal region projects to the parabrachial and ventral pontine nuclei.These efferent connections largely reciprocate the afferent connections of the ventral and dorsal agranular insular cortex, and provide further support for the concept that these regions are portions of an outer ring of limbic cortex which plays a critical role in the expression of motivated, species-typical behaviors.     

Anatomical analysis of afferent projections to the medial prefrontal cortex in the rat

The medial prefrontal cortex (mPFC) has been associated with diverse functions including attentional processes, visceromotor activity, decision making, goal directed behavior, and working memory. Using retrograde tracing techniques, we examined, compared, and contrasted afferent projections to the four divisions of the mPFC in the rat: the medial (frontal) agranular (AGm), anterior cingulate (AC), prelimbic (PL), and infralimbic (IL) cortices. Each division of the mPFC receives a unique set of afferent projections. There is a shift dorsoventrally along the mPFC from predominantly sensorimotor input to the dorsal mPFC (AGm and dorsal AC) to primarily ‘limbic’ input to the ventral mPFC (PL and IL). The AGm and dorsal AC receive afferent projections from widespread areas of the cortex (and associated thalamic nuclei) representing all sensory modalities. This information is presumably integrated at, and utilized by, the dorsal mPFC in goal directed actions. In contrast with the dorsal mPFC, the ventral mPFC receives significantly less cortical input overall and afferents from limbic as opposed to sensorimotor regions of cortex. The main sources of afferent projections to PL/IL are from the orbitomedial prefrontal, agranular insular, perirhinal and entorhinal cortices, the hippocampus, the claustrum, the medial basal forebrain, the basal nuclei of amygdala, the midline thalamus and monoaminergic nuclei of the brainstem. With a few exceptions, there are few projections from the hypothalamus to the dorsal or ventral mPFC. Accordingly, subcortical limbic information mainly reaches the mPFC via the midline thalamus and basal nuclei of amygdala. As discussed herein, based on patterns of afferent (as well as efferent) projections, PL is positioned to serve a direct role in cognitive functions homologous to dorsolateral PFC of primates, whereas IL appears to represent a visceromotor center homologous to the orbitomedial PFC of primates.     

Topographic arrangement of the projection from the anterior thalamic nuclei to the cingulate cortex in the cat

After injection of HRP into the cingulate and its adjacent cortical areas, neuronal cells were retrogradely labeled ipsilaterally in the anterior, lateral, ventral, intralaminar and midline thalamic nuclei. Most of them occurred in the anterior nuclei, and a topographic correlation was revealed in the projections from the anterior thalamic nuclei to the cingulate gyrus: the rostral part of the cingulate gyrus receives fibers predominantly from the lateral part of the AM and additionally from the caudomedial part of the AV. The caudal part of the cingulate gyrus receives fibers from the medial part of the anteromedial nucleus (AM) and the rostromedial part of the anteroventral nucleus (AV). The intermediate part of the cingulate gyrus receives fibers from the intermediate part of the AM and the caudal half of the AV.     

Cortical projections of the anterior thalamic nuclei in the cat

Summary Unilateral stereotaxic lesions were made in the anterior thalamic nuclei of the cat, and the ensuing terminal degeneration traced to the medial cortex by the methods of Nauta-Gygax and Fink-Heimer. The anterodorsal nucleus projects to the retrosplenial, postsubicular and presubicular areas. These projections appear to be organized in the dorsoventral direction. The posterior portion of the retrosplenial area receives no fibers from the anterodorsal nucleus. Fibers from this nucleus are distributed largely in layer I and in layer III and the deep portion of layer II of the posterior limbic cortex. The anteroventral nucleus sends fibers to the cingular area and parts of the retrosplenial, postsubicular and presubicular areas. These projections appear to be organized in a topical manner mediolaterally. When the lesion involves the parvocellular part of the nucleus, degeneration spreads to the lower lip, bank and fundus of the splenial sulcus. There appears to be an anteroposterior organization in the cortical projections of the anteroventral nucleus. Fibers from the anteroventral nucleus are distributed most profusely in layers IV and III and in the superficial portion of layer I of the posterior limbic cortex. The anteromedial nucleus sends fine fibers to the anterior limbic region and to the cingular, retrosplenial, postsubicular and presubicular areas. The cortical projections of the anteromedial nucleus appear to be topographically organized in the dorsoventral direction. Fibers from the anteromedial nucleus are distributed largely in cortical layers V and VI of the anterior and posterior limbic regions.Abbreviations used in Figures a anterior - AD anterodorsal nucleus - AM anteromedial nucleus - AMD dorsolateral part of anteromedial nucleus - AMV ventromedial part of anteromedial nucleus - AV anteroventral nucleus - AVM magnocellular part of anteroventral nucleus - AVP parvocellular part of anteroventral nucleus - CC corpus callosum - Cg cingular area - CM medial central nucleus - Il infralimbic area - LA anterior limbic region - LD dorsal lateral nucleus - MD dorsal medial nucleus - Of orbitofrontal region - p posterior - Pr presubicular area - Prag precentral agranular area - Ps postsubicular area - Pt paratenial nucleus - Pv anterior paraventricular nucleus - R reuniens nucleus - Rs retrosplenial area - Rt thalamic reticular nucleus - SC cruciate sulcus - SM stria medullaris - Sm submedial nucleus - SS splenial sulcus - VA ventral anterior nucleus - VL ventral lateral nucleus - VM ventral medial nucleus     

Thalamic and temporal cortex input to medial prefrontal cortex in rhesus monkeys

 To determine the source of thalamic input to the medial aspect of the prefrontal cortex, we injected retrograde tracers (wheat germ agglutinin conjugated to horseradish peroxidase, nuclear yellow, and/or bisbenzimide) into seven medial prefrontal sites and anterograde tracers (tritiated amino acids) into six thalamic sites, in a total of nine rhesus monkeys. The results indicated that ventral precallosal and subcallosal areas 14 and 25, and the ventral, subcallosal part of area 32, all receive projections from the mediodorsal portion of the magnocellular division of the medial dorsal nucleus (MDmc). The dorsal, precallosal part of area 32 receives projections mainly from the dorsal portion of the parvocellular division of the medial dorsal nucleus (MDpc), which also provides some input to area 14. Polar area 10 receives input from both MDpc and the densocellular division of the medial dorsal nucleus (MDdc), as does supracallosal area 24. Area 24 receives additional input from the anterior medial nucleus and midline nuclei. All medial prefrontal cortical areas were also found to receive projections from a number of cortical regions within the temporal lobe, such as the temporal pole, superior temporal gyrus, and parahippocampal gyrus. Areas 24, 25, and 32 receive, in addition, input from the entorhinal cortex. Combining these results with prior anatomical and behavioral data, we conclude that medial temporal areas that are important for object recognition memory send information directly both to dorsal medial prefrontal areas 24 and 32 and to ventral medial prefrontal areas 14 and 25. Only the latter two areas have additional access to this information via projections from the mediodorsal part of MDmc. Received: 1 March 1996 / Accepted: 13 January 1997     

大鼠丘脑背内侧核的传出联系——WGA-HRP法研究

将WGA-HRP微电泳导入19只大鼠的丘脑背内侧核(DM),又将WGA-HRP注射于17只大鼠前额叶皮质的前扣带回背部,前边缘叶和岛叶无颗粒皮质背部,观察DM的传出投射。 DM投射到前额叶皮质的范围广泛,并有一定的局部定位。DM外侧部主要投射到前扣带回背部,其次为中央前区内侧皮质、前边缘叶、岛叶无颗粒皮质背部及腹外侧眶区等。DM内侧部主要投射到岛叶无颗粒皮质背部,其次为前边缘叶、下边缘叶、内侧眶区及腹侧眶区等。DM中间部主要投射到岛叶无颗粒皮质背部。 DM还投射到某些皮质下核团,如丘脑网状核、外侧视前区、尾壳核、伏隔核、苍白球、丘脑下部外侧区及束旁核等。此外,DM和前额叶皮质的前扣带回背部、中央前区内侧皮质、前边缘叶、下边缘叶及岛叶无颗粒皮质背部以及和丘脑网状核、外侧视前区及丘脑下部外侧区之间均有交互投射。     

Prefrontal projections to the medial nuclei of the dorsal thalamus in the rabbit

Retrograde transport of horseradish peroxidase (HRP) from the mediodorsal (MD), ventromedial (VM), ventroposterior (VP) and intralaminar (IL) nuclei of the dorsal thalamus revealed a topographical pattern of efferents from the frontal cortex. MD injections labeled the midline and insular regions of the prefrontal cortex (Pfc), including the anterior limbic, and most ventral part of the precentral agranular Pfc, as well as the agranular insular cortex. VM injections labeled only the most dorsomedial part of the granular insular cortex, whereas IL and VP injections labeled the dorsal precentral agranular Pfc and a strip of cortex that extended laterally across the superior aspect of the forceps minor. The IL injections also labeled cells that extended ventrally into the granular and agranular insular areas.     

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     

Topography of projections from the primary and non-primary auditory cortical areas to the medial geniculate body and thalamic reticular nucleus in the rat

The functional significance of parallel and redundant information processing by multiple cortical auditory fields remains elusive. A possible function is that they may exert distinct corticofugal modulations on thalamic information processing through their parallel connections with the medial geniculate body and thalamic reticular nucleus. To reveal the anatomical framework for this function, we examined corticothalamic projections of tonotopically comparable subfields in the primary and non-primary areas in the rat auditory cortex. Biocytin was injected in and around cortical area Te1 after determining best frequency at the injection site on the basis of epicortical field potentials evoked by pure tones. The rostral part of area Te1 (primary auditory area) and area temporal cortex, area 2, dorsal (Te2D) (posterodorsal auditory area) dorsal to the caudal end of area Te1, which both exhibited high best frequencies, projected to the ventral zone of the ventral division of the medial geniculate body. The caudal end of area Te1 (auditory area) and the rostroventral part of area Te1 (a part of anterior auditory field), which both exhibited low best frequencies, projected to the dorsal zone of the ventral division of the medial geniculate body. In contrast to the similar topography in the projections to the ventral division of the medial geniculate body, collateral projections to the thalamic reticular nucleus terminated in the opposite dorsal and ventral zones of the lateral and middle tiers of the nucleus in each pair of the tonotopically comparable cortical subfields. In addition, the projections of the non-primary cortical subfields further arborized in the medial tier of the thalamic reticular nucleus. The results suggest that tonotopically comparable primary and non-primary subfields in the auditory cortex provide corticofugal excitatory effects to the same part of the ventral division of the medial geniculate body. On the other hand, corticofugal inhibition via the thalamic reticular nucleus may operate in different parts of the ventral division of the medial geniculate body or different thalamic nuclei. The primary and non-primary cortical auditory areas are presumed to subserve distinct gating functions for auditory attention.     

Subcortical projections to the prefrontal cortex in the rat as revealed by the horseradish peroxidase technique

The sources and distribution of subcortical afferents to the anterior neocortex were investigated in the rat using the horseradish peroxidase technique. Injections into the prefrontal cortex labelled, in addition to the mediodorsal thalamic nucleus, neurons in a total of fifteen subcortical nuclei, distributed in the basal telencephalon, claustrum, amygdala, thalamus, subthalamus, hypothalamus, mesencephalon and pons. Of these, the projections from the zona incerta, the lateroposterior thalamic nucleus, and the parabrachial region of the caudal mesencephalon to the prefrontal cortex have not previously been described.Different parts of the mediodorsal thalamic nucleus project to different areas of the frontal cortex. Thus, horseradish peroxidase injections in the most ventral pregenual part of the medial cortex labelled predominantly neurons in the medial anterior and dorsomedial posterior parts of the mediodorsal nucleus; injections into the more dorsal pregenual area labelled only neurons in the lateral and ventral parts of the nucleus; injections placed supragenually labelled neurons in the dorsolateral posterior part of the nucleus; and injections into the dorsal bank of the anterior rhinal sulcus labelled neurons in the centromedial part of the nucleus.Several other subcortical nuclei had projections overlapping with that of the mediodorsal thalamic nucleus. Five different types of such overlap were distinguished: (1) cell groups labelled after horseradish peroxidase injections into one of the subfields of the projection area of the mediodorsal nucleus (defined as the prefrontal cortex), but not outside this area (parataenial nucleus of the thalamus); (2) cell groups labelled both after injection into a subfield of the projection area of the mediodorsal nucleus and after injections in a restricted area outside this area (anteromedial, ventral and laterposterior thalamic nuclei); (3) cell groups labelled after injections into all subfields of the mediodorsal nucleus projection area, but not outside this area (ventral tegmental area, basolateral nucleus of amygdala); (4) cell groups labelled after injections into any area of the anterior neocortex, including the mediodorsal nucleus projection area (parabrachial neurons of the posterior mesencephalon); (5) cell groups labelled after all neocortical injections investigated (claustrum, magnocellular nuclei of the basal forebrain, lateral hypothalamus, zona incerta, intralaminar thalamic nuclei, nuclei raphe dorsalis and centralis superior, and locus coeruleus).We can draw the following conclusions from these and related findings. First, because of the apparent overlap of projections of the mediodorsal, the anteromedial and ventral thalamic nuclei in the rat, parts of the prefrontal cortex can also be called ‘cingulate’ and ‘premotor’. Second, on the basis of projections from parts of the mediodorsal nucleus, the prefrontal cortex of the rat can be subdivided into areas corresponding to those in other species. Third, the neocortex receives afferents from a large number of subcortical cell groups outside the thalamus, distributed from the telencephalon to the pons; however, the prefrontal cortex seems to be the only neocortical area innervated by the ventral tegmental area and amygdala. Finally, neither the prefrontal cortex nor the mediodorsal thalamic nucleus receives afferents from regions directly involved in sensory and motor functions.     

Suprachiasmatic nucleus projections to the paraventricular thalamic nucleus of the rat

The suprachiasmatic nucleus (SCN) projections to the midline and intralaminar thalamic nuclei were examined in the rat. Stereotaxic injections of the retrograde tracer cholera toxin-β subunit (CTb) were made in 12 different thalamic sites. These included individual midline thalamic nuclei (anterior, middle, and posterior portions of the paraventricular thalamic nucleus (PVT), intermediodorsal, paratenial, rhomboid, or reuniens nuclei) and intralaminar thalamic nuclei (lateral parafascicular, central lateral, or central medial nuclei) as well as the mediodorsal and anteroventral thalamic nuclei. After 10–14 days survival, the brains from these animals were processed histochemically and the distribution of retrogradely-labeled neurons was mapped throughout the rostralcaudal extent of the SCN. Within this collective group of midline and intralaminar thalamic nuclei, the only region innervated by the SCN was the PVT. Approximately 80% of this projection arose from the dorsomedial SCN, and the remaining projection originated from the ventrolateral SCN which targeted mainly the anterior division of the PVT. Virtually no SCN neurons were labeled after CTb injections centered in any of the other midline thalamic nuclei, which includes the intermediodorsal, mediodorsal, paratenial, rhomboid, or reuniens thalamic nuclei. Similarly, no evidence for a SCN projection to the intralaminar thalamic nuclei was found. The discussion focuses on the role of SCN→PVT pathway in modulating cerebral cortical functions.     

Differential projection from the motor and limbic cortical regions to the mediodorsal thalamic nucleus in the dog

The cortical afferents to the mediodorsal thalamic nucleus in the dog were studied by using horseradish peroxidase. Small injections allowed to establish two specific projection zones connected separately with the lateral and medial segments of the nucleus. The lateral segment received the major projection from the dorsal half of the hemisphere. It included premotor and part of the motor cortices in the anterior sigmoid gyrus and precruciate areas as well as the presylvian cortex. The medial segment of the nucleus was innervated by the limbic areas of the ventral half of the hemisphere. These areas included the medioventrally located genual, subcallosal and piriform cortices, as well as the cortex of the ventral bank of the anterior rhinal sulcus and the caudal part of the orbital gyrus. The cortical fields situated between these two main cortical zones, both on the lateral and medial surfaces (rhinal and sylvian sulci and anterior cingular gyrus, respectively) sent projections to both medial and lateral segments of the nucleus. These results indicate that in the mediodorsal thalamic nucleus may take place the integration of information from two functionally defined systems, the motor and limbic ones.     

Efferent connections of the medial prefrontal cortex in the rabbit

The different cytoarchitectonic regions of the medial prefrontal cortex (mPFC) have recently been shown to play divergent roles in associative learning in rabbits. To determine if these subareas of the mPFC, including areas 24 (anterior cingulate cortex), 25 (infralimbic cortex), and 32 (prelimbic cortex) have differential efferent connections with other cortical and subcortical areas in the rabbit, anterograde and retrograde tracing experiments were performed using the Phaseolus vulgaris leukoagglutinin (PHA-L), and horseradish peroxidase (HRP) techniques. All three areas showed local dorsal-ventral projections into each of the other areas, and a contralateral projection to the homologous area on the other side of the brain. All three also revealed a trajectory through the striatum, resulting in heavy innervation of the caudate nucleus, the claustrum, and a lighter projection to the agranular insular cortex. The thalamic projections of areas 24 and 32 were similar, but not identical, with projections to the mediodorsal nucleus (MD) and all of the midline nuclei. However, the primary thalamic projections from area 25 were to the intralaminar and midline nuclei. All three areas also projected to the ventromedial and to a lesser extent to the ventral posterior thalamic nuclei. Projections were also observed in the lateral hypothalamus, in an area just lateral to the descending limb of the fornix. Amygdala projections from areas 32 and 24 were primarily to the lateral, basolateral and basomedial nuclei, but area 25 also projected to the central nucleus. All three areas also showed projections to the midbrain periaqueductal central gray, median raphe nucleus, ventral tegmental area, substantia nigra, locus coeruleus and pontine nuclei. However, only areas 24 and the more dorsal portions of area 32 projected to the superior colliculus. Area 25 and the ventral portions of area 32 also showed a bilateral projection to the parabrachial nuclei and dorsal and ventral medulla. The dorsal portions of area 32, and all of area 24 were, however, devoid of these projections. It is suggested that these differential projections are responsible for the diverse roles that the cytoarchitectonic subfields of the mPFC have been demonstrated to play in associative learning.Abbreviations ACC anterior cingullate cortex - ACN amygdaloid central nucleus - AD anterodorsal nucleus of thalamus - AIC, Iag agranular insular cortex - AM anteromedial nucleus of thalamus - AMG amygdala - AV anteroventral nucleus of thalamus - BL basolateral nucleus of amygdala - BM basomedial nucleus of amygdala - CdN, CD caudate nucleus - CL claustrum - CN centromedian nucleus of thalamus - D MV, DVM dorsal motor nucleus of vagus - IC internal capsule - L lateral nucleus of amygdala - LC locus coeruleus - LH lateral hypothalamus - MB mammillary bodies - MDN mediodorsal nucleus of thalamus - mPFC medial prefrontal cortex - MRN, R median raphe nucleus - MV medioventral nucleus of thalamus - NA nucleus ambiguus - NTS nucleus of solitary tract - PAG periaqueductal central gray - PAV, PV para ventricular nucleus of thalamus - PC paracentral nucleus of thalamus - PF parafascicular nucleus of thalamus - PN,LP pontine nuclei - PS posterior subiculum - PS CG posterior cingulate cortex - PT paratenial nucleus of thalamus - Put putamen - ReN nucleus reuniens of thalamus - RF reticular formation - RN reticular nucleus of thalamus - RhN rhomboid nucleus of thalamus - RS CX retrosplenial cortex - S septum - SC superior colliculus - SN substantia nigra - tt tenia tecta - VL ventrolateral nucleus of thalamus - VM ventromedial nucleus of thalamus - VP ventroposterior nucleus of thalamus - VTA ventral tegmental area     

Laminar and modular organization of prefrontal projections to multiple thalamic nuclei

The prefrontal cortex projects to many thalamic nuclei, in pathways associated with cognition, emotion, and action. We investigated how multiple projection systems to the thalamus are organized in prefrontal cortex after injection of distinct retrograde tracers in the principal mediodorsal (MD), the limbic anterior medial (AM), and the motor-related ventral anterior/ventral lateral (VA/VL) thalamic nuclei in rhesus monkeys. Neurons projecting to these nuclei were organized in interdigitated modules extending vertically within layers VI and V. Projection neurons were also organized in layers. The majority of projection neurons to MD or AM originated in layer VI (∼80%), but a significant proportion (∼20%) originated in layer V. In contrast, prefrontal neurons projecting to VA/VL were equally distributed in layers V and VI. Neurons directed to VA/VL occupied mostly the upper part of layer V, while neurons directed to MD or AM occupied mostly the deep part of layer V. The highest proportions of projection neurons in layer V to each nucleus were found in dorsal and medial prefrontal areas. The laminar organization of prefrontal cortico-thalamic projections differs from sensory systems, where projections originate predominantly or entirely from layer VI. Previous studies indicate that layer V cortico-thalamic neurons innervate through some large terminals thalamic neurons that project widely to superficial cortical layers. The large population of prefrontal projection neurons in layer V may drive thalamic neurons, triggering synchronization by recruiting several cortical areas through widespread thalamo-cortical projections to layer I. These pathways may underlie the synthesis of cognition, emotion and action.     

Re-examination of the thalamostriatal projections in the rat with retrograde tracers

Topographical arrangements of thalamostriatal projection neurons was examined in the rat by the retrograde tract-tracing method. After injecting Fluoro-Gold (FG) and/or cholera toxin beta-subunit (CTB) in different regions of the caudate-putamen (CPu), distribution of retrogradely labeled neurons was observed in the thalamus. The main findings were as follows: (1) Retrogradely labeled neurons were seen in the midline-intralaminar thalamic nuclei in all rats examined in the present study.Neurons in the ventral lateral and posterior thalamic nuclear groups were also labeled in the rats which were injected with the tracer into the dorsal part of Cpu, but not in the rats which were injected with the tracer into the nucleus accumbens (Acb) and its adjavent regions in the ventromedial part of the Cpu. (2) Topographical organization was observed in the projections from the midline-intralaminar thalamic nuclei to the CPu. After the tracer injection into the dorsal part of the CPu or the ventral part of the CPu (including the Acb), labeled neurons in the midline-intralaminar thalamic nuclei were distributed predominantly in the lateral part of the intralaminar nuclei or the midline nuclei, respectively. On the other hand, after the tracer injection into the medial or the lateral part of the CPu, labeled neurons in the midline-intralaminar nuclei were distributed mainly in the dorsal or the ventral part of these nuclei, respectively. (3) Topographical organization was also observed in the thalamostriatal projections from the ventral and Pos. After the tracer injection into the rostral part of the CPu, labeled neurons were distributed mainly in the rostral part of the ventral nuclear group. On the other hand, after the tracer injection into the caudal part of the CPu, labeled neurons were distributed mainly in the caudal part of the ventral nuclear group, as well as in the posterior nuclear group.     

Excitatory amino acid projections to the nucleus accumbens septi in the rat: a retrograde transport study utilizing D[3H]aspartate and [3H]GABA

Afferents to the nucleus accumbens septi utilizing glutamate or aspartate have been investigated in the rat by autoradiography following injection and retrograde transport of D[3H]aspartate. Parallel experiments with the intra-accumbal injection of [3H]GABA were employed to establish the transmitter-selective nature of the retrograde labelling found with D[3H]aspartate. The topography of cortical and thalamic perikarya labelled by D[3H]aspartate was extremely precise. D[3H]Aspartate labelled perikarya were found in layer V of agranular insular cortex; bilaterally within prelimbic and infralimbic subareas perikarya, but predominantly ipsilaterally. Ipsilateral labelling was observed in dorsal, ventral and posterior agranular insular cortices, and in perirhinal cortex. Injections into ventral accumbens labelled perikarya in ipsilateral entorhinal cortex, while infusion of D[3H]aspartate into anterior caudate-putamen resulted in labelling of perikarya in ipsilateral cingulate and lateral precentral cortices. Following infusion of D[3H]aspartate, ipsilateral midline thalamic nuclei contained the highest density of labelled perikarya; infusions centred on nucleus accumbens resulted in heavy retrograde labelling of the parataenial nucleus, but labelling was sparse from a lateral site and not observed after injection into anterior caudate-putamen. Less prominent labelling of perikarya was seen in other thalamic nuclei (mediodorsal, central medial, rhomboid, reuniens and centrolateral), mostly near the midline. Perikaryal labelling was also found in the ipsilateral amygdaloid complex, particularly in basolateral and lateral nuclei. Only weak labelling resulted in ventral subiculum. Numerous labelled cells were present bilaterally in anterior olfactory nucleus, although perikarya were more prominent ipsilaterally. Labelled perikarya were not consistently observed in other regions (ventral tegmental area, medial substantia nigra, raphe nuclei and locus coeruleus) known to innervate nucleus accumbens. Presumptive anterograde labelling was detected in ventral pallidum/substantia innominata, ventral tegmental area and medial substantia nigra. [3H]GABA was generally not retrogradely transported to the same regions labelled by D[3H]aspartate; an exception being the anterior olfactory nucleus, where large numbers of labelled perikarya were found. [3H]GABA failed to label perikarya in thalamus and amygdala, and a topographic distribution of label was absent in neocortex.(ABSTRACT TRUNCATED AT 400 WORDS)     

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。