Area 24c Research Articles

Organization of subcortical pathways for sensory projections to the limbic cortex. II. Afferent projections to the thalamic lateral dorsal nucleus in the rat.

Afferent projections to the thalamic lateral dorsal nucleus were examined in the rat by the use of retrograde axonal transport techniques. Small iontophoretic injections of horseradish peroxidase were placed at various locations within the lateral dorsal nucleus, and the location and morphology of cells of origin of afferent projections were identified by retrograde labeling. For all cases examined, subcortical retrogradely labeled neurons were most prominent in the pretectal complex, the intermediate layers of the superior colliculus, and the ventral lateral geniculate nucleus. Labeled cells were also seen in the thalamic reticular nucleus and the zona incerta. Within the cerebral cortex, labeled cells were prominent in the retrosplenial areas (areas 29b, 29c, and 29d) and the presubiculum. Labeled cells were also seen in areas 17 and 18 of occipital cortex. Peroxidase injections in the dorsal lateral part of the lateral dorsal nucleus result in labeled neurons in all of the ipsilateral pretectal nuclei, but especially those that receive direct retinal afferents. Labeled cells were also seen in the ventral lateral geniculate nucleus and the rostral tip of laminae IV-VI of the superior colliculus. In contrast, peroxidase injections in ventral medial portions of the lateral dorsal nucleus result in fewer labeled pretectal cells, and these labeled cells are found exclusively in the pretectal nuclei that do not receive retinal afferents. Other labeled cells following injections in the rostral and medial portions of the lateral dorsal nucleus are seen contralaterally in the medial pretectal region and nucleus of the posterior commissure, and bilaterally in the rostral tips of laminae IV and V of the superior colliculus. Camera lucida drawings of HRP labeled cells reveal that projecting cells in each pretectal nucleus have a characteristic soma size and dendritic branching pattern. These results are discussed with regard to the type of sensory information that may reach the lateral dorsal nucleus and then be relayed on to the medial limbic cortex.

Cingulate cortex of the rhesus monkey: II. Cortical afferents.

Cortical projections to subdivisions of the cingulate cortex in the rhesus monkey were analyzed with horseradish peroxidase and tritiated amino acid tracers. These projections were evaluated in terms of an expanded cytoarchitectural scheme in which areas 24 and 23 were divided into three ventrodorsal parts, i.e., areas 24a-c and 23a-c. Most cortical input to area 25 originated in the frontal lobe in lateral areas 46 and 9 and orbitofrontal areas 11 and 14. Area 25 also received afferents from cingulate areas 24b, 24c, and 23b, from rostral auditory association areas TS2 and TS3, from the subiculum and CA1 sector of the hippocampus, and from the lateral and accessory basal nuclei of the amygdala (LB and AB, respectively). Areas 24a and 24b received afferents from areas 25 and 23b of cingulate cortex, but most were from frontal and temporal cortices. These included the following areas: frontal areas 9, 11, 12, 13, and 46; temporal polar area TG as well as LB and AB; superior temporal sulcus area TPO; agranular insular cortex; posterior parahippocampal cortex including areas TF, TL, and TH and the subiculum. Autoradiographic cases indicated that area 24c received input from the insula, parietal areas PG and PGm, area TG of the temporal pole, and frontal areas 12 and 46. Additionally, caudal area 24 was the recipient of area PG input but not amygdalar afferents. It was also the primary site of areas TF, TL, and TH projections. The following projections were observed both to and within posterior cingulate cortex. Area 29a-c received inputs from area 46 of the frontal lobe and the subiculum and in turn it projected to area 30. Area 30 had afferents from the posterior parietal cortex (area Opt) and temporal area TF. Areas 23a and 23b received inputs mainly from frontal areas 46, 9, 11, and 14, parietal areas Opt and PGm, area TPO of superior temporal cortex, and areas TH, TL, and TF. Anterior cingulate areas 24a and 24b and posterior areas 29d and 30 projected to area 23. Finally, a rostromedial part of visual association area 19 also projected to area 23. The origin and termination of these connections were expressed in a number of different laminar patterns. Most corticocortical connections arose in layer III and to a lesser extent layer V, while others, e.g., those from the cortex of the superior temporal sulcus, had an equal density of cells in both layers III and V.(ABSTRACT TRUNCATED AT 400 WORDS)

Cingulate cortex of the rhesus monkey: I. Cytoarchitecture and thalamic afferents.

The cytoarchitecture and thalamic afferents of cingulate cortex were evaluated in the rhesus monkey (Macaca mulatta). Area 24 has three divisions of which area 24a is adjacent to the callosal sulcus and has the least laminar differentiation. Area 24b has more clearly defined layers II, III, and Va, and area 24c, which forms the lower bank of the anterior cingulate sulcus, has a particularly dense layer III. Area 23 also has three divisions, each of which has a distinct layer IV. Area 23a is adjacent to the callosal sulcus and has the thinnest layers II-IV, which have the same cell density as layers V and VI. Area 23b has the largest pyramids in layers IIIc and Va, and area 23c, in the depths of the posterior cingulate sulcus, has the broadest external and thinnest internal pyramidal layers. Finally, areas 29 and 30 are located in the posterior depths of the callosal sulcus. Two divisions of area 29 are apparent: one with a granular layer directly adjacent to layer I (area 29a-c) and another with differentiation of layers III and IV (area 29d). Area 30 has a dysgranular layer IV. Injections of the retrograde tracer horseradish peroxidase (HRP) were made into subdivisions of cingulate cortex in the monkey. Area 25 received thalamic input mainly from the midline parataenial (Pt), central densocellular (Cdc), and reuniens nuclei as well as from the dorsal parvicellular division of the mediodorsal nucleus (MDpc). A less dense projection also originated in the intralaminar parafascicular (Pf), central superior, and limitans (Li) nuclei as well as the medial division of the anterior nuclei (AM). Areas 24a and 24b received most thalamic afferents from fusiform and multipolar cells in the Cdc and Pf nuclei with fewer from the ventral anterior (VA) and MDpc and MD densocellular (MDdc) nuclei and only minor input from AM. Most input to premotor cingulate area 24c appeared to originate in VA, MDdc, and Li. Area 29 received the most dense input from nuclei traditionally associated with limbic cortex including the anteroventral (AV), anterodorsal (AD), and laterodorsal (LD) nuclei. Areas 23a and 23b, in contrast, did not receive AV, AD, or LD input, but the greatest proportion of their thalamic afferents arose in AM. Less-pronounced input also came from the lateroposterior (LP), medial pulvinar, and MDdc nuclei.(ABSTRACT TRUNCATED AT 400 WORDS)

Dissociated cingulate cortical neurons: morphology and muscarinic acetylcholine receptor binding properties

Identifiable cortical neurons were obtained from area 29c of rat cingulate cortex using enzymatic and mechanical dissociation techniques. Dissociated neurons were either analyzed morphologically with the electron microscope or processed autoradiographically to evaluate the distribution of specific 3H-propylbenzilylcholine mustard (PrBCM) binding. Ultrastructurally, neurons appeared healthy and contained a full complement of cytoplasmic organelles. Membranes were intact and no presynaptic endings adhered to cell bodies or dendrites. Dendritic spines were not observed in these dissociations and serial sections of identified neurons indicated that all dendritic processes were smooth. Receptor binding studies were conducted on small and medium-to-large pyramidal neurons and multipolar cells. Specific binding of PrBCM was determined by calculating the mean number of grains/10 micron somal perimeter or dendritic length and subtracting mean values from a matched series of neurons that were coincubated in atropine. Specific binding was to somata and dendrites of all neurons. Nonspecific binding was an average of 33% of total binding. A 2 X 2 factorial analysis of variance comparing total and nonspecific binding for pairs of processes indicated that there were no regional differences in dendritic binding, either by cell type or by order of dendritic branching. Both somatic and dendritic PrBCM binding was antagonized by pirenzepine (PZ); however, PZ appeared to be more effective at secondary dendritic, rather than at somatic and primary apical dendritic sites. Thus, the IC50 values for somata and primary apical dendrites of small pyramids were 6 X 10(-7) and 9 X 10(-7) M PZ, respectively, while that for secondary basal dendrites of the same neurons was 5.8 X 10(-8) M. Morphological and pharmacological results together suggest that (1) muscarinic receptors are present on the smooth surfaces of all pyramidal and multipolar neurons; (2) many of the binding sites are high affinity, PZ-sensitive, M1 receptors; and (3) this binding is associated with the postsynaptic specialization of symmetric, cholinergic synapses.

Rabbit cingulate cortex: cytoarchitecture, physiological border with visual cortex, and afferent cortical connections of visual, motor, postsubicular, and intracingulate origin.

The connections of cingulate cortex with visual, motor, and parahippocampal cortices in the rabbit brain are evaluated by using a modified Brodmann cytoarchitectural scheme, electrophysiological mapping techniques, and the pathway tracers horseradish peroxidase (HRP) and tritiated amino acids. Rabbit cingulate cortex can be divided into areas 25, 24, and 29. Area 29 is of particular interest because area 29d has a lateral extension with a granular layer IV, area 29b has a caudal extension in which the connections differ from anterior area 29b, and there is a prominent area 29e. Cytoarchitectural delineation of the lateral border of area 29d with area 17 closely approximates the medial edge of the visual field representation in area 17 as determined electrophysiologically. The main interconnections between visual and cingulate cortices occur between cingulate areas 24b and 29d and visual areas 18 and medial parts of area 17. Projections between areas 29d and 18 are organized in a loose topographic fashion with rostral parts of each and caudal parts of each being reciprocally connected. Neurons mainly in superficial layer II-III of areas 17 and 18 project to layer I of area 29d, while the reciprocal projection originates from neurons in layer V of area 29d and project mainly to layer I of areas 17 and 18. The medial portion of motor area 8 projects to areas 18 and 29d and has a smaller projection to area 17. Postsubicular area 48 is reciprocally connected with area 29d, and it also projects to areas 29b and c. The subiculum projects to areas 29a and 29c but only to the anterior two-thirds of area 29b not the posterior one-third. Rostral area 29d receives the most extensive intrinsic cingulate projections including those from all major cytoarchitectural divisions. Interconnections between areas 29d and 29b appear to be topographically organized in the rostrocaudal plane. Area 29c projects more heavily to area 29b than vice versa. Finally area 29d projects mainly to area 24b in anterior cingulate cortex. In conclusion, rostral area 29d has extensive connections with visual areas 17 and 18, motor area 8, and all subdivisions of cingulate cortex. In light of these connections, it may play a pivotal role in associative functions of the rabbit cerebral cortex including visuomotor integration.

Anatomical studies on the nucleus reticularis tegmenti pontis in the pigmented rat. I. Cytoarchitecture, topography, and cerebral cortical afferents.

The nucleus reticularis tegmenti pontis (NRTP) is a precerebellar reticular nucleus that has been found to be related to cerebropontocerebellar pathways and, more recently, to eye movements. The present study investigates the cytoarchitecture, the topography, and the cerebral cortical projections to the NRTP in the pigmented rat. The cytoarchitecture and topography of the NRTP was determined by examination of Nissl-stained material sectioned in the transverse and sagittal planes. Two cytoarchitectonically distinct portions of the NRTP are apparent; a central subdivision (NRTPc) composed of large multipolar, small spherical, and fusiform neurons, and a pericentral subdivision (NRTPp) composed of loosely packed small fusiform and spherical neurons. The NRTPc is located dorsal to the medial lemniscus and pyramidal tracts over the caudal two-thirds of the pons. It extends caudodorsally to the region just rostral and ventral to the abducens nucleus. The NRTPp is adjacent to the lateral margins of the NRTPc, rostrally, and lies ventral to the caudal portions of the NRTPc. Large injections of horseradish peroxidase (HRP) were made into the cerebellum in order to determine the degree to which each subdivision of the NRTP contributes to the cerebellar projection. A high percentage of NRTPc neurons and a lower percentage of NRTPp neurons were labeled. These differences in labeling density and neuronal morphology noted above confirm the appropriateness of subdividing the NRTP into central and pericentral subdivisions. The cerebral cortical afferents to the NRTP were examined by placing small iontophoretic injections of HRP into the NRTPc and NRTPp. A systematic examination of all cortical areas revealed that the HRP-labeled neurons are entirely localized within pyramidal layer V of three major cortical areas: the ipsilateral prefrontal cortex (Brodmann areas 8, 8a, 11, and 32); the ipsilateral motor and somatosensory cortices (Brodmann areas 2, 4, 6, and 10), and the bilateral cingular cortex (Brodmann areas 24a, 24b, 29c, and 29d). By far, the heaviest cortical labeling with HRP injections into the medial NRTPc is within the cingular cortex that may, in the rat, be homologous to the frontal eye field of the cat and monkey. In contrast, injections involving the lateral NRTPc or the NRTPp produced labeling within wide regions of the cortex with the greatest number in the somatomotor cortex.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent specific localization of muscarinic acetylcholine receptors in cingulate cortex

The laminar distribution of acetylcholine receptors in rat cingulate cortex and their localization to axons of neurons in the anterior thalamic nuclei (ATN) were evaluated with the muscarinic antagonist [3H]propylbenzilylcholine mustard (PrBCM) in vitro. Specific binding of PrBCM in granular area 29 was heterogeneous, with a 57% variation from the highest binding in layer Ia to the lowest in layer II-III. In contrast, binding in area 24 was homogeneous, with only a 14% variation. The heterogeneity of PrBCM binding almost exactly duplicated the distribution of termination of ATN afferents in layers I to IV of area 29c. Four experiments indicated that 50% of the excess binding in layers Ia and IV was due to axonal receptor sites. First, ATN lesions abolished 41% and 27% of total specific binding in layers Ia and IV, respectively. Second, an undercut procedure that totally deafferented layers I to Va showed changes similar to those following ATN lesions, suggesting that other afferents to these layers may not have muscarinic receptors associated with them. Third, the sequence of losses in receptor binding and acetylcholinesterase (AChE) activity was evaluated 2, 3, 5, 9, and 14 days following ATN lesions. Since AChE was present in ATN axons, as evidenced by early postlesion losses, the correlation of both losses as well as previous analyses of axon degeneration in this cortex confirmed that these receptors were in axons. Fourth, binding peaks in layers Ia and IV remained in area 29c following destruction of virtually all neurons with the neurotoxin ibotenic acid. This is the first evidence that the activity of a major neocortical thalamic afferent may be regulated by axonal acetylcholine receptors.

Cortical connections between rat cingulate cortex and visual, motor, and postsubicular cortices.

The connections of rat cingulate cortex with visual, motor, and postsubicular cortices were investigated with retrograde and anterograde tracing techniques. In addition, connections between visual and the postsubicular (area 48) and parasubicular (area 49) cortices were evaluated with the same techniques. The following conclusions were drawn. Area 29 connections: Afferents to area 29 originate mainly from cingulate areas 24 and 25, visual cortex (primarily area 18b), motor cortex area 8, area 11 of frontal cortex, areas 48 and 49, and the subiculum. Efferent connections of area 29 within cingulate cortex and to visual areas differ for each cytoarchitectural subdivision of area 29. Thus, area 29c has limited projections both within cingulate cortex and to areas 48 and 49, while area 29d projects to these areas as well as to area 8, area 18b, and medial area 17. These visual cortex afferents originate mainly from layer V neurons of areas 29b and 29d, while areas 29a and 29c have virtually no projections to visual cortex. Area 24 connections: Afferents to area 24 originate primary from cingulate areas 25 and 29 and visual area 18b and medial area 17. Efferent projections of area 24a are distributed within cingulate cortex, while area 24b has more extensive projections to posterior cingulate and visual cortices. Area 24b is the cingulate subdivision which is both the primary recipient of visual cortex afferents as well as the source of most of the projections of anterior cingulate cortex to visual areas. Visual cortex has reciprocal connections with parts of the postsubicular and parasubicular cortices. Neurons of the internal pyramidal cell layer of both areas 48 and 49 project to areas 17 and 18b, while layers I and III of these parahippocampal areas receive projections from areas 17 and 8b. In conclusion, areas 29d have particularly extensive interconnections with visual cortex, while area 29d also maintains projections to area 8 of motor cortex. This connection scheme supports the view that cingulate cortex may have a role in feature extraction from the sensory environment, as well as in sensorimotor integration. Finally, the postsubiculum may be classified as a limbic association cortex in which extensive visual and cingulate efferents converge.

Brain stem projections from cortical area 18 in the albino rat.

Efferent brain stem projections from area 18 of the albino rat cortex were traced by autoradiography. Since results could have been compromised by spread of injected label to neighboring areas 17 and 29, studies of projections from these areas were used as controls. A hitherto unreported projection from area 18 to the thalamus in the region of its anterior nuclei was found, terminating in a roughly circular area including parts of the anteromedial, ventral, ventromedial and rhomboid nuclei. At this same level, a very light projection was seen in the contralateral anteromedial nucleus. More caudally the projection pattern was similar to that of area 17, with the lateral, lateral posterior, posterior and pretectal nuclei as targets. However, area 18 showed no projections to either division of lateral geniculate nucleus, projections which are commonly seen following injections in area 17. More caudally, the area 18 projection to the superior colliculus was confined to its four deepest laminae, a projection identical to that from areas 29c and 29b. Area 18 also resembled the cingulate cortex in that it sent a small projection to the dorsolateral central gray, although the routes taken to this region were slightly different. It was decided that the projections from this visual association area were, for the most part, unique to that area, although some of them resembled those from either the cingulate cortex or the primary visual area.

Synaptic termination of thalamic and callosal afferents in cingulate cortex of the rat.

The distribution of degenerating thalamic and callosal afferents to cingulate cortex in the rat is analyzed. Both light microscopic silver impregnation and quantitative electron microscopic techniques demonstrate differences in the form, number, and laminar distribution of these two afferents in anterior and posterior cingulate cortices. Afferents from the mediodorsal thalamic nucleus terminate in area 24. Most terminals are in layer IIIb, fewer in layer Ia-b, and least in layers V and VI. In contrast, callosal afferents terminate mainly in layers Ib-c, II, IIIa, V, and VI. Thus, thalamic and callosal afferents terminate in a complementary pattern except in layers Ib and IIIb where they overlap. Quantitative analysis of degenerating axon terminals in area 24 indicates that there may be as many as seven times more callosal than mediodorsal thalamic terminals in this cortex. Projections of the anterior thalamic nuclei terminate in areas 29b and 29c, primarily in layer Ia, with fewer in layers Ib-IV and least in layers V and VI. Callosal afferents end mainly in layers V and VI and less densely in layers I-IV, which results in some overlap of thalamic and callosal afferents in layers Ic, IV, and V. In addition, patterns of termination of callosal afferents in posterior cingulate cortex change at borders between previously defined cytoarchitectural areas. Anterior thalamic terminals in area 29c differ from other thalamocortical afferents described previously in that they form two types of terminals. One is large (2-4 micrometer in diameter) and occurs mainly in layer Ia, whereas the second type is smaller and is present in layers Ib-V. Both types of terminals form asymmetric synapses mainly with dendritic spines.

Form and distribution of neurons in rat cingulate cortex: areas 32, 24, and 29.

AbstractThe cytoarchitecture of rat cingulate cortex is described. This includes the topographical distribution and layering patterns of Brodmann's areas 25, 32, 24, and 29a, b, c, and d. Area 24 is subdivided into a ventral area 24a and a dorsal area 24b, but an area 23 could not be identified between areas 24 and 29An analysis of Golgi impregnations in areas 32, 24, and 29 demonstrates that most neuronal types recognized in neocortical areas are also present in cingulate cortex. Besides typical and inverted pyramidal cells, there is a wide variety of nonpyramidal cells, including multipolar, bitufted, and bipolar cells. Small multipolar cells with small somata, a dendritic tree limited to one or two layers, sparse to moderately spinous dendrites and one of two varieties of short axonal trajectories are present in layers I and II of areas 32, 24, and 29d. Medium multipolar cells occur mainly in layers III and V; they have extensive dendritic trees which traverse three or more layers, moderately spinous dendrites, and an axonal plexus which either ascends or descends in the cortex. Large multipolar cells are also frequent in layers III and V; their extensive dendritic trees are essentially spine free and they have axons which form dense terminations, particularly in the layer above the one in which the cell body is locatedNeurons with elongated somata and a primarily vertical orientation of the dendritic tree are either bitufted or bipolar. Bitufted cells are most frequent in layers II and III of areas 32, 24, and 29d. These cells have dendritic trees which form “hourglass shaped” fields, dendrites which are moderately spinous, and axons which form either extensive horizontal and vertical projections or are “chandelier” in form. Bipolar cells, in contrast, are found in layers II–V; their sparsely spinous dendrites form narrow dendritic trees which are oriented vertically and extend across four or more layers, and their axons have the same vertical orientation as the dendritic treeIt is concluded that the form of the axonal arbors of nonpyramidal cells frequently mimics the extent and shape of their dendritic trees. Thus, small multipolar cells with limited, spherical dendritic trees may have axons which arch sharply and emit short, terminal branches. In contrast, medium and large multipolar cells have more extensive dendritic and axonal arbors which traverse two, three, or more layers. Of the fusiform cells, bitufted ones with their “hourglass” dendritic trees have extensive vertical and horizontally oriented axonal branches, while bipolar cells have narrow, vertically oriented dendritic and axonal arborsThe granular layers II–IV of area 29c contain the following types of neurons: small and fusiform pyramids, medium‐sized pyramids, large stellate cells, and medium multipolar cells. Fusiform pyramids are the only neurons unique to cingulate cortex. They are similar to the variety of pyramidal cells, but have an oval soma and only one basal dendrite which extends from the base of the cell body to arborize in layer IV. Large stellate cells differ from large multipolar cells in that they have densely spinous dendrites and axons which enter the white matter.

Efferent projections of the lateral dorsal nucleus in the rat

The present study was undertaken to determine the efferent projections of the lateral dorsal nucleus of the rat thalamus using procedures based on anterograde degeneration as well as anterograde and retrograde axoplasmic transport. Discrete lesions or injections of [ 3H]leucine were placed at separate anterior and posterior loci in the lateral dorsal nucleus to determine if these portions of the nucleus project to different terminal fields. From both loci, labeled or degenerating axons coursed laterally from the nucleus, passed through the superior thalamic radiation, and entered the caudate-putamen complex. From there, a large number of fibers coursed rostrally in the album cerebri and terminated in layers I and III of anterior cingulate cortical areas 23 and 24. The remaining fibers passed dorsally and entered the posterior cingulate cortex where terminations were observed in areas 29b and 29c. Within area 29b, terminations were arranged parallel to the surface in layers I and III at its border with area 29c. In animals with anteriorly placed lesions or injections, area 29c exhibited input in layers I, III, and IV at the lip of the hemisphere. After injections in the posterior part of the lateral dorsal nucleus, a denser distribution was observed within the same layers at the border of areas 29b and 29c. Projections and areas of termination were also observed from both anterior and posterior lesions or injection sites to the laminae dissecans and externa of the pre- and parasubiculum. These projections were confirmed by retrograde axoplasmic transport of horseradish peroxidase after its injection in the cingulate and subicular cortices. These results indicate that the lateral dorsal nucleus, through its prominent connections with the anterior and posterior parts of the cingulate cortex and subicular region may have significant connections with the limbic system.

Afferent and efferent projections of the region in mouse SmL cortex which contains the posteromedial barrel subfield.

AbstractExperiments using anterograde and retrograde tracing techniques have been used to identify projections to and from the region of mouse SmI cortex which contains the posteromedial barrel subfield (PMBSF, Woolsey and Van der Loos, '70). Microinjections containing horseradish peroxidase (HRP) and tritiated amino acids were placed unilaterally into the topographic center of the PMBSF. Brains were perfuse‐fixed and frozen sectioned. All sections were reacted for HRP and alternate sections were autoradiographed. Examination of sections cut tangential to the pial surface in the region of the injection site showed that diffusion of the injection was limited to cortex above and below the PMBSF in layer IV (i.e., PMBSF cortex). A “column” of HRP reaction product and developed silver grains was present in ipsilateral cortical area 40, in the face area of SmII. HRP positive cell bodies were mainly in layer III and VI of this “column.” A similar “column” was present in ipsilateral cortical area 6, in a region which in the rat corresponds to the vibrissal area of MsI (Hall and Lindholm, '74), but here HRF positive cells bodies were situated mainly in layer V. HRP labeled cells bodies were also present in layer V of ipsilateral cortical area 29c. The ipsilateral nucleus ventralis thalami pars lateralis and the nucleus posterior thalami contained many HRP positive cell bodies and were associated with dense aggregations of developed silver grains. Numerous silver grains were also present over portions of the ipsilateral caudate, reticular nucleus of the thalamus and ventral pontine nuclei, but no HRP positive cell bodies occurred in these regions.HRP‐filled axons left the injection site and traveled via the corpus callosum to contralateral PMBSF cortex where HRF labeled cell bodies were present mainly in layers III and V. Usually only one or two labeled somata were located superficial or deep to a contralateral PMBSF barrel. A few HRF positive cell bodies were also present in layers II and III of contralateral pyriform cortex.These results indicate that PMBSF cortex is reciprocally connected with ipsilateral cortical areas 6 and 40 and with the ipsilateral ventral and posterior nuclei of the thalamus. A small, homotopic callosal connection with contralateral PMBSF cortex has been demonstrated, and it is presumed that this projection is also reciprocal. PMBSF cortex projects to, but receives no projections from the ipsilateral caudate, reticular nucleus of the thalamus and the ventral pontine nuclei. Thus, many of the same projections of primary somatosensory cortex in higher animals, such as the monkey have been shown to occur in the mouse.

RESPIRATORY AND VASCULAR RESPONSES IN MONKEYS FROM TEMPORAL POLE, INSULA, ORBITAL SURFACE AND CINGULATE GYRUS: A PRELIMINARY REPORT

RESPIRATORY AND VASCULAR RESPONSES IN MONKEYS FROM TEMPORAL POLE, INSULA, ORBITAL SURFACE AND CINGULATE GYRUS: <b>A PRELIMINARY REPORT</b>

THE CINGULAR GYRUS: AREA 24

THE CINGULAR GYRUS: AREA 24