Intermediate Divisions Research Articles

Distribution of parvalbumin‐immunoreactive cells and fibers in the human amygdaloid complex

The calcium-binding protein, parvalbumin, was localized immunohistochemically in the human amygdaloid complex. Neuronal cell bodies and fibers that are immunoreactive to parvalbumin were observed in most of the amygdaloid nuclei and cortical areas. Three types of immunoreactive aspiny neurons, ranging from small spherical cells (type 1) to large multipolar cells (type 2) and fusiform cells (type 3), were observed. The densities of the types of neurons that were parvalbumin-immunoreactive varied in the different regions of the amygdala. The highest densities of parvalbumin-immunoreactive neurons were observed in the lateral nucleus, in the magnocellular and intermediate divisions of the basal nucleus, in the magnocellular division of the accessory basal nucleus and in the amygdalohippocampal area. The regions containing the lowest density of parvalbumin-immunoreactive cells were the paralaminar nucleus, the parvicellular division of the basal nucleus, the central nucleus, the medial nucleus and the anterior cortical nucleus. In general, the distribution of immunoreactive fibers and terminals paralleled that of immunoreactive cells. Parvalbumin-immunoreactive varicose fibers formed basket-like plexi and cartridges around the unstained neurons, which suggests that parvalbumin is located in GABAergic basket cells and chandelier cells, respectively. The distribution of parvalbumin-immunoreactive profiles in the human amygdaloid complex was similar to, rather than different from that previously reported in the monkey amygdala (Pitkänen and Amaral [1993] J. Comp. Neurol. 331:14-36). This study provides baseline information about the organization of GABAergic inhibitory circuitries in the human amygdaloid complex.

Electron microscopy of cell islands in layer II of the primate entorhinal cortex

An electron microscopic analysis of cell islands in layer II of the entorhinal cortex from rhesus monkeys was made to determine the ultrastructural features of these unique neuronal clusters. The rostral, intermediate, and caudal divisions of the entorhinal cortex were selected for electron microscopic examination. In the rostral division, neurons were grouped together in prominent clusters, often with 10 or more contiguous somata. Somatic and dendrosomatic appositions were frequent, without intervening cellular processes or specialized junctions. Somata were relatively small, typically 10-15 microns in diameter, with oval or circular nuclei that were euchromatic and contained nucleoli. Small nuclear infoldings were commonly seen. A thin shell of perikaryal cytoplasm contained numerous organelles. Axosomatic synapses were infrequent, with a mean of only 1.0 synapse per neuron per thin section. The neuropil contained numerous synapses, and myelinated axons were seen infrequently. In the intermediate division, somatic appositions were rarely observed. Somata were relatively large, typically 15-20 microns in diameter, and displayed a moderate amount of cytoplasm. Axosomatic synapses were relatively common, with a mean of 3.3 synapses per neuron per thin section. In the caudal division, neurons were typically grouped in clusters of two to three contiguous somata. Neurons were about 15 microns in diameter and displayed a moderate amount of cytoplasm. Axosomatic synapses were of moderate frequency, with a mean of 2.5 synapses per neuron per thin section. The neuropil in the caudal division displayed a relatively high frequency of myelinated axons. Our analysis of three regions of the entorhinal cortex revealed significant differences in the frequency of somatic appositions and axosomatic synapses, and in certain ultrastructural features of the somata and neuropil. These results showed that cell islands in layer II of the entorhinal cortex display regional morphologic differences. The paucity of symmetric axosomatic synapses in the rostral division may correlate with this region's vulnerability in certain diseases.

Projections from the nucleus tractus solitarii to the spinal cord.

Projections from the nucleus tractus solitarii (NTS) to the spinal cord were demonstrated in the male Sprague-Dawley rat. In retrograde transport studies, a horseradish peroxidase conjugate or a fluorescent dye, FluoroGold, were injected into midcervical or upper thoracic spinal segments. Most solitariospinal neurons were multipolar or bipolar and located between the obex and spinomedullary junction. Solitariospinal neurons were concentrated in proximity to the ventral border of the solitary tract and extended dorsally into the intermediate division and ventrolaterally into the intermediate reticular zone (IRt) of the lateral tegmental field. This subgroup predominantly projects to midcervical spinal segments. A subset of small neurons was retrogradely labeled from cervical or thoracic spinal segments in the medial commissural nucleus and contiguous with a periventricular group surrounding the central canal. In anterograde transport studies, iontophoretic deposits of Phaseolus vulgaris leucoagglutinin were centered stereotaxically on sites in NTS identified by retrograde transport data. The lectin was incorporated by neurons of the solitary complex and transported bilaterally by axons that emerged from the nucleus and entered the reticular formation. The solitario-reticular (transtegmental) pathway irradiated diagonally across the IRt and extended caudally into the cervical lateral funiculus and spinal gray. A small periventricular-spinal pathway also descended longitudinally to the neuraxis. Solitariospinal neurons project to superficial lamina of the dorsal horn, laminae VII and X and ventral horn. The projections are predominantly contralateral to phrenic and intercostal motor nuclei and ipsilateral to the intermediolateral cell column. The solitariospinal projection represents the shortest route in the central nervous system, other than the local intraspinal reflex, through which first order visceral afferents signal cardiorespiratory and alimentary motor nuclei.

Dorsal motor nucleus of the vagus nerve: A cyto‐ and chemoarchitectonic study in the human

In order to investigate the topography and subdivisions of the human dorsal motor nucleus of the vagus nerve (10), studies were conducted using cyto- and chemoarchitectonic (acetylcholinesterase and substance P-like immunoreactivity) and computer reconstruction techniques. The six brainstems examined were obtained within 17 hours postmortem from adults with no known neurological disorders. Serial sections cut in transverse, sagittal, and coronal planes were stained with cresyl violet, or tested for acetylcholinesterase or substance P. The neurons of the 10 (16,826 +/- 967) displayed cyto- and chemoarchitectonic heterogeneity and could be classified into six types. Types I-V consist of presumed vagal motor neurons (13,802 +/- 844), while the remaining type (Type VI) consisted of presumed interneurons (3,024 +/- 769). The 10 was subdivided into nine subnuclei grouped regionally into rostral, intermediate, and caudal divisions on the basis of neuronal morphology, cell density, and differential AChE and substance P reactivities. The rostral division contains the dorsorostral (DoR) and the ventrorostral (VeR) subnuclei; the intermediate division contains the rostrointermediate (RoI), dorsointermediate (DoI), centrointermediate (CeI), ventrointermediate (VeI), and caudointermediate (CaI) subnuclei; the caudal division (Ca) is not subdivided. Morphologically, small round or oval cells populate the VeR and VeI. Medium-sized oval cells occur in the DoR, CeI, and Ca, while medium-sized fusiform and multipolar cells are the main features of CaI. Large triangular cells appear mainly in DoI. Glial cells show the highest predilection for CeI, lowest densities in DoI and medial fringe subnucleus (MeF), and intermediate densities in the remaining six subnuclei. VeI showed the strongest AChE reactivity. Although the cell bodies of VeR and DoI are AChE positive, the neuropil (background) is weakly stained. Densely distributed fine granular substance P-like immunoreactivity occurs throughout the entire nucleus, while the intermediate and caudal divisions contain substance P-like-immunoreactive neurons. Three-dimensional computer reconstructions afforded an appreciation of the distinctiveness of the intermediate division (a division that contains the majority of cells) and the caudal division, which displays the lowest density of presumed vagal motoneurons. It is possible that the subnuclei identified herein form functional units innervating specific organs.

Against Skills‐based Testing in Science

Abstract In recent years, considerable attention has been focused on the need to develop effective and efficient strategies and procedures for the assessment of students’ laboratory work, on the assumption that only when practical aspects of doing science are rewarded through allocation of marks and grades will teachers give these activities the curriculum priority that many believe they should have. There is no doubt that examinations do exert a significant influence on the curriculum, and can promote or hinder the adoption of particular classroom activities. So, in one sense, the Ontario Ministry of Education's statement in 1987 that assessment of laboratory work should constitute 15% of the final mark in “all Intermediate and Senior Division science courses”, is to be welcomed. So, too, is the growing interest in the assessment of laboratory work in the USA, Australia and New Zealand, and the renewal of interest in the United Kingdom, where such assessment has a long history. Increasingly, however, the...

Studies of the motoneurons following the injection of horseradish peroxidase into the peripheral branches of the facial nerve in rats.

With the method of retrograde transport of horseradish peroxidase, the present study demonstrated a topographical representation of the peripheral branches of the facial nerve within the rat facial nucleus. The labelled neurons relating to the different peripheral branches were characterized morphometrically with the aid of an image analyser system. While the results were in general agreement with the work of other investigators, a striking difference was observed in this study with respect to the spatial distribution of the labelled neurons of the cervical branch. In the latter, the cells of origin were derived from the dorsal parts of the lateral and intermediate division of the facial nucleus. The present study further demonstrated that the motoneurons giving rise to the respective peripheral branches of the facial nerve varied considerably in cell size. Thus, the neurons of the posterior auricular and the mental branches were significantly larger than those of the nasolabial and zygomatico-orbital branches. Another significant finding in this study was that the neurons supplying the mental branch were predominantly spindle-shaped. It is concluded that the heterogeneity in size and shape of the motoneurons in the facial nucleus is related to the topographical representation of the peripheral branches of the facial nerve.

The anterior ectoylvian sulcal auditory field in the cat: II. A horseradisha peroxidase study of its thalamic and cortical connections

The thalamic and cortical projections to acoustically responsive regions of the anterior ectosylvian sulcus were determined by identifying retrogradely labelled cells after physiologically guided iontophoretic injections of horseradish peroxidase. The medial division of the medial geniculate nucleus, the intermediate division of the posterior nuclear group, the principal division of the ventromedial nucleus, and the lateroposterior complex were consistently labelled after these injections, although each animal showed slightly different patterns of labelling. The suprageniculate nucleus and the lateral and medial divisions of the posterior nuclear group were also labelled in most experiments. The cortex of the suprasylvian sulcus was the most consistently and densely labelled cortical region; each experiment showed a slightly different pattern of labelling throughout the suprasylvian sulcus, with an overall tendency for greater labelling in the ventral (lateral) bank of the middle region of the sulcus. Other cortical regions labelled less consistently included the anterior ectosylvian sulcus itself, the insular cortex of the anterior sylvian gyrus, and the posterior rhinal sulcus. In three experiments the contralateral cortex was examined and a small number of labelled cells was located in the anterior ectosylvian and suprasylvian sulci. Input from extralemniscal auditory thalamus is compatible with previously described auditory response properties of anterior ectosylvian sulcus neurons. The results also confirm the presence of input from visual and multimodal regions of thalamus and cortex, and therefore support claims of overlap of modalities within the sulcus. This overlap, as well as input from motor regions, suggests that the anterior ectosylvian sulcal field serves a sensorimotor role.

Medial forebrain bundle of the rat: IV. Cytoarchitecture of the caudal (lateral hypothalamic) part of the medial forebrain bundle bed nucleus

In the preceding study (Geeraedts et al.: J. Comp. Neurol. 294:507-536, '90), the rostral or telencephalic portion of the rat's bed nucleus of the medial forebrain bundle (MFB) has been parcellated into several cytoarchitectonically distinct cellular groups and subgroups. The purpose of the present investigation is to subject the caudal or lateral hypothalamic (LH) portion of the MFB bed nucleus to a detailed cytoarchitectonic analysis. This analysis is based on the same materials, methods, and cytoarchitectonic criteria that were also employed in the preceding study. In contrast to descriptions in the literature, it was found that the LH-region constitutes a very heterogeneous population of neurons with an evident arrangement into groups, several of which have not been identified previously. Many of these cellular groups are partly or entirely located within the boundary of the LH-trajectory of the MFB as previously established by Nieuwenhuys et al. (J. Comp. Neurol. 206:49-81, '82). These groups are designated here as the MFB-related cellular groups. They appear to be arranged into two longitudinal zones. Both zones are caudally replaced by the ventral tegmental area (VTA) and a part of the mesencephalic tegmentum (TEGM1). The lateral zone lies in close proximity to the internal capsule/cerebral peduncle and comprises the following cellular groups: the ventrolateral subarea of the lateral hypothalamic area (LHVL), the anterolateral subarea of the lateral hypothalamic area (LHAL), the lateral tuberal nucleus (TUL), the pre-subthalamic nucleus (PSUT), the retro-subthalamic nucleus (RSUT), the anterodorsal subarea of the lateral hypothalamic area (LHAD), and the lateral hypothalamic nucleus (LHN). The medial zone consists of the following cellular groups: the intermediate hypothalamic area (IHA), the medial tuberal nucleus (TUM), the perifornical nucleus (PFX), the lateral supramammillary nucleus (SUL), the submammillothalamic nucleus (SMT), and the nucleus geminus posterior (GEP). The cellular groups of the medial zone together with the tuberomammillary nucleus groups of the medial zone together with the tuberomammillary nucleus (TUMM) are positioned at the interface between the lateral and the medial hypothalamus, and form an array of cellular groups indicated in our study as the intermediate division of the hypothalamus. The MFB-related cellular groups are dorsally, medially, ventrally, and laterally surrounded by rather well-known brain structures. Both the MFB-related cellular groups and the surrounding structures have been identified and delimited. This resulted in a new, elaborate cytoarchitectonic atlas of the rat's lateral hypothalamic region.(ABSTRACT TRUNCATED AT 400 WORDS)

Neurogenesis of the magnocellular basal forebrain nuclei in the rhesus monkey

The time of origin of the neurons that comprise the magnocellular basal forebrain nuclei in rhesus monkeys was determined by using [3H]thymidine autoradiography. Thirteen pregnant animals received an injection of [3H]thymidine between embryonic days 27 (E27) and E50 of their 165 day gestation, and their offspring were sacrificed during the early postnatal period. Neurons within this region were generated in a biphasic pattern. An initial burst of [3H]thymidine-labeled magnocellular neurons was first observed throughout short quiescent period, cells of the remaining anterior basal forebrain (inclusive of magnocellular neurons comprising the vertical limb of the diagonal band and the anteromedial and anterolateral regions of the nucleus basalis) were generated between E36 and E45 with a peak of neurogenesis seen on E40-E43. The intermediate division of the nucleus basalis was generated about the same time, but the peak period of neurogenesis in this region occurred slightly earlier (E36 and E40) and was completed by E43. During the second phase of neurogenesis, neurons within the posterior division of the basal forebrain were generated first, with their genesis virtually completed between E33 and E36. The genesis of all neurons comprising the magnocellular basal forebrain nuclei was completed by E48 of gestation. A general caudal to rostral gradient of neurogenesis was observed within this telencephalic region. In contrast, a neurogenic gradient was not discerned in the radial direction. The present data demonstrate that neurons comprising the basal forebrain magnocellular nuclei in monkeys are generated early in gestation with two peak times of neuronal genesis. These nuclei are among the earliest to be generated in the entire telencephalon, which, like neurons of the thalamus and cortical neurons giving rise to cortical-cortical connections, places them in a strategic position to potentially influence their target neurons within the cortical mantle that are generated later in gestation.

Non-motoneurons in the facial and motor trigeminal nuclei projecting to the cerebellar flocculus in the cat

The cerebellar projection from the facial and motor trigeminal nuclei was studied in the cat by means of retrograde axonal transport of wheat germ agglutinin-horseradish peroxidase and fluorescent tracers. The feline facial nucleus was cytoarchitectonically subdivided into ventromedial, ventrolateral, lateral, dorsal, intermediate and medial divisions (see Papez 1927), and the motor trigeminal nucleus into medial, ventral, intermediate, lateral and dorsal divisions. The neurons in the facial and motor trigeminal nuclei were classified as small (ovoid to round cells with a maximum diameter of the cell body of about 20 microns) or large (polygonal to round cells with maximum diameter of about 40 microns). After floccular injections of the wheat germ agglutinin-horseradish peroxidase complex, retrogradely labelled cells were found throughout the facial nucleus, but especially in its medial and dorsal divisions. In the motor trigeminal nucleus, labelled neurons were found only in the ventral, intermediate and lateral divisions. Cases with tracer deposition (implants or injections) in other parts of the cerebellar cortex or nuclei were all negative. All facial and motor trigeminal neurons labelled after floccular injections were smaller than the neurons labelled after injections in the facial mimic and masticatory muscles, and only single-labelled neurons were found following floccular injections of Fluoro-Gold and muscular injections of rhodamine-B-isothiocyanate in the same animals. These observations strongly suggest that the neurons in the facial and motor trigeminal nuclei which project to flocculus are of the non-motoneuron type.

Gustatory innervation in the rabbit: central distribution of sensory and motor components of the chorda tympani, glossopharyngeal, and superior laryngeal nerves.

Although rabbits have been used extensively in neurophysiological studies of the gustatory system, there is little information about the anatomical organization of taste in this species. Afferent and efferent central connections of three nerves innervating oral or laryngeal taste buds in the rabbit, including the chorda tympani (CT), the lingual-tonsillar branch of the glossopharyngeal (IX), and the superior laryngeal nerve (SLN), were traced by means of horseradish peroxidase neurohistochemistry. After entering the brainstem, most afferent fibers of CT, IX, and SLN turned caudally in the solitary tract, with fibers of the CT terminating in the nucleus of the solitary tract from 1.0 mm rostral to 3.8 mm caudal to the caudal border of the dorsal cochlear nucleus. There was terminal label from the CT also in the principal trigeminal nucleus. There was terminal label from the CT also in the principal trigeminal nucleus and the oral and intermediate divisions of the spinal trigeminal nucleus. Preganglionic parasympathetic cell bodies of the superior salivatory nucleus were labeled retrogradely in the reticular formation ventral to the rostral pole of the solitary nucleus. Afferent fibers of the IXth nerve terminated in the solitary nucleus from 0.6 mm rostral to 5.0 mm caudal to the caudal border of the dorsal cochlear nucleus. There were also labeled terminals in the principal trigeminal nucleus and in all three divisions of the spinal trigeminal nucleus. Cell bodies composing the inferior salivatory nucleus were labeled in and around the solitary nucleus and subadjacent reticular formation just rostral to the caudal border of the dorsal cochlear nucleus. There were also a few lightly labeled cells within the nucleus ambiguus at its most rostral extent. Afferent fibers of the SLN terminated in the solitary nucleus from 1.2 to 6.8 mm caudal to the dorsal cochlear nucleus. There was also some terminal label in the intermediate and caudal divisions of the spinal trigeminal nucleus. Many cells were retrogradely labeled in the nucleus ambiguus following application of HRP to the SLN and a few cells were labeled in and around the solitary nucleus just caudal to the dorsal cochlear nucleus. These three nerves show an overlapping rostral to caudal distribution of afferent input within the nucleus of the solitary tract that may be related to their gustatory and visceral functions.

Noncontrollable Costs and Optimal Performance Measurement

Suh [1987] addresses the issue of why it could be optimal to allocate apparently noncontrollable costs for management control purposes in a multiagent, sequential department setting.' He shows that there are situations in which a final division manager has an incentive to collude with an intermediate division manager to get a higher quality of intermediate product than the principal desires. In this case, it could be optimal for the principal to hold the final division manager responsible for those noncontrollable intermediate costs by allocating those costs to the final division, if the principal dislikes their collusion. The purpose of this paper is to show that two other mechanisms (a noisy qualitygenerating process and intermediate division manager's private information), which are not considered in Suh [1987], could also explain noncontrollable cost allocation in a sequential department setting. These two mechanisms are discussed in sections 2 and 3, respectively.

Correlation of the main peripheral branches of the facial nerve with the cytoarchitectonic subdivisions of the facial nucleus in the guinea pig.

Correlation of the main peripheral branches of the facial nerve with morphological subdivisions of the facial nucleus was examined in the guinea pig by the retrograde horseradish peroxidase method. The facial nucleus of the guinea pig was divided cytoarchitectonically into the dorsolateral, lateral, intermediate, medio-intermediate, medial, and ventromedial divisions; the ventromedial division was further divided into the major, dorsal and lateral parts. Six main branches of the facial nerve were identified; the zygomatico-orbital, cervical, posterior auricular, anterior auricular, superior labial, and inferior labial branches. After applying HRP to the main branches of the facial nerve, the pattern of distribution of HRP-labelled neuronal cell bodies within the facial nucleus was examined: the dorsolateral division, dorsal part of the ventromedial division, major part of the ventromedial division, lateral part of the ventromedial division, or medial division contained the cell bodies of respectively the zygomatico-orbital, cervical, posterior auricular, anterior auricular, or superior labial branches, while each of the lateral, intermediate, and medio-intermediate divisions contained the cell bodies of both the superior labial and inferior labial branches.

Connections between the thalamus and the somatosensory areas of the anterior ectosylvian gyrus in the cat

The thalamocortical and corticothalamic connections of the second somatic sensory area (SII) and adjacent cortical areas in the cat were studied with anterograde and retrograde tracers. Injections consisted of horseradish peroxidase conjugated to wheat germ agglutinin (HRP-WGA) or a mixture of equal parts of tritiated leucine and proline. The cortical regions to be injected were electrophysiologically studied with microelectrodes to determine the localization of the selected components of the body representation in SII. The distribution of recording points was correlated in each case with the extent of the injection mass in the cortex. Distributions of retrograde and anterograde labeling in the thalamus were reconstructed from serial coronal sections. The results from cases with injections of tracers exclusively confined to separate parts of the body map in SII indicated a fairly precise topographical organization of projections from the ventrobasal complex (VB) to SII. The labeled cells and fibers were located within a series of lamella-like rods that curved throughout the dorsoventral and rostrocaudal axis of VB. The position and extent of these lamellae shifted from medial and ventral, in the medial subdivision of ventral posterior lateral nucleus (VPLm) for radial forelimb digit zones of SII, to dorsal, posterior, and lateral, in the lateral subdivision of ventral posterior lateral nucleus (VPL1) for proximal leg and trunk regions in SII. For every injected area in SII the densest clustering of labeled cells and fibers was usually more posteriorly represented in VB. The distribution in these dense zones of labeling often extended through the central core of VB. SII projecting neurons were also consistently noted in the extreme rostral portion of the medial subdivision of the posterior nuclei (Pom) that lies dorsal to VB. Corticothalamic and thalamocortical connections for SII were entirely reciprocal. Injections of tracers into cortical areas surrounding SII labeled other parts of the posterior complex but failed to label any part of VB except when the injection mass also diffused into SII. Injections into the somatic sensory cortex located lateral to SII, within the lips and depth of the upper bank of the anterior ectosylvian sulcus (AES), heavily labeled the central and posterior portions of Pom. Substantial labeling was noted in the lateral (Pol) and intermediate (Poi) divisions of Po only when the injections involved some part of the auditory areas located immediately posterior to SII. This region included the anterior auditory area that occupies the most posterior part of the AEG and both banks of the immediately adjoining AES. The magnocellular nucleus of the medial geniculate (MGmc) was labeled only when some part of the auditory cortex was injected. The suprageniculate nucleus (SG) was labeled from the insula and lower bank of the AES. These results indicated that the medial (rostral and caudal Pom) and lateral components (Poi, Pol, MGmc) of the posterior complex have separate cortical projection zones to somatic sensory and auditory cortical regions, respectively. SIV and the lateral extent of area 5a located in the medial bank of the anterior suprasylvian sulcus sent projections to the deep layers of the superior colliculus and the ventrolateral periaqueductal gray. No cortico-tectal projections were seen from SII.

Improved protoplast culture and agarose media

Media solidified with agarose resulted in higher plating efficiency of protoplasts than commonly used agar media. Improved culture efficiency was observed with mesophyll protoplasts of Nicotiana tabacum and N. plumbaginifolia and with protoplasts isolated from cell lines of Daucus carota, Hyoscyamus muticus and two lines of N. tabacum. The improvement with agarose was consistent over a wide cell density range and also for different media. The positive effect was not due to the lower temperature at which the protoplasts could be plated. Culture experiments with mixtures of different agar types generally gave intermediate division frequencies. There was no obvious effect on plating efficiency in experiments where diffusion was permitted between agar and other agar types.

Topography between the entorhinal cortex and the dentate septotemporal axis in rats: I. Medial and intermediate entorhinal projecting cells.

Retrograde tracing experiments were performed to clarify the topographic projection from medial (area 28m) and intermediate (area 28i) divisions of the entorhinal cortex to the dentate gyrus. Pipets filled with horseradish peroxidase (HRP) were positioned by electrophysiologic guidance at one of several septotemporal (S-T) levels in the dentate molecular layer of anesthetized rats; the tracer was expelled iontrophoretically to minimize its spread. Retrograde labeling of neurons within areas 28m and 28i was analyzed in relation to cytoarchitectonic as well as spatial features of the region (obtained by histologic reconstruction). Regardless of the S-T level, ejections of HRP which were confined to the dentate gyrus labeled only layer II neurons of each area. Following septal pole ejections, labeled neurons were located in the posterolateral, extreme posterior, and posteromedial parts of both areas 28m and 28i. Mid S-T ejections produced not only a ventral, but also an anteromedial, shift in the location of entorhinal projection cells; no cells were labeled posterolaterally. After temporal dentate ejections labeled neurons occupied the most anteromedial part of these entorhinal areas. For both areas, but especially for area 28i, convergence of entorhinal efferents upon a single S-T level in the dentate gyrus occurred from neurons which lay in a dorsoventral (i.e., frontal), and to a lesser extent a rostrocaudal, plane. The efferent axes of both areas 28m and 28i thus appear to be curved and are therefore best described in three dimensions. The entorhinal axes begin in a posterodorsolateral location, wrap around the posterior cortical convexity, and end in an anteroventromedial position. The results provide a useful map for in situ exploration of entorhinodentate connections in the rat, emphasize the parallel innervation of the dentate gyrus by distinct entorhinal fiber systems, and reflect the importance of the S-T axis as a framework for interpreting hippocampal organization.

Thalamocortical neurons projecting to the areas surrounding the anterior and middle suprasylvian sulci in the cat. A horseradish peroxidase study.

The thalamic projections to the cortical area surrounding the anterior (ASs) and middle (MSs) suprasylvian sulci in the cat were studied using horseradish peroxidase histochemistry. The medial MSs area (medial wall of the MsS) receives thalamic afferents from the pulvinar-lateralis posterior (Pul-LP) complex, posterior nucleus (Pn) and medial interlaminar nucleus (MIN) and C laminae of the dorsal lateral geniculate nucleus (GLd). Groups of labeled cells in the Pul-LP complex are arranged to form four different neuronal bands oriented dorsoventrally. The four neuronal bands are located, laterally to medially, in the lateral and medial parts of Pul and in the lateral and central parts of LP. The ventral ends of the first (in the lateral Pul) and the third (in the lateral LP) bands extend to MIN and Pn, respectively. The locations of the four bands in the Pul-LP complex appear to correspond to the terminal fields of afferents from four different regions (retina, pretectum, visual cortex and superior colliculus) related to visual function. The anterior part of the lateral MSs area (lateral wall of the MSs) receives thalamic fibers from the lateral and intermediate divisions of the posterior nuclear group (PO1 and POi), while its posterior part receives fibers from the dorsal and medial parts of LP and POi. Both walls of the ASs receive fibers from the ventrolateral part of LP as well as from the anterior part of PO1 and the PO1-POm border. In addition, the ASs-MSs area receives fibers from the central lateral nucleus (CL). It is of interest to correlate the locations of cells projecting to the ASs-MSs area with the pathways terminating in thalamic regions. It is clear that, from the hodological point of view, the ASs-MSs area is functionally segregated, which is in agreement with previous studies we have made corticocortical connections.

Projections of the pulvinar-lateral posterior complex to visual cortical areas in the cat

The projections of the pulvinar-lateral posterior complex of the cat were studied using the autoradiographic tracing method and related to 15 previously defined cortical areas. The results indicate that each of three separate zones within the pulvinar-lateral posterior complex has a different pattern of projection. The most lateral zone, the pulvinar, sends fibers to at least seven cortical areas, most of which are known to have input from other visual areas within the brain: the splenial visual area, the cingulate gyrus, and areas 5, 7, 19, 20a and 21a. A zone located just medial to the pulvinar, the lateral division of the lateral posterior complex, projects to at least eight visual areas in the cortex: areas 17, 18, 19, 20a, 21a, 21b, the posteromedial lateral suprasylvian area and the ventral lateral suprasylvian area. The most medial zone, the intermediate division of the lateral posterior complex, projects to at least four cortical areas: 20a, the posterior suprasylvian area, the posterolateral lateral suprasylvian area and the dorsal lateral suprasylvian area. Of the 15 cortical areas that receive fibers from the pulvinar-lateral posterior complex, only three (areas 19, 20a and 21a) receive projections from more than one of these thalamic zones, and only one of the cortical areas (20a) receives fibers from all three zones. Thus, the data support the division of the pulvinar lateral posterior complex into three zones on the basis of their unique and largely non-overlapping projections to the visual cortex.

Acoustic input to single neurons in pulvinar-posterior complex of cat thalamus

1. Extracellular microelectrode recordings have been made of 429 single neurons in the pulvinar-posterior (Pul-PO) complex and adjacent regions of the thalamus of cats anesthetized with either sodium pentobarbital or alpha-chloralose. Controlled acoustic stimuli were presented by sealed systems incorporating probe microphone assemblies. 2. Neurons in pulvinar, lateralis posterior, and nucleus posterior were unresponsive to acoustic stimulation. Few cells in medial PO were observed to receive acoustic input, while sensitivity to tonal stimuli was a general feature of driven cells in other PO divisions. 3. Cells in lateral PO were generally sharply tuned to stimulus frequency, while the majority of cells in magnocellular medial geniculate and intermediate division of PO were broadly tuned. 4. Neurons in lateral PO and magnocellular medial geniculate had short response latencies to acoustic stimulation. Cells in intermediate division of PO were more often long latency. 5. Divisions of PO could not be differentiated on the basis of their binaural properties. Cells receiving excitatory input from solely the contralateral ear (E/O) or fros with onset discharge patterns showed occlusive binaural interaction properties. For cells with multiple-component discharge patterns, individual response components frequently had different patterns of binaural input and/or interaction. 6. On the basis of their discharge patterns, short latency, and frequency-tuning properties, it is suggested that lateral PO and magnocellular medial geniculate might derive their acoustic input from different divisions of the inferior colliculus. In contrast, the long latencies of units in PO intermediate division suggests a corticofugal input. 7. These data support anatomical parcelations of the Pul-PO complex, and the suggestion that this complex might provide acoustic input to the association cortices is evaluated.

Topographical representation of peripheral branches of the facial nerve within the facial nucleus: A HRP study in the cat

Representation of peripheral branches of the facial nerve within the facial nucleus of the cat was examined by utilizing retrograde axonal transport of horseradish peroxidase (HRP), which was injected into groups of muscles supplied by each of the main peripheral branches of the facial nerve. The cervical branch was represented in the ventromedial division of the facial nucleus, the posterior auricular branch in the medial division, the temporal branch in the intermediate division, the zygomatico-orbital branch in the dorsal division, the superior labial branch in the lateral division and the inferior labial branch in the ventrolateral division.