Olivary body exposure through far lateral and lower retrosigmoid approaches. Comparative analysis of the exposed surface and angle of attack.

OBJECTIVES: Throughout neurosurgical history, the treatment of intrinsic lesions located in the brainstem has been subject of much controversy. The brainstem is the anatomical structure of the central nervous system (CNS) that presents the highest concentration of nuclei and fibers, and its simple manipulation can lead to significant morbidity and mortality. Once one of the safe entry points at the medulla oblongata has been established, we wanted to evaluate the safest approach to the olivary body (the most used safe entry zone on the anterolateral surface of the medulla oblongata). The proposed objective was to evaluate the working channel from the surface of each of the far lateral and retrosigmoid approaches to the olivary body: distances, angles of attack and channel content. MATERIAL AND METHODS: To complete this work, a total of 10 heads injected with red/blue silicone were used. A total of 40 approaches were made in the 10 heads used (20 retrosigmoid and 20 far lateral). After completing the anatomical study and obtaining the data referring to all the approaches performed, it was decided to expand the sample of this research study by using 30 high-definition magnetic resonance imaging of anonymous patients without cranial or cerebral pathology. The reference points used were the same ones defined in the anatomical study. After defining the working channels in each of the approaches, the working distances, angle of attack, exposed surface, and the number of neurovascular structures present in the central trajectory were analyzed. RESULTS: The distances to the cranial and medial region of the olivary body were 52.71 mm (SD 3.59) from the retrosigmoid approach and 27.94 mm (SD 3.99) from the far lateral; to the most basal region of the olivary body, the distances were 49.93 (SD 3.72) from the retrosigmoid approach and 18.1 mm (SD 2.5) from the far lateral. The angle of attack to the caudal region was 19.44° (SD 1.3) for the retrosigmoid approach and 50.97° (SD 8.01) for the far lateral approach; the angle of attack to the cranial region was 20.3° (SD 1.22) for the retrosigmoid and 39.9° (SD 5.12) for the far lateral. Regarding neurovascular structures, the probability of finding an arterial structure is higher for the lateral far, whereas a neural structure will be more likely from a retrosigmoid approach. CONCLUSIONS: As conclusions of this work, we can say that far lateral approach presents more favorable conditions for the microsurgical treatment of intrinsic bulbar and bulbomedullary lesions approached through the caudal half of the olivary body. In those cases of bulbar and pontine-bulbar lesions approached through the cranial half of the olivary body, the retrosigmoid approach can be considered for selected cases.

Revisão de anatomia e correlações clínicas do tronco encefálico, parte i: bulbo / Review of brain anatomy and clinical correlations, part i: medulla

O Tronco encefálico (TE) é uma estrutura singular do sistema nervoso central, pois nele passam tratos sensoriais ascendentes da medula espinal, tratos sensoriais da cabeça e do pescoço, os tratos descendentes motores originados no prosencéfalo (divisão mais rostral do encéfalo), e as vias ligadas aos centros de movimento dos olhos. Contém ainda os núcleos dos nervos cranianos e está envolvido na regulação do nível de consciência através de projeções ao prosencéfalo oriundas da formação reticular. Todas essas estruturas coexistem em um espaço muito exíguo, o que faz com que o TE seja um local muito sensível às alterações patológicas, sendo que os pacientes apresentam muitos sinais neurológicos mesmo com lesões muito pequenas nesse local. Compreender a anatomia interna do TE é essencial para o diagnóstico neurológico e a prática da medicina clínica. Outros profissionais da saúde também se beneficiam desse conhecimento para melhor manejo dos seus pacientes neurológicos. Essa revisão apresenta detalhes da anatomia macroscópica e microscópica do bulbo, bem como seus correlatos clínicos frente às lesões mais comuns dessa divisão particular do TE, conhecidas como síndromes bulbares.

The brainstem is a unique structure in the central nervous system, since it gives way to ascending sensory tracts from the spinal cord, sensory tracts from the head and neck, motor descending tracts originating from the forebrain, and the pathways connected to the eye movement centers. It also contains the cranial nerve nuclei and is involved in the regulation of consciousness levels through projections to the forebrain originating in the reticular formation. All these structures coexist in a very small space, which makes the brainstem very sensitive to pathological changes, with patients presenting several neurological symptoms even with very small brainstem lesions. Understanding the internal anatomy of the brainstem is essential for neurological diagnosis and the practice of clinical medicine. Other health professionals also benefit from this knowledge to better manage their neurological patients. This review presents detailed information on the macroscopic and microscopic anatomy of the medulla, as well as its clinical correlates in the face of the most common lesions of this particular division of the brainstem, known as medullary syndromes.

Excitatory and inhibitory modulation of parafacial respiratory neurons in the control of active expiration.

In order to increase ventilation, the respiratory system engages active expiration through recruitment of abdominal muscles. Here, we reviewed the new advances in the modulation of parafacial respiratory (pF) region to trigger active expiration. In addition, we also made a comprehensive discussion of experiments indicating that the lateral aspect of the pF (pFL) is anatomically and functionally distinct from the adjacent and partially overlapping chemosensitive neurons of the ventral aspect of the pF (pFV) also named the retrotrapezoid nucleus. Recent evidence suggest a complex network responsible for the generation of active expiration and neuromodulatory systems that influence its activity. The activity of the pFL is tonically inhibited by inhibitory inputs and also receives excitatory inputs from chemoreceptors (central x peripheral) as well as from catecholaminergic C1 neurons. Therefore, the modulatory inputs and the physiological conditions under which these mechanisms are used to recruit active expiration and increase ventilation need further investigation.

Functional organization and connectivity of the dorsal column nuclei complex reveals a sensorimotor integration and distribution hub.

The dorsal column nuclei complex (DCN-complex) includes the dorsal column nuclei (DCN, referring to the gracile and cuneate nuclei collectively), external cuneate, X, and Z nuclei, and the median accessory nucleus. The DCN are organized by both somatotopy and modality, and have a diverse range of afferent inputs and projection targets. The functional organization and connectivity of the DCN implicate them in a variety of sensorimotor functions, beyond their commonly accepted role in processing and transmitting somatosensory information to the thalamus, yet this is largely underappreciated in the literature. To consolidate insights into their sensorimotor functions, this review examines the morphology, organization, and connectivity of the DCN and their associated nuclei. First, we briefly discuss the receptors, afferent fibers, and pathways involved in conveying tactile and proprioceptive information to the DCN. Next, we review the modality and somatotopic arrangements of the remaining constituents of the DCN-complex. Finally, we examine and discuss the functional implications of the myriad of DCN-complex projection targets throughout the diencephalon, midbrain, and hindbrain, in addition to their modulatory inputs from the cortex. The organization and connectivity of the DCN-complex suggest that these nuclei should be considered a complex integration and distribution hub for sensorimotor information.

Neurogenic Cough Associated with Hyperintensity in Dorsal Medulla: Case Report and Anatomical Discussion.

BACKGROUND: The nucleus tractus solitarius and paratrigeminal nucleus, which are implicated in the processing of airway-derived sensory information, are found in the dorsal medulla. The mechanism and localization of higher-order processing of urge to cough is poorly understood, and much of the existing anatomical localization is limited to animal studies. CASE DESCRIPTION: A 44-year-old Caucasian lady underwent elective foramen magnum decompression for symptomatic Chiari I malformation; postoperatively she had resolution of Chiari symptoms but developed an intractable neurogenic cough. She has no significant medical history or premorbid respiratory issues. Postoperative magnetic resonance imaging of her head demonstrated signal change in the left dorsal medulla, corresponding with the nucleus tractus solitarius and paratrigeminal nucleus. CONCLUSIONS: We suggest that this lesion explains her isolated new cough and localizes the pathway for "urge to cough" to this region of the medulla.

Structural and functional connectivity from the dorsomedial hypothalamus to the ventral medulla as a chronological amplifier of sympathetic outflow.

Psychological stress activates the hypothalamus, augments the sympathetic nervous output, and elevates blood pressure via excitation of the ventral medullary cardiovascular regions. However, anatomical and functional connectivity from the hypothalamus to the ventral medullary cardiovascular regions has not been fully elucidated. We investigated this issue by tract-tracing and functional imaging in rats. Retrograde tracing revealed the rostral ventrolateral medulla was innervated by neurons in the ipsilateral dorsomedial hypothalamus (DMH). Anterograde tracing showed DMH neurons projected to the ventral medullary cardiovascular regions with axon terminals in contiguity with tyrosine hydroxylase-immunoreactive neurons. By voltage-sensitive dye imaging, dynamics of ventral medullary activation evoked by electrical stimulation of the DMH were analyzed in the diencephalon-lower brainstem-spinal cord preparation of rats. Although the activation of the ventral medulla induced by single pulse stimulation of the DMH was brief, tetanic stimulation caused activation of the DMH sustained into the post-stimulus phase, resulting in delayed recovery. We suggest that prolonged excitation of the DMH, which is triggered by tetanic electrical stimulation and could also be triggered by psychological stress in a real life, induces further prolonged excitation of the medullary cardiovascular networks, and could contribute to the pathological elevation of blood pressure. The connectivity from the DMH to the medullary cardiovascular networks serves as a chronological amplifier of stress-induced sympathetic excitation. This notion will be the anatomical and pathophysiological basis to understand the mechanisms of stress-induced sustained augmentation of sympathetic activity.

Midbrain, Pons, and Medulla: Anatomy and Syndromes.

The anatomy of the brainstem is complex. It contains numerous cranial nerve nuclei and is traversed by multiple tracts between the brain and spinal cord. Improved MRI resolution now allows the radiologist to identify a higher level of anatomic detail, but an understanding of functional anatomy is crucial for correct interpretation of disease. Brainstem syndromes are most commonly due to occlusion of the posterior circulation or mass effect from intrinsic space-occupying lesions. These syndromes can have subtle imaging findings that may be missed by a radiologist unfamiliar with the anatomy or typical manifesting features. This article presents the developmental anatomy of the brainstem and discusses associated pathologic syndromes. Congenital and acquired syndromes are described and correlated with anatomic locations at imaging, with diagrams to provide a reference to aid in radiologic interpretation. ©RSNA, 2019.

Serotonergic projections to the ventral respiratory column from raphe nuclei in rats.

The ventral respiratory column (VRC) generates rhythmical respiration and is divided into four compartments: the Bötzinger complex (BC), pre-Bötzinger complex (PBC), rostral ventral respiratory group (rVRG), and caudal ventral respiratory group (cVRG). Serotonergic nerve fibers are densely distributed in the rostral to caudal VRC and serotonin would be one of the important modulators for the respiratory control in the VRC. In the present study, to elucidate detailed distribution of serotonergic neurons in raphe nuclei projecting to the various rostrocaudal levels of VRC, we performed combination of retrograde tracing technique by cholera toxin B subunit (CTB) with immunohistochemistry for tryptophan hydroxylase 2 (TPH2). The double-immunoreactive neurons with CTB and TPH2 were distributed in the both rostral and caudal raphe nuclei, i.e. dorsal raphe nucleus, raphe magnus nucleus, gigantocellular reticular nucleus alpha and ventral parts, lateral paragigantocellular nucleus, parapyramidal area, raphe obscurus nucleus, and raphe pallidus nucleus. The distributions of double-immunoreactive neurons were similar among injection groups of BC, PBC, anterior rVRG, and posterior rVRG/cVRG. In conclusion, serotonergic neurons in both rostral and caudal raphe nuclei projected throughout the VRC and these serotonergic projections may contribute to respiratory responses to various environmental and vital changes.

The effect of single-bulb garlic oil extract toward the hematology and histopathology of the liver and kidney in mice

Single garlic has been used as a traditional medicine for hypercholesterolemia and increasing stamina. The aim of this research was to analyze the effect of single-bulb garlic oil (SGO) extract toward hematology and histopathology liver and kidney in mice. Male mice (strain Balb-C, 12 weeks old, weight of 28±3 g) was treated by SGO for 28 days (once per days) with various doses K- (Normal); K+ (SGO 0.0 mg/kg BW); T1 (SGO 6.25 mg/kg BW); T2 (SGO 12.5 mg/kg BW); T3 (SGO 25.0 mg/kg BW); T4 (SGO 50.0 mg/kg BW). The end of the treated mice was sacrificed. Blood was collected to analyze hematology. Liver and kidney were collected then made microanatomy slide with Hematoxylin-Eosin staining. Parameters of hematology are the levels of hemoglobin, hematocrit, number of erythrocytes, and number of leukocytes. Histopathology of liver and kidney determine by cell necrosis. The result of the research showed that SGO increased the number of erythrocytes and leucocytes but there is no effect on the levels of hemoglobin and hematocrit. Histopathology on liver and kidney showed there is no effect in necrosis. The conclusion is the single-bulb garlic oil extract safe if consumed continuously

Variability of the medullary arcuate nucleus in humans.

INTRODUCTION: The arcuate nucleus is a component of the ventral medullary surface involved in chemoreception and breathing control. The hypoplasia of this nucleus is a very frequent finding in victims of sudden unexplained fetal and infant death (from the last weeks of pregnancy to the first year of life). On the contrary, this developmental alteration is rarely present in age-matched controls who died of defined causes. These observations lead to hypothesize that a well-developed and functional arcuate nucleus is generally required to sustain life. The aim of this study was to investigate whether the arcuate nucleus maintains the same supposed function throughout life. METHODS: We carried out neuropathological examinations of brainstems obtained from 25 adult subjects, 18 males and 7 females, aged between 34 and 89 years, who died from various causes. RESULTS: For almost half of the cases (44%) microscopic examinations of serial histological sections of medulla oblongata showed a normal cytoarchitecture of the arcuate nucleus, extending along the pyramids. For the remaining 56% of cases, various degrees of hypodevelopment of this nucleus were observed, validated through the application of quantitative morphometric investigations, from decreased area, neuron number and volume, to full aplasia. CONCLUSIONS: These unexpected findings indicate that the involvement of the arcuate nucleus in chemoreception in adulthood is questionable, given the possibility of living until late age without this nucleus. This opens new perspectives for researchers on the role and function of the arcuate nucleus in humans from birth to old age.

3D microsurgical anatomy of the cortico-spinal tract and lemniscal pathway based on fiber microdissection and demonstration with tractography. / Anatomía microquirúrgica en 3D del tracto corticoespinal y de la vía del lemnisco basada en microdisección de fibras y demostración a través de tractografía.

OBJECTIVE: To demonstrate tridimensionally the anatomy of the cortico-spinal tract and the medial lemniscus, based on fiber microdissection and diffusion tensor tractography (DTT). MATERIAL AND METHODS: Ten brain hemispheres and brain-stem human specimens were dissected and studied under the operating microscope with microsurgical instruments by applying the fiber microdissection technique. Brain magnetic resonance imaging was obtained from 15 healthy subjects using diffusion-weighted images, in order to reproduce the cortico-spinal tract and the lemniscal pathway on DTT images. RESULTS: The main bundles of the cortico-spinal tract and medial lemniscus were demonstrated and delineated throughout most of their trajectories, noticing their gross anatomical relation to one another and with other white matter tracts and gray matter nuclei the surround them, specially in the brain-stem; together with their corresponding representation on DTT images. CONCLUSIONS: Using the fiber microdissection technique we were able to distinguish the disposition, architecture and general topography of the cortico-spinal tract and medial lemniscus. This knowledge has provided a unique and profound anatomical perspective, supporting the correct representation and interpretation of DTT images. This information should be incorporated in the clinical scenario in order to assist surgeons in the detailed and critic analysis of lesions located inside the brain-stem, and therefore, improve the surgical indications and planning, including the preoperative selection of optimal surgical strategies and possible corridors to enter the brainstem, to achieve safer and more precise microsurgical technique.

Localization of the motor neuron somata of geniohyoid muscle in rat: A horseradish peroxidase study.

The aim of the study was to investigate the location of motor neuron somata of geniohyoid muscle in rat. Nine Sprague-Dawley rats were used in this study. Operations were performed under general anaesthesia. Nembutal sodium, 40 mg per kg intraperitoneally was used for anaesthesia. 0.02 to 0.05 ml of 30% horseradish peroxidase (Sigma Type VI) solution in normal saline was injected into the exposed right geniohyoid muscle. After 48 hr, the animals were fixed by perfusion through left ventricle of heart, first by 100 ml normal saline and then with 500 ml of 1.25% glutaraldehyde and 1% paraformaldehyde in 0.1 M phosphate buffer, pH 7.4, at room temperature, and finally with 500 ml of 10% sucrose in the same buffer at 4°C. The medulla oblongata and first cervical segment of spinal cord were removed, kept in 10% sucrose in above phosphate buffer at 4°C for 24 hr. Thereafter, their serial transverse sections were cut in a cryostat at a thickness of 60 µm. The sections were treated according to tetramethyl benzidine (TMB)-horseradish peroxidase (HRP) method. HRP-labelled neuron somata were observed at the following sites: (a) In ventral part of right main hypoglossal nucleus in upper two-thirds of the closed part of medulla oblongata. (b) In ventrolateral subnucleus of hypoglossal nucleus in lower third of closed part of medulla oblongata. (c) At spinomedullary junction, they were located in dorsomedial part of right ventral grey column; a few were also seen here scattered on right side of central canal and among corticospinal fibres.

Angular and metric analysis of the neural structures in the cerebellopontine angle.

INTRODUCTION: The cerebellopontine angle (CPA) is a subarachnoid space in the lateral aspect of the posterior fossa. In this study, we propose a complementary analysis of the CPA from the cerebellopontine fissure. METHODS: We studied 50 hemi-cerebelli in the laboratory of neuroanatomy and included a description of the CPA anatomy from the cerebellopontine fissure and its relationship with the flocculus and the 5th, 6th, 7th, and 8th cranial nerves (CN) origins. RESULTS: The average distance from the 5th CN to the mid-line (ML) was 19.2 mm, 6th CN to ML was 4.4 mm, 7-8 complex to ML was 15.8 mm, flocculus to ML was 20.5 mm, and flocculus to 5th CN was 11.5 mm, additionally, and the diameter of the flocculus was 9.0 mm. The angle between the vertex in the flocculus and the V CN and the medullary-pontine line was 64.8 degrees. DISCUSSION: The most common access to the CPA is through the retrosigmoid-suboccipital region and this approach can be done with the help of an endoscope. The anatomy of origins of neural structures tends to be preserved in cases of CPA lesions. CONCLUSION: Knowledge of the average distances between the neural structures in the cerebellar-pontine fissure and the angular relationships between these structures facilitates the use of surgical approaches such as microsurgery and endoscopy.

A crustacean lobula plate: Morphology, connections, and retinotopic organization.

The lobula plate is part of the lobula complex, the third optic neuropil, in the optic lobes of insects. It has been extensively studied in dipterous insects, where its role in processing flow-field motion information used for controlling optomotor responses was discovered early. Recently, a lobula plate was also found in malacostracan crustaceans. Here, we provide the first detailed description of the neuroarchitecture, the input and output connections and the retinotopic organization of the lobula plate in a crustacean, the crab Neohelice granulata using a variety of histological methods that include silver reduced staining and mass staining with dextran-conjugated dyes. The lobula plate of this crab is a small elongated neuropil. It receives separated retinotopic inputs from columnar neurons of the medulla and the lobula. In the anteroposterior plane, the neuropil possesses four layers defined by the arborizations of such columnar inputs. Medulla projecting neurons arborize mainly in two of these layers, one on each side, while input neurons arriving from the lobula branch only in one. The neuropil contains at least two classes of tangential elements, one connecting with the lateral protocerebrum and the other that exits the optic lobes toward the supraesophageal ganglion. The number of layers in the crab's lobula plate, the retinotopic connections received from the medulla and from the lobula, and the presence of large tangential neurons exiting the neuropil, reflect the general structure of the insect lobula plate and, hence, provide support to the notion of an evolutionary conserved function for this neuropil.

Low Retrosigmoid Infratonsillar Approach to Lateral Medullary Lesions.

OBJECTIVE: In our study, we comprehensively detail the technique of the low retrosigmoid approach to the lateral medullary area, including the inferior cerebellar peduncle, postolivary sulcus, pontomedullary sulcus, and inferior olivary nucleus, as well as the lateral recess of the fourth ventricle. METHODS: Four formalin-fixed, silicone-injected, cadaveric human heads were examined under the operating microscope to demonstrate pertinent descriptive anatomy using the low retrosigmoid approach in a stepwise manner. Clinical parameters of a patient with a lateral medullary lesion were reviewed retrospectively to describe preoperative and postoperative examination and surgical details of the approach to the lateral medulla. RESULTS: The clinical case report describes a low retrosigmoid craniotomy performed to access the exiting points of cranial nerves IX (glossopharyngeal) and X (vagus), foramen of Luschka, inferior cerebellar peduncle (lateral medullary zone), postolivary sulcus, and olivary nucleus. The lesion was exposed using the inferior cerebellar peduncle and removed using standard microsurgical technique. CONCLUSIONS: The lower retrosigmoid infratonsillar approach provides excellent exposure to medullary safe entry zones, including the transolivary, postolivary sulcus, pontomedullary sulcus, and lateral medullary (inferior cerebellar peduncle) zones, for removal of lesions in this area.

A Secure Approach to the Inferior Horn Using the Deep Medullary Vein as an Anatomic Guide.

BACKGROUND: Safe entry to the inferior horn is required for a selective approach to the medial temporal region. This can be challenging sometimes for inexperienced surgeons. Our objective was to verify the usefulness of the deep medullary vein (DMV) as an intraoperative landmark for safely entering the inferior horn during the transsylvian selective approach to the mesial temporal region. METHODS: Videos of 8 cases of transsylvian selective amygdalohippocampectomies performed at the University of Tokyo Hospital from 2013 to 2015 were reviewed. Consistency of the DMV and time required to open the inferior horn via the temporal stem through the inferior limiting sulcus were retrospectively evaluated. RESULTS: DMVs were identified in all cases; the average number identified was 2.5 ± 0.3 (mean ± SE). The inferior horn was opened without disorientation in all cases, with mean dissecting time of 7.0 minutes ± 1.1. No complications were caused by disorientation within the temporal stem white matter. CONCLUSIONS: Consideration of the venous system within the white matter and following the DMV could reduce the risk of disorientation and enable the surgeon to reach the inferior horn in a straightforward manner without accidental white matter damage.

Methodological considerations for a chronic neural interface with the cuneate nucleus of macaques.

While the response properties of neurons in the somatosensory nerves and anterior parietal cortex have been extensively studied, little is known about the encoding of tactile and proprioceptive information in the cuneate nucleus (CN) or external cuneate nucleus (ECN), the first recipients of upper limb somatosensory afferent signals. The major challenge in characterizing neural coding in CN/ECN has been to record from these tiny, difficult-to-access brain stem structures. Most previous investigations of CN response properties have been carried out in decerebrate or anesthetized animals, thereby eliminating the well-documented top-down signals from cortex, which likely exert a strong influence on CN responses. Seeking to fill this gap in our understanding of somatosensory processing, we describe an approach to chronically implanting arrays of electrodes in the upper limb representation in the brain stem in primates. First, we describe the topography of CN/ECN in rhesus macaques, including its somatotopic organization and the layout of its submodalities (touch and proprioception). Second, we describe the design of electrode arrays and the implantation strategy to obtain stable recordings. Third, we show sample responses of CN/ECN neurons in brain stem obtained from awake, behaving monkeys. With this method, we are in a position to characterize, for the first time, somatosensory representations in CN and ECN of primates.NEW & NOTEWORTHY In primates, the neural basis of touch and of our sense of limb posture and movements has been studied in the peripheral nerves and in somatosensory cortex, but coding in the cuneate and external cuneate nuclei, the first processing stage for these signals in the central nervous system, remains an enigma. We have developed a method to record from these nuclei, thereby paving the way to studying how sensory information from the limb is encoded there.

Mapping and Analysis of the Connectome of Sympathetic Premotor Neurons in the Rostral Ventrolateral Medulla of the Rat Using a Volumetric Brain Atlas.

Spinally projecting neurons in the rostral ventrolateral medulla (RVLM) play a critical role in the generation of vasomotor sympathetic tone and are thought to receive convergent input from neurons at every level of the neuraxis; the factors that determine their ongoing activity remain unresolved. In this study we use a genetically restricted viral tracing strategy to definitively map their spatially diffuse connectome. We infected bulbospinal RVLM neurons with a recombinant rabies variant that drives reporter expression in monosynaptically connected input neurons and mapped their distribution using an MRI-based volumetric atlas and a novel image alignment and visualization tool that efficiently translates the positions of neurons captured in conventional photomicrographs to Cartesian coordinates. We identified prominent inputs from well-established neurohumoral and viscero-sympathetic sensory actuators, medullary autonomic and respiratory subnuclei, and supramedullary autonomic nuclei. The majority of inputs lay within the brainstem (88-94%), and included putative respiratory neurons in the pre-Bötzinger Complex and post-inspiratory complex that are therefore likely to underlie respiratory-sympathetic coupling. We also discovered a substantial and previously unrecognized input from the region immediately ventral to nucleus prepositus hypoglossi. In contrast, RVLM sympathetic premotor neurons were only sparsely innervated by suprapontine structures including the paraventricular nucleus, lateral hypothalamus, periaqueductal gray, and superior colliculus, and we found almost no evidence of direct inputs from the cortex or amygdala. Our approach can be used to quantify, standardize and share complete neuroanatomical datasets, and therefore provides researchers with a platform for presentation, analysis and independent reanalysis of connectomic data.

Commentary on: Saper CB, Loewy AD, Swanson LW, Cowan WM. (1976) Direct hypothalamo-autonomic connections. Brain Research 117:305-312.

The 1970s saw the introduction of new technologies for tracing axons both anterogradely and retrogradely. These methods allowed us to visualize fine, unmyelinated pathways for the first time, such as the hypothalamic pathways that control the autonomic nervous system. As a result, we were able to identify the paraventricular nucleus and lateral hypothalamus as the key sites that provide direct inputs to the autonomic preganglionic neurons in the medulla and spinal cord. These findings revolutionized our understanding of hypothalamic control of the autonomic nervous system.