Cholinergic and Nadph-δ neurons in the pedunculopontine and laterodorsal tegmental nuclei of human and nonhuman primates.

The brainstem pedunculopontine (PPN) and laterodorsal tegmental (LDTg) nuclei are involved in multifarious activities, including motor control. Yet, their exact cytoarchitectural boundaries are still uncertain. We therefore initiated a comparative study of the topographical and neurochemical organization of the PPN and LDTg in cynomolgus monkeys (Macaca fascicularis) and humans. The distribution and morphological characteristics of neurons expressing choline acetyltransferase (ChAT) and/or nicotinamide adenine dinucleotide phosphate diaphorase (Nadph-δ) were documented. The number and density of the labeled neurons were obtained by stringent stereological methods, whereas their topographical distribution was reported upon corresponding magnetic resonance imaging (MRI) planes. In both human and nonhuman primates, the PPN and LDTg are populated by three neurochemically distinct types of neurons (ChAT-/Nadph-δ+, ChAT+/Nadph-δ-, and ChAT+/Nadph-δ+), which are distributed according to a complex spatial interplay. Three-dimensional reconstructions reveal that ChAT+ neurons in the PPN and LDTg form a continuum with some overlaps with pigmented neurons of the locus coeruleus, dorsally, and of the substantia nigra (SN) complex, ventrally. The ChAT+ neurons in the PPN and LDTg are -two to three times more numerous in humans than in monkeys but their density is -three to five times higher in monkeys than in humans. Neurons expressing both ChAT and Nadph-δ have a larger cell body and a longer primary dendritic arbor than singly labeled neurons. Stereological quantification reveals that 25.6% of ChAT+ neurons in the monkey PPN are devoid of Nadph-δ staining, a finding that questions the reliability of Nadph-δ as a marker for cholinergic neurons in primate brainstem.

Combatting malaria disease among gold miners: a qualitative research within the Malakit project.

Malaria is endemic in French Guiana, in particular, where illegal gold mining activities take place. Gold miners travel from Brazil to remote camps in the Guiana forest to carry out mining activities, exposing themselves to the presumed contamination area. This article presents the results of a qualitative case study of the Malakit project, an intervention where health facilitators offer appropriate training and distribution of self-diagnosis and self-treatment kits to manage an episode of malaria at resting sites on the French Guiana borders. The objectives were: (i) Determine the contextual elements influencing the use of Malakit; (ii) Understand the way gold miners perceive Malakit; (iii) Identify the elements that are favorable and unfavorable to the use of Malakit; (iv4) Identify what can be improved in the project. The data were collected using three methods: on-site observation, semi-structured individual interviews (n = 26), and group interviews (n = 2). The results indicate that Malakit responds to the need for treatment and facilitates access to care. Gold miners say they trust the facilitators and receive accurate explanations, the kit is easy to use and carry, and explanations given are sufficient. Nonetheless, the results lead us to believe that contextual elements influence exposure to numerous risk factors and that malaria among gold miners working illegally in French Guiana is a question of social inequalities in health. Thus, malaria intervention practices such as Malakit cannot be carried out without considering the complexity generated by social inequalities in health.

A Topographic Atlas of the Human Brainstem in the Ponto-Mesencephalic Junction Plane.

The human brainstem harbors neuronal aggregates that ensure the maintenance of several vital functions. It also acts as a major relay structure for the neuronal information that travels between the cerebral cortex, the cerebellum and the spinal cord. As such, this relatively small portion of the human brain houses a multitude of ascending and descending fibers that course among numerous nuclei whose exact boundaries are still uncertain. Such a large number of nuclei and fiber tracts confined to a relatively small and compact brain region imposes upon the brainstem a highly complex cytoarchitectonic organization that still needs to be deciphered. The present work provides a topographic atlas of the human brainstem composed of 45 anatomical plates, each containing a pair of adjacent sections stained with Cresyl Violet and Luxol Fast Blue to help delineating brainstem nuclei and fiber tracts, respectively. The plates, which cover the entire midbrain, pons and medulla oblongata, are composed of equally-spaced sections referenced and aligned parallel to the ponto-mesencephalic junction rather than the fastigium or the obex. This topographic landmark is particularly suitable for neurosurgical interventions aiming at specific nuclei of the mesencephalic tegmentum. In complement, we provide 8 anatomical plates containing adjacent sections stained for choline acetyltransferase and Luxol Fast Blue, taken through the midbrain and the pons. This open access atlas of the human brainstem is intended to assist neuroanatomists, neurosurgeons and neuropathologists in their work.

The highly selective mGlu2 receptor positive allosteric modulator LY-487,379 alleviates l-DOPA-induced dyskinesia in the 6-OHDA-lesioned rat model of Parkinson's disease.

l-3,4-Dihydroxyphenylalanine (l-DOPA) is the most effective treatment for Parkinson's disease (PD), but its use over a long period is marred by motors complications such as dyskinesia. We previously demonstrated that selective metabotropic glutamate 2/3 (mGlu2/3 ) receptor activation with LY-354,740 alleviates dyskinesia in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned marmoset and the 6-hydroxydopamine (6-OHDA)-lesioned rat. Here, we sought to determine the role played by selective mGlu2 activation in the anti-dyskinetic effect of mGlu2/3 stimulation and have investigated the effect of the highly selective mGlu2 positive allosteric modulator LY-487,379 at alleviating established, and preventing the development of, l-DOPA-induced dyskinesia in the 6-OHDA-lesioned rat. First, dyskinetic 6-OHDA-lesioned rats were administered l-DOPA in combination with LY-487,379 (0.1, 1 and 10 mg/kg) or vehicle, and the severity of dyskinesia was determined. Second, 6-OHDA-lesioned rats were administered LY-487,379 (0.1 or 1 mg/kg), started concurrently with l-DOPA, once daily for 22 days, and dyskinesia severity was evaluated weekly for four consecutive weeks. We also assessed the effect of LY-487,379 on l-DOPA anti-parkinsonian effect. We found that acute challenges of LY-487,379 0.1 mg/kg in combination with l-DOPA, significantly diminished dyskinesia severity, by ≈54% (p < .01), when compared to vehicle. Moreover, animals treated with l-DOPA/LY-487,379 0.1 and 1 mg/kg during the dyskinesia induction phase exhibited milder dyskinesia, by ≈74% and ≈61%, respectively (both p < .01), when compared to l-DOPA/vehicle. LY-487,379 did not impair l-DOPA anti-parkinsonian activity. These results suggest that mGlu2 activation may be an effective and promising therapeutic strategy to alleviate the severity and prevent the development of dyskinesia.

Berengario da Carpi and the Renaissance of Brain Anatomy.

Berengario da Carpi (Jacopo Barigazzi) was born around 1460 in the small Italian town of Carpi near Modena. Berengario's father, Faustino, was a reputable barber-surgeon who initiated his son early into the art of anatomy and surgery. After his graduation from the University of Bologna in 1489, Berengario rapidly acquired an enviable reputation as a physician and surgeon following the successful treatment of several dignitaries, including Lorenzo de' Medici, Duke of Urbino who suffered a severe head injury in 1517. While professor of anatomy and surgery at the University of Bologna, Berengario published in 1518 his De fractura cranei, a landmark work on cranio-cerebral surgery. Berengario's masterpiece, however, is undoubtedly his detailed Commentaria on the famous medieval anatomy treatise of Mondino de' Liuzzi (ca. 1270-1326) that he published in 1521. A shorter version entitled Isagogae Breves appeared a year later. Besides a facsimile of Mondino's work, Berengario's Commentaria contains a wealth of new information, including observations that challenged Galenic physiology. Galen taught that the rete mirabile-a vascular plexus believed to occur at the basis of the human brain-is the locus where the vital spirit is transformed into the more sophisticated animal spirit that is stored in the brain ventricles to be later released at the periphery through a journey within hollow nerves. Courageously, Berengario wrote that despite many attempts he was unable to detect the famous rete mirabile in humans. He also noted that the nerves linked to the brain are solid structures, not hollow tubes, as advocated by Galen. His conclusions were based on a systematic dissection method that he called anatomia sensibilis, a term that emphasizes the sensory over textual versions of the truth. Berengario contributed significantly to human brain anatomy, with a detailed description of the meninges and cranial nerves and the first comprehensive view of the ventricular system, including choroid plexuses, interventricular foramen, infundibulum, pituitary stalk and gland. Berengario, who died around 1530 in Ferrara, should be remembered for his catalyzing role in the transmutation of medieval morphological knowledge into a modern anatomical science based upon direct observation and experimental demonstration.

Deep Brain Stimulation of the Pedunculopontine Nucleus Area in Parkinson Disease: MRI-Based Anatomoclinical Correlations and Optimal Target.

BACKGROUND: Experimental studies led to testing of deep brain stimulation (DBS) of the pedunculopontine nucleus (PPN) as a new therapy to treat freezing of gait (FOG) in Parkinson disease (PD). Despite promising initial results fueling a growing interest toward that approach, several clinical studies reported heterogeneity in patient responses. Variation in the position of electrode contacts within the rostral brainstem likely contributes to such heterogeneity. OBJECTIVE: To provide anatomoclinical correlations of the effect of DBS of the caudal mesencephalic reticular formation (cMRF) including the PPN to treat FOG by comparing the normalized positions of the active contacts among a series of 11 patients at 1- and 2-yr follow-up and to provide an optimal target through an open-label study. METHODS: We defined a brainstem normalized coordinate system in relation to the pontomesencephalic junction. Clinical evaluations were based on a composite score using objective motor measurements and questionnaires allowing classification of patients as "bad responders" (2 patients), "mild responders" (1 patient) and "good responders" (6 patients). Two patients, whose long-term evaluation could not be completed, were excluded from the analysis. RESULTS: Most effective DBS electrode contacts to treat FOG in PD patients were located in the posterior part of the cMRF (encompassing the posterior PPN and cuneiform nucleus) at the level of the pontomesencephalic junction. CONCLUSION: In the present exploratory study, we performed an anatomoclinical analysis using a new coordinate system adapted to the brainstem in 9 patients who underwent PPN area DBS. We propose an optimal DBS target that allows a safe and efficient electrode implantation in the cMRF.

Single-axon tracing of the corticosubthalamic hyperdirect pathway in primates.

Individual axons that form the hyperdirect pathway in Macaca fascicularis were visualized following microiontophoretic injections of biotinylated dextran amine in layer V of the primary motor cortex (M1). Twenty-eight singly labeled axons were reconstructed in 3D from serial sections. The M1 innervation of the subthalamic nucleus (STN) arises essentially from collaterals of long-ranged corticofugal axons en route to lower brainstem regions. Typically, after leaving M1, these large caliber axons (2-3 µm) enter the internal capsule and travel between caudate nucleus and putamen without providing any collateral to the striatum. More ventrally, they emit a thin collateral (0.5-1.5 µm) that runs lateromedially within the dorsal region of the STN, providing boutons en passant in the sensorimotor territory of the nucleus. In some cases, the medial tip of the collateral enters the lenticular fasciculus dorsally and yields a few beaded axonal branches in the zona incerta. In other cases, the collateral runs caudally and innervates the ventrolateral region of the red nucleus where large axon varicosities (up to 1.7 µm in diameter) are observed, many displaying perisomatic arrangements. Our ultrastructural analysis reveals a high synaptic incidence (141%) of cortical VGluT1-immunoreactive axon varicosities on distal dendrites of STN neurons, and on various afferent axons. Our single-axon reconstructions demonstrate that the so-called hyperdirect pathway derives essentially from collaterals of long-ranged corticofugal axons that are rarely exclusively devoted to the STN, as they also innervate the red nucleus and/or the zona incerta.

Une formation complémentaire et appliquée : un besoin pour la relève en recherche interventionnelle en santé des populations.

Population Health Intervention Research (PHIR) is an emerging and distinct field that combines scientific research and public health practice. However, traditional academic training in research, which is founded on specific disciplinary orientations, does not sufficiently inform and prepare new PHIR researchers. In this commentary, we advance the idea that PHIR requires a broader range of competencies and knowledge that must be developed through a complementary and applied training program. Drawing on our experience as 4P Strategic Training Program fellows, we identified key elements of the program that have helped prepare us in our careers as future and new PHIR researchers. We believe that complementary and applied training programs such as the 4P Program are a promising strategy in training and supporting the next generation of PHIR researchers in their efforts to improve population health.

Evidence for Sprouting of Dopamine and Serotonin Axons in the Pallidum of Parkinsonian Monkeys.

This light and electron microscopie immunohistochemical quantitative study aimed at determining the state of the dopamine (DA) and serotonin (5-HT) innervations of the internal (GPi) and external (GPe) segments of the pallidum in cynomolgus monkeys (Macaca fascicularis) rendered parkinsonian by systemic injections of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). In contrast to the prominent DA denervation of striatum, the GPi in MPTP monkeys was found to be markedly enriched in DA (TH+) axon varicosities. The posterior sensorimotor region of this major output structure of the basal ganglia was about 8 times more intensely innervated in MPTP monkeys (0.71 ± 0.08 × 106 TH+ axon varicosities/mm3) than in controls (0.09 ± 0.01 × 106). MPTP intoxication also induced a two-fold increase in the density of 5-HT (SERT+) axon varicosities in both GPe and GPi. This augmentation was particularly pronounced anteriorly in the so-called associative and limbic pallidal territories. The total length of the labeled pallidal axons was also significantly increased in MPTP monkeys compared to controls, but the number of DA and 5-HT axon varicosities per axon length unit remained the same in the two groups, indicating that the DA and 5-HT pallidal hyperinnervations seen in MPTP monkeys result from axon sprouting rather than from the appearance of newly formed axon varicosities on non-growing axons. At the ultrastructural level, pallidal TH+ and SERT+ axons were morphologically similar in MPTP and controls, and their synaptic incidence was very low suggesting a volumic mode of transmission. Altogether, our data reveal a significant sprouting of DA and 5-HT pallidal afferents in parkinsonian monkeys, the functional significance of which remains to be determined. We suggest that the marked DA hyperinnervation of the GPi represents a neuroadaptive change designed to normalize pallidal firing patterns associated with the delayed appearance of motor symptoms, whereas the 5-HT hyperinnervation might be involved in the early expression of non-motor symptoms in Parkinson's disease.

Impacts of online and group perinatal education: a mixed methods study protocol for the optimization of perinatal health services.

BACKGROUND: Prenatal education is a core component of perinatal care and services provided by health institutions. Whereas group prenatal education is the most common educational model, some health institutions have opted to implement online prenatal education to address accessibility issues as well as the evolving needs of future parents. Various studies have shown that prenatal education can be effective in acquisition of knowledge on labour and delivery, reducing psychological distress and maximising father's involvement. However, these results may depend on educational material, organization, format and content. Furthermore, the effectiveness of online prenatal education compared to group prenatal education remains unclear in the literature. This project aims to evaluate the impacts of group prenatal education and online prenatal education on health determinants and users' health status, as well as on networks of perinatal educational services maintained with community-based partners. METHODS: This multipronged mixed methods study uses a collaborative research approach to integrate and mobilize knowledge throughout the process. It consists of: 1) a prospective cohort study with quantitative data collection and qualitative interviews with future and new parents; and 2) a multiple case study integrating documentary sources and interviews with stakeholders involved in the implementation of perinatal information service networks and collaborations with community partners. Perinatal health indicators and determinants will be compared between prenatal education groups (group prenatal education and online prenatal education) and standard care without these prenatal education services (control group). DISCUSSION: This study will provide knowledge about the impact of online prenatal education as a new technological service delivery model compared to traditional group prenatal education. Indicators related to the complementarity of these interventions and those available in community settings will refine our understanding of regional perinatal services networks. Results will assist decision-making regarding service organization and delivery models of prenatal education services. PROTOCOL VERSION: Version 1 (February 9 2018).

A Tribute to James Parkinson.

Exactly 200 years ago, the London surgeon-apothecary James Parkinson (1755-1824) published a 66-page-long booklet entitled An Essay on the Shaking Palsy, which contains the first clear clinical description of the shaking palsy or paralysis agitans, which we now refer to as Parkinson's disease. However, the value of this essay was not fully recognized during Parkinson's lifetime, which spanned the American Revolution, the French Revolution, and the Napoleonic Wars. James Parkinson was one of the most singular figures of his time and place. He was successively or concomitantly a virulent political activist, a popular medical writer, a scholarly medical contributor, a highly appreciated parish doctor, a prominent amateur chemist, a devoted madhouse doctor, and a renowned paleontologist. It is that branch of geology that brought Parkinson fame during his lifetime. He was an insatiable collector of fossils, minerals, and shells that came to form the core of the museum that he set out at his home in Shoreditch, England. These specimens are beautifully illustrated in his Organic Remains of a Former World (1804-1811), a three-volume treatise that rapidly became a standard paleontology textbook. Parkinson was a founding member of the Geological Society of London, and in recognition of his contribution to the nascent field of paleontology his name was given to many fossils, particularly ammonites (e.g. Nautilus parkinsoni). Hence, we owe much to Mr. Parkinson, the Paleontologist, as he used to be referred to after his death, for such a vast and multifaceted contribution to natural science and medicine.

A dense cluster of D1 + cells in the mouse nucleus accumbens.

The striatum is known to be largely composed of intermingled medium-sized projection neurons expressing either the D1 or the D2 dopamine receptors. In the present study, we took advantage of the double BAC Drd1a-TdTomato/Drd2-GFP (D1 /D2 ) transgenic mice to reveal the presence of a peculiar cluster of densely-packed D1 + cells located in the shell compartment of the nucleus accumbens. This spherical cluster has a diameter of 110 µm and is exclusively composed by D1 + cells, which are all immunoreactive for the neuronal nuclear marker (NeuN). However, in contrast to other D1 + or D2 + striatal cells, those that form the accumbens cluster are devoid of calbindin (CB) and DARPP-32, two faithful markers for striatal projection neurons. Using GAD-GFP transgenic mice, we confirm the GABAergic nature of the D1 + clustered neurons. Intracellular injections from fixed brain slices indicate that these neurons are endowed with distinctive morphological features, including a small (5-6 µm), round cell body giving rise to a single primary dendrite that branches into two secondary processes. Single-neuronal injections combined to electron microscopy reveal the existence of GAP junctions linking these D1 + cells. Based on their location, morphological characteristics and neurochemical phenotype, we conclude that the D1 + accumbens cluster form a highly compact group of small neurons distinct from the larger and more diffusely distributed D1 + or D2 + striatal projection neurons that surround it. This remarkable nucleus might play a crucial role in the limbic function of the murine striatum.

The number of striatal cholinergic interneurons expressing calretinin is increased in parkinsonian monkeys.

The most abundant interneurons in the primate striatum are those expressing the calcium-binding protein calretinin (CR). The present immunohistochemical study provides detailed assessments of their morphological traits, number, and topographical distribution in normal monkeys (Macaca fascicularis) and in monkeys rendered parkinsonian (PD) by MPTP intoxication. In primates, the CR+ striatal interneurons comprise small (8-12µm), medium (12-20µm) and large-sized (20-45µm) neurons, each with distinctive morphologies. The small CR+ neurons were 2-3 times more abundant than the medium-sized CR+ neurons, which were 20-40 times more numerous than the large CR+ neurons. In normal and PD monkeys, the density of small and medium-sized CR+ neurons was twice as high in the caudate nucleus than in the putamen, whereas the inverse occurred for the large CR+ neurons. Double immunostaining experiments revealed that only the large-sized CR+ neurons expressed choline acetyltransferase (ChAT). The number of large CR+ neurons was found to increase markedly (4-12 times) along the entire anteroposterior extent of both the caudate nucleus and putamen of PD monkeys compared to controls. Comparison of the number of large CR-/ChAT+ and CR+/ChAT+ neurons together with experiments involving the use of bromo-deoxyuridine (BrdU) as a marker of newly generated cells showed that it is the expression of CR by the large ChAT+ striatal interneurons, and not their absolute number, that is increased in the dopamine-depleted striatum. These findings reveal the modulatory role of dopamine in the phenotypic expression of the large cholinergic striatal neurons, which are known to play a crucial role in PD pathophysiology.

Franciscus Sylvius on Clinical Teaching, Iatrochemistry and Brain Anatomy.

Born in Hanau, Germany, in 1614, Franciscus (Dele Boë) Sylvius received his medical doctor diploma from Basel University in 1637 and became Professor of Practical Medicine at Leiden University in 1658. One of the founders of medical biochemistry, Sylvius was also an outstanding anatomopathologist, with contributions ranging from the first description of the pulmonary tubercles to that of the lateral fissure of the brain. Thanks to Sylvius, a gifted teacher and one of the greatest physicians of his time, Leiden became a major European medical training center. He died in 1772 after having served as Rector Magnificus at Leiden University.

Asynaptic feature and heterogeneous distribution of the cholinergic innervation of the globus pallidus in primates.

The internal (GPi) and external (GPe) segments of the primate globus pallidus receive a significant cholinergic (ACh) innervation from the brainstem pedunculopontine tegmental nucleus. The present immunohistochemical study describes this innervation in the squirrel monkey (Saimiri sciureus), as visualized with an antibody raised against choline acetyltransferase (ChAT). At the light microscopic level, unbiased stereological quantification of ChAT positive (+) axon varicosities reveals a significantly lower density of innervation in GPi (0.26 ± 0.03 × 10(6)) than in GPe (0.47 ± 0.07 × 10(6) varicosities/mm(3) of tissue), with the anterior half of both segments more densely innervated than the posterior half. Neuronal density of GPi (3.00 ± 0.13 × 10(3) neurons/mm(3)) and GPe (3.62 ± 0.22 × 10(3) neurons/mm(3)) yields a mean ratio of ChAT+ axon varicosities per pallidal neuron of 74 ± 10 in the GPi and 128 ± 28 in the GPe. At the electron microscopic level, the pallidal ChAT+ axon varicosities are significantly smaller than their unlabeled counterparts, but are comparable in size and shape in the two pallidal segments. Only a minority of ChAT+ varicosities displays a synaptic specialization (12 % in the GPi and 17 % in the GPe); these scarce synaptic contacts are mostly of the symmetrical type and occur exclusively on pallidal dendrites. No ChAT+ axo-axonic synaptic contacts are observed, suggesting that ACh exerts its modulatory action on pallidal afferents through diffuse transmission, whereas pallidal neurons may be influenced by both volumic and synaptic delivery of ACh.

Reflexivity in PHIR: let's have a reflexive talk!

In 2009, a group of researchers who gathered in the context of the Population Health Intervention Research Initiative for Canada (PHIRIC) agreed upon the need to define a specific set of competencies for population health intervention research (PHIR). Following this event, a consultative process allowed the definition of six domains of core competencies in PHIR, which were released for the first time last summer. In this comment, we would like to respond to this set of competencies and, more specifically, to the "reflective researcher" domain of the competencies. We believe that propositions in this domain are rooted in a narrow and oversimplified definition of reflexivity. Furthermore, we are concerned that disseminating such propositions is not only misleading but could also encourage a false practice of reflexivity, impeding the evolution of the PHIR field and its capacity to improve population health. In order to illustrate our point, we build on commonly accepted definitions of reflexivity to critically examine the initial propositions of the group and suggest new ones. As researchers in the population health intervention field, we believe that a more accurate definition of what is a reflective researcher is crucial in order to foster the continuous development of the field and its capacity to improve population health.

Distribution and morphological characteristics of striatal interneurons expressing calretinin in mice: a comparison with human and nonhuman primates.

Striatal interneurons display a morphological and chemical heterogeneity that has been particularly well characterized in rats, monkeys and humans. By comparison much less is known of striatal interneurons in mice, although these animals are now widely used as transgenic models of various neurodegenerative diseases. The present immunohistochemical study aimed at characterizing striatal interneurons expressing calretinin (CR) in mice compared to those in squirrel monkeys and humans. The mouse striatum contains both small (9-12 µm) and medium-sized (15-20 µm) CR+ cells. The small cells are intensely stained with a single, slightly varicose and moderately arborized process. They occur throughout the striatum (77±9 cells/mm(3)), but prevail in the area of the subventricular zone and subcallosal streak, with statistically significant anteroposterior and dorsoventral decreasing gradients. The medium-sized cells are less intensely immunoreactive and possess 2-3 long, slightly varicose and poorly branched dendrites. They are rather uniformly scattered throughout the striatum and three times more numerous (224±31 cells/mm(3)) than the smaller CR+ cells. Double immunostaining experiments with choline acetyltransferase (ChAT) as a cholinergic marker in normal and Drd1a-tdTomato/Drd2-EGFP double transgenic mice reveal that none of the small or medium-sized CR+ cells express ChAT or D1 and D2 dopamine receptors. In contrast, the striatum in human and nonhuman primates harbors small and medium-sized CR+/ChAT- cells, as well as large CR+/ChAT+ interneurons that are absent in mice. Such a difference between rodents and primates must be taken into consideration if one hopes to better understand the striatal function in normal and pathological conditions.

Niels Stensen: a 17th century scientist with a modern view of brain organization.

In 1665 the Danish scholar Niels Stensen (1638-1686) reached Paris, where he pronounced a discourse on brain anatomy that was to orient neuroscientists for years to come. In his lecture, Stensen rejected ancient speculations about animal spirits and criticized René Descartes and his followers who, despite a poor knowledge of brain anatomy, elaborated complex models to explain the multifaceted function of what he considered the principal organ of the human mind. He advocated the need for studying the brain through a comparative, developmental and pathological convergent approach and called for appropriate dissection methods and accurate illustrations. His own careful anatomical studies permitted him to precisely depict many brain structures. After pioneering works in paleontology and geology, he devoted himself to theology. In 1677 Stensen converted from Lutheranism to Catholicism and, while working relentlessly as a bishop and apostolic vicar in Northern Europe, he died in self-imposed poverty at age 48.