Tractography dissection variability: What happens when 42 groups dissect 14 white matter bundles on the same dataset?

White matter bundle segmentation using diffusion MRI fiber tractography has become the method of choice to identify white matter fiber pathways in vivo in human brains. However, like other analyses of complex data, there is considerable variability in segmentation protocols and techniques. This can result in different reconstructions of the same intended white matter pathways, which directly affects tractography results, quantification, and interpretation. In this study, we aim to evaluate and quantify the variability that arises from different protocols for bundle segmentation. Through an open call to users of fiber tractography, including anatomists, clinicians, and algorithm developers, 42 independent teams were given processed sets of human whole-brain streamlines and asked to segment 14 white matter fascicles on six subjects. In total, we received 57 different bundle segmentation protocols, which enabled detailed volume-based and streamline-based analyses of agreement and disagreement among protocols for each fiber pathway. Results show that even when given the exact same sets of underlying streamlines, the variability across protocols for bundle segmentation is greater than all other sources of variability in the virtual dissection process, including variability within protocols and variability across subjects. In order to foster the use of tractography bundle dissection in routine clinical settings, and as a fundamental analytical tool, future endeavors must aim to resolve and reduce this heterogeneity. Although external validation is needed to verify the anatomical accuracy of bundle dissections, reducing heterogeneity is a step towards reproducible research and may be achieved through the use of standard nomenclature and definitions of white matter bundles and well-chosen constraints and decisions in the dissection process.

Primary visual cortex in neandertals as revealed from the occipital remains from the El Sidrón site, with emphasis on the new SD-2300 specimen.

The comparative analysis of the endocranial surface of the El Sidrón new occipital fragment SD-2300 shows meaningful differences in the configuration of the occipital pole region between neandertals and anatomically modern humans (AMH). The particular asymmetries found in neandertals in the venous sinus drainage and the petalial patterns are recognizable in this new specimen as well. In addition, the supra- and infracalcarine fossae of the occipital pole region appear to deviate obliquely from the mid-line when compared with sapiens. Due to the excellent preservation conditions of SD-2300, the main sulci and gyri of the occipital pole area have been identified, this degree of detail being uncommon in a fossil specimen; in general, the gyrification pattern is similar to AMH, but with some notable differences. Particularly interesting is the description of the lunate and the calcarine sulci. The lunate sulcus is located close to the occipital pole, in a similar posterior position to in other Homo species. Regarding the calcarine sulcus, there are significant differences in the primary visual cortex, with the V1 area, or Brodmann area 17, being larger in Homo neanderthalensis than in Homo sapiens. This may lead to greater visual acuity in neandertals than in sapiens.

Low and high dietary folic acid levels perturb postnatal cerebellar morphology in growing rats.

The brain is particularly sensitive to folate metabolic disturbances, because methyl groups are critical for brain functions. This study aimed to investigate the effects of different dietary levels of folic acid (FA) on postnatal cerebellar morphology, including the architecture and organisation of the various layers. A total of forty male OFA rats (a Sprague-Dawley strain), 5 weeks old, were classified into the following four dietary groups: FA deficient (0 mg/kg FA); FA supplemented (8 mg/kg FA); FA supra-supplemented (40 mg/kg FA); and control (2 mg/kg FA) (all n 10 per group). Rats were fed ad libitum for 30 d. The cerebellum was quickly removed and processed for histological and immunohistochemical analysis. Slides were immunostained for glial fibrillary acidic protein (to label Bergmann glia), calbindin (to label Purkinje cells) and NeuN (to label post-mitotic neurons). Microscopic analysis revealed two types of defect: partial disappearance of fissures and/or neuronal ectopia, primarily in supra-supplemented animals (incidence of 80 %, P≤0·01), but also in deficient and supplemented groups (incidence of 40 %, P≤0·05), compared with control animals. The primary fissure was predominantly affected, sometimes accompanied by defects in the secondary fissure. Our findings show that growing rats fed an FA-modified diet, including both deficient and supplemented diets, have an increased risk of disturbances in cerebellar corticogenesis. Defects caused by these diets may have functional consequences in later life. The present study is the first to demonstrate that cerebellar morphological defects can arise from deficient, as well as high, FA levels in the diet.

Grapheme-color synesthetes show peculiarities in their emotional brain: cortical and subcortical evidence from VBM analysis of 3D-T1 and DTI data.

Grapheme-color synesthesia is a neurological phenomenon in which viewing achromatic letters/numbers leads to automatic and involuntary color experiences. In this study, voxel-based morphometry analyses were performed on T1 images and fractional anisotropy measures to examine the whole brain in associator grapheme-color synesthetes. These analyses provide new evidence of variations in emotional areas (both at the cortical and subcortical levels), findings that help understand the emotional component as a relevant aspect of the synesthetic experience. Additionally, this study replicates previous findings in the left intraparietal sulcus and, for the first time, reports the existence of anatomical differences in subcortical gray nuclei of developmental grapheme-color synesthetes, providing a link between acquired and developmental synesthesia. This empirical evidence, which goes beyond modality-specific areas, could lead to a better understanding of grapheme-color synesthesia as well as of other modalities of the phenomenon.

Comparative morphology and morphometric assessment of the Neandertal occipital remains from the El Sidrón site (Asturias, Spain: years 2000-2008).

This paper analyses the occipital remains recovered from the El Sidrón (Asturias, Spain) Neandertal site between the years of 2000-2008. The sample is represented by three specimens, SD-1219, SD-1149, and SD-370a. Descriptive morphology, linear measurements, 3D geometric morphometrics, and virtual anthropological methods were employed to address the morphological, morphometric, and phylogenetic affinities of these fossils. The fossils display Neandertal autapomorphies (e.g., bilaterally protruding transverse occipital torus, suprainiac fossa). SD-1219 also preserves a strongly projecting juxtamastoid eminence and shows occipital bunning. In linear distances, the El Sidrón occipitals are similar to each other and close to the Neandertal mean. The centroid size of SD-1219 is slightly larger than the Neandertal average. All of the evidence taken together points to the hypothesis that SD-1219 belongs to a smaller Neandertal male. Linear measurements and the vault thickness of SD-1149 also suggest a robust male individual. The gracility of SD-370a points towards an immature individual. Virtual anthropological methods were used to reconstruct a 3D model of the SD-1219 occipital for geometric morphometrics, which reveals that SD-1219 shows relatively broad and low occipital plane proportions. Within the European Pleistocene lineage sample, this fossil falls geometrically closer to primitive rather than to derived morphologies because of its increased width, and a lower, anterior position of inion relative to the biasterionic axis. These results may imply that cranial sphericity could be an important feature of intraspecific Neandertal variability. Our findings open the way for further studies of intraspecific variation in Neandertal populations, in which the El Sidrón sample may play a significant role.

Immunohistochemical localization of fibrillin-1 protein in the cells of chick corneal and conjunctival epithelia during pre- and postnatal development.

Fibrillin-1 protein is a microfibrillar glycoprotein component of the extracellular matrix, widely distributed in ocular connective tissues. In this work, we show for the first time the expression pattern of fibrillin-1 protein in the corneal and conjunctival epithelia and in stromal keratocytes during embryo development. After hatching, protein expression was maintained in the corneal epithelium cells and nonsecreting epithelium cells of the conjunctiva and disappeared in the stromal keratocytes. In the limbus region, the basal cells were negative, while superficial cells were positive for the antibody. The expression in corneal epithelial cells suggests a role for fibrillin in development and disease. Therefore, some basal cells of the limbus region do not show fibrillin-1 immunolocalization, and this may be correlated with stem cell or stem-like properties.

Cranial Pair 0: The Nervus Terminalis.

Originally discovered in elasmobranchs by Fritsh in 1878, the nervus terminalis has been found in virtually all species, including humans. After more than one-century debate on its nomenclature, it is nowadays recognized as cranial pair zero. The nerve mostly originates in the olfactory placode, although neural crest contribution has been also proposed. Developmentally, the nervus terminalis is clearly observed in human embryos; subsequently, during the fetal period loses some of its ganglion cells, and it is less recognizable in adults. Fibers originating in the nasal cavity passes into the cranium through the middle area of the cribiform plate of the ethmoid bone. Intracranially, fibers joint the telencephalon at several sites including the olfactory trigone and the primordium of the hippocampus to reach preoptic and precommissural regions. The nervus terminalis shows ganglion cells, that sometimes form clusters, normally one or two located at the base of the crista galli, the so-called ganglion of the nervus terminalis. Its function is uncertain. It has been described that its fibers facilitates migration of luteinizing hormone-releasing hormone cells to the hypothalamus thus participating in the development of the hypothalamic-gonadal axis, which alteration may provoke Kallmann's syndrome in humans. This review summarizes current knowledge on this structure, incorporating original illustrations of the nerve at different developmental stages, and focuses on its anatomical and clinical relevance. Anat Rec, 302:394-404, 2019. © 2018 Wiley Periodicals, Inc.

Expression of EphA receptors and ligands during chick cerebellar development.

The cerebellum is a modular structure that integrates information in a topographical manner. The membrane receptors of the Eph family and their ligands play important roles in early regionalization, as well as in the formation of topographic connections of the nervous system. Here, we show that the expression of the Eph receptors -A4 and -A7, and of their ligands ephrin-A5 and -A2 correlates with the establishment of territories along the rostro-caudal axis and with the formation of topographically organized connections between the cortex and the cerebellar nuclei. While some sites where co-expression of receptors and ligands are evident, their relative expression mainly define sharp limits along the rostro-caudal axis and, at later stages, complementary gradients in the Purkinje cell layer and the deep cerebellar nuclei.

[Colors, tastes, numbers?: synesthesia in a Spanish sample]. / Colores, sabores, números?: la sinestesia en una muestra española.

INTRODUCTION: Synesthesia is a neural phenomenon in which stimulation in one sensory or cognitive stream leads to associated experiences in a second, unstimulated stream. These activations occur involuntarily, automatically and consistently over time. AIM: To estimate the relative frequency of the different modalities of the phenomenon in a Spanish sample. SUBJECTS AND METHODS: Study performed in educational (55.04%), labor (20.54%) and digital contexts (24.4%) using the Synesthesia Questionnaire created by Artecitta Foundation. RESULTS: The analysis of the responses given by 803 participants suggests that 13.95% of the sample experience any synesthesia. The analysis of the relative frequencies shows that the most frequent modality is spatial sequence synesthesia (44.6%). 33.9% see colors when listening to sounds and/or music, 25.9% associate colors to temporal concepts, 20.5% assign gender and personality to letters and numbers, 10.7% experience grapheme-color synesthesia and 5.4% feel a specific flavor when hearing words. CONCLUSIONS: These data suggest that the presence of synesthesia in the Spanish sample under study is high, and that the investigation of the phenomenon and its different modalities needs to be approached on the basis of the current knowledge about its phenomenological variability and its genetic and neurophysiologic characteristics. Likewise, the results are useful to adjust the questionnaire items and increase their discriminative power.

TITLE: Colores, sabores, numeros?: la sinestesia en una muestra española.Introduccion. La sinestesia es un fenomeno neurologico caracterizado por la activacion simultanea de dos sistemas (o atributos) sensoriales, uno de los cuales no ha sido estimulado directamente. Dicha activacion se produce de una forma involuntaria, automatica y consistente a lo largo del tiempo. Objetivo. Estimar la frecuencia relativa de las diferentes modalidades de sinestesia en una muestra española. Sujetos y metodos. Estudio realizado en contextos educativos (55,04%), laborales (20,54%) y digitales (24,4%) mediante el cuestionario de sinestesia de la Fundacion Artecitta. Resultados. El analisis de las respuestas de 803 participantes sugiere que un 13,95% de la muestra estudiada experimenta alguna sinestesia. El analisis de la frecuencia relativa de las diferentes modalidades muestra que la mas frecuente es la que relaciona conceptos temporales con configuraciones espaciales (44,6%). Un 33,9% percibe colores cuando escucha sonidos o musica, un 25,9% asocia colores a los conceptos temporales, un 20,5% asigna genero o personalidad a las letras y numeros, un 10,7% experimenta la modalidad grafema-color, y un 5,4% siente un sabor especifico en su boca al escuchar palabras. Conclusiones. Los datos sugieren que la presencia de sinestesia en la muestra española estudiada es elevada y que la investigacion sobre el fenomeno y sus diferentes modalidades ha de ser abordada basandose en el conocimiento actual sobre su variabilidad fenomenologica y sus bases geneticas y neurofisiologicas. Asimismo, los resultados obtenidos son utiles para ajustar los items del cuestionario y aumentar su capacidad discriminativa.

Ciliary muscle in avian is derived from mesenchymal and epithelial cells.

It has long been maintained that the ciliary muscle derives from mesenchymal cells. The embryonic development of the avian ciliary muscle was studied in chick embryos from stage 25 HH to the time of hatching. Serial sections of the eye were stained routinely or immunocytochemically using the monoclonal antibody 13F4, which recognizes a cytoplasmic antigen specific for all types of muscle cells. We found that the mesenchymal immunoreactive cells, at stage 37 HH, are arranged in two distinct orientations forming the anterior and posterior portions of the ciliary muscle. At stages 38 and 39 HH the pigmented epithelium contained 13F4 positive cells, which detach from the epithelium and apparently migrate into stroma. These epithelial cells may differentiate into muscle cells. Within this same time period a progressive accumulation of myoblasts was detected between the pigmented epithelium and the ciliary muscle. Some myoblasts containing melanin were also observed. At stage 40 HH the internal portion of the ciliary muscle was visible. These findings indicate that the immunopositive epithelial cells participate in the formation of the internal portion of the muscle. We conclude that the ciliary muscle derives not only from the mesenchymal cells but also from the pigmented epithelium.

Temporal lobe sulcal pattern and the bony impressions in the middle cranial fossa: the case of the el Sidrón (Spain) neandertal sample.

Correspondence between temporal lobe sulcal pattern and bony impressions on the middle cranial fossae (MCF) was analyzed. MCF bone remains (SD-359, SD-315, and SD-1219) from the El Sidrón (Spain) neandertal site are analyzed in this context. Direct comparison of the soft and hard tissues from the same individual was studied by means of: 1) dissection of two human heads; 2) optic (white light) surface scans; 3) computed tomography and magnetic resonance of the same head. The inferior temporal sulcus and gyrus are the features most strongly influencing MCF bone surface. The Superior temporal sulcus and middle temporal and fusiform gyri also leave imprints. Temporal lobe form differs between Homo sapiens and neandertals. A wider and larger post-arcuate fossa (posterior limit of Brodmann area 20 and the anterior portion of area 37) is present in modern humans as compared to neandertals. However other traits of the MCF surface are similar in these two large-brained human groups. A conspicuous variation is appreciated in the more vertical location of the inferior temporal gyrus in H. sapiens. In parallel, structures of the lower surface of the temporal lobe are more sagittally orientated. Grooves accommodating the fusiform and the lower temporal sulci become grossly parallel to the temporal squama. These differences can be understood within the context of a supero-lateral deployment of the lobe in H. sapiens, a pattern previously identified (Bastir et al., Nat Commun 2 (2011) 588-595). Regarding dural sinus pattern, a higher incidence of petrosquamous sinus is detected in neandertal samples.

Differential growth and development of the upper and lower human thorax.

The difficulties in quantifying the 3D form and spatial relationships of the skeletal components of the ribcage present a barrier to studies of the growth of the thoracic skeleton. Thus, most studies to date have relied on traditional measurements such as distances and indices from single or few ribs. It is currently known that adult-like thoracic shape is achieved early, by the end of the second postnatal year, with the circular cross-section of the newborn thorax transforming into the ovoid shape of adults; and that the ribs become inclined such that their anterior borders come to lie inferior to their posterior. Here we present a study that revisits growth changes using geometric morphometrics applied to extensive landmark data taken from the ribcage. We digitized 402 (semi) landmarks on 3D reconstructions to assess growth changes in 27 computed tomography-scanned modern humans representing newborns to adults of both sexes. Our analyses show a curved ontogenetic trajectory, resulting from different ontogenetic growth allometries of upper and lower thoracic units. Adult thoracic morphology is achieved later than predicted, by diverse modifications in different anatomical regions during different ontogenetic stages. Besides a marked increase in antero-posterior dimensions, there is an increase in medio-lateral dimensions of the upper thorax, relative to the lower thorax. This transforms the pyramidal infant thorax into the barrel-shaped one of adults. Rib descent is produced by complex changes in 3D curvature. Developmental differences between upper and lower thoracic regions relate to differential timings and rates of maturation of the respiratory and digestive systems, the spine and the locomotor system. Our findings are relevant to understanding how changes in the relative rates of growth of these systems and structures impacted on the development and evolution of modern human body shape.

Paleoneurology of two new neandertal occipitals from El Sidrón (asturias, Spain) in the context of homo endocranial evolution.

The endocranial surface description and comparative analyses of two new neandertal occipital fragments (labelled SD-1149 and SD-370a) from the El Sidrón site (Asturias, Spain) reveal new aspects of neandertal brain morphological asymmetries. The dural sinus drainage pattern, as observed on the sagittal-transverse system, as well as the cerebral occipito-petalias, point out a slightly differential configuration of the neandertal brain when compared to other Homo species, especially H. sapiens. The neandertal dural sinus drainage pattern is organized in a more asymmetric mode, in such a way that the superior sagittal sinus (SSS) drains either to the right or to the left transverse sinuses, but in no case in a confluent mode (i.e. simultaneous continuation of SSS with both right (RTS) and left (LTS) transverse sinuses). Besides, the superior sagittal sinus shows an accentuated deviation from of the mid-sagittal plane in its way to the RTS in 35% of neandertals. This condition, which increases the asymmetry of the system, is almost nonexistent neither in the analyzed Homo fossil species sample nor in that of anatomically modern humans. Regarding the cerebral occipito-petalias, neandertals manifest one of the lowest percentages of left petalia of the Homo sample (including modern H. sapiens). As left occipito-petalia is the predominant pattern in hominins, it seems as if neandertals would have developed a different pattern of brain hemispheres asymmetry. Finally, the relief and position of the the cerebral sulci and gyri impressions observed in the El Sidrón occipital specimens look similar to those observed in modern H. sapiens.

Evolution of the base of the brain in highly encephalized human species.

The increase of brain size relative to body size-encephalization-is intimately linked with human evolution. However, two genetically different evolutionary lineages, Neanderthals and modern humans, have produced similarly large-brained human species. Thus, understanding human brain evolution should include research into specific cerebral reorganization, possibly reflected by brain shape changes. Here we exploit developmental integration between the brain and its underlying skeletal base to test hypotheses about brain evolution in Homo. Three-dimensional geometric morphometric analyses of endobasicranial shape reveal previously undocumented details of evolutionary changes in Homo sapiens. Larger olfactory bulbs, relatively wider orbitofrontal cortex, relatively increased and forward projecting temporal lobe poles appear unique to modern humans. Such brain reorganization, beside physical consequences for overall skull shape, might have contributed to the evolution of H. sapiens' learning and social capacities, in which higher olfactory functions and its cognitive, neurological behavioral implications could have been hitherto underestimated factors.

Microarchitectural changes during development of the cerebellar cortex.

The cerebellum is a highly conserved structure in the Central Nervous System (CNS) of vertebrates, and is involved in the coordination of voluntary motor behaviour. Supporting this function, the cerebellar cortex presents a layered structure which requires a precise spatial and temporal coordination of proliferation, migration and differentiation events. One of the characteristics of the developing cortex is the formation of the external granule cell layer (EGL) in the outermost part. The EGL is a highly proliferative transient layer which disappears when cells migrate inwards to form the inner granule cell layer. The balance between proliferation and migration leads to changes in EGL thickness, and might be related to "indentations" observed in the surface of the developing chick cerebellum. We have extended the observation of this feature to quail and mouse, supporting the idea that this phenomenon forms part of the mechanisms of cerebellar morphogenesis. Different factors involved in both mitotic activity and migration were analyzed in this study. Our results indicate that proliferation, more than formation of raphes for cell migration, is involved in the formation of indentations in the EGL. In addition, we show that vessels penetrating from the pial surface divide the EGL into regular regions at the time of the appearance of bulges and furrows. We conclude that indentations are the result of a coincidence in time of both the increase in thickness of the EGL and the establishment of the embryonic vascular pattern, which confers a characteristic transitory morphology to the surface of folia.

Remodeling patterns of occipital growth: a preliminary report.

Occipital growth depends on coordinated deposition and resorption on the external and internal surface and includes interrelated processes of movement: cortical drift, displacement, and relocation. The current work aspires to map patterns of remodeling activity on the endocranial surface of the occipital bone from childhood to adulthood using a larger study sample compared with previous studies. The study sample consists of 5 adult and 10 immature (2(1/4) to 8 years old) occipital bones from skeletal remains from the eighteenth and nineteenth century. Preparation of the samples includes the elaboration of negative impressions, positive replicas coated with gold, and observed with the reflected light microscope. Cerebellar fossae are typically resorptive in both immature and adult specimens. Cerebral fossae, on the other hand, exhibit a resorptive surface in early childhood and turn into depository around the age of 7 years, which places this transition within the age interval of the completion of cerebral development. Depository fields are also observed in adult cerebral fossae. The remodeling map presented here is consistent with the results of Mowbray (Anat Rec B New Anat 2005;283B:14-22) and differs from cellular patterns described by Enlow. Future research implicating more elements of the neurocapsule can shed light on the factors affecting and driving occipital growth.

Endocranial occipito-temporal anatomy of SD-1219 from the Neandertal El Sidrón Site (Asturias, Spain).

We addressed the brain drainage system as inferred by the endocranial morphology of the occipito-temporal region of the El Sidrón Neandertal specimen SD-1219. Morphological details of the endocranial surface and its anatomical implications were analyzed for the reconstruction of the dural sinus drainage pattern and its comparison with Neandertals and other hominids. The specimen SD-1219 shows a pattern in which the superior sagittal sinus goes into the right transverse sinus. Comparative analyses with a large sample of fossil hominids reveal a pattern of the SD-1219 fossil that is typical for Neandertals. The analysis of the proportions of the occipital lobes prints within the occipital fossae reveals that the left occipital pole projects toward the right. This possibly indicates brain asymmetry (petalia) in this Neandertal individual, similar to that observed in some modern human brains. Conversely, no such asymmetry was observed in the cerebellar fossae. A particular feature of this fossil is the presence of two crests, located at the middle of the left cerebellar fossa that can be related to either an imprinting of a cerebellar fissure or some bone response to mechanical influence on internal bone surface morphology during cerebellar development. Specific aspects of the paleoneurology of Neandertals are discussed. Further quantitative studies on the endocranial morphology of the occipito-temporal and -mastoid region will shed light on the paleoneurological significance of this important anatomical region for the understanding of human evolution.

¿Colores, sabores, números?: la sinestesia en una muestra española / Colors, tastes, numbers?: synesthesia in a Spanish sample

Introducción. La sinestesia es un fenómeno neurológico caracterizado por la activación simultánea de dos sistemas (o atributos) sensoriales, uno de los cuales no ha sido estimulado directamente. Dicha activación se produce de una forma involuntaria, automática y consistente a lo largo del tiempo. Objetivo. Estimar la frecuencia relativa de las diferentes modalidades de sinestesia en una muestra española. Sujetos y métodos. Estudio realizado en contextos educativos (55,04%), laborales (20,54%) y digitales (24,4%) mediante el cuestionario de sinestesia de la Fundación Artecittá. Resultados. El análisis de las respuestas de 803 participantes sugiere que un 13,95% de la muestra estudiada experimenta alguna sinestesia. El análisis de la frecuencia relativa de las diferentes modalidades muestra que la más frecuente es la que relaciona conceptos temporales con configuraciones espaciales (44,6%). Un 33,9% percibe colores cuando escucha sonidos o música, un 25,9% asocia colores a los conceptos temporales, un 20,5% asigna género o personalidad a las letras y números, un 10,7% experimenta la modalidad grafema-color, y un 5,4% siente un sabor específico en su boca al escuchar palabras. Conclusiones. Los datos sugieren que la presencia de sinestesia en la muestra española estudiada es elevada y que lainvestigación sobre el fenómeno y sus diferentes modalidades ha de ser abordada basándose en el conocimiento actual sobre su variabilidad fenomenológica y sus bases genéticas y neurofisiológicas. Asimismo, los resultados obtenidos son útiles para ajustar los ítems del cuestionario y aumentar su capacidad discriminativa (AU)

Introduction. Synesthesia is a neural phenomenon in which stimulation in one sensory or cognitive stream leads to associated experiences in a second, unstimulated stream. These activations occur involuntarily, automatically and consistently over time. Aim. To estimate the relative frequency of the different modalities of the phenomenon in a Spanish sample. Subjects and methods. Study performed in educational (55.04%), labor (20.54%) and digital contexts (24.4%) using the Synesthesia Questionnaire created by Artecittá Foundation. Results. The analysis of the responses given by 803 participants suggests that 13.95% of the sample experience any synesthesia. The analysis of the relative frequencies shows that the most frequent modality is spatial sequence synesthesia (44.6%). 33.9% see colors when listening to sounds and/or music, 25.9% associate colors to temporal concepts, 20.5% assign gender and personality to letters and numbers, 10.7% experience grapheme-color synesthesia and 5.4% feel a specific flavor when hearing words. Conclusions. These data suggest that the presence of synesthesia in the Spanish sample under study is high, and that the investigation of the phenomenon and its different modalities needs to be approached on the basis of the current knowledge about its phenomenological variability and its genetic and neurophysiologic characteristics. Likewise, the results are useful to adjust the questionnaire items and increase their discriminative power (AU)

Homocysteine modifies development of neurulation and dorsal root ganglia in chick embryos.

BACKGROUND: The formation of the neural tube (neurulation) involves two mechanisms: primary and secondary neurulation. In chicks, there is also an overlap zone, where both mechanisms work together. Homocysteine (Hcy) may have an important teratogenic role in neural tube defects (NTD) when folic acid levels are considered normal. Recently, Hcy capability to generate NTD and modify neural crest cell migration has been demonstrated in chick embryos. This study was aimed to evaluate the effects of Hcy on neurulation and the development of the dorsal root ganglia (DRG). METHODS: Chick embryos were treated with L-Hcy thiolactone 20 micromol to produce the highest rate of survival with embryos carrying neural tube defect (NTD) in the spine. Embryos at stages (st) 3-10 were treated and harvested at st 18-23. Only externally normal embryos or those carrying spinal NTD embryos were considered. RESULTS: Histological sections of Hcy-treated embryos showed: open spina bifida (39% of embryos), more than one tube forming the spinal cord (26%), disorganized spinal cord (26%), always affecting lumbosacral regions, probably in the overlap zone. Additionally, 32% of embryos had small and continuous DRG, associated with a slimmed roof plate. Three-dimensional reconstruction showed unsegmented DRG until the C8 ganglion level. There was a 75% reduction of C3 DRG cells in treated embryos in comparison to untreated ganglia. CONCLUSION: Hcy teratogenicity in avian embryos affected the neural tube in the overlap zone, secondary neurulation and the cervical DRG.

Debunking myths and building realities: Human body donation in times of crisis

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