Functional neuroanatomy of basal forebrain projections to the basolateral amygdala: Transmitters, receptors, and neuronal subpopulations.

The projections of the basal forebrain (BF) to the hippocampus and neocortex have been extensively studied and shown to be important for higher cognitive functions, including attention, learning, and memory. Much less is known about the BF projections to the basolateral nuclear complex of the amygdala (BNC), although the cholinergic innervation of this region by the BF is actually far more robust than that of cortical areas. This review will focus on light and electron microscopic tract-tracing and immunohistochemical (IHC) studies, many of which were published in the last decade, that have analyzed the relationship of BF inputs and their receptors to specific neuronal subtypes in the BNC in order to better understand the anatomical substrates of BF-BNC circuitry. The results indicate that BF inputs to the BNC mainly target the basolateral nucleus of the BNC (BL) and arise from cholinergic, GABAergic, and perhaps glutamatergic BF neurons. Cholinergic inputs mainly target dendrites and spines of pyramidal neurons (PNs) that express muscarinic receptors (MRs). MRs are also expressed by cholinergic axons, as well as cortical and thalamic axons that synapse with PN dendrites and spines. BF GABAergic axons to the BL also express MRs and mainly target BL interneurons that contain parvalbumin. It is suggested that BF-BL circuitry could be very important for generating rhythmic oscillations known to be critical for emotional learning. BF cholinergic inputs to the BNC might also contribute to memory formation by activating M1 receptors located on PN dendritic shafts and spines that also express NMDA receptors.

Decomposing cortical activity through neuronal tracing connectome-eigenmodes in marmosets.

Deciphering the complex relationship between neuroanatomical connections and functional activity in primate brains remains a daunting task, especially regarding the influence of monosynaptic connectivity on cortical activity. Here, we investigate the anatomical-functional relationship and decompose the neuronal-tracing connectome of marmoset brains into a series of eigenmodes using graph signal processing. These cellular connectome eigenmodes effectively constrain the cortical activity derived from resting-state functional MRI, and uncover a patterned cellular-functional decoupling. This pattern reveals a spatial gradient from coupled dorsal-posterior to decoupled ventral-anterior cortices, and recapitulates micro-structural profiles and macro-scale hierarchical cortical organization. Notably, these marmoset-derived eigenmodes may facilitate the inference of spontaneous cortical activity and functional connectivity of homologous areas in humans, highlighting the potential generalizing of the connectomic constraints across species. Collectively, our findings illuminate how neuronal-tracing connectome eigenmodes constrain cortical activity and improve our understanding of the brain's anatomical-functional relationship.

Unveiling the neuroanatomy of Josephoartigasia monesi and the evolution of encephalization in caviomorph rodents.

Caviomorph rodents are an exceptional model for studying the effects of ecological factors and size relations on brain evolution. These mammals are not only speciose and ecologically diverse but also present wide body size disparity, especially when considering their fossil relatives. Here, we described the brain anatomy of the largest known rodent, Josephoartigasia monesi, uncovering distinctive features within this species regarding other taxa. Albeit resembling extant pacarana Dinomys branickii, J. monesi stands out due to its longer olfactory tract and well-developed sagittal sinus. Challenging the previous hypothesis that giant rodents possessed comparatively smaller brains, we found that J. monesi and another giant extinct rodent, Neoepiblema acreensis, are within the encephalization range of extant caviomorphs. This was unraveled while developing the a Phylogenetic Encephalization Quotient (PEQ) for Caviomorpha. With PEQ, we were able to trace brain-size predictions more accurately, accounting for species-shared ancestry while adding the extinct taxa phenotypic diversity into the prediction model. According to our results, caviomorphs encephalization patterns are not the product of ecological adaptations, and brain allometry is highly conservative within the clade. We challenge future studies to investigate caviomorphs encephalization within different taxonomic ranks while increasing the sampled taxa diversity, especially of extinct forms, in order to fully comprehend the magnitude of this evolutionary stasis.

Mode-based morphometry: A multiscale approach to mapping human neuroanatomy.

Voxel-based morphometry (VBM) and surface-based morphometry (SBM) are two widely used neuroimaging techniques for investigating brain anatomy. These techniques rely on statistical inferences at individual points (voxels or vertices), clusters of points, or a priori regions-of-interest. They are powerful tools for describing brain anatomy, but offer little insights into the generative processes that shape a particular set of findings. Moreover, they are restricted to a single spatial resolution scale, precluding the opportunity to distinguish anatomical variations that are expressed across multiple scales. Drawing on concepts from classical physics, here we develop an approach, called mode-based morphometry (MBM), that can describe any empirical map of anatomical variations in terms of the fundamental, resonant modes-eigenmodes-of brain anatomy, each tied to a specific spatial scale. Hence, MBM naturally yields a multiscale characterization of the empirical map, affording new opportunities for investigating the spatial frequency content of neuroanatomical variability. Using simulated and empirical data, we show that the validity and reliability of MBM are either comparable or superior to classical vertex-based SBM for capturing differences in cortical thickness maps between two experimental groups. Our approach thus offers a robust, accurate, and informative method for characterizing empirical maps of neuroanatomical variability that can be directly linked to a generative physical process.

Fractals in Neuroanatomy and Basic Neurosciences: An Overview.

The introduction of fractal geometry to the neurosciences has been a major paradigm shift over the last decades as it has helped overcome approximations and limitations that occur when Euclidean and reductionist approaches are used to analyze neurons or the entire brain. Fractal geometry allows for quantitative analysis and description of the geometric complexity of the brain, from its single units to the neuronal networks.As illustrated in the second section of this book, fractal analysis provides a quantitative tool for the study of the morphology of brain cells (i.e., neurons and microglia) and its components (e.g., dendritic trees, synapses), as well as the brain structure itself (cortex, functional modules, neuronal networks). The self-similar logic which generates and shapes the different hierarchical systems of the brain and even some structures related to its "container," that is, the cranial sutures on the skull, is widely discussed in the following chapters, with a link between the applications of fractal analysis to the neuroanatomy and basic neurosciences to the clinical applications discussed in the third section.

The neuroanatomy of visual extinction following right hemisphere brain damage: Insights from multivariate and Bayesian lesion analyses in acute stroke.

Multi-target attention, that is, the ability to attend and respond to multiple visual targets presented simultaneously on the horizontal meridian across both visual fields, is essential for everyday real-world behaviour. Given the close link between the neuropsychological deficit of extinction and attentional limits in healthy subjects, investigating the anatomy that underlies extinction is uniquely capable of providing important insights concerning the anatomy critical for normal multi-target attention. Previous studies into the brain areas critical for multi-target attention and its failure in extinction patients have, however, produced heterogeneous results. In the current study, we used multivariate and Bayesian lesion analysis approaches to investigate the anatomical substrate of visual extinction in a large sample of 108 acute right hemisphere stroke patients. The use of acute stroke patient data and multivariate/Bayesian lesion analysis approaches allowed us to address limitations associated with previous studies and so obtain a more complete picture of the functional network associated with visual extinction. Our results demonstrate that the right temporo-parietal junction (TPJ) is critically associated with visual extinction. The Bayesian lesion analysis additionally implicated the right intraparietal sulcus (IPS), in line with the results of studies in neurologically healthy participants that highlighted the IPS as the area critical for multi-target attention. Our findings resolve the seemingly conflicting previous findings, and emphasise the urgent need for further research to clarify the precise cognitive role of the right TPJ in multi-target attention and its failure in extinction patients.

Rabies virus-based barcoded neuroanatomy resolved by single-cell RNA and in situ sequencing.

Mapping the connectivity of diverse neuronal types provides the foundation for understanding the structure and function of neural circuits. High-throughput and low-cost neuroanatomical techniques based on RNA barcode sequencing have the potential to map circuits at cellular resolution and a brain-wide scale, but existing Sindbis virus-based techniques can only map long-range projections using anterograde tracing approaches. Rabies virus can complement anterograde tracing approaches by enabling either retrograde labeling of projection neurons or monosynaptic tracing of direct inputs to genetically targeted postsynaptic neurons. However, barcoded rabies virus has so far been only used to map non-neuronal cellular interactions in vivo and synaptic connectivity of cultured neurons. Here we combine barcoded rabies virus with single-cell and in situ sequencing to perform retrograde labeling and transsynaptic labeling in the mouse brain. We sequenced 96 retrogradely labeled cells and 295 transsynaptically labeled cells using single-cell RNA-seq, and 4130 retrogradely labeled cells and 2914 transsynaptically labeled cells in situ. We found that the transcriptomic identities of rabies virus-infected cells can be robustly identified using both single-cell RNA-seq and in situ sequencing. By associating gene expression with connectivity inferred from barcode sequencing, we distinguished long-range projecting cortical cell types from multiple cortical areas and identified cell types with converging or diverging synaptic connectivity. Combining in situ sequencing with barcoded rabies virus complements existing sequencing-based neuroanatomical techniques and provides a potential path for mapping synaptic connectivity of neuronal types at scale.

In the brain, messages are relayed from one cell to the next through intricate networks of axons and dendrites that physically interact at junctions known as synapses. Mapping out this synaptic connectivity ­ that is, exactly which neurons are connected via synapses ­ remains a major challenge. Monosynaptic tracing is a powerful approach that allows neuroscientists to explore neural networks by harnessing viruses which spread between neurons via synapses, in particular the rabies virus. This pathogen travels exclusively from 'postsynaptic' to 'presynaptic' neurons ­ from the cell that receives a message at a synapse, back to the one that sends it. A modified variant of the rabies virus can therefore be used to reveal the presynaptic cells connecting to a population of neurons in which it has been originally introduced. However, this method does not allow scientists to identify the exact postsynaptic neuron that each presynaptic cell is connected to. One way to bypass this issue is to combine monosynaptic tracing with RNA barcoding to create distinct versions of the modified rabies virus, which are then introduced into separate populations of neurons. Tracking the spread of each version allows neuroscientists to spot exactly which presynaptic cells signal to each postsynaptic neuron. So far, this approach has been used to examine synaptic connectivity in neurons grown in the laboratory, but it remains difficult to apply it to neurons in the brain. In response, Zhang, Jin et al. aimed to demonstrate how monosynaptic tracing that relies on barcoded rabies viruses could be used to dissect neural networks in the mouse brain. First, they confirmed that it was possible to accurately detect which version of the virus had spread to presynaptic neurons using both in situ and single-cell RNA sequencing. Next, they described how this information could be analysed to build models of potential neural networks, and what type of additional experiments are required for this work. Finally, they used the approach to identify neurons that tend to connect to the same postsynaptic cells and then investigated what these have in common, showing how the technique enables a finer understanding of neural circuits. Overall, the work by Zhang, Jin et al. provides a comprehensive review of the requirements and limitations associated with monosynaptic tracing experiments based on barcoded rabies viruses, as well as how the approach could be optimized in the future. This information will be of broad interest to scientists interested in mapping neural networks in the brain.

Comparison of histological delineations of medial temporal lobe cortices by four independent neuroanatomy laboratories.

The medial temporal lobe (MTL) cortex, located adjacent to the hippocampus, is crucial for memory and prone to the accumulation of certain neuropathologies such as Alzheimer's disease neurofibrillary tau tangles. The MTL cortex is composed of several subregions which differ in their functional and cytoarchitectonic features. As neuroanatomical schools rely on different cytoarchitectonic definitions of these subregions, it is unclear to what extent their delineations of MTL cortex subregions overlap. Here, we provide an overview of cytoarchitectonic definitions of the entorhinal and parahippocampal cortices as well as Brodmann areas (BA) 35 and 36, as provided by four neuroanatomists from different laboratories, aiming to identify the rationale for overlapping and diverging delineations. Nissl-stained series were acquired from the temporal lobes of three human specimens (two right and one left hemisphere). Slices (50 µm thick) were prepared perpendicular to the long axis of the hippocampus spanning the entire longitudinal extent of the MTL cortex. Four neuroanatomists annotated MTL cortex subregions on digitized slices spaced 5 mm apart (pixel size 0.4 µm at 20× magnification). Parcellations, terminology, and border placement were compared among neuroanatomists. Cytoarchitectonic features of each subregion are described in detail. Qualitative analysis of the annotations showed higher agreement in the definitions of the entorhinal cortex and BA35, while the definitions of BA36 and the parahippocampal cortex exhibited less overlap among neuroanatomists. The degree of overlap of cytoarchitectonic definitions was partially reflected in the neuroanatomists' agreement on the respective delineations. Lower agreement in annotations was observed in transitional zones between structures where seminal cytoarchitectonic features are expressed less saliently. The results highlight that definitions and parcellations of the MTL cortex differ among neuroanatomical schools and thereby increase understanding of why these differences may arise. This work sets a crucial foundation to further advance anatomically-informed neuroimaging research on the human MTL cortex.

Neuron parvum fluorescens, un Término con Influencia Anglo-Greco-Latina. Propuesta a Terminologia Neuroanatomica y Terminologia Histologica / Neuron Parvum Fluorescens, a Term with Anglo-Greco-Latin Influence. A Proposal to Terminologia Neuroanatomica and Terminologia Histologica

Las terminologías son utilizadas como instrumento lingüístico que permite la transmisión de conocimiento de manera precisa y sin ambigüedades en el ámbito de las ciencias. Los lineamientos de la Federative International Programme for Anatomical Terminology (FIPAT) refieren que la denominación de nombres estructurales debe ser descriptivos e informativos. Este estudio analiza las raíces lingüísticas que componen el término Neuron parvum valde fluorescens vigente en Terminologia Histologica y el término Neuron parvum fluorescens vigente en Terminologia Neuroanatomica. Las células pequeñas intensamente fluorescentes son neuronas que se encuentran en el sistema nervioso autónomo, distribuidas en los ganglios simpáticos. Estas células presentan sinapsis aferentes con terminales nerviosas simpáticas preganglionares y sinapsis eferentes con las dendritas de las neuronas posganglionares. Su función es regular la transmisión ganglionar, actuando como interneuronas con señalización paracrina y endocrina. Además, se caracterizan por ser células fluorescentes, que expresan catecolaminas; serotonina, noradrenalina y dopamina. Se realizó una búsqueda en Terminologia Histologica y Terminologia Neuroanatomica, con una traducción de los términos al español. Además, la búsqueda se complementó en un diccionario etimológico en inglés para los términos correspondientes. Esta investigación encontró diferencia entre la traducción del latín al español del término fluorescens, quien posee un origen etimológico muy diferente a su significado en español. El término Neuron parvum valde fluorescens en Terminologia Histologica y el término Neuron parvum fluorescens en Terminologia Neuroanatomica, identifican a la misma estructura. Se sugiere reemplazar ambos términos por Cateconeuron ganglionare, entregando así una correcta descripción de este tipo de neurona, considerando su ubicación y función. Además, de esta manera ser un término concordante en latín para su incorporación en Terminologia Neuroanatomica y Terminologia Histologica.

SUMMARY: Terminologies are used as a linguistic tool to convey knowledge in a precise and unambiguous manner in science. The guidelines of the Federative International Programme for Anatomical Terminology (FIPAT) state that the names given to structures should be both descriptive and informative. This study analyses the linguistic roots of the term Neuron parvum valde fluorescens in Terminologia Histologica and the term Neuron parvum fluorescens in Terminologia Neuroanatomica. Small intensely fluorescent cells are neurons found in the autonomic nervous system, distributed in the sympathetic ganglia, they have afferent synapses with preganglionic sympathetic nerve terminals and efferent synapses with the dendrites of postganglionic neurons, whose function is to regulate ganglionic transmission, acting as interneurons with paracrine and endocrine signalling. They are also characterized as fluorescent cells, producing the catecholamines: serotonin, noradrenaline and dopamine. A search was carried out in Terminologia Histologica and Terminologia Neuroanatomica, with a translation of the terms into Spanish. This was complemented by a search in an English etymological dictionary for the corresponding terms. This research found a difference between the Latin to English translation of the term fluorescens, which has a very different etymological origin to its English meaning. The term Neuron parvum valde fluorescens in Terminologia Histologica and the term Neuron parvum fluorescens in Terminologia Neuroanatomica identify the same structure. The proposal is to replace both terms with Cateconeuron ganglionare, thus affording an accurate description of this type of neuron, considering its location and function. Moreover, it would also be a concordant term in Latin for its incorporation into the Terminologia Neuroanatomica and Terminologia Histologica.

Developing a novel dual-injection FDG-PET imaging methodology to study the functional neuroanatomy of gait.

Gait is an excellent indicator of physical, emotional, and mental health. Previous studies have shown that gait impairments in ageing are common, but the neural basis of these impairments are unclear. Existing methodologies are suboptimal and novel paradigms capable of capturing neural activation related to real walking are needed. In this study, we used a hybrid PET/MR system and measured glucose metabolism related to both walking and standing with a dual-injection paradigm in a single study session. For this study, 15 healthy older adults (10 females, age range: 60.5-70.7 years) with normal cognition were recruited from the community. Each participant received an intravenous injection of [18F]-2-fluoro-2-deoxyglucose (FDG) before engaging in two distinct tasks, a static postural control task (standing) and a walking task. After each task, participants were imaged. To discern independent neural functions related to walking compared to standing, we applied a bespoke dose correction to remove the residual 18F signal of the first scan (PETSTAND) from the second scan (PETWALK) and proportional scaling to the global mean, cerebellum, or white matter (WM). Whole-brain differences in walking-elicited neural activity measured with FDG-PET were assessed using a one-sample t-test. In this study, we show that a dual-injection paradigm in healthy older adults is feasible with biologically valid findings. Our results with a dose correction and scaling to the global mean showed that walking, compared to standing, increased glucose consumption in the cuneus (Z = 7.03), the temporal gyrus (Z = 6.91) and the orbital frontal cortex (Z = 6.71). Subcortically, we observed increased glucose metabolism in the supraspinal locomotor network including the thalamus (Z = 6.55), cerebellar vermis and the brainstem (pedunculopontine/mesencephalic locomotor region). Exploratory analyses using proportional scaling to the cerebellum and WM returned similar findings. Here, we have established the feasibility and tolerability of a novel method capable of capturing neural activations related to actual walking and extended previous knowledge including the recruitment of brain regions involved in sensory processing. Our paradigm could be used to explore pathological alterations in various gait disorders.

Comparison of the study performance of dental students in different subfields of neuroanatomy at the Charité - Universitätsmedizin Berlin and evaluation of the neuroanatomy course in the fourth preclinical semester.

INTRODUCTION: The dentist's main working area is the head and neck region, which is innervated by the cranial nerves. On a daily basis, dentists must administer local anaesthesia to ensure pain-free treatment and differentiate between dental pain and neuropathies to avoid mistreatment. Therefore, neuroanatomical training, especially on the cranial nerves, is of immense importance for clinical practice. In order to adopt the curriculum, it is essential to constantly evaluate the quality of the training and to investigate whether there is a correlation between the students' performance and the relevance of the subfields to their work. MATERIAL AND METHODS: To address this issue, the results of MC exams in the neuroanatomy course for dental students at Charité-Universitätsmedizin Berlin from winter semester 2014/2015 to winter semester 2019/2020 were analysed. Each question was assigned to a specific subfield of neuroanatomy. We then compared cranial nerves and cranial nerve nuclei (clinically relevant) with the remaining subfields (clinically less/not relevant) to investigate whether students performed better in anatomy subfields that are more aligned with the clinical practice of a dentist. We also conducted an anonymous survey (n=201) of the dental students. RESULTS: From winter semester 2014/2015 to winter semester 2019/2020, students performed significantly (***, p< 0.001) better on the clinically relevant questions of the MC examination than on the less/not clinically relevant questions. However, when looking at each of the eleven semesters separately, only three semesters actually performed significantly better on the clinically relevant questions. Our survey also showed that students perceived the subfield of cranial nerves and cranial nerve nuclei to be the most relevant and studied it more intensively out of their own interest. DISCUSSION: The study showed that students perceived the subfield of cranial nerves and cranial nerve nuclei to be the most relevant. However, there was no direct correlation between student performance and clinically relevant questions. Using student performance alone as an indicator of relevance is not optimal, as factors such as motivation to learn can have a significant impact. CONCLUSION: Greater clinical relevance influences what students learn more intensively out of their own interest, but does not influence the results of the MC examination in favour of the subspecialty. Based on the available evidence, it is recommended that the structure of the neuroanatomy course be reconsidered.

Creation of a microsurgical neuroanatomy laboratory and virtual operating room: a preliminary study.

OBJECTIVE: A comprehensive understanding of microsurgical neuroanatomy, familiarity with the operating room environment, patient positioning in relation to the surgery, and knowledge of surgical approaches is crucial in neurosurgical education. However, challenges such as limited patient exposure, heightened patient safety concerns, a decreased availability of surgical cases during training, and difficulties in accessing cadavers and laboratories have adversely impacted this education. Three-dimensional (3D) models and augmented reality (AR) applications can be utilized to depict the cortical and white matter anatomy of the brain, create virtual models of patient surgical positions, and simulate the operating room and neuroanatomy laboratory environment. Herein, the authors, who used a single application, aimed to demonstrate the creation of 3D models of anatomical cadaver dissections, surgical approaches, patient surgical positions, and operating room and laboratory designs as alternative educational materials for neurosurgical training. METHODS: A 3D modeling application (Scaniverse) was employed to generate 3D models of cadaveric brain specimens and surgical approaches using photogrammetry. It was also used to create virtual representations of the operating room and laboratory environment, as well as the surgical positions of patients, by utilizing light detection and ranging (LiDAR) sensor technology for accurate spatial mapping. These virtual models were then presented in AR for educational purposes. RESULTS: Virtual representations in three dimensions were created to depict cadaver specimens, surgical approaches, patient surgical positions, and the operating room and laboratory environment. These models offer the flexibility of rotation and movement in various planes for improved visualization and understanding. The operating room and laboratory environment were rendered in three dimensions to create a simulation that could be navigated using AR and mixed reality technology. Realistic cadaveric models with intricate details were showcased on internet-based platforms and AR platforms for enhanced visualization and learning. CONCLUSIONS: The utilization of this cost-effective, straightforward, and readily available approach to generate 3D models has the potential to enhance neuroanatomical and neurosurgical education. These digital models can be easily stored and shared via the internet, making them accessible to neurosurgeons worldwide for educational purposes.

Mixed reality compared to the traditional ex cathedra format for neuroanatomy learning: the value of a three-dimensional virtual environment to better understand the real world.

OBJECTIVE: Neuroanatomy comprehension is a keystone of understanding intracranial surgeries. Traditionally taught to students during ex cathedra courses, neuroanatomy is described as complex. Mixed reality (MxR) opens new perspectives in the learning process. This study aims to compare MxR-based courses with traditional ex cathedra lectures for neuroanatomy education. METHODS: Two lectures describing the neuroanatomy of the anterior circulation arteries ("Vascular Lecture" [VS]) and important white matter fiber tracts ("White Fibers Lecture" [WF]) were designed and delivered in ex cathedra and MxR-based formats with the same audio content. Ninety-one medical students were randomly assigned to group A (ex cathedra WF/MxR VS) or group B (MxR WF/ex cathedra VS). The MxR content was delivered via MxR goggles. Prior to each lecture, students took a 10-item multiple choice question (MCQ) pretest. After the lectures, students took a 20-item MCQ posttest (75% neuroanatomy, 25% clinical correlation). RESULTS: The pretest scores showed no statistical difference between groups. Median posttest scores increased by 14.3% after using the MxR-based format compared to the ex cathedra format (16.00 [13.0, 18.0] vs 14.0 [11.0, 17.0], respectively, p < 0.01). Regarding the VS, students scored 21.7% better using the MxR format compared to the ex cathedra format (14.0 [12.0, 16.0] vs 11.5 [10.0, 14.0], p < 0.001). Concerning the WF, the median score using MxR was 18.0 (17.0, 19.0), and the median score using the ex cathedra format was 17.0 (16.0, 18.0; p < 0.01). Students showed high motivation to learn neuroanatomy in the future using MxR (74%) rather than ex cathedra format (25%; p < 0.001). Mild discomfort using the MxR goggles was reported by 48.3% of participants. Most participants (95.5%) preferred the MxR-based teaching. CONCLUSIONS: Students acquired a better knowledge of the anatomy of the anterior circulation arteries and white fiber tracts using MxR-based teaching as compared to the standard ex cathedra format. The perception of lecture quality and learning motivation was better using MxR-based teaching despite some mild discomfort. The development of MxR-based solutions is promising to improve neuroanatomy education.

Neuroanatomy in virtual reality: Development and pedagogical evaluation of photogrammetry-based 3D brain models.

Anatomy studies are an essential part of medical training. The study of neuroanatomy in particular presents students with a unique challenge of three-dimensional spatial understanding. Virtual Reality (VR) has been suggested to address this challenge, yet the majority of previous reports have implemented computer-generated or imaging-based models rather than models of real brain specimens. Using photogrammetry of real human bodies and advanced editing software, we developed 3D models of a real human brain at different stages of dissection. Models were placed in a custom-built virtual laboratory, where students can walk around freely, explore, and manipulate (i.e., lift the models, rotate them for different viewpoints, etc.). Sixty participants were randomly assigned to one of three learning groups: VR, 3D printed models or read-only, and given 1 h to study the white matter tracts of the cerebrum, followed by theoretical and practical exams and a learning experience questionnaire. We show that following self-guided learning in virtual reality, students demonstrate a gain in spatial understanding and an increased satisfaction with the learning experience, compared with traditional learning approaches. We conclude that the models and virtual lab described in this work may enhance learning experience and improve learning outcomes.

Revealing the confusion of the evolution of the term sagittal stratum. Historical overview and systematic literature review.

The fiber dissection technique is one of the earliest methods used to demonstrate the internal structures of the brain, but until the development of fiber tractography, most neuroanatomy studies were related to the cerebral cortex and less attention was given to the white matter. During the historical evolution of white matter dissection, debates have arisen about tissue preservation methods, dissection methodology, nomenclature, and efforts to adopt findings from primates to the human brain. Since its first description, the sagittal stratum has been one of the white matter structures subject to controversy and has not been sufficiently considered in the literature. With recent functional studies suggesting potential functions of the sagittal stratum, the importance of attaining a precise understanding of this structure and its constituent fiber tracts is further highlighted. This study revisits the historical background of white matter dissection, unveils the early synonymous descriptions of the sagittal stratum, and provides a systematic review of the current literature. Through evaluation of the historical statements about the sagittal stratum, we provide an understanding of the divergence and explain the reasons for the ambiguity. We believe that acquiring such an understanding will lead to further investigations on this subject, which has the potential to benefit in addressing various neuropsychiatric conditions, maintaining functional connectivity, and optimizing surgical outcomes.

Projection of realistic three-dimensional photogrammetry models using stereoscopic display: A technical note.

The 3D stereoscopic technique consists in providing the illusional perception of depth of a given object using two different images mimicking how the right and left eyes capture the object. Both images are slightly different and when overlapped gives a three-dimensional (3D) experience. Considering the limitations for establishing surgical laboratories and dissections courses in some educational institutions, techniques such as stereoscopy and photogrammetry seem to play an important role in neuroanatomy and neurosurgical education. The aim of this study was to describe how to combine and set up realistic models acquired with photogrammetry scans in 3D stereoscopic projections. Three donors, one dry skull, embalmed brain and head, were scanned using photogrammetry. The software used for displaying the final realistic 3D models (Blender, Amsterdam, the Netherlands) is a free software and allows stereoscopic projection without compromising the interactivity of each model. By default, the model was exported and immediately displayed as a red cyan 3D mode. The 3D projector used in the manuscript required a side-by-side 3D mode which was set up with simple commands on the software. The final stereoscopy projection offered depth perception and a visualization in 360° of each donor; this perception was noted especially when visualizing donors with different cavities and fossae. The combination of 3D techniques is of paramount importance for neuroanatomy education. Stereoscopic projections could provide a valuable tool for neuroanatomy instruction directed at clinical trainees and could be especially useful when access to laboratory-based learning is limited.

The Mayo, Cushing, and Osler Influence on A. L. Rhoton: A Historical Vignette of the Interconnectedness Between Highly Influential Neurosurgery Leaders over 100 Years.

The careers of the Mayo brothers, Harvey Cushing, and Sir William Osler greatly shaped medical and surgical practice in the late 19th century and early 20th century and created a legacy to influence decades of physicians to follow. Additionally, these individuals were instrumental in the founding of neurosurgery as a distinct surgical specialty. Alongside these great men, Dr. Albert L. Rhoton Jr., revolutionized neurosurgical practice through his study of neuroanatomy and development of microsurgical technique in the second half of the 20th century. This review of the interactions and relationships between the Mayo brothers, Cushing, and Osler and their influences on Rhoton highlights the 100-year-long interconnectedness shared between these giants in the history of neurosurgery.

Early Australian neuroscientists and the tyranny of distance.

Australian neuroscientists at the turn of the twentieth century and in the succeeding decades faced formidable obstacles to communication and supply due to their geographical isolation from centers of learning in Europe and North America. Consequently, they had to spend significant periods of their lives overseas for training and experience. The careers of six pioneers-Laura Forster, James Wilson, Grafton Elliot Smith, Alfred Campbell, Raymond Dart, and John Eccles-are presented in the form of vignettes that address their lives and most enduring scientific contributions. All six were medically trained and, although they never collaborated directly with one another, they were linked by their neuroanatomical interests and by shared mentors, who included Nobelists Ramon y Cajal and Charles Sherrington. By the 1960s, as the so-called "tyranny of distance" was overcome by advances in communication and transport technology, local collaborative groups of neuroscientists emerged in several Australian university departments that built on the individual achievements of these pioneers. This in turn led to the establishment of the Australasian Neuroscience Society in 1981.

Art and Neurosurgery: The Importance of Medical Illustration.

Art in neurosurgery has been a critical part of the discipline for centuries. Numerous cultures, such as ancient India, China, and Egypt, and more contemporary scientists, such as Leonardo da Vinci, Max Brödel, and Norman Dott, have significantly contributed to medical illustration. Today, advancements in three-dimensional technology have allowed for the creation of detailed neuroanatomy models for surgical planning and education. Medical illustrations are also used for research and outcome documentation as they help visualize anatomy and surgical procedures. Its use in education, surgical planning, and navigation remains integral to the advancement of neurosurgery. This review demonstrates the invaluable contribution of art in neurosurgery and how it has enabled continuous progress in the field.