Volume electron microscopy analysis of synapses in primary regions of the human cerebral cortex.

Functional and structural studies investigating macroscopic connectivity in the human cerebral cortex suggest that high-order associative regions exhibit greater connectivity compared to primary ones. However, the synaptic organization of these brain regions remains unexplored. In the present work, we conducted volume electron microscopy to investigate the synaptic organization of the human brain obtained at autopsy.

3D synaptic organization of layer III of the human anterior cingulate and temporopolar cortex.

The human anterior cingulate and temporopolar cortices have been proposed as highly connected nodes involved in high-order cognitive functions, but their synaptic organization is still basically unknown due to the difficulties involved in studying the human brain. Using Focused Ion Beam/Scanning Electron Microscopy (FIB/SEM) to study the synaptic organization of the human brain obtained with a short post-mortem delay allows excellent results to be obtained. We have used this technology to analyze layer III of the anterior cingulate cortex (Brodmann area 24) and the temporopolar cortex, including the temporal pole (Brodmann area 38 ventral and dorsal) and anterior middle temporal gyrus (Brodmann area 21).

Neuroanatomical and psychological considerations in temporal lobe epilepsy.

Temporal lobe epilepsy (TLE) is the most common form of focal epilepsy and is associated with a variety of structural and psychological alterations. Recently, there has been renewed interest in using brain tissue resected during epilepsy surgery, in particular 'non-epileptic' brain samples with normal histology that can be found alongside epileptic tissue in the same epileptic patients - with the aim being to study the normal human brain organization using a variety of methods. An important limitation is that different medical characteristics of the patients may modify the brain tissue.

Cortical synapses of the world's smallest mammal: An FIB/SEM study in the Etruscan shrew.

The main aim of the present study was to determine if synapses from the exceptionally small brain of the Etruscan shrew show any peculiarities compared to the much larger human brain. We analyzed the cortical synaptic density and a variety of structural characteristics of 7,239 3D reconstructed synapses, using using Focused Ion Beam/Scanning Electron Microscopy (FIB/SEM). We found that some of the general synaptic characteristics are remarkably similar to those found in the human cerebral cortex.

Emerging insights into synapse dysregulation in Alzheimer's disease.

Alzheimer's disease is the leading cause of dementia and a growing worldwide problem, with its incidence expected to increase in the coming years. Since synapse loss is a major pathology and is correlated with symptoms in Alzheimer's disease, synapse dysfunction and loss may underlie pathophysiology. In this context, this review focuses on emerging insights into synaptic changes at the ultrastructural level.

Three-Dimensional Synaptic Organization of Layer III of the Human Temporal Neocortex.

In the present study, we have used focused ion beam/scanning electron microscopy (FIB/SEM) to perform a study of the synaptic organization of layer III of Brodmann's area 21 in human tissue samples obtained from autopsies and biopsies. We analyzed the synaptic density, 3D spatial distribution, and type (asymmetric/symmetric), as well as the size and shape of each synaptic junction of 4945 synapses that were fully reconstructed in 3D. Significant differences in the mean synaptic density between autopsy and biopsy samples were found (0.

Three-dimensional analysis of synaptic organization in the hippocampal CA1 field in Alzheimer's disease.

Alzheimer's disease is the most common form of dementia, characterized by a persistent and progressive impairment of cognitive functions. Alzheimer's disease is typically associated with extracellular deposits of amyloid-β peptide and accumulation of abnormally phosphorylated tau protein inside neurons (amyloid-β and neurofibrillary pathologies). It has been proposed that these pathologies cause neuronal degeneration and synaptic alterations, which are thought to constitute the major neurobiological basis of cognitive dysfunction in Alzheimer's disease.

Three-dimensional synaptic organization of the human hippocampal CA1 field.

The hippocampal CA1 field integrates a wide variety of subcortical and cortical inputs, but its synaptic organization in humans is still unknown due to the difficulties involved studying the human brain via electron microscope techniques. However, we have shown that the 3D reconstruction method using Focused Ion Beam/Scanning Electron Microscopy (FIB/SEM) can be applied to study in detail the synaptic organization of the human brain obtained from autopsies, yielding excellent results. Using this technology, 24,752 synapses were fully reconstructed in CA1, revealing that most of them were excitatory, targeting dendritic spines and displaying a macular shape, regardless of the layer examined.

Area-Specific Synapse Structure in Branched Posterior Nucleus Axons Reveals a New Level of Complexity in Thalamocortical Networks.

Thalamocortical posterior nucleus (Po) axons innervating the vibrissal somatosensory (S1) and motor (MC) cortices are key links in the brain neuronal network that allows rodents to explore the environment whisking with their motile snout vibrissae. Here, using fine-scale high-end 3D electron microscopy, we demonstrate in adult male C57BL/6 wild-type mice marked differences between MC versus S1 Po synapses in (1) bouton and active zone size, (2) neurotransmitter vesicle pool size, (3) distribution of mitochondria around synapses, and (4) proportion of synapses established on dendritic spines and dendritic shafts. These differences are as large, or even more pronounced, than those between Po and ventro-posterior thalamic nucleus synapses in S1.

Subregional Density of Neurons, Neurofibrillary Tangles and Amyloid Plaques in the Hippocampus of Patients With Alzheimer's Disease.

A variety of anatomical alterations have been reported in the hippocampal formation of patients with Alzheimer's Disease (AD) and these alterations have been correlated with cognitive symptoms in the early stages of the disease. Major hallmarks in AD are the presence of paired helical filaments of tau protein (PHF) within neurons, also known as neurofibrillary tangles (NFTs), and aggregates of amyloid-β protein (Aβ) which form plaques in the extracellular space. Nevertheless, how the density of plaques and NFTs relate to the severity of cell loss and cognitive decline is not yet clear.

InTool Explorer: An Interactive Exploratory Analysis Tool for Versatile Visualizations of Neuroscientific Data.

The bottleneck for progress in many research areas within neuroscience has shifted from the data acquisition to the data analysis stages. In the present article, we propose a method named InTool Explorer that we have developed to perform interactive exploratory data analysis, focusing on neuroanatomy as an example of its utility. This tool is freely-available software that has been designed to facilitate the study of complex neuroscience data.

A Study of Amyloid-β and Phosphotau in Plaques and Neurons in the Hippocampus of Alzheimer's Disease Patients.

The main pathological hallmarks in Alzheimer's disease (AD) are the presence of extracellular amyloid plaques, primarily consisting of amyloid-β (Aβ) peptide, and the accumulation of paired helical filaments of hyperphosphorylated tau protein (PHF-Tau) within neurons. Since CA1 is one of the most affected regions in AD, mainly at early stages, we have performed a detailed analysis of the CA1 region from 11 AD patients (demented and clinically similar; Braak stages IV-VI) to better understand the possible relationship between the presence and distribution of different neurochemical types of Aβ plaques and PHF-Tau immunoreactive  (- ir)  neurons. Hence, we have examined hippocampal sections in confocal microscopy images from double and triple-immunostained sections, to study labeled plaques and PHF-Tau-ir neurons using specific software tools.

Voxel-Based Diagnosis of Alzheimer's Disease Using Classifier Ensembles.

Functional magnetic resonance imaging (fMRI) is one of the most promising noninvasive techniques for early Alzheimer's disease (AD) diagnosis. In this paper, we explore the application of different machine learning techniques to the classification of fMRI data for this purpose. The functional images were first preprocessed using the statistical parametric mapping toolbox to output individual maps of statistically activated voxels.

Reconstruction and Simulation of Neocortical Microcircuitry.

Unlabelled: We present a first-draft digital reconstruction of the microcircuitry of somatosensory cortex of juvenile rat. The reconstruction uses cellular and synaptic organizing principles to algorithmically reconstruct detailed anatomy and physiology from sparse experimental data. An objective anatomical method defines a neocortical volume of 0.

3D segmentations of neuronal nuclei from confocal microscope image stacks.

In this paper, we present an algorithm to create 3D segmentations of neuronal cells from stacks of previously segmented 2D images. The idea behind this proposal is to provide a general method to reconstruct 3D structures from 2D stacks, regardless of how these 2D stacks have been obtained. The algorithm not only reuses the information obtained in the 2D segmentation, but also attempts to correct some typical mistakes made by the 2D segmentation algorithms (for example, under segmentation of tightly-coupled clusters of cells).

Alterations of the microvascular network in the sclerotic hippocampus of patients with temporal lobe epilepsy.

Hippocampal sclerosis is the most frequent pathology encountered in resected tissue obtained from patients with temporal lobe epilepsy. The main hallmarks of hippocampal sclerosis are neuronal loss and gliosis. Several authors have proposed that an increase in blood vessel density is a further indicator, based on interpretations from staining of markers related to both blood-brain barrier disruption and the formation of new blood vessels.

Machine learning approach for the outcome prediction of temporal lobe epilepsy surgery.

Epilepsy surgery is effective in reducing both the number and frequency of seizures, particularly in temporal lobe epilepsy (TLE). Nevertheless, a significant proportion of these patients continue suffering seizures after surgery. Here we used a machine learning approach to predict the outcome of epilepsy surgery based on supervised classification data mining taking into account not only the common clinical variables, but also pathological and neuropsychological evaluations.

Synaptic changes in the dentate gyrus of APP/PS1 transgenic mice revealed by electron microscopy.

Numerous studies have reported widespread synaptic dysfunction or loss in early stages of both Alzheimer disease (AD) patients and animal models; it is widely accepted that synapse loss is the major structural correlate of cognitive dysfunction. Elucidation of the changes that may affect synapses is crucial for understanding the pathogenic mechanisms underlying AD, but ultrastructural preservation of human postmortem brain tissue is often poor, and classical methods for quantification of synapses have significant technical limitations. We previously observed changes in dendritic spines in plaque-free regions of the neuropil of the dentate gyrus of double-transgenic APP/PS1 (amyloid precursor protein/presenilin 1) model mice by light microscopy.

Facilitation of AMPA receptor synaptic delivery as a molecular mechanism for cognitive enhancement.

Cell adhesion molecules and downstream growth factor-dependent signaling are critical for brain development and synaptic plasticity, and they have been linked to cognitive function in adult animals. We have previously developed a mimetic peptide (FGL) from the neural cell adhesion molecule (NCAM) that enhances spatial learning and memory in rats. We have now investigated the cellular and molecular basis of this cognitive enhancement, using biochemical, morphological, electrophysiological, and behavioral analyses.

Espina: a tool for the automated segmentation and counting of synapses in large stacks of electron microscopy images.

The synapses in the cerebral cortex can be classified into two main types, Gray's type I and type II, which correspond to asymmetric (mostly glutamatergic excitatory) and symmetric (inhibitory GABAergic) synapses, respectively. Hence, the quantification and identification of their different types and the proportions in which they are found, is extraordinarily important in terms of brain function. The ideal approach to calculate the number of synapses per unit volume is to analyze 3D samples reconstructed from serial sections.

A stereological study of synapse number in the epileptic human hippocampus.

Hippocampal sclerosis is the most frequent pathology encountered in resected mesial temporal structures from patients with intractable temporal lobe epilepsy (TLE). Here, we have used stereological methods to compare the overall density of synapses and neurons between non-sclerotic and sclerotic hippocampal tissue obtained by surgical resection from patients with TLE. Specifically, we examined the possible changes in the subiculum and CA1, regions that seem to be critical for the development and/or maintenance of seizures in these patients.

Counting Synapses Using FIB/SEM Microscopy: A True Revolution for Ultrastructural Volume Reconstruction.

The advent of transmission electron microscopy (TEM) in the 1950s represented a fundamental step in the study of neuronal circuits. The application of this technique soon led to the realization that the number of synapses changes during the course of normal life, as well as under certain pathological or experimental circumstances. Since then, one of the main goals in neurosciences has been to define simple and accurate methods to estimate the magnitude of these changes.

Alterations of the microvascular network in sclerotic hippocampi from patients with epilepsy.

The main hallmarks of human hippocampal sclerosis are neuronal loss and gliosis; reductions in microvasculature labeling in the cornu Ammonis 1 in this condition have been detected using alkaline phosphatase histochemistry. To determine whether the reduction in alkaline phosphatase activity is coupled with a loss of blood vessels,we examined the volume fraction occupied by blood vessels in toluidine blue-stained hippocampal sections from 24 epilepsy patient resections (19 with hippocampal sclerosis, 5 without hippocampal sclerosis) and 5 normal autopsy controls. Light and electron microscopy and immunohistochemistry were used to determine the distribution of collagen Type IV in relation to the fine structure of the hippocampal microvascular network.