Integration of Feedforward and Feedback Information Streams in the Modular Architecture of Mouse Visual Cortex.

Radial cell columns are a hallmark feature of cortical architecture in many mammalian species. It has long been held, based on the lack of orientation columns, that such functional units are absent in rodent primary visual cortex (V1). These observations led to the view that rodent visual cortex has a fundamentally different network architecture than that of carnivores and primates. While columns may be lacking in rodent V1, we describe in this review that modular clusters of inputs to layer 1 and projection neurons in the layers below are prominent features of the mouse visual cortex. We propose that modules organize thalamocortical inputs, intracortical processing streams, and transthalamic communications that underlie distinct sensory and sensorimotor functions.

A dominant role for the beta 4 nicotinic receptor subunit in nicotinic modulation of glomerular microcircuits in the mouse olfactory bulb.

Nicotinic acetylcholine receptors (nAChRs) regulate information transfer across the main olfactory bulb by instituting a high-pass intensity filter allowing for the filtering out of weak inputs. Excitation-driven inhibition of the glomerular microcircuit via GABA release from periglomerular cells appears to underlie this effect of nAChR activation. The multiplicity of nAChR subtypes and cellular locations raises questions about their respective roles in mediating their effects on the glomerular output. In this study, we address this issue by targeting heteromeric nAChRs using receptor knockouts (KOs) for the two dominant nAChR ß-subunit genes known to be expressed in the central nervous system. KOs of the ß2-nAChR subunit did not affect nAChR currents from mitral cells (MCs) but attenuated those from the external tufted (ET) cells. In slices from these animals, activation of nAChRs still effectively inhibited excitatory postsynaptic currents (EPSCs) and firing on MCs evoked by the olfactory nerve (ON) stimulation, thereby indicating that the filter mechanism was intact. On the other hand, recordings from ß4-KOs showed that nAChR responses from MCs were abolished and those from ET cells were attenuated. Excitation-driven feedback was abolished as was the effect of nAChR activation on ON-evoked EPSCs. Experiments using calcium imaging showed that one possible consequence of the ß2-subunit activation might be to alter the time course of calcium transients in juxtaglomerular neurons suggesting a role for these receptors in calcium signaling. Our results indicate that nAChRs containing the ß4-subunit are critical in the filtering of odor inputs and play a determinant role in the cholinergic modulation of glomerular output. NEW & NOTEWORTHY In this study, using receptor gene knockouts we examine the relative contributions of heteromeric nAChR subtypes located on different cell types to this effect of receptor activation. Our results demonstrate that nAChRs containing the ß4-subunit activate MCs resulting in feedback inhibition from glomerular interneurons. This period of inhibition results in the selective filtering of weak odor inputs providing one mechanism by which nAChRs can enhance discrimination between two closely related odors.

3D Facial Effects of a Simulated Dental Build-up.

OBJECTIVE: The purpose of this study was to evaluate the 3D-stereophotogrammetry technique to detect differences in facial appearance after a simulated rehabilitation. MATERIALS AND METHODS: Eleven volunteers without tooth wear participated. A 3D-stereophotograph was taken in five different situations: resting position, teeth in occlusion, and teeth in occlusion with a 1 mm-, 3 mm- or 5 mm resin block between the first molars. Cephalometric measurements were performed on the 3D-stereophotographs using the software program Maxilim® (Medicim NV Mechelen, Belgium). Four anatomical parameters were analyzed: (1) Subnasale-Gnathion, (2) Subnasale-Stomion, (3) Stomion-Gnathion, and (4) Masseter right-Masseter left. A paired Student's T-test was applied to detect significant differences (p < 0.05). RESULTS: Statistically significant changes in facial appearance of the lower facial height were detected in all measured positions, teeth in occlusion, 1 mm-, 3 mm-, and 5 mm block (p < 0.05). For the main distance (Subnasale-Gnathion) the mean measured differences were, respectively, 3.2 mm; 5.2 mm; and 6.7 mm. CONCLUSIONS: With 3D-stereophotograph imaging technology, it was possible to detect changes in facial appearance after an artificial increase of vertical dimension of occlusion. This finding implies that reconstruction of loss of tooth substance may cause a visible change in facial appearance of the patient. CLINICAL SIGNIFICANCE: This study reveals a new 3D imaging technique that may be used for a better and more comprehensive treatment planning in patients with severe tooth wear. (J Esthet Restor Dent 28:397-404, 2016).

Modular horizontal network within mouse primary visual cortex.

Interactions between feedback connections from higher cortical areas and local horizontal connections within primary visual cortex (V1) were shown to play a role in contextual processing in different behavioral states. Layer 1 (L1) is an important part of the underlying network. This cell-sparse layer is a target of feedback and local inputs, and nexus for contacts onto apical dendrites of projection neurons in the layers below. Importantly, L1 is a site for coupling inputs from the outside world with internal information. To determine whether all of these circuit elements overlap in L1, we labeled the horizontal network within mouse V1 with anterograde and retrograde viral tracers. We found two types of local horizontal connections: short ones that were tangentially limited to the representation of the point image, and long ones which reached beyond the receptive field center, deep into its surround. The long connections were patchy and terminated preferentially in M2 muscarinic acetylcholine receptor-negative (M2-) interpatches. Anterogradely labeled inputs overlapped in M2-interpatches with apical dendrites of retrogradely labeled L2/3 and L5 cells, forming module-selective loops between topographically distant locations. Previous work showed that L1 of M2-interpatches receive inputs from the lateral posterior thalamic nucleus (LP) and from a feedback network from areas of the medial dorsal stream, including the secondary motor cortex. Together, these findings suggest that interactions in M2-interpatches play a role in processing visual inputs produced by object-and self-motion.

Non-CG DNA methylation and MeCP2 stabilize repeated tuning of long genes that distinguish closely related neuron types.

The extraordinary diversity of neuron types in the mammalian brain is delineated at the highest resolution by subtle gene expression differences that may require specialized molecular mechanisms to be maintained. Neurons uniquely express the longest genes in the genome and utilize neuron-enriched non-CG DNA methylation (mCA) together with the Rett syndrome protein, MeCP2, to control gene expression, but the function of these unique gene structures and machinery in regulating finely resolved neuron type-specific gene programs has not been explored. Here, we employ epigenomic and spatial transcriptomic analyses to discover a major role for mCA and MeCP2 in maintaining neuron type-specific gene programs at the finest scale of cellular resolution. We uncover differential susceptibility to MeCP2 loss in neuronal populations depending on global mCA levels and dissect methylation patterns and intragenic enhancer repression that drive overlapping and distinct gene regulation between neuron types. Strikingly, we show that mCA and MeCP2 regulate genes that are repeatedly tuned to differentiate neuron types at the highest cellular resolution, including spatially resolved, vision-dependent gene programs in the visual cortex. These repeatedly tuned genes display genomic characteristics, including long length, numerous intragenic enhancers, and enrichment for mCA, that predispose them to regulation by MeCP2. Thus, long gene regulation by the MeCP2 pathway maintains differential gene expression between closely-related neurons to facilitate the exceptional cellular diversity in the complex mammalian brain.

Nicotinic receptor-mediated filtering of mitral cell responses to olfactory nerve inputs involves the α3ß4 subtype.

Acetylcholine (ACh) plays a major role in the processing of sensory inputs. Cholinergic input to the mammalian olfactory bulb modulates odor discrimination and perceptual learning by mechanisms that have yet to be elucidated. We have used the mouse olfactory bulb to examine the role of nicotinic ACh receptors (nAChRs) in regulating the responses of mitral cells (MCs), the output neurons of the olfactory bulb, to olfactory nerve input. We show that ACh activates α3ß4* nAChRs (* denotes the possible presence of other subunits) on MCs, leading to their excitation. Despite depolarizing MCs directly, the net effect of nAChR activation is to suppress olfactory nerve-evoked responses in these cells via activity-dependent feedback GABAergic mechanisms. Our results indicate that nAChRs gate incoming olfactory nerve input wherein weak input stimuli are filtered out, whereas strong stimuli are transmitted via the MCs. Based on our observations, we provide a mechanistic model for the sharpening of MC receptive fields by nAChRs, which could aid in odor discrimination and perceptual learning.

Nicotinic receptors modulate olfactory bulb external tufted cells via an excitation-dependent inhibitory mechanism.

Olfactory bulb (OB) glomeruli, the initial sites of synaptic processing of odor information, exhibit high levels of nicotinic acetylcholine receptor (nAChR) expression and receive strong cholinergic input from the basal forebrain. The role of glomerular nAChRs in olfactory processing, however, remains to be elucidated. External tufted (ET) cells are a major source of excitation in the glomerulus and an important component of OB physiology. We have examined the role of nAChRs in modulating ET cell activity using whole-cell electrophysiology in mouse OB slices. We show here that the activation of glomerular nAChRs leads to direct ET cell excitation, as well as an increase in the frequency of spontaneous postsynaptic GABAergic currents. ß2-containing nAChRs, likely the α4ß2*-nAChR subtype (* represents the possible presence of other subunits), were significant contributors to these effects. The nAChR-mediated increase in spontaneous postsynaptic GABAergic current frequency on ET cells was, for the most part, dependent on glutamate receptor activation, thus implicating a role for excitation-dependent inhibition within the glomerulus. ß2-containing nAChRs also regulate the frequency of miniature inhibitory postsynaptic currents on ET cells, implying nicotinic modulation of dendrodendritic signaling between ET and periglomerular cells. Our data also indicate that nAChR activation does not affect spontaneous or evoked transmission at the olfactory nerve-to-ET cell synapse. The results from this study suggest that ET cells, along with mitral cells, play an important role in the nicotinic modulation of glomerular inhibition.

Hierarchical and nonhierarchical features of the mouse visual cortical network.

Neocortical computations underlying vision are performed by a distributed network of functionally specialized areas. Mouse visual cortex, a dense interareal network that exhibits hierarchical properties, comprises subnetworks interconnecting distinct processing streams. To determine the layout of the mouse visual hierarchy, we have evaluated the laminar patterns formed by interareal axonal projections originating in each of ten areas. Reciprocally connected pairs of areas exhibit feedforward/feedback relationships consistent with a hierarchical organization. Beta regression analyses, which estimate a continuous hierarchical distance measure, indicate that the network comprises multiple nonhierarchical circuits embedded in a hierarchical organization of overlapping levels. Single-unit recordings in anaesthetized mice show that receptive field sizes are generally consistent with the hierarchy, with the ventral stream exhibiting a stricter hierarchy than the dorsal stream. Together, the results provide an anatomical metric for hierarchical distance, and reveal both hierarchical and nonhierarchical motifs in mouse visual cortex.

Spatial Clustering of Inhibition in Mouse Primary Visual Cortex.

Whether mouse visual cortex contains orderly feature maps is debated. The overlapping pattern of geniculocortical inputs with M2 muscarinic acetylcholine receptor-rich patches in layer 1 (L1) suggests a non-random architecture. Here, we found that L1 inputs from the lateral posterior thalamus (LP) avoid patches and target interpatches. Channelrhodopsin-2-assisted mapping of excitatory postsynaptic currents (EPSCs) in L2/3 shows that the relative excitation of parvalbumin-expressing interneurons (PVs) and pyramidal neurons (PNs) by dLGN, LP, and cortical feedback is distinct and depends on whether the neurons reside in clusters aligned with patches or interpatches. Paired recordings from PVs and PNs show that unitary inhibitory postsynaptic currents (uIPSCs) are larger in interpatches than in patches. The spatial clustering of inhibition is matched by dense clustering of PV terminals in interpatches. The results show that the excitation/inhibition balance across V1 is organized into patch and interpatch subnetworks, which receive distinct long-range inputs and are specialized for the processing of distinct spatiotemporal features.

Feline calicivirus strains isolated in Italy.

Feline Calicivirus (FCV) has been recognised as major oral and respiratory pathogen of cats. The high correlation among the field viruses and FCV-F9 serotype has represented the immunological bases for the employ of FCV-F9 serotype as a vaccine for calicivirosis in cats. The aim of this paper was to evaluate, by in vitro neutralization assays, the antigenic correlation among the vaccine F9 and FCV field strains isolated in Sicily (Italy) from cats showing clinical forms referable to calicivirus infection. The results confirm the low correlation between FCV-F9 strain and calicivirus strains spread in the feline population.

Serological survey on Aujeszky's disease, swine influenza and porcine reproductive and respiratory syndrome virus infections in Italian pigs.

Aujeszky's disease (AD), Porcine reproductive and respiratory syndrome (PRRS) and Swine influenza (SI) are among the principal agents of respiratory diseases of pigs. The aim of the study was to determine the prevalence of antibodies to SHV-1, PRRSV and SIV in pigs reared in Sicily. An Enzyme Linked Immunosorbent Assay for the glicoprotein gE of pseudorabies virus, for PRRSV and for SIV was performed. Antibodies against gE of SHV-1 were detected in 171 serum samples (14.6%), whereas PRRSV antibodies occurred at a higher frequency than SHV-1 with 289 (31.1%) samples being positive. The seroprevalence of SIV was found to be 33.3%. This study demonstrated the circulation of ADV, PRRSV and SIV viruses in Sicilian swine population. This is the first report on this topics in Sicily.

Accuracy of Three Software Applications for Breast Volume Calculations from Three-Dimensional Surface Images.

BACKGROUND: Knowing breast volumes before certain surgeries helps the surgeon to obtain breast symmetry. Calculating breast volumes from three-dimensional surface images is possible with specialized software applications. However, limited data exist concerning the accuracy of such volume calculations. The purpose of this study was to investigate the accuracy of breast volume calculations performed with the 3D BreAST, 3dMD Vultus, and VECTRA software applications. METHODS: Twenty-six subjects who underwent 44 mastectomies were enrolled. Preoperative three-dimensional surface images were acquired with a VECTRA-XT stereophotogrammetry device. Breast volumes were calculated from these images with the three software applications. The mastectomy specimens were weighed to derive their actual volume and compared with the software calculations. RESULTS: For all three methods, a positive correlation between the breast volume and absolute calculation error was found (p < 0.001), but not for the errors as a percentage of the breast volume (p = 0.17, p = 0.80, and p = 0.42). The 3D BreAST, 3dMD Vultus, and VECTRA applications provided mean volume calculation errors of 21, 186, and -32 ml (p = 0.27, p < 0.001, and p = 0.14) or 2 ± 25, 48 ± 26, and -6 ± 27 percent of the breast volume (p = 0.67, p < 0.001, and p = 0.16), respectively. CONCLUSIONS: Despite that two applications calculated accurate mean breast volumes, all applications showed a high standard deviation in terms of the percentage of the breast volume. Therefore, the usefulness of absolute breast volume calculations from three-dimensional surface images seems limited. CLINICAL QUESTION/LEVEL OF EVIDENCE: Diagnostic, II.

Virtual Incision Pattern Planning using Three-Dimensional Images for Optimization of Syndactyly Surgery.

Syndactyly is a congenital condition characterized by fusion of the fingers. If not treated correctly during infancy, syndactyly may hinder the normal development of hand function. Many surgical techniques have been developed, with the main goal to create a functional hand with the smallest number of operative corrections. Therefore, exact preoperative planning of the reconstructive procedure is essential. An imaging method commonly used for preoperative planning is 3-dimensional (3D) surface imaging. The goal of this study was to implement the use of this technique in hand surgery, by designing a virtual planning tool for a desyndactylization procedure based on 3D hand images. A 3D image of a silicon syndactyly model was made on which the incision pattern was virtually designed. A surgical template of this pattern was printed, placed onto the silicon model and delineated. The accuracy of the transfer from the virtual delineation toward the real delineation was calculated, resulting in a mean difference of 0.82 mm. This first step indicates that by using 3D images, a virtual incision pattern can be created and transferred back onto the patient successfully in an easy and accurate way by using a template. Thereafter, 3D hand images of 3 syndactyly patients were made, and individual virtual incision patterns were created. Each pattern was transferred onto the patient by using a 3D printed template. The resulting incision pattern needed minor modifications by the surgeon before the surgery was performed. Further research and validation are necessary to develop the virtual planning of desyndactylization procedures.

A Laminar Organization for Selective Cortico-Cortical Communication.

The neocortex is central to mammalian cognitive ability, playing critical roles in sensory perception, motor skills and executive function. This thin, layered structure comprises distinct, functionally specialized areas that communicate with each other through the axons of pyramidal neurons. For the hundreds of such cortico-cortical pathways to underlie diverse functions, their cellular and synaptic architectures must differ so that they result in distinct computations at the target projection neurons. In what ways do these pathways differ? By originating and terminating in different laminae, and by selectively targeting specific populations of excitatory and inhibitory neurons, these "interareal" pathways can differentially control the timing and strength of synaptic inputs onto individual neurons, resulting in layer-specific computations. Due to the rapid development in transgenic techniques, the mouse has emerged as a powerful mammalian model for understanding the rules by which cortical circuits organize and function. Here we review our understanding of how cortical lamination constrains long-range communication in the mammalian brain, with an emphasis on the mouse visual cortical network. We discuss the laminar architecture underlying interareal communication, the role of neocortical layers in organizing the balance of excitatory and inhibitory actions, and highlight the structure and function of layer 1 in mouse visual cortex.

Single-Step Resection of an Intraosseous Meningioma and Cranial Reconstruction: Technical Note.

OBJECTIVE: Simultaneous tumor resection and cranial reconstruction can be a challenging task. Surgical navigation is an indispensable tool in making this single-step procedure possible. In this technical note, we describe a new technique for this procedure to ensure a precise resection and optimal fit of the implant in a patient with an intraosseous meningioma. METHODS: We generated a 3-dimensional (3D) model of the patient's skull based on a computed tomography scan and created a digital "resection line" object using 3D Studio Max 2016 software. Based on this object, the patient-specific implant was generated and printed with a 3D printer. Before surgery, the digital object was transferred to the neuronavigation system to enable a navigated resection of the lesion to ensure maximum precision. During surgery, the craniotomy was performed, and the custom-made implant was fitted in a single step. RESULTS: The planned resection was achieved, and the implant could be fitted without need for further adjustments to the resection border. CONCLUSIONS: We provide a simple technique to digitally define a planned resection site and create a custom-made implant using specialized software and 3D printing to enable single-step resection of a skull lesion and cranial reconstruction, thereby reducing surgical time and costs and ensuring a good cosmetic result.

3D stereophotogrammetry in upper-extremity lymphedema: An accurate diagnostic method.

BACKGROUND: Upper-extremity lymphedema is a frequent complication in patients treated for breast cancer. Current diagnostic methods for the upper-extremity volume measurements are cumbersome or time consuming. The purpose of this study was to assess the validity and reliability of three-dimensional (3D) stereophotogrammetry for volume measurements in patients with upper-extremity lymphedema. METHOD: Patients with unilateral upper-extremity lymphedema were included. The water displacement volume measurement of both arms was performed using a standardized method. In addition, 3D stereophotogrammetry volume measurements were conducted. RESULTS: Eleven patients (22 arms) were included. The mean volumes obtained by 3D stereophotogrammetry and water displacement show a high correlation, with a Pearson's correlation coefficient of 0.99 (p = 0.01). The variance calculated by 3D stereophotogrammetry measurements (205 mL) was statistically significant less than that obtained via water displacement measurements (1540 mL) (p < 0.001). CONCLUSION: 3D stereophotogrammetry is an accurate method for measuring upper-extremity volume in patients with lymphedema and gives a lower variance value compared to that of the water displacement measurements. We recommend the use of this method in the diagnosis and follow-up of patients with lymphedema.

Accuracy of virtually 3D planned resection templates in mandibular reconstruction.

OBJECTIVE: Since reconstruction of composite defects in the head and neck region is a challenging and demanding problem for head and neck surgeons, surgical aids have been sought for decades. The purpose of this study was to evaluate the accuracy of prefabricated surgical resection templates used in mandibular segmental resections in comparison to the virtual surgical plan. MATERIALS AND METHODS: A prospective study was performed in 11 consecutive patients, with a primary T4 oral squamous cell carcinoma or osteoradionecrosis of the mandible. Preoperatively, a CBCT scan was acquired to delineate the size and extension of tumor invasion; a virtual patient-specific resection template was designed based on this information. Intraoperatively, the resection template was positioned on the mandible and secured using four fixation screws. Postoperatively, a CBCT scan was acquired. This scan was superimposed on the preoperative scan. Positioning of the resection template and inclination of the resection planes were evaluated on the virtual head model. In order to test the interobserver reliability of these new measurement methods, two different observers executed all measurements. RESULTS: The mean shift of the proximal resection templates was 3.76 mm (standard deviation [SD] 3.10 mm). For the distal resection templates, the mean shift was 3.06 mm (SD 1.57 mm) with no significant interobserver difference (ICC = 0.99). An absolute mean deviation of 8.5° (SD 5.3°) was found for the proximal resection angle and 10.4° (SD 5.0°) for the distal resection angle. Again, no significant interobserver differences were found (ICC = 0.98). CONCLUSION: The resection templates used in this study proved reasonably accurate. Although the concept of virtual surgical planning aids significantly in mandibular reconstruction with microvascular free flaps, further improvement of resection accuracy is necessary for further improvement of reconstruction accuracy.

Modularity in the Organization of Mouse Primary Visual Cortex.

Layer 1 (L1) of primary visual cortex (V1) is the target of projections from many brain regions outside of V1. We found that inputs to the non-columnar mouse V1 from the dorsal lateral geniculate nucleus and feedback projections from multiple higher cortical areas to L1 are patchy. The patches are matched to a pattern of M2 muscarinic acetylcholine receptor expression at fixed locations of mouse, rat, and monkey V1. Neurons in L2/3 aligned with M2-rich patches have high spatial acuity, whereas cells in M2-poor zones exhibited high temporal acuity. Together M2+ and M2- zones form constant-size domains that are repeated across V1. Domains map subregions of the receptive field, such that multiple copies are contained within the point image. The results suggest that the modular network in mouse V1 selects spatiotemporally distinct clusters of neurons within the point image for top-down control and differential routing of inputs to cortical streams.

Engineering strontium binding affinity in an EF-hand motif: a quantum chemical and molecular dynamics study.

Proteins with the ability to specifically bind strontium would potentially be of great use in the field of nuclear waste management. Unfortunately, no such peptides or proteins are known -- indeed, it is uncertain whether they exist under natural conditions due to low environmental concentrations of strontium. To investigate the possibility of devising such molecules, one of us (CV), in a previous experimental study, proposed starting from an EF-hand motif of the protein calmodulin and mutating some residues to change the motif's specificity for calcium into one for strontium. In this paper, which represents a theoretical complement to the experimental work, we analyzed small-molecule crystallographic structures and performed quantum chemical calculations to identify possible mutations. We then constructed seven mutant sequences of the EF-hand motif and analyzed their dynamical and binding behaviors using molecular dynamics simulations and free-energy calculations (using the MM/PBSA method). As a result of these analyzes we were able to isolate some characteristics that could lead to mutant peptides with enhanced strontium affinity.

Serological analysis and identification of feline calicivirus strains isolated in Sicily.

The isolation and characterization of calicivirus strains from symptomatic cats are reported. The correlations between the feline calicivirus strains isolated and the vaccinal strain FCV F9 were investigated by a virus-neutralization test, suggesting a strong antigenic variability.