Accuracy of augmented reality-assisted vs template-guided apicoectomy - an ex vivo comparative study.

AIM: The aim of the present ex vivo study was to examine the accuracy of augmented reality-assisted apicoectomies (AR-A) versus template-guided apicoectomies (TG-A). MATERIALS AND METHODS: In total, 40 apicoectomies were performed in 10 cadaver pig mandibles. Every pig mandible underwent two AR-A and two TG-A in molar and premolar teeth. A crossed experimental design was applied. AR-A was performed using Microsoft HoloLens 2, and TG-A using SMOP software. Postoperative CBCT scans were superimposed with the presurgical planning data. The deviation between the virtually planned apicoectomy and the surgically performed apicoectomy was measured. The primary (angular deviation [degrees]) and secondary (depth deviation [mm]) outcome parameters were measured. RESULTS: Overall, 36 out of 40 apicoectomies could be included in the study. Regarding the primary outcome parameter (angular deviation), there was no significant difference between AR-A and TG-A. The mean values were 5.33 degrees (± 2.96 degrees) in the AR-A group, and 5.23 degrees (± 2.48 degrees) in the TG-A group. The secondary outcome parameter (depth deviation) showed no significant difference between the AR-A group of 0.27 mm (± 2.32 mm) and the TG-A group of 0.90 mm (± 1.84 mm). In this crossed experimental design, both techniques overshot the target depth in posterior sites, as opposed to not reaching the target depth in anterior sites (P < 0.001). CONCLUSION: Augmented reality (AR) technology has the potential to be introduced into apicoectomy surgery in case further development is implemented.

A Computational Perspective of the Role of the Thalamus in Cognition.

The thalamus has traditionally been considered as only a relay source of cortical inputs, with hierarchically organized cortical circuits serially transforming thalamic signals to cognitively relevant representations. Given the absence of local excitatory connections within the thalamus, the notion of thalamic relay seemed like a reasonable description over the past several decades. Recent advances in experimental approaches and theory provide a broader perspective on the role of the thalamus in cognitively relevant cortical computations and suggest that only a subset of thalamic circuit motifs fits the relay description. Here, we discuss this perspective and highlight the potential role for the thalamus, and specifically the mediodorsal (MD) nucleus, in the dynamic selection of cortical representations through a combination of intrinsic thalamic computations and output signals that change cortical network functional parameters. We suggest that through the contextual modulation of cortical computation, the thalamus and cortex jointly optimize the information and cost trade-off in an emergent fashion. We emphasize that coordinated experimental and theoretical efforts will provide a path to understanding the role of the thalamus in cognition, along with an understanding to augment cognitive capacity in health and disease.

High-frequency oscillations in human and monkey neocortex during the wake-sleep cycle.

Beta (ß)- and gamma (γ)-oscillations are present in different cortical areas and are thought to be inhibition-driven, but it is not known if these properties also apply to γ-oscillations in humans. Here, we analyze such oscillations in high-density microelectrode array recordings in human and monkey during the wake-sleep cycle. In these recordings, units were classified as excitatory and inhibitory cells. We find that γ-oscillations in human and ß-oscillations in monkey are characterized by a strong implication of inhibitory neurons, both in terms of their firing rate and their phasic firing with the oscillation cycle. The ß- and γ-waves systematically propagate across the array, with similar velocities, during both wake and sleep. However, only in slow-wave sleep (SWS) ß- and γ-oscillations are associated with highly coherent and functional interactions across several millimeters of the neocortex. This interaction is specifically pronounced between inhibitory cells. These results suggest that inhibitory cells are dominantly involved in the genesis of ß- and γ-oscillations, as well as in the organization of their large-scale coherence in the awake and sleeping brain. The highest oscillation coherence found during SWS suggests that fast oscillations implement a highly coherent reactivation of wake patterns that may support memory consolidation during SWS.

Spatiotemporal dynamics of neocortical excitation and inhibition during human sleep.

Intracranial recording is an important diagnostic method routinely used in a number of neurological monitoring scenarios. In recent years, advancements in such recordings have been extended to include unit activity of an ensemble of neurons. However, a detailed functional characterization of excitatory and inhibitory cells has not been attempted in human neocortex, particularly during the sleep state. Here, we report that such feature discrimination is possible from high-density recordings in the neocortex by using 2D multielectrode arrays. Successful separation of regular-spiking neurons (or bursting cells) from fast-spiking cells resulted in well-defined clusters that each showed unique intrinsic firing properties. The high density of the array, which allowed recording from a large number of cells (up to 90), helped us to identify apparent monosynaptic connections, confirming the excitatory and inhibitory nature of regular-spiking and fast-spiking cells, thus categorized as putative pyramidal cells and interneurons, respectively. Finally, we investigated the dynamics of correlations within each class. A marked exponential decay with distance was observed in the case of excitatory but not for inhibitory cells. Although the amplitude of that decline depended on the timescale at which the correlations were computed, the spatial constant did not. Furthermore, this spatial constant is compatible with the typical size of human columnar organization. These findings provide a detailed characterization of neuronal activity, functional connectivity at the microcircuit level, and the interplay of excitation and inhibition in the human neocortex.

Simultaneous chin onlay bone graft using elongated coronoid in the treatment of temporomandibular joint ankylosis.

Temporomandibular joint (TMJ) ankylosis is a disabling condition that causes problems in mastication, digestion, speech, appearance, and hygiene. Treatment goals are to restore the joint function, to improve facial appearance, and to reestablish harmony among them. To achieve these goals, various strategies have been reported as 1-stage or multistage protocols. We describe a novel method to augment the chin structure with elongated coronoid process of the mandible, which is a sequence of TMJ ankylosis. By this 1-stage treatment that includes gap arthroplasty with interpositional temporalis fascia graft and chin augmentation with autogenous bone graft (elongated coronoid), functional disability and facial deformity of the patient with TMJ ankylosis were improved simultaneously.

Intracranial meningioma at the site of a previous cranial penetrating trauma due to shrapnel.

Meningiomas are common and mostly benign intracranial tumors, which originate from arachnoid cells of the meninges, and account for approximately 25% of all primary intracranial tumors. Many external etiological factors have been described as etiology of meningioma in the literature, one of which is head trauma. However, trauma as a cause of meningioma remains a controversial subject. Here, a case of a patient with posttraumatic meningioma, who was wounded 25 years before, is presented. The assessment of the clinical characteristics of the patient and those reported in the literature seem to confirm that, in some cases, head trauma may be a factor contributing to the development of meningioma.

Comprehensive treatment and rehabilitation of a patient with maxillary arteriovenous malformation.

Arteriovenous malformations (AVMs) of the maxilla are rare and potentially life-threatening conditions that can pose a therapeutic dilemma. We reported the first case of maxillary AVM in a 15-year-old girl who was treated by marginal hemimaxillectomy including overlying palatal mucosa and immediate replantation of the segment after removing the AVM tissues and teeth and covering by a full-thickness pedicled temporal muscle flap rotated into the mouth. Then, this preserved bone underwent distraction osteogenesis and dental implant rehabilitation successfully. This method was previously used for the definitive treatment of mandibular AVMs, and in this case, we applied this method for the first time in maxillary AVMs. In conclusion, this surgical method may be considered as a safe, convenient, and effective treatment and reconstructive modality for such vascular malformations in the maxilla and restores function and symmetry of the jaws while obviating the need for bone harvesting and future major reconstructive operations.

Open Data In Neurophysiology: Advancements, Solutions & Challenges.

Across the life sciences, an ongoing effort over the last 50 years has made data and methods more reproducible and transparent. This openness has led to transformative insights and vastly accelerated scientific progress1,2. For example, structural biology3 and genomics4,5 have undertaken systematic collection and publication of protein sequences and structures over the past half-century, and these data have led to scientific breakthroughs that were unthinkable when data collection first began (e.g.6). We believe that neuroscience is poised to follow the same path, and that principles of open data and open science will transform our understanding of the nervous system in ways that are impossible to predict at the moment. To this end, new social structures along with active and open scientific communities are essential7 to facilitate and expand the still limited adoption of open science practices in our field8. Unified by shared values of openness, we set out to organize a symposium for Open Data in Neuroscience (ODIN) to strengthen our community and facilitate transformative neuroscience research at large. In this report, we share what we learned during this first ODIN event. We also lay out plans for how to grow this movement, document emerging conversations, and propose a path toward a better and more transparent science of tomorrow.

Pseudoaneurysm of the superficial temporal artery following penetrating trauma.

Pseudoaneurysm of superficial temporal artery (STA) is an uncommon complication of blunt and penetrating trauma. It accounts for only 1% of all traumatic aneurysms. Most pseudoaneurysms of STA present as a painless pulsating mass, and its diagnosis can be made with physical examination and ultrasound or computed tomography angiogram. The treatment of choice is ligation and resection. This report includes a review of the anatomy, histopathology, etiology, diagnosis, and treatment options for STA pseudoaneurysm and presents a very rare documented case of STA pseudoaneurysm following penetrating trauma that was presented to the hospital with severe hemorrhage, and surgical resection of the lesion mandated the external carotid artery to be exposed for proximal control.

Keratoameloblastoma, a very rare variant of ameloblastoma.

The keratoameloblastoma is a rare histologic variant of ameloblastoma. Fewer than 15 cases of keratoameloblastoma have been documented in the literature. We report a new case of keratoameloblastoma in a 21-year-old female patient with a unilocular radiolucent lesion between the roots of the right mandibular incisors. We describe the clinical, radiographic, and histopathologic features of this lesion along with a review on the characteristics of previous cases. We also discuss about classification and management of this lesion.

The antibacterial properties of composite resin containing nanosilver against Streptococcus mutans and Lactobacillus.

AIM: The aim was to evaluate the antibacterial properties of composite resin containing nanosilver against Streptococcus mutans (SM) and Lactobacillus (L). MATERIALS AND METHODS: Nanosilver was added to Z250 composite at 0.5 and 1% by weight. In order to confirm the homogenous distribution of the nanoparticles in the composite resin, SEM-EDX analysis was performed on one sample in each group. Z250 composite without nanosilver was used as control. Direct contact test was used to test the antibacterial properties of nanoparticle-loaded composites: 0.001 ml of 0.5 Mc Farland suspension of MS and L was placed on composite disks, and incubated for 1 hour in 5 to 10% CO2 incubator at 37°C. Samples were placed in 0.5 ml of sterile BHI broth and incubated for 2 hours in CO2 incubator. Afterwards, 0.001 ml liquid from each medium was distributed on blood agar plates and incubated for 48 hours in CO2 incubator. The numbers of bacterial colonies were counted visually. Data were analyzed using Two-way ANOVA and Tukey HSD test. Significance level was set at 0.05. RESULTS: Addition of nanosilver to composite resin had a significant effect on reduction of the number of SM and L colonies (p = 0.000). The antibacterial properties of composite resins are different depending on the concentration of nanosilver (p = 0.014). Tukey test indicated that increase in the concentration of nanosilver caused the increase in antibacterial properties of composite resin. CONCLUSION: Addition of silver nanoparticles to Z250 composite could significantly inhibit the growth of Streptococcus mutans and Lactobacillus on the surface of this composite. CLINICAL SIGNIFICANCE: The addition of nanosilver to Z250 composite could inhibit the growth of SM and L on the surface of the restoration and therefore prevent the occurrence of secondary caries.

Depression of cortical activity in humans by mild hypercapnia.

The effects of neural activity on cerebral hemodynamics underlie human brain imaging with functional magnetic resonance imaging and positron emission tomography. However, the threshold and characteristics of the converse effects, wherein the cerebral hemodynamic and metabolic milieu influence neural activity, remain unclear. We tested whether mild hypercapnia (5% CO2 ) decreases the magnetoencephalogram response to auditory pattern recognition and visual semantic tasks. Hypercapnia induced statistically significant decreases in event-related fields without affecting behavioral performance. Decreases were observed in early sensory components in both auditory and visual modalities as well as later cognitive components related to memory and language. Effects were distributed across cortical regions. Decreases were comparable in evoked versus spontaneous spectral power. Hypercapnia is commonly used with hemodynamic models to calibrate the blood oxygenation level-dependent response. Modifying model assumptions to incorporate the current findings produce a modest but measurable decrease in the estimated cerebral metabolic rate for oxygen change with activation. Because under normal conditions, low cerebral pH would arise when bloodflow is unable to keep pace with neuronal activity, the cortical depression observed here may reflect a homeostatic mechanism by which neuronal activity is adjusted to a level that can be sustained by available bloodflow. Animal studies suggest that these effects may be mediated by pH-modulating presynaptic adenosine receptors. Although the data is not clear, comparable changes in cortical pH to those induced here may occur during sleep apnea, sleep, and exercise. If so, these results suggest that such activities may in turn have generalized depressive effects on cortical activity.

Emergence of synchronous EEG spindles from asynchronous MEG spindles.

Sleep spindles are bursts of rhythmic 10-15 Hz activity, lasting ∼0.5-2 s, that occur during Stage 2 sleep. They are coherent across multiple cortical and thalamic locations in animals, and across scalp EEG sites in humans, suggesting simultaneous generation across the cortical mantle. However, reports of MEG spindles occurring without EEG spindles, and vice versa, are inconsistent with synchronous distributed generation. We objectively determined the frequency of MEG-only, EEG-only, and combined MEG-EEG spindles in high density recordings of natural sleep in humans. About 50% of MEG spindles occur without EEG spindles, but the converse is rare (∼15%). Compared to spindles that occur in MEG only, those that occur in both MEG and EEG have ∼1% more MEG coherence and ∼15% more MEG power, insufficient to account for the ∼55% increase in EEG power. However, these combined spindles involve ∼66% more MEG channels, especially over frontocentral cortex. Furthermore, when both MEG and EEG are involved in a given spindle, the MEG spindle begins ∼150 ms before the EEG spindle and ends ∼250 ms after. Our findings suggest that spindles begin in focal cortical locations which are better recorded with MEG gradiometers than referential EEG due to the biophysics of their propagation. For some spindles, only these regions remain active. For other spindles, these locations may recruit other areas over the next 200 ms, until a critical mass is achieved, including especially frontal cortex, resulting in activation of a diffuse and/or multifocal generator that is best recorded by referential EEG derivations due to their larger leadfields.

Magnetoencephalography demonstrates multiple asynchronous generators during human sleep spindles.

Sleep spindles are approximately 1 s bursts of 10-16 Hz activity that occur during stage 2 sleep. Spindles are highly synchronous across the cortex and thalamus in animals, and across the scalp in humans, implying correspondingly widespread and synchronized cortical generators. However, prior studies have noted occasional dissociations of the magnetoencephalogram (MEG) from the EEG during spindles, although detailed studies of this phenomenon have been lacking. We systematically compared high-density MEG and EEG recordings during naturally occurring spindles in healthy humans. As expected, EEG was highly coherent across the scalp, with consistent topography across spindles. In contrast, the simultaneously recorded MEG was not synchronous, but varied strongly in amplitude and phase across locations and spindles. Overall, average coherence between pairs of EEG sensors was approximately 0.7, whereas MEG coherence was approximately 0.3 during spindles. Whereas 2 principle components explained approximately 50% of EEG spindle variance, >15 were required for MEG. Each PCA component for MEG typically involved several widely distributed locations, which were relatively coherent with each other. These results show that, in contrast to current models based on animal experiments, multiple asynchronous neural generators are active during normal human sleep spindles and are visible to MEG. It is possible that these multiple sources may overlap sufficiently in different EEG sensors to appear synchronous. Alternatively, EEG recordings may reflect diffusely distributed synchronous generators that are less visible to MEG. An intriguing possibility is that MEG preferentially records from the focal core thalamocortical system during spindles, and EEG from the distributed matrix system.

Comparative power spectral analysis of simultaneous elecroencephalographic and magnetoencephalographic recordings in humans suggests non-resistive extracellular media.

The resistive or non-resistive nature of the extracellular space in the brain is still debated, and is an important issue for correctly modeling extracellular potentials. Here, we first show theoretically that if the medium is resistive, the frequency scaling should be the same for electroencephalogram (EEG) and magnetoencephalogram (MEG) signals at low frequencies (<10 Hz). To test this prediction, we analyzed the spectrum of simultaneous EEG and MEG measurements in four human subjects. The frequency scaling of EEG displays coherent variations across the brain, in general between 1/f and 1/f(2), and tends to be smaller in parietal/temporal regions. In a given region, although the variability of the frequency scaling exponent was higher for MEG compared to EEG, both signals consistently scale with a different exponent. In some cases, the scaling was similar, but only when the signal-to-noise ratio of the MEG was low. Several methods of noise correction for environmental and instrumental noise were tested, and they all increased the difference between EEG and MEG scaling. In conclusion, there is a significant difference in frequency scaling between EEG and MEG, which can be explained if the extracellular medium (including other layers such as dura matter and skull) is globally non-resistive.

Comparative power spectral analysis of simultaneous electroencephalographic and magnetoencephalographic recordings in humans suggests non-resistive extracellular media : EEG and MEG power spectra.

The resistive or non-resistive nature of the extracellular space in the brain is still debated, and is an important issue for correctly modeling extracellular potentials. Here, we first show theoretically that if the medium is resistive, the frequency scaling should be the same for electroencephalogram (EEG) and magnetoencephalogram (MEG) signals at low frequencies (<10 Hz). To test this prediction, we analyzed the spectrum of simultaneous EEG and MEG measurements in four human subjects. The frequency scaling of EEG displays coherent variations across the brain, in general between 1/f and 1/f (2). In a given region, although the variability of the frequency scaling exponent was higher for MEG compared to EEG, both signals consistently scale with a different exponent. In some cases, the scaling was similar, but only when the signal-to-noise ratio of the MEG was low. Several methods of noise correction for environmental and instrumental noise were tested, and they all increased the difference between EEG and MEG scaling. In conclusion, there is a significant difference in frequency scaling between EEG and MEG, which can be explained if the extracellular medium (including other layers such as dura matter and skull) is globally non-resistive.

Experimental validation of the influence of white matter anisotropy on the intracranial EEG forward solution.

Forward solutions with different levels of complexity are employed for localization of current generators, which are responsible for the electric and magnetic fields measured from the human brain. The influence of brain anisotropy on the forward solution is poorly understood. The goal of this study is to validate an anisotropic model for the intracranial electric forward solution by comparing with the directly measured 'gold standard'. Dipolar sources are created at known locations in the brain and intracranial electroencephalogram (EEG) is recorded simultaneously. Isotropic models with increasing level of complexity are generated along with anisotropic models based on Diffusion tensor imaging (DTI). A Finite Element Method based forward solution is calculated and validated using the measured data. Major findings are (1) An anisotropic model with a linear scaling between the eigenvalues of the electrical conductivity tensor and water self-diffusion tensor in brain tissue is validated. The greatest improvement was obtained when the stimulation site is close to a region of high anisotropy. The model with a global anisotropic ratio of 10:1 between the eigenvalues (parallel: tangential to the fiber direction) has the worst performance of all the anisotropic models. (2) Inclusion of cerebrospinal fluid as well as brain anisotropy in the forward model is necessary for an accurate description of the electric field inside the skull. The results indicate that an anisotropic model based on the DTI can be constructed non-invasively and shows an improved performance when compared to the isotropic models for the calculation of the intracranial EEG forward solution.

Ensemble inhibition and excitation in the human cortex: An Ising-model analysis with uncertainties.

The pairwise maximum entropy model, also known as the Ising model, has been widely used to analyze the collective activity of neurons. However, controversy persists in the literature about seemingly inconsistent findings, whose significance is unclear due to lack of reliable error estimates. We therefore develop a method for accurately estimating parameter uncertainty based on random walks in parameter space using adaptive Markov-chain Monte Carlo after the convergence of the main optimization algorithm. We apply our method to the activity patterns of excitatory and inhibitory neurons recorded with multielectrode arrays in the human temporal cortex during the wake-sleep cycle. Our analysis shows that the Ising model captures neuronal collective behavior much better than the independent model during wakefulness, light sleep, and deep sleep when both excitatory (E) and inhibitory (I) neurons are modeled; ignoring the inhibitory effects of I neurons dramatically overestimates synchrony among E neurons. Furthermore, information-theoretic measures reveal that the Ising model explains about 80-95% of the correlations, depending on sleep state and neuron type. Thermodynamic measures show signatures of criticality, although we take this with a grain of salt as it may be merely a reflection of long-range neural correlations.

Oral lipoma: Case report and review of literature.

Lipoma is a benign neoplasm that primarily affects the middle-aged individuals and has a rare oral cavity occurrence. Given its noninvasive behavior and low recurrence rate, surgical conservative management should be regarded as the best therapeutic option. This paper highlights two patients along with their improved conditions following the treatment.

Theoretical Principles of Multiscale Spatiotemporal Control of Neuronal Networks: A Complex Systems Perspective.

Success in the fine control of the nervous system depends on a deeper understanding of how neural circuits control behavior. There is, however, a wide gap between the components of neural circuits and behavior. We advance the idea that a suitable approach for narrowing this gap has to be based on a multiscale information-theoretic description of the system. We evaluate the possibility that brain-wide complex neural computations can be dissected into a hierarchy of computational motifs that rely on smaller circuit modules interacting at multiple scales. In doing so, we draw attention to the importance of formalizing the goals of stimulation in terms of neural computations so that the possible implementations are matched in scale to the underlying circuit modules.