Functional brain mapping: overview of techniques and their application to neurosurgery

Cell therapy for neurological disorders

Cell therapies for neurological disorders are entering the clinic and present unique challenges and opportunities compared with conventional medicines. They have the potential to replace damaged nervous tissue and integrate into the brain or spinal cord to produce functional effects for the lifetime of the patient, which could revolutionize the way clinicians treat debilitating neurological disorders. The major challenge has been cell sourcing, which historically relied mainly on fetal brain tissue. This has largely been overcome with the advent of pluripotent stem cell technology and the ability to make almost any cell of the nervous system at scale. Furthermore, advances in gene editing now allow the generation of genetically modified cells that could perform better and evade the immune system. With all the remarkable new approaches to treat neurological disorders, we take a critical look at the state of current clinical trials and how challenges may be overcome with the evolving technology and innovation occurring in the stem cell field.

Transcranial magnetic stimulation and magnetoencephalography are feasible alternatives to invasive methods in optimizing responsive neurostimulation device placement

Responsive neurostimulation (RNS) is a treatment option for patients with refractory epilepsy when surgical resection is not possible due to overlap of the irritative zone and eloquent cortex. Presurgical evaluations for RNS placement typically rely on invasive methods. This study investigated the potential of transcranial magnetic stimulation (TMS) and magnetoencephalography (MEG) to provide key presurgical information non-invasively. We hypothesized that these non-invasive methods may assist in optimizing RNS placement by providing useful information for seizure localization by MEG and eloquent cortex mapping by TMS. A retrospective chart review identified nine patients who underwent RNS placement (mean age = 20.4 years [SD = 5.6], two-thirds were female). Characterization of the irritative zone using MEG was successful in eight of nine patients. Non-invasive mapping of relevant eloquent cortex was attempted in all patients. TMS was successful in eight of nine patients, and MEG was successful in two of six patients. Importantly, patients mapped with non-invasive modalities experienced an average seizure reduction of 77 % at their most recent clinic visit, compared to 75 % seizure reduction in those with invasive evaluations, indicating appropriate RNS placement. These data demonstrate that TMS and MEG can provide key information for RNS and may be feasible alternatives to invasive methods for assisting in decision making regarding RNS placement. Non-invasive methods for determining RNS placement have a high rate of success when data from multiple non-invasive modalities converge and can inform more accurate placement of intracranial electrodes prior to RNS placement or mitigate their need.

Review of the Brain's Behaviour after Injury and Disease for Its Application in an Agent-Based Model (ABM)

The brain is the most complex organ in the human body and, as such, its study entails great challenges (methodological, theoretical, etc.). Nonetheless, there is a remarkable amount of studies about the consequences of pathological conditions on its development and functioning. This bibliographic review aims to cover mostly findings related to changes in the physical distribution of neurons and their connections-the connectome-both structural and functional, as well as their modelling approaches. It does not intend to offer an extensive description of all conditions affecting the brain; rather, it presents the most common ones. Thus, here, we highlight the need for accurate brain modelling that can subsequently be used to understand brain function and be applied to diagnose, track, and simulate treatments for the most prevalent pathologies affecting the brain.

Application of a Standardized Treatment Paradigm as a Strategy to Achieve Optimal Onco-Functional Balance in Glioma Surgery

BACKGROUND

Gliomas, characterized by their invasive persistence and tendency to affect critical brain regions, pose a challenge in surgical resection due to the risk of neurological deficits. This study focuses on a personalized approach to achieving an optimal onco-functional balance in glioma resections, emphasizing maximal tumor removal while preserving the quality of life.

METHODS

A retrospective analysis of 57 awake surgical resections of gliomas at the National University Hospital, Singapore, was conducted. The inclusion criteria were based on diagnosis, functional boundaries determined by direct electrical stimulation, preoperative Karnofsky Performance Status score, and absence of multifocal disease on MRI. The treatment approach included comprehensive neuropsychological evaluation, determination of suitability for awake surgery, and standard asleep-awake-asleep anesthesia protocol. Tumor resection techniques and postoperative care were systematically followed.

RESULTS

The study included 53 patients (55.5% male, average age 39 years), predominantly right-handed. Over half reported seizures as their chief complaint. Tumors were mostly low-grade gliomas. Positive mapping of the primary motor cortex was conducted in all cases, with awake surgery completed in 77.2% of cases. New neurological deficits were observed in 26.3% of patients at 1 month after operation; most showed significant improvement at 6 months.

CONCLUSION

The standardized treatment paradigm effectively achieved an optimal onco-functional balance in glioma patients. While some patients experienced neurological deficits postoperatively, the majority recovered to their preoperative baseline within 3 months. The approach prioritizes patient empowerment and customized utilization of functional mapping techniques, considering the challenge of preserving diverse languages in a multilingual patient population.

Differentiation between Anterior and Posterior Roots Using Compound Muscle Action Potential in Intradural Extramedullary Spinal Tumor Surgery

This study aims to determine the cutoff values for the compound muscle action potential (CMAP) stimulus in anatomically identified anterior (motor nerve) and posterior roots (sensory nerve) during cervical intradural extramedullary tumor surgery. The connection between CMAP data from nerve roots and postoperative neurological symptoms in thoracolumbar tumors was compared with data from cervical lesions. The participants of the study included 22 patients with intradural extramedullary spinal tumors (116 nerve roots). The lowest stimulation intensity to the nerve root at which muscle contraction occurs was defined as the minimal activation intensity (MAI) in the CMAP. In cervical tumors, the MAI was measured after differentiating between the anterior and posterior roots based on the anatomical placement of the dentate ligament and nerve roots. The MAIs for 20 anterior roots in eight cervical tumors were between 0.1 and 0.3 mA, whereas those for 19 posterior roots were between 0.4 and 2.0 mA. The cutoff was <0.4 mA for both the anterior and posterior roots, and sensitivity and specificity were both 100%. In thoracolumbar tumors, the nerve root was severed in 12 of 14 cases. All MAIs were determined to be at the dorsal roots as their scores were higher than the cutoff and did not indicate motor deficits. The MAIs of the anatomically identified anterior and posterior root CMAPs were found to have a cutoff value of <0.4 mA in the cervical lesions. Similar MAI cutoffs were also applicable to thoracolumbar lesions. Thus, CMAP may be useful in detecting anterior and posterior roots in spinal tumor surgery.

Investigation of the neural correlation with task performance and its effect on cognitive load level classification

Electroencephalogram (EEG)-based cognitive load assessment is now an important assignment in psychological research. This type of research work is conducted by providing some mental task to the participants and their responses are counted through their EEG signal. In general assumption, it is considered that during different tasks, the cognitive workload is increased. This paper has investigated this specific idea and showed that the conventional hypothesis is not correct always. This paper showed that cognitive load can be varied according to the performance of the participants. In this paper, EEG data of 36 participants are taken against their resting and task (mental arithmetic) conditions. The features of the signal were extracted using the empirical mode decomposition (EMD) method and classified using the support vector machine (SVM) model. Based on the classification accuracy, some hypotheses are built upon the impact of subjects' performance on cognitive load. Based on some statistical consideration and graphical justification, it has been shown how the hypotheses are valid. This result will help to construct the machine learning-based model in predicting the cognitive load assessment more appropriately in a subject-independent approach.

Comparison of Short-Term Surgery Outcomes and Clinical Characteristics Between Elderly and Non-Elderly Patients with Middle Third Parasagittal and Parafalcine Meningiomas

Purpose

This study aims to compare the short-term surgery outcomes of the resection of meningiomas and clinical characteristics between elderly and non-elderly patients.

Patients and Methods

This retrospective study included patients who underwent a resection of middle third parasagittal and parafalcine meningiomas between January 2011 and December 2020. All lesions arise from the middle third of the parafalcine or infiltrate superior sagittal sinus (SSS). The clinical characteristics studied included neurological deficit, peritumoral brain edema (PTBE), SSS invasion, tumor size, and symptoms; perioperative complications, and short-term surgery outcomes including neurological deficit, operative blood loss, postoperative hospitalization duration, and WHO classification were compared.

Results

A total of 43 elderly patients and 63 non-elderly patients were included. Compared with non-elderly patients, elderly patients had larger lesions (P = 0.013) and presented with a larger PTBE (P = 0.019). SSS blockage was identified in 28.57% of elderly patients and 19.57% of non-elderly patients. Compared with non-elderly patients, elderly patients tended to suffer from more aggressive lesions (WHO II/III meningioma 6 vs 3, P = 0.154) and presented with longer postoperative hospital stays (17.25 ± 5.8 vs 13.50 ± 3.8, P = 0.009); conversely, while the non-elderly patients experienced more blood loss (P = 0.022) and had more perioperative reoperations (3 vs 1). No significant difference in neurological deficit was detected between the two groups (P = 0.97). After total tumor resection, patients with neurological deficits in both groups can recover during the follow-up period.

Conclusion

Among the 106 patients with middle third parasagittal and falx meningiomas in our hospital, elderly patients had larger lesions, presented with more severe PTBE, and had longer postoperative hospital stays than younger patients. Conversely, younger patients had more blood loss and serious complications than elderly patients. Postoperative neurological dysfunction in elderly patients was similar to that in middle-aged and young patients.

Resection of high-grade glioma involving language areas assisted by multimodal techniques under general anesthesia: a retrospective study

BACKGROUND

Multimodal techniques-assisted resection of glioma under general anesthesia (GA) has been shown to achieve similar clinical outcomes as awake craniotomy (AC) in some studies. In this study, we aim to validate the use of multimodal techniques can achieve the maximal safe resection of high-grade glioma involving language areas (HGILAs) under GA.

METHODS

HGILAs cases were reviewed and collected between January 2009 and December 2020 in our center. Patients were separated into multimodal group (using neuronavigation, intraoperative MRI combined with direct electrical stimulation [DES] and neuromonitoring [IONM]) and conventional group (neuronavigation alone) and clinical outcomes were compared between groups. Studies of HGILAs were reviewed systematically and the meta-analysis results of previous (GA or AC) studies were compared with our results.

RESULTS

Finally, there were 263 patients in multimodal group and 137 patients in conventional group. Compared to the conventional group, the multimodal group achieved the higher median EOR (100% versus 94.32%, P < 0.001) and rate of gross total resection (GTR) (73.8% versus 36.5%, P < 0.001) and the lower incidence of permanent language deficit (PLD) (9.5% versus 19.7%, P = 0.004). The multimodal group achieved the longer median PFS (16.8 versus 10.3 months, P < 0.001) and OS (23.7 versus 15.7 months, P < 0.001) than the conventional group. The multimodal group achieved a higher rate of GTR than the cohorts in previous multimodal studies under GA and AC (73.8% versus 55.7% [95%CI 32.0-79.3%] versus 53.4% [35.5-71.2%]). The multimodal group had a lower incidence of PLD than the cohorts in previous multimodal studies under GA (9.5% versus 14.0% [5.8-22.1%]) and our incidence of PLD was a little higher than that of previous multimodal studies under AC (9.5% versus 7.5% [3.7-11.2%]). Our multimodal group also achieved a relative longer survival than previous studies.

CONCLUSIONS

Surgery assisted by multimodal techniques can achieve maximal safe resection for HGILAs under GA. Further prospective studies are needed to compare GA with AC for HGILAs.

Functional imaging of the exposed brain

When the brain is exposed, such as after a craniotomy in neurosurgical procedures, we are provided with the unique opportunity for real-time imaging of brain functionality. Real-time functional maps of the exposed brain are vital to ensuring safe and effective navigation during these neurosurgical procedures. However, current neurosurgical practice has yet to fully harness this potential as it pre-dominantly relies on inherently limited techniques such as electrical stimulation to provide functional feedback to guide surgical decision-making. A wealth of especially experimental imaging techniques show unique potential to improve intra-operative decision-making and neurosurgical safety, and as an added bonus, improve our fundamental neuroscientific understanding of human brain function. In this review we compare and contrast close to twenty candidate imaging techniques based on their underlying biological substrate, technical characteristics and ability to meet clinical constraints such as compatibility with surgical workflow. Our review gives insight into the interplay between technical parameters such sampling method, data rate and a technique's real-time imaging potential in the operating room. By the end of the review, the reader will understand why new, real-time volumetric imaging techniques such as functional Ultrasound (fUS) and functional Photoacoustic Computed Tomography (fPACT) hold great clinical potential for procedures in especially highly eloquent areas, despite the higher data rates involved. Finally, we will highlight the neuroscientific perspective on the exposed brain. While different neurosurgical procedures ask for different functional maps to navigate surgical territories, neuroscience potentially benefits from all these maps. In the surgical context we can uniquely combine healthy volunteer studies, lesion studies and even reversible lesion studies in in the same individual. Ultimately, individual cases will build a greater understanding of human brain function in general, which in turn will improve neurosurgeons' future navigational efforts.

Predictive model of language deficit after removing glioma involving language areas under general anesthesia

Purpose

To establish a predictive model to predict the occurrence of language deficit for patients after surgery of glioma involving language areas (GILAs) under general anesthesia (GA).

Methods

Patients with GILAs were retrospectively collected in our center between January 2009 and December 2020. Clinical variables (age, sex, aphasia quotient [AQ], seizures and KPS), tumor-related variables (recurrent tumor or not, volume, language cortices invaded or not, shortest distance to language areas [SDLA], supplementary motor area or premotor area [SMA/PMA] involved or not and WHO grade) and intraoperative multimodal techniques (used or not) were analyzed by univariate and multivariate analysis to identify their association with temporary or permanent language deficits (TLD/PLD). The predictive model was established according to the identified significant variables. Receiver operating characteristic (ROC) curve was used to assess the accuracy of the predictive model.

Results

Among 530 patients with GILAs, 498 patients and 441 patients were eligible to assess TLD and PLD respectively. The multimodal group had the higher EOR and rate of GTR than conventional group. The incidence of PLD was 13.4% in multimodal group, which was much lower than that (27.6%, P<0.001) in conventional group. Three factors were associated with TLD, including SDLA (OR=0.85, P<0.001), preoperative AQ (OR=1.04, P<0.001) and multimodal techniques used (OR=0.41, P<0.001). Four factors were associated with PLD, including SDLA (OR=0.83, P=0.001), SMA/PMA involved (OR=3.04, P=0.007), preoperative AQ (OR=1.03, P=0.002) and multimodal techniques used (OR=0.35, P<0.001). The optimal shortest distance thresholds in detecting the occurrence of TLD/PLD were 1.5 and 4mm respectively. The optimal AQ thresholds in detecting the occurrence of TLD/PLD were 52 and 61 respectively. The cutoff values of the predictive probability for TLD/PLD were 23.7% and 16.1%. The area under ROC curve of predictive models for TLD and PLD were 0.70 (95%CI: 0.65-0.75) and 0.72 (95%CI: 0.66-0.79) respectively.

Conclusion

The use of multimodal techniques can reduce the risk of postoperative TLD/PLD after removing GILAs under general anesthesia. The established predictive model based on clinical variables can predict the probability of occurrence of TLD and PLD, and it had a moderate predictive accuracy.

A Neurosurgical Functional Dissection of the Middle Precentral Gyrus during Speech Production

Classical models have traditionally focused on the left posterior inferior frontal gyrus (Broca's area) as a key region for motor planning of speech production. However, converging evidence suggests that it is not critical for either speech motor planning or execution. Alternative cortical areas supporting high-level speech motor planning have yet to be defined. In this review, we focus on the precentral gyrus, whose role in speech production is often thought to be limited to lower-level articulatory muscle control. In particular, we highlight neurosurgical investigations that have shed light on a cortical region anatomically located near the midpoint of the precentral gyrus, hence called the middle precentral gyrus (midPrCG). The midPrCG is functionally located between dorsal hand and ventral orofacial cortical representations and exhibits unique sensorimotor and multisensory functions relevant for speech processing. This includes motor control of the larynx, auditory processing, as well as a role in reading and writing. Furthermore, direct electrical stimulation of midPrCG can evoke complex movements, such as vocalization, and selective injury can cause deficits in verbal fluency, such as pure apraxia of speech. Based on these findings, we propose that midPrCG is essential to phonological-motoric aspects of speech production, especially syllabic-level speech sequencing, a role traditionally ascribed to Broca's area. The midPrCG is a cortical brain area that should be included in contemporary models of speech production with a unique role in speech motor planning and execution.

Organic Electrochemical Transistors for In Vivo Bioelectronics

Organic electrochemical transistors (OECTs) are presently a focus of intense research and hold great potential in expanding the horizons of the bioelectronics industry. The notable characteristics of OECTs, including their electrolyte-gating, which offers intimate interfacing with biological environments, and aqueous stability, make them particularly suitable to be operated within a living organism (in vivo). Unlike the existing in vivo bioelectronic devices, mostly based on rigid metal electrodes, OECTs form a soft mechanical contact with the biological milieu and ensure a high signal-to-noise ratio because of their powerful amplification capability. Such features make OECTs particularly desirable for a wide range of in vivo applications, including electrophysiological recordings, neuron stimulation, and neurotransmitter detection, and regulation of plant processes in vivo. In this review, a systematic compilation of the in vivo applications is presented that are addressed by the OECT technology. First, the operating mechanisms, and the device design and materials design principles of OECTs are examined, and then multiple examples are provided from the literature while identifying the unique device properties that enable the application progress. Finally, one critically looks at the future of the OECT technology for in vivo bioelectronic applications.

Patient-Specific Network Connectivity Combined With a Next Generation Neural Mass Model to Test Clinical Hypothesis of Seizure Propagation

Dynamics underlying epileptic seizures span multiple scales in space and time, therefore, understanding seizure mechanisms requires identifying the relations between seizure components within and across these scales, together with the analysis of their dynamical repertoire. In this view, mathematical models have been developed, ranging from single neuron to neural population. In this study, we consider a neural mass model able to exactly reproduce the dynamics of heterogeneous spiking neural networks. We combine mathematical modeling with structural information from non invasive brain imaging, thus building large-scale brain network models to explore emergent dynamics and test the clinical hypothesis. We provide a comprehensive study on the effect of external drives on neuronal networks exhibiting multistability, in order to investigate the role played by the neuroanatomical connectivity matrices in shaping the emergent dynamics. In particular, we systematically investigate the conditions under which the network displays a transition from a low activity regime to a high activity state, which we identify with a seizure-like event. This approach allows us to study the biophysical parameters and variables leading to multiple recruitment events at the network level. We further exploit topological network measures in order to explain the differences and the analogies among the subjects and their brain regions, in showing recruitment events at different parameter values. We demonstrate, along with the example of diffusion-weighted magnetic resonance imaging (dMRI) connectomes of 20 healthy subjects and 15 epileptic patients, that individual variations in structural connectivity, when linked with mathematical dynamic models, have the capacity to explain changes in spatiotemporal organization of brain dynamics, as observed in network-based brain disorders. In particular, for epileptic patients, by means of the integration of the clinical hypotheses on the epileptogenic zone (EZ), i.e., the local network where highly synchronous seizures originate, we have identified the sequence of recruitment events and discussed their links with the topological properties of the specific connectomes. The predictions made on the basis of the implemented set of exact mean-field equations turn out to be in line with the clinical pre-surgical evaluation on recruited secondary networks.

Pre-surgical fMRI Localization of the Hand Motor Cortex in Brain Tumors: Comparison Between Finger Tapping Task and a New Visual-Triggered Finger Movement Task

Introduction: Pre-surgical mapping is clinically essential in the surgical management of brain tumors to preserve functions. A common technique to localize eloquent areas is functional magnetic resonance imaging (fMRI). In tumors involving the peri-rolandic regions, the finger tapping task (FTT) is typically administered to delineate the functional activation of hand-knob area. However, its selectivity may be limited. Thus, here, a novel cue-induced fMRI task was tested, the visual-triggered finger movement task (VFMT), aimed at eliciting a more accurate functional cortical mapping of the hand region as compared with FTT.

Method: Twenty patients with glioma in the peri-rolandic regions underwent pre-operative mapping performing both FTT and VFMT. The fMRI data were analyzed for surgical procedures. When the craniotomy allowed to expose the motor cortex, the correspondence with intraoperative direct electrical stimulation (DES) was evaluated through sensitivity and specificity (mean sites = 11) calculated as percentage of true-positive and true-negative rates, respectively.

Results: Both at group level and at single-subject level, differences among the tasks emerged in the functional representation of the hand-knob. Compared with FTT, VFMT showed a well-localized activation within the hand motor area and a less widespread activation in associative regions. Intraoperative DES confirmed the greater specificity (97%) and sensitivity (100%) of the VFMT in determining motor eloquent areas.

Conclusion: The study provides a novel, external-triggered fMRI task for pre-surgical motor mapping. Compared with the traditional FTT, the new VFMT may have potential implications in clinical fMRI and surgical management due to its focal identification of the hand-knob region and good correspondence to intraoperative DES.

Multi-modal Mapping of the Face Selective Ventral Temporal Cortex-A Group Study With Clinical Implications for ECS, ECoG, and fMRI

Face recognition is impaired in patients with prosopagnosia, which may occur as a side effect of neurosurgical procedures. Face selective regions on the ventral temporal cortex have been localized with electrical cortical stimulation (ECS), electrocorticography (ECoG), and functional magnetic resonance imagining (fMRI). This is the first group study using within-patient comparisons to validate face selective regions mapping, utilizing the aforementioned modalities. Five patients underwent surgical treatment of intractable epilepsy and joined the study. Subdural grid electrodes were implanted on their ventral temporal cortices to localize seizure foci and face selective regions as part of the functional mapping protocol. Face selective regions were identified in all patients with fMRI, four patients with ECoG, and two patients with ECS. From 177 tested electrode locations in the region of interest (ROI), which is defined by the fusiform gyrus and the inferior temporal gyrus, 54 face locations were identified by at least one modality in all patients. fMRI mapping showed the highest detection rate, revealing 70.4% for face selective locations, whereas ECoG and ECS identified 64.8 and 31.5%, respectively. Thus, 28 face locations were co-localized by at least two modalities, with detection rates of 89.3% for fMRI, 85.7% for ECoG and 53.6 % for ECS. All five patients had no face recognition deficits after surgery, even though five of the face selective locations, one obtained by ECoG and the other four by fMRI, were within 10 mm to the resected volumes. Moreover, fMRI included a quite large volume artifact on the ventral temporal cortex in the ROI from the anatomical structures of the temporal base. In conclusion, ECS was not sensitive in several patients, whereas ECoG and fMRI even showed activation within 10 mm to the resected volumes. Considering the potential signal drop-out in fMRI makes ECoG the most reliable tool to identify face selective locations in this study. A multimodal approach can improve the specificity of ECoG and fMRI, while simultaneously minimizing the number of required ECS sessions. Hence, all modalities should be considered in a clinical mapping protocol entailing combined results of co-localized face selective locations.

Functional organization of the human primary somatosensory cortex: A stereo-electroencephalography study

OBJECTIVE

The classical homunculus of the human primary somatosensory cortex (S1) established by Penfield has mainly portrayed the functional organization of convexial cortex, namely Brodmann area (BA) 1. However, little is known about the functions in fissural cortex including BA2 and BA3. We aim at drawing a refined and detailed somatosensory homunculus of the entire S1.

METHODS

We recruited 20 patients with drug-resistant focal epilepsy who underwent stereo-electroencephalography for preoperative assessments. Direct electrical stimulation was performed for functional mapping. Montreal Neurological Institute coordinates of the stimulation sites lying in S1 were acquired.

RESULTS

Stimulation of 177 sites in S1 yielded 149 positive sites (84%), most of which were located in the sulcal cortex. The spatial distribution of different body-part representations across the S1 surface revealed that the gross medial-to-lateral sequence of body representations within the entire S1 was consistent with the classical "homunculus". And we identified several unreported body-part representations from the sulcal cortex, such as forehead, deep elbow and wrist joints, and some dorsal body regions.

CONCLUSIONS

Our results reveal general somatotopical characteristics of the entire S1 cortex and differences with the previous works of Penfield.

SIGNIFICANCE

The classical S1 homunculus was extended by providing further refinement and additional detail.

The Glioma-Network Interface: A Review of the Relationship Between Glioma Molecular Subtype and Intratumoral Function

Gliomas are a major cause of morbidity. Direct cortical stimulation mapping offers the ability to identify functional areas within the broader neural network both cortically and subcortically. Since the World Health Organization (WHO) 2016 classification categorized gliomas into molecular subgroups with varied molecular signatures and clinical behavior, it is possible that gliomas may demonstrate rates of functional network integration. We therefore retrospectively reviewed a data registry of 181 patients with dominant hemisphere frontal, parietal, insular, or temporal gliomas. Our goal was to test the hypothesis that WHO glioma histopathology and molecular subtype influences functional language or motor sites identified within the tumor. Intratumoral function as determined by direct cortical and subcortical stimulation mapping was identified at the highest rate in isocitrate dehydrogenase mutant astrocytomas and oligodendrogliomas. Finally, we reviewed the emerging literature exploring the interface between functional neural networks and gliomas. These data shed light on glioma molecular and histological characteristics most commonly associated within intratumoral function.

Toll-Like Receptor 4 Signaling in Focal Cerebral Ischemia: a Focus on the Neurovascular Unit

A robust innate immune activation leads to downstream expression of inflammatory mediators that amplify tissue damage and consequently increase the morbidity after stroke. The Toll-like receptor 4 (TLR4) pathway is a major innate immune pathway activated acutely and chronically after stroke. Hence, understanding the intricacies of the temporal profile, specific control points, and cellular specificity of TLR4 activation is crucial for the development of any novel therapeutics targeting the endogenous innate immune response after focal cerebral ischemia. The goal of this review is to summarize the current findings related to TLR4 signaling after stroke with a specific focus on the components of the neurovascular unit such as astrocytes, neurons, endothelial cells, and pericytes. In addition, this review will examine the effects of focal cerebral ischemia on interaction of these neurovascular unit components.

The impact of neuroimaging advancement on neurocognitive evaluation in pediatric brain tumor survivors: A review

Pediatric brain tumors are a type of tumors that are commonly present in children and young adults. With the improvement of treatment, the quality of life, especially the cognitive functioning, is gaining increasingly more attention. Apart from cognitive evaluations, neuroimaging studies begin to play an important part in neurocognitive functioning investigation. In this way, the brain tissue changes caused by tumor variables (including tumor location and tumor size) and treatment variables (including surgery, chemotherapy and radiotherapy) can be detected by neuroimaging. Recent advancement of neuroimaging techniques, such as functional-MRI (fMRI) and diffusion tensor imaging (DTI), made great contributions to understanding cognitive dysfunction and quantifying the effects of tumor variables and treatment variables. In recent years, laminar-fMRI provided a potentially valuable tool for examining the exact origins of neural activity and cognitive function. On the other hand, molecular fMRI might guide diagnosis and treatment of brain disease in the future by using new biomarkers, and DTI can detect white matter changes and obtain some anatomically specific information.