Global MEG Resting State Functional Connectivity in Children with Autism and Sensory Processing Dysfunction

Sensory processing dysfunction not only affects most individuals with autism spectrum disorder (ASD), but at least 5% of children without ASD also experience dysfunctional sensory processing. Our understanding of the relationship between sensory dysfunction and resting state brain activity is still emerging. This study compared long-range resting state functional connectivity of neural oscillatory behavior in children aged 8-12 years with autism spectrum disorder (ASD; N=18), those with sensory processing dysfunction (SPD; N=18) who do not meet ASD criteria, and typically developing control participants (TDC; N=24) using magnetoencephalography (MEG). Functional connectivity analyses were performed in the alpha and beta frequency bands, which are known to be implicated in sensory information processing. Group differences in functional connectivity and associations between sensory abilities and functional connectivity were examined. Distinct patterns of functional connectivity differences between ASD and SPD groups were found only in the beta band, but not in the alpha band. In both alpha and beta bands, ASD and SPD cohorts differed from the TDC cohort. Somatosensory cortical beta-band functional connectivity was associated with tactile processing abilities, while higher-order auditory cortical alpha-band functional connectivity was associated with auditory processing abilities. These findings demonstrate distinct long-range neural synchrony alterations in SPD and ASD that are associated with sensory processing abilities. Neural synchrony measures could serve as potential sensitive biomarkers for ASD and SPD.

Glioblastoma remodelling of human neural circuits decreases survival

Gliomas synaptically integrate into neural circuits1,2. Previous research has demonstrated bidirectional interactions between neurons and glioma cells, with neuronal activity driving glioma growth1-4 and gliomas increasing neuronal excitability2,5-8. Here we sought to determine how glioma-induced neuronal changes influence neural circuits underlying cognition and whether these interactions influence patient survival. Using intracranial brain recordings during lexical retrieval language tasks in awake humans together with site-specific tumour tissue biopsies and cell biology experiments, we find that gliomas remodel functional neural circuitry such that task-relevant neural responses activate tumour-infiltrated cortex well beyond the cortical regions that are normally recruited in the healthy brain. Site-directed biopsies from regions within the tumour that exhibit high functional connectivity between the tumour and the rest of the brain are enriched for a glioblastoma subpopulation that exhibits a distinct synaptogenic and neuronotrophic phenotype. Tumour cells from functionally connected regions secrete the synaptogenic factor thrombospondin-1, which contributes to the differential neuron-glioma interactions observed in functionally connected tumour regions compared with tumour regions with less functional connectivity. Pharmacological inhibition of thrombospondin-1 using the FDA-approved drug gabapentin decreases glioblastoma proliferation. The degree of functional connectivity between glioblastoma and the normal brain negatively affects both patient survival and performance in language tasks. These data demonstrate that high-grade gliomas functionally remodel neural circuits in the human brain, which both promotes tumour progression and impairs cognition.

Phase alignment of low-frequency neural activity to the amplitude envelope of speech reflects evoked responses to acoustic edges, not oscillatory entrainment

The amplitude envelope of speech is crucial for accurate comprehension. Considered a key stage in speech processing, the phase of neural activity in the theta-delta bands (1 - 10 Hz) tracks the phase of the speech amplitude envelope during listening. However, the mechanisms underlying this envelope representation have been heavily debated. A dominant model posits that envelope tracking reflects entrainment of endogenous low-frequency oscillations to the speech envelope. Alternatively, envelope tracking reflects a series of evoked responses to acoustic landmarks within the envelope. It has proven challenging to distinguish these two mechanisms. To address this, we recorded magnetoencephalography while participants (n=12, 6 female) listened to natural speech, and compared the neural phase patterns to the predictions of two computational models: An oscillatory entrainment model and a model of evoked responses to peaks in the rate of envelope change. Critically, we also presented speech at slowed rates, where the spectro-temporal predictions of the two models diverge. Our analyses revealed transient theta phase-locking in regular speech, as predicted by both models. However, for slow speech we found transient theta and delta phase-locking, a pattern that was fully compatible with the evoked response model but could not be explained by the oscillatory entrainment model. Furthermore, encoding of acoustic edge magnitudes was invariant to contextual speech rate, demonstrating speech rate normalization of acoustic edge representations. Taken together, our results suggest that neural phase locking to the speech envelope is more likely to reflect discrete representation of transient information rather than oscillatory entrainment.Significance statement:Oganian and colleagues probe a highly debated topic in speech perception - the neural mechanisms underlying the cortical representation of the temporal envelope of speech. It is well established that the slow intensity profile of the speech signal, its envelope, elicits a robust brain response that "tracks" these envelope fluctuations. The oscillatory entrainment model posits that envelope tracking reflects phase alignment of endogenous neural oscillations. Here the authors provide evidence for a distinct mechanism. They show that neural speech envelope tracking arises from transient evoked neural responses to rapid increases in the speech envelope. Explicit computational modeling provides direct and compelling evidence that evoked responses are the primary mechanism underlying cortical speech envelope representations, with no evidence for oscillatory entrainment.

CNSC-07. MECHANISMS OF GLIOBLASTOMA-INDUCED CORTICAL REMODELING IDENTIFY THERAPEUTIC VULNERABILITIES

Prior work demonstrated synaptic integration of malignant gliomas into neural circuits induces local hyperexcitability and tumor proliferation. However, prognostication and therapeutic vulnerabilities are lacking from preclinical models. Here, we integrate in vivo and in vitro neurophysiology spatially matched with gene expression programs and protein signaling mechanisms across 66 IDH WT glioblastoma patients to identify thrombospondin-1 (TSP-1) as a molecular driver of glioma-induced network remodeling. Bulk and single cell RNA-sequencing of 11 intratumoral regions maintaining functional connectivity (13,730 cells analyzed) revealed a distinct neurogenic signature enriched for the synaptogenic factor TSP-1. Mechanistic and functional studies validating therapeutic vulnerabilities to TSP-1 silencing by shRNA knockdown and FDA-approved inhibitors (Gabapentin and LSKL) of excitatory synapse formation through the gabapentin a2d-1 receptor was performed in vitro and in vivo. Glioma-neuron co-culture of TSP-1 overexpressing cells demonstrated increased Ki67 proliferation and tumor microtube (TMT) formation when cultured in the presence of neurons. Pharmacological inhibition of TSP-1 using gabapentin or TSP-1 shRNA inhibited the proliferation and TMT-mediated expansion. Hippocampal xenografted mice with TSP-1 over expressing primary patient cultures demonstrated shorter survival and gabapentin treatment of xenografted mice significantly reduced the proliferation of TSP-1 overexpressing cells in vivo. Electrophysiological properties of glioma-neuron co-cultures analyzed using multi-electrode array (MEA) demonstrated increased neuronal spiking activity and network burst synchrony in the presence of TSP-1 over expressing cells. Strikingly, these increases were eliminated in the presence of gabapentin. We modeled survival risk in patients incorporating the effects of glioma intrinsic neuronal activity, molecular, therapeutic, and clinical factors on overall survival by recursive partitioning. Three risk groups were identified based on tumor intrinsic neuronal activity, pre- and post-operative tumor volume with shortest overall survival in patients with glioma intrinsic neuronal activity. These data identify glioma-induced secretion of TSP-1 as a key contributor of tumor proliferation shedding light on new therapies.

CNSC-05. ELECTROPHYSIOLOGICAL PATTERNS OF GLIOMA-INDUCED NEURONAL NETWORK REMODELING ARE CONSERVED ACROSS TUMOR SUBTYPE

Recent evidence indicates that diffuse gliomas engage with neurons at the single-unit and circuit level through differing mechanisms. Certain malignant gliomas form glioma-neuron excitatory glutamatergic synapses and modulate neuron-neuron synapses through activity-dependent paracrine signaling, while others establish glioma-glioma connections via tumor microtubes. It is therefore possible that diffuse gliomas remodel neuronal circuits in a defined and predictable manner and demonstrate distinct electrophysiological profiles with prognostic and therapeutic significance. Here we apply machine learning principles in 140 patients across glioma subtypes to uncover unique electrophysiological features non-invasively via magnetoencephalography (discovery dataset) followed by feature validation using subdural electrocorticography (validation dataset). Following spatial-temporal registration, we fit an elastic net logistic regression classifier to distinguish between power spectra arising from glioma-remodeled cortex and within-subject control conditions. Model significance was determined non-parametrically by re-training each model 1,000 times with randomly permuted class labels and testing the true phi coefficient against the null distribution. In the discovery dataset, we were able to classify glioma infiltration based on tumor intrinsic neuronal activity (p < 0.05) in 127 patients (90.7%). We identified 30 electrophysiological features which revealed increased power in the delta range (1-4 Hz) and decreased power in the beta range (12-20 Hz) as a unique signature of glioma remodeling (p < 0.05) which was preserved in the validation dataset as well as across WHO 2021 diffuse glioma subtypes. In order to identify gene expression programs and signaling mechanisms that may contribute to glioma-induced remodeling but are potentially not identified in the current clinical classification scheme, we assessed targeted, next generation sequencing and DNA mutations as covariates, which again demonstrated the significance of the delta-beta spectral features. These data support converging mechanisms of glioma-induced neuronal network remodeling across tumor subtypes, setting the stage for novel therapies such as neuromodulation.

Magnetoencephalography Imaging Reveals Abnormal Information Flow in Temporal Lobe Epilepsy

Background/Introduction: Widespread network disruption has been hypothesized to be an important predictor of outcomes in patients with refractory temporal lobe epilepsy (TLE). Most studies examining functional network disruption in epilepsy have largely focused on the symmetric bidirectional metrics of the strength of network connections. However, a more complete description of network dysfunction impacts in epilepsy requires an investigation of the potentially more sensitive directional metrics of information flow. Methods: This study describes a whole-brain magnetoencephalography-imaging approach to examine resting-state directional information flow networks, quantified by phase-transfer entropy (PTE), in patients with TLE compared with healthy controls (HCs). Associations between PTE and clinical characteristics of epilepsy syndrome are also investigated. Results: Deficits of information flow were specific to alpha-band frequencies. In alpha band, while HCs exhibit a clear posterior-to-anterior directionality of information flow, in patients with TLE, this pattern of regional information outflow and inflow was significantly altered in the frontal and occipital regions. The changes in information flow within the alpha band in selected brain regions were correlated with interictal spike frequency and duration of epilepsy. Conclusions: Impaired information flow is an important dimension of network dysfunction associated with the pathophysiological mechanisms of TLE.

Neuronal synchrony abnormalities associated with subclinical epileptiform activity in early-onset Alzheimer's disease

Since the first demonstrations of network hyperexcitability in scientific models of Alzheimer's disease, a growing body of clinical studies have identified subclinical epileptiform activity and associated cognitive decline in patients with Alzheimer's disease. An obvious problem presented in these studies is lack of sensitive measures to detect and quantify network hyperexcitability in human subjects. In this study we examined whether altered neuronal synchrony can be a surrogate marker to quantify network hyperexcitability in patients with Alzheimer's disease. Using magnetoencephalography (MEG) at rest, we studied 30 Alzheimer's disease patients without subclinical epileptiform activity, 20 Alzheimer's disease patients with subclinical epileptiform activity and 35 age-matched controls. Presence of subclinical epileptiform activity was assessed in patients with Alzheimer's disease by long-term video-EEG and a 1-h resting MEG with simultaneous EEG. Using the resting-state source-space reconstructed MEG signal, in patients and controls we computed the global imaginary coherence in alpha (8-12 Hz) and delta-theta (2-8 Hz) oscillatory frequencies. We found that Alzheimer's disease patients with subclinical epileptiform activity have greater reductions in alpha imaginary coherence and greater enhancements in delta-theta imaginary coherence than Alzheimer's disease patients without subclinical epileptiform activity, and that these changes can distinguish between Alzheimer's disease patients with subclinical epileptiform activity and Alzheimer's disease patients without subclinical epileptiform activity with high accuracy. Finally, a principal component regression analysis showed that the variance of frequency-specific neuronal synchrony predicts longitudinal changes in Mini-Mental State Examination in patients and controls. Our results demonstrate that quantitative neurophysiological measures are sensitive biomarkers of network hyperexcitability and can be used to improve diagnosis and to select appropriate patients for the right therapy in the next-generation clinical trials. The current results provide an integrative framework for investigating network hyperexcitability and network dysfunction together with cognitive and clinical correlates in patients with Alzheimer's disease.

Clinical Validation of the Champagne Algorithm for Evoked Response Source Localization in Magnetoencephalography

Magnetoencephalography (MEG) is a robust method for non-invasive functional brain mapping of sensory cortices due to its exceptional spatial and temporal resolution. The clinical standard for MEG source localization of functional landmarks from sensory evoked responses is the equivalent current dipole (ECD) localization algorithm, known to be sensitive to initialization, noise, and manual choice of the number of dipoles. Recently many automated and robust algorithms have been developed, including the Champagne algorithm, an empirical Bayesian algorithm, with powerful abilities for MEG source reconstruction and time course estimation (Wipf et al. 2010; Owen et al. 2012). Here, we evaluate automated Champagne performance in a clinical population of tumor patients where there was minimal failure in localizing sensory evoked responses using the clinical standard, ECD localization algorithm. MEG data of auditory evoked potentials and somatosensory evoked potentials from 21 brain tumor patients were analyzed using Champagne, and these results were compared with equivalent current dipole (ECD) fit. Across both somatosensory and auditory evoked field localization, we found there was a strong agreement between Champagne and ECD localizations in all cases. Given resolution of 8mm voxel size, peak source localizations from Champagne were below 10mm of ECD peak source localization. The Champagne algorithm provides a robust and automated alternative to manual ECD fits for clinical localization of sensory evoked potentials and can contribute to improved clinical MEG data processing workflows.

073 Whole-brain network analysis of neural oscillations during light sleep

Introduction

Sleep is a highly stereotyped phenomenon that is ubiquitous across species. Although behaviorally appearing as a homogeneous process, sleep has been recognized as cortically heterogenous and locally dynamic. PET/fMRI studies have provided key insights into regional activation and deactivation with sleep onset, but they lack the high temporal resolution and electrophysiology for understanding neural interactions. Using simultaneous electrocorticography (EEG) and magnetoencephalography (MEG) imaging, we systematically characterize whole-brain neural oscillations and identify frequency specific, cortically-based patterns associated with sleep onset.

Methods

In this study, 14 healthy subjects underwent simultaneous EEG and MEG imaging. Sleep states were determined by scalp EEG. Eight 15s artifact-free epochs, e.g. 120s sensor time series, were selected to represent each behavioral state: N1, N2 and wake. Atlas-based source reconstruction was performed using adaptive beamforming methods. Functional connectivity measures were computed using imaginary coherence and across regions of interests (ROIs, segmentation of 210 cortical regions with Brainnetome Atlas) in multiple frequency bands, including delta (1-4Hz), theta (4-8Hz), alpha (8-12Hz), sigma (12-15Hz), beta (15-30Hz), and gamma (30-50Hz). Directional phase transfer entropy (PTE) was also evaluated to determine the direction of information flow with transition to sleep.

Results

We show that the transition to sleep is encoded in a spatially and temporally specific dynamic pattern of whole-brain functional connectivity. With sleep onset, there is increased functional connectivity diffusely within the delta frequency, while spatially specific profiles in other frequency bands, e.g. increased fronto-temporal connectivity in the alpha frequency band and fronto-occipital connectivity in the theta band. In addition, rather than a decoupling of anterior-posterior regions with transition to sleep, there is a spectral shift to delta frequencies observed in the synchrony and information flow of neural activity.

Conclusion

Sleep onset is cortically heterogeneous, composed of spatially and temporally specific patterns of whole-brain functional connectivity, which may play an essential role in the transition to sleep.

Support (if any)

Research reported in this publication was supported by the National Center for Advancing Translational Sciences of the NIH under Award Number (5TL1TR001871-05 to JMF). Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the NIH.

P100 Recruitment barriers in multicentre collaborative studies as demonstrated by a single unit experience of the Management of Acutely Symptomatic Hernias (MASH) study

Introduction

MASH is a multi-centre prospective cohort study assessing the management of patients presenting with symptomatic abdominal wall hernia. Consenting patients are recruited during acute admission, with telephone follow up at day 30 and 90. We performed a retrospective review of all patients referred to a single general surgical unit with a symptomatic hernia to quantify recruitment rate and identify barriers to recruitment.

Methods

Patients meeting the inclusion criteria 1st August to 18th September were identified from prospective handover lists and electronic records and compared to the prospectively compiled screening log. Reason for not enrolment was coded according to protocol with an additional code added for patients not identified at time of admission.

Results

8/23 (35%) eligible patients were enrolled. 15/23 (65%) were not enrolled due to; Patient not identified at time of admission n = 9 (60%), declined n = 2 (13.3%), too unwell to consent n = 2 (13.3%), translational barrier n = 1 (6.6%) and lacking capacity n = 1 (6.6%). Patients not identified at time of admission included those seen by clinicians not involved in study (new starters and locums) and those discharged directly from A&E with insufficient time and resources to gain consent.

Conclusion

In our unit 65% of eligible patients were not recruited, the majority of whom were missed at time of presentation. This study will generate important information on management and outcomes of acute hernias however strategies are required to recognise and mitigate recruitment bias. Staff turnover may be a significant factor in prospective studies, particularly those prolonged during the COVID-19 pandemic.

TAMI-21. MALIGNANT GLIOMAS REMODEL FUNCTIONAL NEURAL CIRCUITS THROUGH PARACRINE SIGNALING WHICH CONFERS A NEGATIVE PROGNOSIS

BACKGROUND

Unlike cancers affecting many solid organs, gliomas exist within the context of complex neural circuitry. It remains unknown whether glioma-neuron interactions play a role in maintaining functional circuits underlying cognition. We test the hypothesis that malignant gliomas remodel functional circuits through glioma-neuron interactions.

METHODS

Using language processing as a model for functional circuit dynamics, we enrolled 53 patients with dominant hemisphere IDH-wild-type glioblastoma. Task related circuit dynamics were measured using electrocorticography. Magnetoencephalography measures of functional connectivity identified intratumoral connectivity (HFC) and suppressed connectivity (LFC) regions. Primary patient samples and cultures from HFC and LFC-sites were assessed by single-cell RNA sequencing, pre/post-synaptic marker expression, cocultured with murine hippocampal neurons, and induced neuron organoids. Hippocampal tumor xenografts were created. Language/survival statistics were performed to correlate with functional connectivity measures.

RESULTS

Speech production evokes neuronal population spikes within the entire area of tumor-infiltrated cortex, far beyond the cortical territory normally involved in expressive language. Primary patient samples from HFC-regions are enriched for glioblastoma cells with a synaptogenic profile as characterized by pre-and post-synaptic marker expression at both tissue and cellular levels. RNA-sequencing and proteomic analyses from HFC samples revealed a neurogenic signature including thrombospondin-1 originating from glioma cells in HFC-regions and non-tumor astrocytes in LFC-regions. HFC xenografts demonstrated increased total number of synapses. Importantly, when compared with gliomas without intratumoral functional connectivity, connected gliomas have worse language task performance (r= -0.54,p=0.03) and shorter OS (medianOS-64 weeks compared with 107-weeks,p=0.04).

CONCLUSION

Glioma infiltrated regions generate task-relevant neural responses, with speech production evoking neuronal activity throughout tumor-involved cortex in the dominant hemisphere. An enriched population of synaptogenic glioma cells are organized within functionally connected intratumoral regions and this confers negative functional and survival outcomes. Together, these findings indicate that malignant gliomas can functionally remodel neural circuitry, thereby impairing neurological function and promoting tumor progression.

NUTMEG: Open Source Software for M/EEG Source Reconstruction

Neurodynamic Utility Toolbox for Magnetoencephalo- and Electroencephalography (NUTMEG) is an open-source MATLAB-based toolbox for the analysis and reconstruction of magnetoencephalography/electroencephalography data in source space. NUTMEG includes a variety of options for the user in data import, preprocessing, source reconstruction, and functional connectivity. A group analysis toolbox allows the user to run a variety of inferential statistics on their data in an easy-to-use GUI-driven format. Importantly, NUTMEG features an interactive five-dimensional data visualization platform. A key feature of NUTMEG is the availability of a large menu of interference cancelation and source reconstruction algorithms. Each NUTMEG operation acts as a stand-alone MATLAB function, allowing the package to be easily adaptable and scripted for the more advanced user for interoperability with other software toolboxes. Therefore, NUTMEG enables a wide range of users access to a complete "sensor-to- source-statistics" analysis pipeline.

Optimizing Magnetoencephalographic Imaging Estimation of Language Lateralization for Simpler Language Tasks

Magnetoencephalographic imaging (MEGI) offers a non-invasive alternative for defining preoperative language lateralization in neurosurgery patients. MEGI indeed can be used for accurate estimation of language lateralization with a complex language task - auditory verb generation. However, since language function may vary considerably in patients with focal lesions, it is important to optimize MEGI for estimation of language function with other simpler language tasks. The goal of this study was to optimize MEGI laterality analyses for two such simpler language tasks that can have compliance from those with impaired language function: a non-word repetition (NWR) task and a picture naming (PN) task. Language lateralization results for these two tasks were compared to the verb-generation (VG) task. MEGI reconstruction parameters (regions and time windows) for NWR and PN were first defined in a presurgical training cohort by benchmarking these against laterality indices for VG. Optimized time windows and regions of interest (ROIs) for NWR and PN were determined by examining oscillations in the beta band (12-30 Hz) a marker of neural activity known to be concordant with the VG laterality index (LI). For NWR, additional ROIs include areas MTG/ITG and for both NWR and PN, the postcentral gyrus was included in analyses. Optimal time windows for NWR were defined as 650-850 ms (stimulus-locked) and -350 to -150 ms (response-locked) and for PN -450 to -250 ms (response-locked). To verify the optimal parameters defined in our training cohort for NWR and PN, we examined an independent validation cohort (n = 30 for NWR, n = 28 for PN) and found high concordance between VG laterality and PN laterality (82%) and between VG laterality and NWR laterality (87%). Finally, in a test cohort (n = 8) that underwent both the intracarotid amobarbital procedure (IAP) test and MEG for VG, NWR, and PN, we identified excellent concordance (100%) with IAP for VG + NWR + PN composite LI, high concordance for PN alone (87.5%), and moderate concordance for NWR alone (66.7%). These findings provide task options for non-invasive language mapping with MEGI that can be calibrated for language abilities of individual patients. Results also demonstrate that more accurate estimates can be obtained by combining laterality estimates obtained from multiple tasks. MEGI.

Motor Cortical Network Plasticity in Patients With Recurrent Brain Tumors

Objective: The adult brain’s potential for plastic reorganization is an important mechanism for the preservation and restoration of function in patients with primary glial neoplasm. Patients with recurrent brain tumors requiring multiple interventions over time present an opportunity to examine brain reorganization. Magnetoencephalography (MEG) is a noninvasive imaging modality that can be used for motor cortical network mapping which, when performed at regular intervals, offers insight into this process of reorganization. Utilizing MEG-based motor mapping, we sought to characterize the reorganization of motor cortical networks over time in a cohort of 78 patients with recurrent glioma.

Methods: MEG-based motor cortical maps were obtained by measuring event-related desynchronization (ERD) in ß-band frequency during unilateral index finger flexion. Each patient presented at our Department at least on two occasions for tumor resection due to tumor recurrence, and MEG-based motor mapping was performed as part of preoperative assessment before each surgical resection. Whole-brain activation patterns from first to second MEG scan (obtained before first and second surgery) were compared. Additionally, we calculated distances of activation peaks, which represent the location of the primary motor cortex (MC), to determine the magnitude of movement in motor eloquent areas between the first and second MEG scan. We also explored which demographic, anatomic, and pathological factors influence these shifts.

Results: The whole-brain activation motor maps showed a subtle movement of the primary MC from first to second timepoint, as was confirmed by the determination of motor activation peaks. The shift of ipsilesional MC was directly correlated with a frontal-parietal tumor location (p < 0.001), presence of motor deficits (p = 0.021), and with a longer period between MEG scans (p = 0.048). Also, a disengagement of wide areas in the contralesional (ipsilateral to finger movement) hemisphere at the second time point was observed.

Conclusions: MEG imaging is a sensitive method for depicting the plasticity of the motor cortical network. Although the location of the primary MC undergoes only subtle changes, appreciable shifts can occur in the setting of a stronger and longer impairment of the tumor on the MC. The ipsilateral hemisphere may serve as a reservoir for functional recovery.

Global resting-state functional connectivity of neural oscillations in tinnitus with and without hearing loss

This study examined global resting-state functional connectivity of neural oscillations in individuals with chronic tinnitus and normal and impaired hearing. We tested the hypothesis that distinct neural oscillatory networks are engaged in tinnitus with and without hearing loss. In both tinnitus groups, with and without hearing loss, we identified multiple frequency band-dependent regions of increased and decreased global functional connectivity. We also found that the auditory domain of tinnitus severity, assayed by the Tinnitus Functional Index, was associated with global functional connectivity in both auditory and nonauditory regions. These findings provide candidate biomarkers to target and monitor treatments for tinnitus with and without hearing loss.

TMIC-46. GLIOMA-INDUCED SYNAPTOGENESIS IS ENRICHED WITHIN FUNCTIONAL CONNECTIVITY NETWORK HUBS AND INFLUENCES LANGUAGE PROCESSING IN ADULT IDH WT GLIOBLASTOMA

INTRODUCTION

Little is known about the mechanisms by which gliomas integrate into functional neural networks and influence complex cognitive processes such as language. Glioma-neuron interactions are bidirectional, with increased neuronal activity promoting tumor growth and the latter in turn influencing neuronal excitability and synaptic connections. It remains unknown whether glioma-neuron interactions play a role in maintaining long-range neural networks subserving cognition in humans. We test the hypothesis that glioma-neuron interactions (“synaptogenic glioma cells”) are enriched within intratumoral high functional connectivity (FC) network hubs, thereby influencing language processing via release of synaptogenic factors into the tumor microenvironment.

METHODS

We employed magnetoencephalography imaginary coherence measures to identify intratumoral high (HFC) and low (LFC) functional connectivity network hubs in newly diagnosed glioblastoma patients. Primary patient samples and cultures from HFC and LFC sites were assessed for pre and post-synaptic marker expression (IF), cocultured with murine hippocampal neurons, and induced neuron organoids. ECOG Field recordings were performed on HFC/LFC tumors. Secreted proteins were measured from patient serum and LFC/HFC culture supernatant. Language assessments were performed to correlate task performance with FC measures.

RESULTS

Primary patient samples from HFC regions are enriched for glioblastoma cells with a synaptogenic profile as characterized by pre- and post-synaptic marker expression at both tissue and cellular level (coculture with mouse hippocampal neuron and organoid models). RNA sequencing and proteomic analyses from HFC samples revealed a neurogenic signature including thrombospondin 1 (TSP1). Overexpression of TSP1 in LFC primary patient cultures rescues the synaptogenic and proliferative phenotype. Importantly, we found a linear relationship between intratumoral HFC with patient serum TSP1 (ELISA) with a further correlation with language task performance.

CONCLUSION

An enriched population of synaptogenic glioma cells are organized within intratumoral high network connectivity regions. Glioma-induced neuronal synaptogenesis contributes to the microenvironment in support of network connectivity through secretion of TSP1.

MEG imaging of recurrent gliomas reveals functional plasticity of hemispheric language specialization

In patients with gliomas, changes in hemispheric specialization for language determined by magnetoencephalography (MEG) were analyzed to elucidate the impact of treatment and tumor recurrence on language networks. Demonstration of reorganization of language networks in these patients has significant implications on the prevention of postoperative functional loss and recovery. Whole-brain activity during an auditory verb generation task was estimated from MEG recordings in a group of 73 patients with recurrent gliomas. Hemisphere of language dominance was estimated using the language laterality index (LI), a measure derived from the task. The initial scan was performed prior to resection; patients subsequently underwent surgery and adjuvant treatment. A second scan was performed upon recurrence prior to repeat resection. The relationship between the shift in LI between scans and demographics, anatomic location, pathology, and adjuvant treatment was analyzed. Laterality shifts were observed between scans; the median percent change was 29.1% across all patients. Laterality shift magnitude and relative direction were associated with the initial position of language dominance; patients with increased lateralization experienced greater shifts than those presenting more bilateral representation. A change in LI from left or right to bilateral (or vice versa) occurred in 23.3% of patients; complete switch occurred in 5.5% of patients. Patients with tumors within the language-dominant hemisphere experienced significantly greater shifts than those with contralateral tumors. The majority of patients with glioma experience shifts in language network organization over time which correlate with the relative position of language lateralization and tumor location.

Quantifying the Effects of 16p11.2 Copy Number Variants on Brain Structure: A Multisite Genetic-First Study

BACKGROUND

16p11.2 breakpoint 4 to 5 copy number variants (CNVs) increase the risk for developing autism spectrum disorder, schizophrenia, and language and cognitive impairment. In this multisite study, we aimed to quantify the effect of 16p11.2 CNVs on brain structure.

METHODS

Using voxel- and surface-based brain morphometric methods, we analyzed structural magnetic resonance imaging collected at seven sites from 78 individuals with a deletion, 71 individuals with a duplication, and 212 individuals without a CNV.

RESULTS

Beyond the 16p11.2-related mirror effect on global brain morphometry, we observe regional mirror differences in the insula (deletion > control > duplication). Other regions are preferentially affected by either the deletion or the duplication: the calcarine cortex and transverse temporal gyrus (deletion > control; Cohen's d > 1), the superior and middle temporal gyri (deletion < control; Cohen's d < -1), and the caudate and hippocampus (control > duplication; -0.5 > Cohen's d > -1). Measures of cognition, language, and social responsiveness and the presence of psychiatric diagnoses do not influence these results.

CONCLUSIONS

The global and regional effects on brain morphometry due to 16p11.2 CNVs generalize across site, computational method, age, and sex. Effect sizes on neuroimaging and cognitive traits are comparable. Findings partially overlap with results of meta-analyses performed across psychiatric disorders. However, the lack of correlation between morphometric and clinical measures suggests that CNV-associated brain changes contribute to clinical manifestations but require additional factors for the development of the disorder. These findings highlight the power of genetic risk factors as a complement to studying groups defined by behavioral criteria.

Magnetoencephalographic imaging of resting-state functional connectivity predicts postsurgical neurological outcome in brain gliomas

BACKGROUND

The removal of brain tumors in perieloquent or eloquent cortex risks causing new neurological deficits in patients. The assessment of the functionality of perilesional tissue is essential to avoid postoperative neurological morbidity.

OBJECTIVE

To evaluate preoperative magnetoencephalography-based functional connectivity as a predictor of short- and medium-term neurological outcome after removal of gliomas in perieloquent and eloquent areas.

METHODS

Resting-state whole-brain magnetoencephalography recordings were obtained from 79 consecutive subjects with focal brain gliomas near or within motor, sensory, or language areas. Neural activity was estimated using adaptive spatial filtering. The mean imaginary coherence between voxels in and around brain tumors was compared with contralesional voxels and used as an index of their functional connectivity with the rest of the brain. The connectivity values of the tissue resected during surgery were correlated with the early (1 week postoperatively) and medium-term (6 months postoperatively) neurological morbidity.

RESULTS

Patients undergoing resection of tumors with decreased functional connectivity had a 29% rate of a new neurological deficit 1 week after surgery and a 0% rate at 6-month follow-up. Patients undergoing resection of tumors with increased functional connectivity had a 60% rate of a new deficit at 1 week and a 25% rate at 6 months.

CONCLUSION

Magnetoencephalography connectivity analysis gives a valuable preoperative evaluation of the functionality of the tissue surrounding tumors in perieloquent and eloquent areas. These data may be used to optimize preoperative patient counseling and surgical strategy.

Aberrant Oscillatory Activity during Simple Movement in Task-Specific Focal Hand Dystonia

In task-specific focal hand dystonia (tspFHD), the temporal dynamics of cortical activity in the motor system and how these processes are related to impairments in sensory and motor function are poorly understood. Here, we use time-frequency reconstructions of magnetoencephalographic (MEG) data to elaborate the temporal and spatial characteristics of cortical activity during movement. A self-paced finger tapping task during MEG recording was performed by 11 patients with tspFHD and 11 matched healthy controls. In both groups robust changes in beta (12-30 Hz) and high gamma (65-90 Hz) oscillatory activity were identified over sensory and motor cortices during button press. A significant decrease [p < 0.05, 1% False Discovery Rate (FDR) corrected] in high gamma power during movements of the affected hand was identified over ipsilateral sensorimotor cortex in the period prior to (-575 ms) and following (725 ms) button press. Furthermore, an increase (p < 0.05, 1% FDR corrected) in beta power suppression following movement of the affected hand was identified over visual cortex in patients with tspFHD. For movements of the unaffected hand, a significant (p < 0.05, 1% FDR corrected) increase in beta power suppression was identified over secondary somatosensory cortex (S2) in the period following button press in patients with tspFHD. Oscillatory activity within in the tspFHD group was however not correlated with clinical measures. Understanding these aberrant oscillatory dynamics can provide the groundwork for interventions that focus on modulating the timing of this activity.

A case of wrist tenosynovitis caused by Mycobacterium kansasii in a renal transplant recipient

Mycobacterial infection in an organ transplant recipient is a diagnostic and therapeutic challenge. Diagnosis is often delayed, resulting in significant morbidity. Anti-microbial chemotherapy needs careful selection to prevent potentially significant complications, such as organ rejection and dose-related toxicities. We present the case of a 61-year-old Caucasian male kidney transplant recipient with chronic tenosynovitis of the left wrist. Histological findings of the synovial biopsy revealed multinucleated giant cell epithelioid granuloma. Culture of synovial fluid grew Mycobacterium kansasii. Treatment with rifampicin, ethambutol, and clarithromycin proved curative, but the patient developed irreversible ethambutol-related optic neuritis.

Preoperative localization of hand motor cortex by adaptive spatial filtering of magnetoencephalography data

Object

The goal of this study was to examine the sensitivity and specificity in preoperative localization of hand motor cortex by imaging regional event-related desynchronization (ERD) of brainwaves in the β frequency band (15–25 Hz) involved in self-paced movement.

Methods

Using magnetoencephalography (MEG), the authors measured ERD that occurred before self-paced unilateral index finger flexion in 66 patients with brain tumors, epilepsy, and arteriovenous malformations.

Results

The authors applied an adaptive spatial filtering algorithm to MEG data and found that peaks of the tomographic distribution of β-band ERD sources reliably localized hand motor cortex compared with electrical cortical stimulation. They also observed high specificity in estimating contralateral hand motor cortical representations relative to somatosensory cortex. Neither presence nor location of tumor changed the qualitative or quantitative location of motor cortex relative to somatosensory cortex.

Conclusions

An imaging protocol using ERD obtained by adaptive spatial filtering of MEG data can be used for extremely reliable preoperative localization of hand motor cortex.

Predicting the location of mouth motor cortex in patients with brain tumors by using somatosensory evoked field measurements

Object

Before resective brain surgery, localization of the functional regions is necessary to minimize postoperative deficits. The face area has been relatively difficult to map noninvasively by using functional imaging techniques. Preoperative localization of face somatosensory cortex with magnetoencephalography (MEG) may allow the surgeon to predict the location of mouth motor areas.

Methods

The authors compared the location of face somatosensory cortex obtained with somatosensory evoked fields during preoperative MEG with the mouth motor areas identified during intraoperative electrocortical stimulation (ECS) mapping in 13 patients undergoing resection of brain tumor.

Results

In this group of patients, ECS mouth motor sites were usually anterior and lateral to MEG localizations of lip somatosensory cortex. The consistent quantitative relationship between results of these two mapping procedures allows the practitioner to predict the location of mouth motor cortex based on noninvasive preoperative MEG measurements.

Conclusions

Based on this result, the authors suggest that somatosensory mapping using MEG can be used to guide intraoperative mapping and neurosurgical planning.

Natural experiments: an underused tool for public health?

Policymakers and public health researchers alike have demanded better evidence of the effects of interventions on health inequalities. These calls have been repeated most recently in the UK in the final Wanless report, which spoke of the "almost complete lack of an evidence base on the cost-effectiveness of public health interventions", and pointed more generally to the limited evidence base for public health policy and practice. Wanless and others have suggested that the gaps may be partially filled by exploiting the opportunities offered by "natural experiments", such as changes in employment opportunities, housing provision, or cigarette pricing. Natural experiments have an important contributions to make within the health inequalities agenda. First, they can play an important role in investigating the determinants of health inequalities. Second, they can assist in the identification of effective interventions, an area where it is widely acknowledged that the evidence-base is currently sparsely populated. This paper discusses some of the benefits and limitations of using this type of evidence, drawing on two ongoing quasi-experimental studies as examples.

Large scale food retailing as an intervention for diet and health: quasi-experimental evaluation of a natural experiment

OBJECTIVES

To assess the effect on fruit and vegetable consumption, self reported, and psychological health of a "natural experiment"-the introduction of large scale food retailing in a deprived Scottish community.

DESIGN

Prospective quasi-experimental design comparing baseline and follow up data in an "intervention" community with a matched "comparison" community in Glasgow, UK.

PARTICIPANTS

412 men and women aged 16 or over for whom follow up data on fruit and vegetable consumption and GHQ-12 were available.

MAIN OUTCOME MEASURES

Fruit and vegetable consumption in portions per day, poor self reported health, and poor psychological health (GHQ-12).

MAIN RESULTS

Adjusting for age, sex, educational attainment, and employment status there was no population impact on daily fruit and vegetable consumption, self reported, and psychological health. There was some evidence for a net reduction in the prevalence of poor psychological health for residents who directly engaged with the intervention.

CONCLUSIONS

Government policy has advocated using large scale food retailing as a social intervention to improve diet and health in poor communities. In contrast with a previous uncontrolled study this study did not find evidence for a net intervention effect on fruit and vegetable consumption, although there was evidence for an improvement in psychological health for those who directly engaged with the intervention. Although definitive conclusions about the effect of large scale retailing on diet and health in deprived communities cannot be drawn from non-randomised controlled study designs, evaluations of the impacts of natural experiments may offer the best opportunity to generate evidence about the health impacts of retail interventions in poor communities.

Assessing practice nurses' change in nutrition knowledge following training from a primary care dietitian

The expanding role of the Primary Health Care Team (PHCT) has led to more opportunities to offer dietary advice to patients. However, members of the PHCT appear to lack nutritional knowledge and confidence when giving dietary advice. This work assesses the changes in Practice Nurses' (PNs) nutrition knowledge and confidence when giving dietary advice to patients, following training from a dietitian. Base line nutrition knowledge of PNs and their confidence when giving dietary advice was assessed in 30 GP Practices by questionnaire. Following Practice-based training from a dietitian, change in knowledge and confidence was assessed using the same questionnaire. Paired and unpaired analysis was carried out on the PN's knowledge and confidence scores respectively. Nutrition knowledge increased significantly after training. The mean difference (95% confidence interval) pre- and post-training was 11.6 (7.8, 15.4). After training 88% of PNs reported having good or excellent confidence compared with 27% before training (chi-squared test p < 0.001). Nutrition training from a dietitian improves nutrition knowledge of PNs. It also improves their confidence and is recommended to support their role in providing accurate and consistent dietary advice to patients.

Tapping the television cable

Immediate access to patient data is essential to support good clinical decision making and support. However, away from the surgery, the doctor is currently unable to have any access to the clinical database. Solutions exist to support remote access, such as modems or radio data networks, but these are slow, with typical speeds in the 2-10 kbaud region. We propose a novel solution, to use the TV cable already installed in many homes. Using this technology, a suitably equipped computer (RF modern) is capable of connecting at speeds in excess of 500 kbaud and will run applications in exactly the same way as if connected to a surgery network: the cable TV becomes a LAN, but on a metropolitan scale. Brunel University, in collaboration with the Cable Corporation, has been piloting such a network. Issues include not only levels of service, but also security on the network and access, since the data are being effectively received in every home. However, close scrutiny of channel use can create closed networks reserved for specific users. The technology involves use of an RF modem to transmit data on a reverse channel (based at 16 MHz) on each subnet to a router at the head end of the cable network. This frequency translates the packet and retransmits it to all the subnets on a forward channel (based at 178 MHz). Each channel occupies the bandwidth normally allocated to one TV channel. Access is based on a modified CSMA/CD protocol, so treating the cable network as single multiple access network. The modem comes as a standard card installed in a PC and appears much as an ethernet card, but at reduced speed. With an NDIS driver it is quite able to support almost any network software, and has successfully demonstrated Novell and TCP/IP. We describe the HomeWorker network and the results from a pilot study being undertaken to determine the performance of the system and its impact on working practice.

The use of anti-depressants and benzodiazepines in the perpetrators and victims of accidents

The objective of this study was to determine whether there is a greater incidence of psychotropic drugs in the blood of those 'responsible' for an accident compared with those not 'responsible' for an accident. Blood samples were taken from people involved in accidents presenting at the accident and emergency departments of two teaching hospitals over a five-month period and analysed for the presence of alcohol, tricyclic anti-depressants (TCAs) and benzodiazepines (BZs). Details of the accident were used to produce a test group (accidents where a drug may have contributed) and a control group (accidents where the presence of a drug could not have been a factor). In total, 229 samples were collected. The only criterion for inclusion in the study was that the accident was of sufficient severity to merit the routine taking of a blood sample, in which case an additional amount was taken for the purposes of this investigation. In all, 63 samples (27.5%) were positive for at least one of alcohol, TCA or BZ. Of the accidents represented by these samples, 48 could have been caused by the presence of the drug (responsible group) and 15 could not (not responsible group). There was a significantly greater representation of TCAs and BZs in the blood taken from the responsible group compared with the not responsible group (P < 0.0045).

Alcohol misuse in Scotland--is there a growing health problem?

This paper reviews currently available data on alcohol related morbidity and mortality in Scotland. It confirms that admissions to psychiatric hospitals are unlikely to be a reliable indicator of trends in alcohol-related conditions because of the influence of local practice. Discharge rates for general (non-psychiatric) hospitals where an alcohol-related diagnosis has been made are reviewed and even using caution in interpreting the data, the results suggest that there is a worrying increase in rates of discharges with an alcohol-related diagnosis. Finally trends in deaths for both alcoholic liver disease (ICD 571.0-3) and unspecified chronic liver disease (ICD 571.4-9) are examined. It is concluded that other indicators of health related harm should be considered. These might include data from those presently seen in out-patient departments with an alcohol related condition as well as patients misusing alcohol who attend their General Practitioner (GP).

A migration channels approach to the study of high level manpower movements: a theoretical perspective

"There can be little doubt that major changes have taken place in recent years in the nature and organisation of skilled manpower moves. This short article sets out to investigate the ways in which these trends in high level manpower moves might be analysed. It arises from the discussions of a group of British geographers who commenced investigations on this topic in 1985 under the auspices of a working party of the Institute of British Geographers. The article commences by briefly considering the significance of skilled international migration before turning to consider a theoretical framework by which such movements might be analysed. It pays particular attention to the impact of skilled international migration on sub-national units or regions [of developed countries], and tries to link together the findings of the working party on this topic with particular reference to a set of papers presented to a workshop held at the University of Liverpool in March 1989." (SUMMARY IN FRE AND SPA)