Biology subjects

Mai, R.

Publications and source records attributed to Mai, R..

7 recordsLinked to original sources

bioRxiv2026

Frequency modulations of cortical synchronization in human cortex during wakefulness and sleep

Vigilance states are associated with reproducible reconfigurations of large-scale brain dynamics, reflected in changes in inter-areal phase synchronization and cross-frequency phase-amplitude coupling. Here, we characterized how these two forms of phase-based coordination jointly organize across sleep and wakefulness in the human brain at local and regional levels. We analysed phase-locking value (PLV) and phase-amplitude coupling (PAC) from intracranial stereo-electroencephalography (SEEG) recordings in 46 individuals with drug-resistant focal epilepsy, focusing on contacts outside the epileptogenic zone (non-epileptogenic zone, nEZ) to define physiological coupling profiles and comparing them with contacts within the EZ. For each subject, representative epochs of wakefulness, NREM sleep stages N2 and N3, and REM sleep were examined. Across vigilance states, large-scale phase synchronization exhibited distinct spectral fingerprints. Theta and sigma synchronization predominated during NREM sleep, beta synchronization increased during REM sleep, and theta interactions characterized wakefulness. PAC showed complementary state-dependent reorganizations: N3 was characterized by delta-driven modulation of broadband high-frequency activity; N2 additionally exhibited theta- and spindle-phase modulation of beta-gamma amplitudes; REM sleep showed reduced coupling; and wakefulness was marked by theta-to-beta interactions. Within vigilance states, epileptogenic regions displayed increased delta and gamma synchronization and enhanced delta-to-beta/gamma PAC, most prominently during N2 sleep and wakefulness, whereas differences between EZ and nEZ tissue were attenuated during REM sleep. Using partial least squares analysis, we further identified system-specific patterns of PLV-PAC covariation, with prominent involvement of temporal networks during NREM sleep and visual and limbic systems during REM sleep. Together, these findings delineate a frequency-specific, state-dependent architecture linking phase synchronization and phase-amplitude coupling in the human brain and describe how epileptogenic networks deviate from physiological coupling profiles across vigilance states.

neuroscience↗

bioRxiv2026

REM sleep reconfigures large-scale network dynamics: a link to its suppressive role in epilepsy

Converging evidence suggests that human brain activity operates near a critical-like regime in which balanced excitation and inhibition support efficient large-scale communication. The brains proximity to criticality may be dynamically reset across the sleep-wake cycle and altered by epilepsy, leading to aberrant oscillatory dynamics. Building on recent work demonstrating a tripartite interaction between networks synchronization, oscillatory amplitude bistability, and cross-frequency coupling in the human brain that seems to favour epileptic activity, we examined how this interaction, and its underlying large-scale dynamics are modulated across vigilance states. We analyzed overnight recordings from 20 patients with drug-resistant epilepsy undergoing presurgical evaluation and selected overall 20 minutes of continuous, artifact free stereo-electroencephalography (SEEG) spanning REM sleep, NREM stages N2 and N3, and eyes-closed resting wakefulness. Across states, we quantified phase synchronization, phase-amplitude coupling, bistability and their correlation. REM sleep was consistently associated with a reduction of these dynamics relative to NREM sleep and wakefulness. Importantly, the canonical correlation between these measures -- reflecting the strength of the tripartite interaction -- was significantly weaker during REM sleep. These findings indicate that vigilance states modulate this previously identified multiscale interaction in human brain networks and suggest that the reduced epileptogenicity of REM sleep can be associated with a disruption of coordinated synchronization, coupling, and bistable dynamics at the large-scale network level.

neuroscience↗

bioRxiv2025

Foraging in conceptual spaces: hippocampal oscillatory dynamics underlying searching for concepts in memory

How does the brain access stored knowledge? It has been proposed that conceptual search engages neurocognitive processes similar to foraging in physical space. We tested this idea using intracranial EEG in patients performing a verbal fluency task, where they spontaneously explored their own knowledge of the world, sampling words from semantic memory. We found that hippocampal theta power increased during conceptual search and scaled with the semantic distance between successive words, paralleling dynamics observed in spatial navigation. Critically, people transitioned between conceptual clusters, resembling transitions between resource patches in foraging behavior. These shifts were marked by enhanced theta-gamma coupling, both within the hippocampus and between the hippocampus and lateral temporal cortex, a key hub of the semantic network. These findings support a mechanistic account of memory search grounded in navigation and foraging principles, suggesting that the hippocampus orchestrates local computations and long-range interactions to enable flexible retrieval of conceptual knowledge.

neuroscience↗

bioRxiv2022

NLP-based tools for localization of the Epileptogenic Zone in patients with drug-resistant focal epilepsy

BackgroundDrug-resistant focal epilepsy, defined by failure of two antiepileptic drugs, affects about 30% of patients with epilepsy. Epilepsy surgery may represent an alternative options for this population. However, defining the epileptogenic zone to be surgically removed requires highly specialised medical expertise as well as advanced technologies. The aim of this work is building a cost-effective support system based on text, in particular based on the semiological descriptions of the seizures (temporal vs extratemporal lobe; right vs left hemisphere), in order to predict the localization of seizure origin. MethodsAmong a population of 121 surgically treated and seizure-free drug-resistant patients suffering with focal epilepsy, recruited at the Niguarda Hospital in Milan, we extracted a total number of 509 descriptions of seizures. After a data pre-processing phase, we used natural language processing tools to build numerical representations of the seizures descriptions, both using embedding and countbased methods. We then used machine learning models performing a binary classification into right/left and temporal/extra-temporal. ResultsAll predictive models show a better performance when using the representations relying on embedding models respect to count-based ones. Between all the combinations of representations and classifiers, the best performance obtained in terms of F1-score is 84.7% {+/-} 0.6. DiscussionThis preliminary work reached encouraging results considering both localization tasks. The main advantage is that no specific knowledge about epilepsy is used to build the models, rendering our pipeline applicable also in other scenarios. The major limitation lies in the fact that the text is highly specific to the writer.

bioengineering↗

bioRxiv2020

High-throughput, low-cost and rapid DNA sequencing using surface-coating techniques

The speed1-3, expense1-4 and throughput2 of genomic sequencing impose limitations on its use for time-sensitive acute cases, such as rare4,5 or antibiotic resistant infections6, and large-scale testing that is necessary for containing COVID-19 outbreaks using source-tracing7-9. The major bottleneck for increasing the bandwidth and decreasing operating costs of next-generation sequencers (NGS) is the flow cell that supplies reagents for the biochemical processes; this subsystem has not significantly improved since 200510-12. Here we report a new method for sourcing reagents based on surface coating technology (SCT): the DNA adhered onto the biochip is directly contacted by a reagent-coated polymeric strip. Compared with flow cells the reagent layers are an order of magnitude thinner while both the reagent exchange rate and biochip area are orders of magnitude greater. These improvements drop the turn-around time from days to twelve hours and the cost for whole genome sequencing (WGS) from about $1000 to $15, as well as increase data production by several orders of magnitude. This makes NGS more affordable than many blood tests while rapidly providing detailed genomic information about microbial and viral pathogens6,13, cancers14 and genetic disorders for targeted treatments6 and personalized medicine6,15. This data can be pooled in population-wide databases for accelerated research and development as well providing detailed real-time data for tracking and containing outbreaks, such as the current COVID-19 pandemic.

bioengineering↗

bioRxiv2019

Human Chrysomya bezziana myiasis: A systematic review

BackgroundMyiasis due to Old World screw-worm fly, Chrysomya bezziana, is an important obligate zoonotic disease in the OIE-list of diseases and is found throughout much of Africa, the Indian subcontinent, southeast and east Asia. C. bezziana myiases cause not only morbidity and death to animals and humans, but also economic losses in the livestock industries. Because of the aggressive and destructive nature of this disease in hosts, we initiated this study to provide a comprehensive understanding of human myiasis caused by C. bezziana.\n\nMethodsWe conducted a systematic search of the databases in English (PubMed, Embase and African Index Medicus) and Chinese (CNKI, Wanfang, and Duxiu), and international government online reports to 6th February, 2019, to identify studies concerning Chrysomya bezziana. Another ten human cases in China and Papua New Guinea that our team had recorded were also included.\n\nResultsWe retrieved 1,048 reports from which 202 studies were ultimately eligible for inclusion in the present descriptive analyses. Since the first human case due to C. bezziana was reported in 1909, we have summarized 291 cases and found that these cases often occurred in poor hygiene, low socio-economic conditions, old age, and underlying diseases including infections, age-related diseases, and noninfectious chronic diseases. But C. bezziana myiasis appears largely neglected as a serious medical or veterinary condition, with human and animal cases only reported in 16 and 24 countries respectively, despite this fly species recorded as present in 44 countries worldwide.\n\nConclusionOur findings indicate that cryptic myiasis cases due to the obligate parasite, C. bezziana, are under-recognized. Through this in-depth study to clarify the knowledge of human C. bezziana myiasis including its etiology, clinical features, diagnosis, treatment, epidemiology, prevention and control, we call for more vigilance and awareness of the disease from governments, health authorities, clinicians, veterinary workers, nursing homes, and also the general public.\n\nAuthor summaryChrysomya bezziana larvae are characterized by feeding aggressively on the living tissues and body fluids of the host. The nightmare-like feelings of patients suffering from this myiasis, severe tissues and bones destruction, even death, and enormous economic loss in the livestock industries have been described in the previous reports. But our findings indicate that C. bezziana myiases still appear to be under-recognized as a serious medical or veterinary condition throughout the world. Both in China and the world at large, it is probable that C. bezziana distribution could be greater than currently reported. For the first time, we have therefore systematically investigated human myiasis caused by C. bezziana. Our study provides an opportunity for clinicians and health authorities to gain a better understanding of this disease from its etiology, pathology, clinical features, diagnosis, treatment, epidemiology, prevention and control. In addition, our findings will hopefully engage governments, health staff, veterinary workers, the elderly homes, and also the general public in efforts to recognize, prevent and control such infestations.

epidemiology↗

bioRxiv2019

Stereotactic electroencephalography in humans reveals multisensory signal in early visual and auditory cortices

Unequivocally demonstrating the presence of multisensory signals at the earliest stages of cortical processing remains challenging in humans. In our study, we relied on the unique spatio-temporal resolution provided by intracranial stereotactic electroencephalographic (SEEG) recordings in patients with drug-resistant epilepsy to characterize the signal extracted from early visual (calcarine and pericalcarine) and auditory (Heschls gyrus and planum temporale) regions during a simple audio-visual oddball task. We provide evidences that both cross-modal responses (visual responses in auditory cortex or the reverse) and multisensory processing (alteration of the unimodal responses during bimodal stimulation) can be observed in intracranial event-related potentials (iERPs) and in power modulations of oscillatory activity at different temporal scales within the first 150 ms after stimulus onset. The temporal profiles of the iERPs are compatible with the hypothesis that MSI occurs by means of direct pathways linking early visual and auditory regions. Our data indicate, moreover, that MSI mainly relies on modulations of the low-frequency bands (foremost the theta band in the auditory cortex and the alpha band in the visual cortex), suggesting the involvement of feedback pathways between the two sensory regions. Remarkably, we also observed high-gamma power modulations by sounds in the early visual cortex, thus suggesting the presence of neuronal populations involved in auditory processing in the calcarine and pericalcarine region in humans.

neuroscience↗