The influence of inter-regional delays in generating large-scale brain networks of phase synchronization.

Large-scale networks of phase synchronization are considered to regulate the communication between brain regions fundamental to cognitive function, but the mapping to their structural substrates, i.e., the structure-function relationship, remains poorly understood. Biophysical Network Models (BNMs) have demonstrated the influences of local oscillatory activity and inter-regional anatomical connections in generating alpha-band (8-12 Hz) networks of phase synchronization observed with Electroencephalography (EEG) and Magnetoencephalography (MEG). Yet, the influence of inter-regional conduction delays remains unknown. In this study, we compared a BNM with standard "distance-dependent delays", which assumes constant conduction velocity, to BNMs with delays specified by two alternative methods accounting for spatially varying conduction velocities, "isochronous delays" and "mixed delays". We followed the Approximate Bayesian Computation (ABC) workflow, i) specifying neurophysiologically informed prior distributions of BNM parameters, ii) verifying the suitability of the prior distributions with Prior Predictive Checks, iii) fitting each of the three BNMs to alpha-band MEG resting-state data (N = 75) with Bayesian optimization for Likelihood-Free Inference (BOLFI), and iv) choosing between the fitted BNMs with ABC model comparison on a separate MEG dataset (N = 30). Prior Predictive Checks revealed the range of dynamics generated by each of the BNMs to encompass those seen in the MEG data, suggesting the suitability of the prior distributions. Fitting the models to MEG data yielded reliable posterior distributions of the parameters of each of the BNMs. Finally, model comparison revealed the BNM with "distance-dependent delays", as the most probable to describe the generation of alpha-band networks of phase synchronization seen in MEG. These findings suggest that distance-dependent delays might contribute to the neocortical architecture of human alpha-band networks of phase synchronization. Hence, our study illuminates the role of inter-regional delays in generating the large-scale networks of phase synchronization that might subserve the communication between regions vital to cognition.

Modules in connectomes of phase-synchronization comprise anatomically contiguous, functionally related regions.

Modules in brain functional connectomes are essential to balancing segregation and integration of neuronal activity. Connectomes are the complete set of pairwise connections between brain regions. Non-invasive Electroencephalography (EEG) and Magnetoencephalography (MEG) have been used to identify modules in connectomes of phase-synchronization. However, their resolution is suboptimal because of spurious phase-synchronization due to EEG volume conduction or MEG field spread. Here, we used invasive, intracerebral recordings from stereo-electroencephalography (SEEG, N = 67), to identify modules in connectomes of phase-synchronization. To generate SEEG-based group-level connectomes affected only minimally by volume conduction, we used submillimeter accurate localization of SEEG contacts and referenced electrode contacts in cortical gray matter to their closest contacts in white matter. Combining community detection methods with consensus clustering, we found that the connectomes of phase-synchronization were characterized by distinct and stable modules at multiple spatial scales, across frequencies from 3 to 320 Hz. These modules were highly similar within canonical frequency bands. Unlike the distributed brain systems identified with functional Magnetic Resonance Imaging (fMRI), modules up to the high-gamma frequency band comprised only anatomically contiguous regions. Notably, the identified modules comprised cortical regions involved in shared repertoires of sensorimotor and cognitive functions including memory, language and attention. These results suggest that the identified modules represent functionally specialised brain systems, which only partially overlap with the brain systems reported with fMRI. Hence, these modules might regulate the balance between functional segregation and functional integration through phase-synchronization.

Long-range phase synchronization of high-frequency oscillations in human cortex.

Inter-areal synchronization of neuronal oscillations at frequencies below ~100 Hz is a pervasive feature of neuronal activity and is thought to regulate communication in neuronal circuits. In contrast, faster activities and oscillations have been considered to be largely local-circuit-level phenomena without large-scale synchronization between brain regions. We show, using human intracerebral recordings, that 100-400 Hz high-frequency oscillations (HFOs) may be synchronized between widely distributed brain regions. HFO synchronization expresses individual frequency peaks and exhibits reliable connectivity patterns that show stable community structuring. HFO synchronization is also characterized by a laminar profile opposite to that of lower frequencies. Importantly, HFO synchronization is both transiently enhanced and suppressed in separate frequency bands during a response-inhibition task. These findings show that HFO synchronization constitutes a functionally significant form of neuronal spike-timing relationships in brain activity and thus a mesoscopic indication of neuronal communication per se.

[The computerized outpatient management of subjects at neoplastic risk]. / Gestione ambulatoriale computerizzata di soggetti a rischio neoplastico.

The authors reviewed literature data regarding risk factors of cancer in order to produce a software that could identify asymptomatic subjects at "neoplastic risk" by means of the analysis of the relative risk (RR) of each factor of his/her life-style. More in detail, the relationship between diet and cancer, tobacco use, alcohol consumption, sexual behaviour, parity and other obstetric-gynecologic aspects, medications, occupational hazards, environmental pollution and genetic susceptibility were reviewed. A complex multi-parametric evaluation system was realized to calculate risk of cancers through computerized elaboration. The program operates on anamnestic, objective and instrumental data derived from a clinical data-base.

[A retrospective study on the efficacy of the treatment of functional dyspepsia. An evaluation of 166 cases]. / Studio retrospettivo sull'efficacia del trattamento della dispepsia funzionale. Valutazione di 166 casi.

A retrospective study is reported carried out on a group of 166 patients affected by dyspeptic syndrome who presented at least 3 of the 9 symptoms which characterise this pathology. One hundred and twenty-eight patients underwent prokinetic drug therapy and 38 received placebo. Clinical parameters were evaluated following one month of therapy all patients in order to compare them to basal values. The results obtained confirm a satisfactory efficacy of the prokinetic treatment in improving dyspeptic symptoms. Although administered to a smaller number of patients, placebo was also found to play an important role in the multifactorial etiopathogenesis of the dyspeptic syndrome on a functional basis.

[A comparative evaluation of computerized diagnostic decisional support in gastroenterology in relation to typical clinical pictures]. / Valutazione comparativa di un supporto decisionale diagnostico computerizzato in gastroenterologia in rapporto alla tipicità dei quadri clinici.

On the basis of the results obtained in a previous perspective comparative study aimed to compare the diagnostic accuracy of a computerized diagnostic decisional support in gastroenterology with that of non-specialist physicians, the Authors have carried out a retrospective study, based on the same series and on the same results, but disaggregating the global comparisons according to the feature of the clinical presentations. The latter were therefore classified by independent gastroenterologists as "typical", "atypical", or "borderline", and for each group the difference of diagnostic accuracy between program and physicians was again evaluated. Even if the program proved more accurate in all groups, the greatest difference was observed in the "borderline" group which the Authors claim to include the kind of presentation which more than any other needs a decisional aid. This should suggest a possible useful implementation of the system in daily clinical practice.

[Computerized dynamic endothermography of the gastrointestinal mucosa as an indirect index of the state of vascularization of the abdominal organs. A preliminary note]. / L'endotermografia dinamica computerizzata della mucosa gastrointestinale quale indice indiretto dello stato di vascolarizzazione degli organi addominali. Nota preliminare.

Computerized Dynamic Endothermy (CDE) has been applied to the evaluation of the gastroenteric microcirculation. This new method enables mucosal temperature changes to be detected in a dynamic and functional way. With preventive induction of a temperature change (cold stimulus), the instrument measures the time required for the establishment of previous mucosal temperature. Computerized data are displayed in the form of a time/temperature curve. Results obtained on rabbits showed, during ischaemic conditions, a greater reduction of gastric layer temperature during cold stimulus than in basal conditions, followed by a slower return to basal temperature during the recovery time.