Studying brain connectivity: a new multimodal approach for structure and function integration \u200b

Il cervello \ue8 un sistema che integra organizzazioni anatomiche e funzionali. Negli ultimi dieci anni, la comunit\ue0 neuroscientifica si \ue8 posta la domanda sulla relazione struttura-funzione. Essa pu\uf2 essere esplorata attraverso lo studio della connettivit\ue0. Nello specifico, la connettivit\ue0 strutturale pu\uf2 essere definita dal segnale di risonanza magnetica pesato in diffusione seguito dalla computazione della trattografia; mentre la correlazione funzionale del cervello pu\uf2 essere calcolata a partire da diversi segnali, come la risonanza magnetica funzionale o l\u2019elettro-/magneto-encefalografia, che consente la cattura del segnale di attivazione cerebrale a una risoluzione temporale pi\uf9 elevata. Recentemente, la relazione struttura-funzione \ue8 stata esplorata utilizzando strumenti di elaborazione del segnale sui grafi, che estendono e generalizzano le operazioni di elaborazione del segnale ai grafi. In specifico, alcuni studi utilizzano la trasformata di Fourier applicata alla connettivit\ue0 strutturale per misurare la decomposizione del segnale funzionale in porzioni che si allineano (\u201caligned\u201d) e non si allineano (\u201cliberal\u201d) con la sottostante rete di materia bianca. Il relativo allineamento funzionale con l\u2019anatomia \ue8 stato associato alla flessibilit\ue0 cognitiva, sottolineando forti allineamenti di attivit\ue0 corticali, e suggerendo che i sistemi sottocorticali contengono pi\uf9 segnali liberi rispetto alla corteccia. Queste relazioni multimodali non sono, per\uf2, ancora chiare per segnali con elevata risoluzione temporale, oltre ad essere ristretti a specifiche zone cerebrali. Oltretutto, al giorno d'oggi la ricostruzione della trattografia \ue8 ancora un argomento impegnativo, soprattutto se utilizzata per l'estrazione della connettivit\ue0 strutturale. Nel corso dell'ultimo decennio si \ue8 vista una proliferazione di nuovi modelli per ricostruire la trattografia, ma il loro conseguente effetto sullo strumento di connettivit\ue0 non \ue8 ancora chiaro. In questa tesi, ho districato i dubbi sulla variabilit\ue0 dei trattogrammi derivati da diversi metodi di trattografia, confrontandoli con un paradigma di test-retest, che consente di definire la specificit\ue0 e la sensibilit\ue0 di ciascun modello. Ho cercato di trovare un compromesso tra queste, per definire un miglior metodo trattografico. Inoltre, ho affrontato il problema dei grafi pesati confrontando alcune possibili stime, evidenziando la sufficienza della connettivit\ue0 binaria e la potenza delle propriet\ue0 microstrutturali di nuova generazione nelle applicazioni cliniche. Qui, ho sviluppato un modello di proiezione che consente l'uso dei filtri aligned e liberal per i segnali di encefalografia. Il modello estende i vincoli strutturali per considerare le connessioni indirette, che recentemente si sono dimostrate utili nella relazione struttura-funzione. I risultati preliminari del nuovo modello indicano un\u2019implicazione dinamica di momenti pi\uf9 aligned e momenti pi\uf9 liberal, evidenziando le fluttuazioni presenti nello stato di riposo. Inoltre, viene presentata una relazione specifica di periodi pi\uf9 allineati e liberali per il paradigma motorio. Questo modello apre la prospettiva alla definizione di nuovi biomarcatori. Considerando che l\u2019encefalografia \ue8 spesso usata nelle applicazioni cliniche, questa integrazione multimodale applicata su dati di Parkinson o di ictus potrebbe combinare le informazioni dei cambiamenti strutturali e funzionali nelle connessioni cerebrali, che al momento sono state dimostrate individualmente.The brain is a complex system of which anatomical and functional organization is both segregated and integrated. A longstanding question for the neuroscience community has been to elucidate the mutual influences between structure and function. To that aim, first, structural and functional connectivity need to be explored individually. Structural connectivity can be measured by the Diffusion Magnetic Resonance signal followed by successive computational steps up to virtual tractography. Functional connectivity can be established by correlation between the brain activity time courses measured by different modalities, such as functional Magnetic Resonance Imaging or Electro/Magneto Encephalography. Recently, the Graph Signal Processing (GSP) framework has provided a new way to jointly analyse structure and function. In particular, this framework extends and generalizes many classical signal-processing operations to graphs (e.g., spectral analysis, filtering, and so on). The graph here is built by the structural connectome; i.e., the anatomical backbone of the brain where nodes represent brain regions and edge weights strength of structural connectivity. The functional signals are considered as time-dependent graph signals; i.e., measures associated to the nodes of the graph. The concept of the Graph Fourier Transform then allows decomposing regional functional signals into, on one side, a portion that strongly aligned with the underlying structural network (\u201caligned"), and, on the other side, a portion that is not well aligned with structure (\u201cliberal"). The proportion of aligned-vs-liberal energy in functional signals has been associated with cognitive flexibility. However, the interpretation of these multimodal relationships is still limited and unexplored for higher temporal resolution functional signals such as M/EEG. Moreover, the construction of the structural connectome itself using tractography is still a challenging topic, for which, in the last decade, many new advanced models were proposed, but their impact on the connectome remains unclear. In the first part of this thesis, I disentangled the variability of tractograms derived from different tractography methods, comparing them with a test-retest paradigm, which allows to define specificity and sensitivity of each model. I want to find the best trade-off between specificity and sensitivity to define the best model that can be deployed for analysis of functional signals. Moreover, I addressed the issue of weighing the graph comparing few estimates, highlighting the sufficiency of binary connectivity, and the power of the latest-generation microstructural properties in clinical applications. In the second part, I developed a GSP method that allows applying the aligned and liberal filters to M/EEG signals. The model extends the structural constraints to consider indirect connections, which recently demonstrated to be powerful in the structure/function link. I then show that it is possible to identify dynamic changes in aligned-vs-liberal energy, highlighting fluctuations present motor task and resting state. This model opens the perspective of novel biomarkers. Indeed, M/EEG are often used in clinical applications; e.g., multimodal integration in data from Parkinson\u2019s disease or stroke could combine changes of both structural and functional connectivity

Ancient Ways in Current Days: Ethno-Cultural Arts and Acculturation

This research investigates the benefits of traditional/ethnic arts participation on well-being for immigrant and ethnic minority groups. While arts programs are increasingly seen as beneficial, little empirical evidence exists to support this belief, especially regarding ethnic groups in cross-cultural transition and multicultural environments. Three phases of research were undertaken, the first being qualitative, followed by two quantitative studies. Study 1 was a qualitative research into feelings of migrant and minority artists about how their arts practices affected their lives and acculturation processes. Practitioners from a number of ethno-cultural groups of both traditional and contemporary/Western arts were included to determine whether there were differences in effects of practices between those categories. Several broad themes emerged specific to the traditional/ethnic arts category, providing strong evidence for distinction between ethnic and contemporary/Western arts in effect for ethnic peoples: Cultural knowledge, the learning of cultural history, behaviours, and mores, Connectedness, the feeling of connection to family, peers, and community, as well as to other ethnic communities, Ethnic identity development, the sense of belongingness and meaning arising from ethno-cultural group membership. Study 2 examined data from longitudinal study of New Zealand youth (Youth Connectedness Project), specifically addressing differences based on arts participation for Maori and Pasifika (Polynesian) youth. Results demonstrated that youth who participated in any arts reported greater connectedness and well-being over those who participated in no arts, and that youth who participated in traditional Polynesian cultural arts had the highest ethnic identity scores. The processes involved were modelled and tested with path modelling. Study 3 was designed to investigate components of ethnic arts practices to understand why and how the improvements in ethnic identity, connectedness, and well-being observed in the previous studies come about. Participants were recruited internationally, from a wide range of ethnicities and arts practices. The outcomes of this study include construction of cross-cultural measure of traditional arts participation factors and a structural equation which models the process by which Well-Being is enhanced. Factors arising in exploratory and confirmatory factor analyses of the scale were centrality, pride, belongingness, and cultural knowledge. In the process model tested, level of traditional/ethnic arts participation positively influenced levels of Connectedness and Ethnic Identity, which both served as mediators between level of traditional arts participation and increased Well-Being outcomes. In summary, these studies demonstrate that there are specific individual and group level benefits from participation in traditional arts for members of ethnic cultures and their communities. These benefits operate through enhancement of ethnic identity and connectedness, which in turn positively influence well-being outcomes. The results suggest that public support of such arts and programs which include such arts would lead to better adaptation outcomes for immigrant and ethnic minority groups

Ancient Ways in Current Days: Ethno-Cultural Arts and Acculturation

This research investigates the benefits of traditional/ethnic arts participation on well-being for immigrant and ethnic minority groups. While arts programs are increasingly seen as beneficial, little empirical evidence exists to support this belief, especially regarding ethnic groups in cross-cultural transition and multicultural environments. Three phases of research were undertaken, the first being qualitative, followed by two quantitative studies. Study 1 was a qualitative research into feelings of migrant and minority artists about how their arts practices affected their lives and acculturation processes. Practitioners from a number of ethno-cultural groups of both traditional and contemporary/Western arts were included to determine whether there were differences in effects of practices between those categories. Several broad themes emerged specific to the traditional/ethnic arts category, providing strong evidence for distinction between ethnic and contemporary/Western arts in effect for ethnic peoples: Cultural knowledge, the learning of cultural history, behaviours, and mores, Connectedness, the feeling of connection to family, peers, and community, as well as to other ethnic communities, Ethnic identity development, the sense of belongingness and meaning arising from ethno-cultural group membership. Study 2 examined data from longitudinal study of New Zealand youth (Youth Connectedness Project), specifically addressing differences based on arts participation for Maori and Pasifika (Polynesian) youth. Results demonstrated that youth who participated in any arts reported greater connectedness and well-being over those who participated in no arts, and that youth who participated in traditional Polynesian cultural arts had the highest ethnic identity scores. The processes involved were modelled and tested with path modelling. Study 3 was designed to investigate components of ethnic arts practices to understand why and how the improvements in ethnic identity, connectedness, and well-being observed in the previous studies come about. Participants were recruited internationally, from a wide range of ethnicities and arts practices. The outcomes of this study include construction of cross-cultural measure of traditional arts participation factors and a structural equation which models the process by which Well-Being is enhanced. Factors arising in exploratory and confirmatory factor analyses of the scale were centrality, pride, belongingness, and cultural knowledge. In the process model tested, level of traditional/ethnic arts participation positively influenced levels of Connectedness and Ethnic Identity, which both served as mediators between level of traditional arts participation and increased Well-Being outcomes. In summary, these studies demonstrate that there are specific individual and group level benefits from participation in traditional arts for members of ethnic cultures and their communities. These benefits operate through enhancement of ethnic identity and connectedness, which in turn positively influence well-being outcomes. The results suggest that public support of such arts and programs which include such arts would lead to better adaptation outcomes for immigrant and ethnic minority groups

Programming the cerebellum

It is argued that large-scale neural network simulations of cerebellar cortex and nuclei, based on realistic compartmental models of me major cell populations, are necessary before the problem of motor learning in the cerebellum can be solved, [HOUK et al.; SIMPSON et al.

A Holmes and Doyle Bibliography, Volume 5: Periodical Articles--Secondary References, Alphabetical Listing

This bibliography is a work in progress. It attempts to update Ronald B. De Waal’s comprehensive bibliography, The Universal Sherlock Holmes, but does not claim to be exhaustive in content. New works are continually discovered and added to this bibliography. Readers and researchers are invited to suggest additional content. Volume 5 includes "passing" or "secondary" references, i.e. those entries that are passing in nature or contain very brief information or content

A Holmes and Doyle Bibliography, Volume 6: Periodical Articles, Subject Listing, By De Waal Category

This bibliography is a work in progress. It attempts to update Ronald B. De Waal’s comprehensive bibliography, The Universal Sherlock Holmes, but does not claim to be exhaustive in content. New works are continually discovered and added to this bibliography. Readers and researchers are invited to suggest additional content. Volume 6 presents the periodical literature arranged by subject categories (as originally devised for the De Waal bibliography and slightly modified here)

A Holmes and Doyle Bibliography, Volume 9: All Formats—Combined Alphabetical Listing

This bibliography is a work in progress. It attempts to update Ronald B. De Waal’s comprehensive bibliography, The Universal Sherlock Holmes, but does not claim to be exhaustive in content. New works are continually discovered and added to this bibliography. Readers and researchers are invited to suggest additional content. This volume contains all listings in all formats, arranged alphabetically by author or main entry. In other words, it combines the listings from Volume 1 (Monograph and Serial Titles), Volume 3 (Periodical Articles), and Volume 7 (Audio/Visual Materials) into a comprehensive bibliography. (There may be additional materials included in this list, e.g. duplicate items and items not yet fully edited.) As in the other volumes, coverage of this material begins around 1994, the final year covered by De Waal's bibliography, but may not yet be totally up-to-date (given the ongoing nature of this bibliography). It is hoped that other titles will be added at a later date. At present, this bibliography includes 12,594 items