1,720,965 research outputs found
In vivo structural connectome of arousal and motor brainstem nuclei by 7 Tesla and 3 Tesla MRI
Get PDFBrainstem nuclei are key participants in the generation and maintenance of arousal, which is a basic function that modulates wakefulness/sleep, autonomic responses, affect, attention, and consciousness. Their mechanism is based on diffuse pathways ascending from the brainstem to the thalamus, hypothalamus, basal forebrain and cortex. Several arousal brainstem nuclei also participate in motor functions that allow humans to respond and interact with the surrounding through a multipathway motor network. Yet, little is known about the structural connectivity of arousal and motor brainstem nuclei in living humans. This is due to the lack of appropriate tools able to accurately visualize brainstem nuclei in conventional imaging. Using a recently developed in vivo probabilistic brainstem nuclei atlas and 7 Tesla diffusion-weighted images (DWI), we built the structural connectome of 18 arousal and motor brainstem nuclei in living humans (n = 19). Furthermore, to investigate the translatability of our findings to standard clinical MRI, we acquired 3 Tesla DWI on the same subjects, and measured the association of the connectome across scanners. For both arousal and motor circuits, our results showed high connectivity within brainstem nuclei, and with expected subcortical and cortical structures based on animal studies. The association between 3 Tesla and 7 Tesla connectivity values was good, especially within the brainstem. The resulting structural connectome might be used as a baseline to better understand arousal and motor functions in health and disease in humans
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Models of BOLD Signal Change in Breath Hold Studies: Methodological Issues and Interpretation
No full textThis work of thesis aims at studying neural correlates of respiration control with the goal of gaining knowledge towards the determination of the physiopathology of abnormal periodic breathing patterns such as Cheyne-Stokes respiration. Functional magnetic resonance imaging is used to investigate brain areas devoted to the closed-loop control system of respiration in healthy subjects, in particular those areas related to sensing of carbon dioxide levels and integration with peripheral chemoreceptors. Subjects were asked to perform about thirty-seconds-long voluntary apnoea with periods of about sixty seconds. The analysis is focused on the brainstem, thalamic nuclei and surrounding cortical areas, and originates from the work of Pattinson et al. (2009) to investigate the presence of nonlinear responses in carbon dioxide sensing networks, and their eventual role in allowing a separation between BOLD fluctuations caused by respiration-related neural activity and changes in the fMRI signal due to physiological noise from respiration or cardiac activity. A general linear model is applied to fMRI data, including static nonlinearities in the way described in Magri et al. (2011). The critical role of retrospective correction for physiological noise is deeply studied, in order to discuss on the optimal preprocessing path to be followed whenever in fMRI studies there is an interest over respiration-related brain activity. Methodological issues regarding correction for multiple tests were faced by testing both cluster-based methods and voxel-wise correcting techniques based on permutations. Finally, since the analysis produced a huge number of models, differing in terms of complexity and delays, different statistical model selection techniques are discussed, based on different comparison criteria such as adjusted R2 or BIC, testing also different approaches such as leave-one-subject-out cross validation, that may allow to reduce problems of overfitting. The study allowed to highlight activity in the thalamus, diencephalon, globus pallidum and caudate nucleus but failed to provide inter-subject consistent activations in the brainstem. The determination of some parameters defining region-specific responses, performed though model selection, may allow to determine time constants and the presence of eventual nonlinearities characterizing the mechanisms of the ventilatory drive. In this context, this work offers a framework that may inspire future works in approaching fMRI analysis with spatially-parametrized hierarchical linear models
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Structural connectivity of autonomic, pain, limbic, and sensory brainstem nuclei in living humans based on 7 Tesla and 3 Tesla MRI
Get PDFAutonomic, pain, limbic, and sensory processes are mainly governed by the central nervous system, with brainstem nuclei as relay centers for these crucial functions. Yet, the structural connectivity of brainstem nuclei in living humans remains understudied. These tiny structures are difficult to locate using conventional in vivo MRI, and ex vivo brainstem nuclei atlases lack precise and automatic transformability to in vivo images. To fill this gap, we mapped our recently developed probabilistic brainstem nuclei atlas developed in living humans to high‐spatial resolution (1.7 mm isotropic) and diffusion weighted imaging (DWI) at 7 Tesla in 20 healthy participants. To demonstrate clinical translatability, we also acquired 3 Tesla DWI with conventional resolution (2.5 mm isotropic) in the same participants. Results showed the structural connectome of 15 autonomic, pain, limbic, and sensory (including vestibular) brainstem nuclei/nuclei complex (superior/inferior colliculi, ventral tegmental area‐parabrachial pigmented, microcellular tegmental–parabigeminal, lateral/medial parabrachial, vestibular, superior olivary, superior/inferior medullary reticular formation, viscerosensory motor, raphe magnus/pallidus/obscurus, parvicellular reticular nucleus‐alpha part), derived from probabilistic tractography computation. Through graph measure analysis, we identified network hubs and demonstrated high intercommunity communication in these nuclei. We found good (r = .5) translational capability of the 7 Tesla connectome to clinical (i.e., 3 Tesla) datasets. Furthermore, we validated the structural connectome by building diagrams of autonomic/pain/limbic connectivity, vestibular connectivity, and their interactions, and by inspecting the presence of specific links based on human and animal literature. These findings offer a baseline for studies of these brainstem nuclei and their functions in health and disease, including autonomic dysfunction, chronic pain, psychiatric, and vestibular disorders
Systematic review of Parkinson's disease investigated using electroencephalographic technique and linear and nonlinear signal analysis methods.
No full textopenIl morbo di Parkinson è una malattia neurodegenerativa complessa che richiede tecniche avanzate per il suo studio e diagnosi. Questa tesi si focalizza sull'utilizzo di tecniche lineari e non lineari per l'analisi dei segnali Elettroencefalografici (EEG) nei pazienti affetti da Parkinson, attraverso una revisione sistematica della letteratura. Abbiamo effettuato una ricerca nel database PubMed (https://pubmed.ncbi.nlm.nih.gov/), utilizzando una specifica interrogazione "parkinson"[Title/Abstract] AND ("EEG"[Title/Abstract] OR "ELECTROENCEPHALOGRAPHY"[Title/Abstract]), che ha restituito un totale di 738 articoli. Successivamente, mediante la revisione dei titoli e degli abstract, abbiamo identificato 323 articoli rilevanti per l'inclusione nella revisione sistematica.
Analizzando questi 323 articoli, abbiamo esaminato in dettaglio le metodologie utilizzate e i risultati ottenuti da ciascuno studio. Questa indagine offre una panoramica delle tecniche più promettenti, delineando le metodologie innovative che possono supportare futuri sviluppi nella ricerca e nella pratica clinica del Parkinson. Il nostro lavoro fornisce un contributo significativo alla comprensione delle migliori pratiche per l'analisi dei segnali EEG, aprendo nuove prospettive per il miglioramento delle diagnosi e dei trattamenti per i pazienti affetti da questa malattia
Neuronal damage and cognitive impairment in Parkinson's disease: the relation among serum biomarkers, brain atrophy and cognitive performance
Get PDFopenParkinson’s disease (PD) is the second most widespread neurodegenerative pathology after Alzheimer’s one. During the early stages it presents highly heterogeneous features and, as time progresses, it leads patients to present symptoms of a not only motor nature. Among the main motor symptoms, it is possible to find cognitive impairment, apathy, depression, anxiety, impulse control disorders, sleep disturbance, fatigue, pain, visual hallucinations and autonomic dysfunction. At present, the mechanism by which these collateral symptoms can develop during the disease progression and/or what type of physiological factors they are linked to, is not yet well understood. The development of new magnetic resonance imaging techniques has had a great impact on the characterization of many neurodegenerative pathologies, including Parkinson’s disease.
The objective of this thesis is to carry out a morphometric analysis on the patients' magnetic resonance images and to investigate the relationship between morphometric results, blood parameters and cognitive status.
To do this, it was considered a cohort of 57 PD patients, part of which affected by mild cognitive impairment (MCI), while another part characterized by a normal cognitive state (NC). The structural images considered were acquired using high-field magnetic resonance imaging and the sequences used for the morphometry were mainly T1-weighted and FLAIR T2-weighted. The biomarkers considered were nuerofilament light chain (NFL), Glial fibrillary acidic protein (GFAP), phosporilated Tau 181 and the GFAP/NFL ratio, while the cognitive scales used were the Montreal Cognitive Assessment (MOCA) and the Mini Mental State Examination (MMSE).
To obtain brain morphometrics both a surface-based/voxel-based hybrid model on FreeSurfer and a voxel-based model on SPM were used. The morphometry results of the two models were compared. From the statistical parameters of the morphometry, the brain volumes were extracted and, so, the correlations between those of MCI and those of NC patients were calculated. Then, the correlations between volumes and biomarkers were evaluated and comparisons on the values of the biomarkers, dividing the population by gender, cognitive state and score on the cognitive scales were carried out.
The results showed that there is a significant linear correlation between FreeSurfer and SPM results for most of the cortical volume estimates, although a scaling factor is present, while the situation in the subcortex is much more heterogenous, presenting areas for which there is little or no correlation. The morphometrics obtained with Freesurfer are in line with the literature. Gray matter atrophy was found in the cingulate, entorhinal, fusiform, parahippocampal and temporal cortex, other than in the orbital regions and in the paracentral lobule.
Trends were observed between volumes and blood biomarkers and statistical tests suggested links between biomarker values and demographic parameters like age, gender and cognitive status. However, applying the Bonferroni-Holm multiple testing correction method, the significance values found earlier did not survive.
Although the study was limited by the relatively small size of the dataset available, these preliminary results highlight how this line of research could reveal new insights in the specificity of these biomarkers and further studies could lead to a clearer picture of the neurodegenerative phenomenon dictated by Parkinson’s disease in all its aspects.Parkinson’s disease (PD) is the second most widespread neurodegenerative pathology after Alzheimer’s one. During the early stages it presents highly heterogeneous features and, as time progresses, it leads patients to present symptoms of a not only motor nature. Among the main motor symptoms, it is possible to find cognitive impairment, apathy, depression, anxiety, impulse control disorders, sleep disturbance, fatigue, pain, visual hallucinations and autonomic dysfunction. At present, the mechanism by which these collateral symptoms can develop during the disease progression and/or what type of physiological factors they are linked to, is not yet well understood. The development of new magnetic resonance imaging techniques has had a great impact on the characterization of many neurodegenerative pathologies, including Parkinson’s disease.
The objective of this thesis is to carry out a morphometric analysis on the patients' magnetic resonance images and to investigate the relationship between morphometric results, blood parameters and cognitive status.
To do this, it was considered a cohort of 57 PD patients, part of which affected by mild cognitive impairment (MCI), while another part characterized by a normal cognitive state (NC). The structural images considered were acquired using high-field magnetic resonance imaging and the sequences used for the morphometry were mainly T1-weighted and FLAIR T2-weighted. The biomarkers considered were nuerofilament light chain (NFL), Glial fibrillary acidic protein (GFAP), phosporilated Tau 181 and the GFAP/NFL ratio, while the cognitive scales used were the Montreal Cognitive Assessment (MOCA) and the Mini Mental State Examination (MMSE).
To obtain brain morphometrics both a surface-based/voxel-based hybrid model on FreeSurfer and a voxel-based model on SPM were used. The morphometry results of the two models were compared. From the statistical parameters of the morphometry, the brain volumes were extracted and, so, the correlations between those of MCI and those of NC patients were calculated. Then, the correlations between volumes and biomarkers were evaluated and comparisons on the values of the biomarkers, dividing the population by gender, cognitive state and score on the cognitive scales were carried out.
The results showed that there is a significant linear correlation between FreeSurfer and SPM results for most of the cortical volume estimates, although a scaling factor is present, while the situation in the subcortex is much more heterogenous, presenting areas for which there is little or no correlation. The morphometrics obtained with Freesurfer are in line with the literature. Gray matter atrophy was found in the cingulate, entorhinal, fusiform, parahippocampal and temporal cortex, other than in the orbital regions and in the paracentral lobule.
Trends were observed between volumes and blood biomarkers and statistical tests suggested links between biomarker values and demographic parameters like age, gender and cognitive status. However, applying the Bonferroni-Holm multiple testing correction method, the significance values found earlier did not survive.
Although the study was limited by the relatively small size of the dataset available, these preliminary results highlight how this line of research could reveal new insights in the specificity of these biomarkers and further studies could lead to a clearer picture of the neurodegenerative phenomenon dictated by Parkinson’s disease in all its aspects
Association between serum biomarkers and morphometric brain alterations in Parkinson's patients with and without cognitive deficits
No full textreservedLa Malattia di Parkinson (PD) è una patologia neurodegenerativa, annoverata tra i disordini del movimento. A livello neuropatologico è caratterizzata dalla degenerazione della substantia nigra pars compacta e dall’accumulo di α-sinucleina, che innesca processi di neurodegenerazione e neuroinfiammazione a livello multisistemico. Il quadro clinico è composto da sintomi motori cardine e da sintomi non motori ad ampio spettro. Tra questi, i disturbi cognitivi sono certamente i più impattanti sulla qualità della vita del paziente e del caregiver, ed interessano fino al 40-50% dei pazienti. Attualmente, le principali sfide nella gestione del PD includono la difficoltà di diagnosi precoce, il miglioramento dell’accuratezza diagnostica e la previsione della progressione della malattia. Di conseguenza, si ritiene estremamente necessario introdurre nuovi biomarcatori che permettano di far fronte a tali sfide. Lo studio proposto nel presente elaborato esplora l’associazione tra i livelli sierici di due biomarcatori di neurodegenerazione e neuroinfiammazione - NfL e GFAP - e le alterazioni morfometriche cerebrali in pazienti con PD con e senza deficit cognitivi. 84 partecipanti con PD sono stati sottoposti a valutazione neuropsicologica, prelievo sanguigno e risonanza magnetica cerebrale (MRI) per valutare la volumetria corticale e sottocorticale. I risultati indicano che tali biomarcatori sierici riflettono la degenerazione di aree critiche per il funzionamento motorio, cognitivo, emotivo e sensoriale come l’amigdala, l’insula e l’area motoria primaria, suggerendo che la combinazione di biomarcatori sierici e neuroimaging possa migliorare considerevolmente la comprensione dei meccanismi patologici del PD e facilitare l’identificazione precoce di pazienti a rischio di declino cognitivo
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