Search

The human connectome is a comprehensive description of neural elements and connections reflecting the complex organization of the brain. Modern network neuroscience has led to a paradigmatic improvement in understanding the brain-network organization and has challenged the traditional framework that many neurological disorders involves exclusively focal alterations. Consciousness is the product of multiple brain structures and depends on the brain's ability to integrate different complex patterns of internal communication. Although several studies demonstrated that the fronto-parietal and default mode networks play a key role in in conscious processes [1,2], it is still not clear whether the brain network organization is altered at the global level in patients with disorders of consciousness (DOC). Herein, we investigated the functional connectivity of DOC patients, diagnosed either as unresponsive wakefulness syndrome (UWS) or minimally conscious state (MCS), from a network perspective. EEG recording was performed in resting-state condition and pairwise brain connectivity between cortical areas was estimated across all time in order to compute a weighted functional network. Network-based statistical analysis revealed a subnetwork of decreased functional connectivity in UWS compared to the MCS patients (p = 0.004). Interestingly, apart from a few intrahemispheric pathways linking limbic regions with frontal and parietal areas, these patterns of reduced connectivity mainly involved the interhemispheric fronto-parietal network. Robust correlations between the strength of the connectivity patterns and the CRS-R were found. Global network topological analysis identified increased values of LCP-corr, as well as of high clustering coefficient and modularity in UWS patients compared to MCS patients. At the nodal level, the UWS patients showed increased nodal degree and betweenness centrality in several limbic and temporo-parieto-occipital regions. Taken together, our results highlight i) the involvement of the interhemispheric fronto-parietal network in the pathophysiology of consciousness disorders and ii) an aberrant network organization both at the global and at the nodal level in UWS compared to the MCS patients. [ABSTRACT FROM AUTHOR]

The human pulvinar is considered a prototypical associative thalamic nucleus as it represents a key node in several cortico-subcortical networks. Through this extensive connectivity to widespread brain areas, it has been suggested that the pulvinar may play a central role in modulating cortical oscillatory dynamics of complex cognitive and executive functions. Additionally, derangements of pulvinar activity are involved in different neuropsychiatric conditions including Lewy-body disease, Alzheimer's disease, and schizophrenia. Anatomical investigations in nonhuman primates have demonstrated a topographical organization of cortico-pulvinar connectivity along its dorsoventral and rostrocaudal axes; this specific organization shows only partial overlap with the traditional subdivision into subnuclei (anterior, lateral, medial, and inferior) and is thought to coordinate information processing within specific brain networks. However, despite its relevance in mediating higher-order cognitive functions, such a structural and functional organization of the pulvinar in the human brain remains poorly understood. Track-weighted dynamic functional connectivity (tw-dFC) is a recently developed technique that combines structural and dynamic functional connectivity, allowing the identification of white matter pathways underlying the fluctuations observed in functional connectivity between brain regions over time. Herein, we applied a data-driven parcellation approach to reveal topographically organized connectivity clusters within the human pulvinar complex, in two large cohorts of healthy human subjects. Unsupervised clustering of tw-dFC time series within the pulvinar complex revealed dorsomedial, dorsolateral, ventral anterior, and ventral posterior connectivity clusters. Each of these clusters shows functional coupling to specific, widespread cortico-subcortical white matter brain networks. Altogether, our findings represent a relevant step towards a better understanding of pulvinar anatomy and function, and a detailed characterization of his role in healthy and pathological conditions., (© 2024 The Author(s). Human Brain Mapping published by Wiley Periodicals LLC.)