Monday, Jun 24: 5:45 PM - 7:00 PM
Oral Sessions
COEX
Room: ASEM Ballroom 202
This session provides a pivotal exploration of neuroanatomy, enhanced by advanced imaging methods. It highlights how multi-modal imaging uncovers complex networks of short relay fibers, challenging previous notions of brain connectivity. The impact of general anesthesia on brain connectivity patterns opens new understanding of neurological responses across species. Precision neuroimaging showcases individualized brain mapping, emphasizing the uniqueness of brain structures. Innovative dissection techniques and the creation of a white matter atlas illuminate the the anatomy and unctional specialization of brain regions. Lastly, the session examines inter-individual variability in the visual cortex, further enriching our comprehension of neuroanatomy. This series of talks collectively advances our knowledge of the brain's intricate architecture and functioning.
Presentations
Obtaining accurate connectional neuroanatomy across scales and modalities ex vivo is crucial to inform the interpretation of in-vivo diffusion MRI (dMRI) findings and advance our understanding of brain circuitry. Here we combine data across multiple modalities, scales, and species to show that low spatial resolution may result in artifactual long-range connections. We focus on the dorsal superior longitudinal fasciculus (SLF-I), a major fiber association system running within the superior frontal gyrus (SFG). Tracing studies in monkeys describe the SLF-I as connecting the postero-medial parietal regions (PGm, PE, PEc) to different frontal regions (6D, 8B, 9)[1]. Due to the complexity of the SFG, with shorter, superficial fibers running parallel to longer, association fibers, the morphology of the human SLF-I remains controversial. Tractography and post-mortem dissections have yielded conflicting results, some supporting direct, long connections, and others supporting shorter or no SLF-I fibers [2,3]. Here, we combine multi-scale, multi-species, multi-modality data to investigate the mesoscopic organization within the SLF-I fiber system.
Presenter
Chiara Maffei, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital Boston, MA
United States
The human brain is characterised by idiosyncratic patterns of spontaneous thought, rendering each brain uniquely identifiable from its neural activity (Amico and Goñi, 2018; Finn et al., 2015). However, deep general anaesthesia suppresses subjective experience. Does it also suppress what makes each brain unique? We attack this question from three conceptual angles. First, we compare brain connectivity within and across individuals. Second, we compare brain activity against the canonical brain maps of human cognition. Third, we ask whether anaesthesia makes the human brain less distinctive from another species: the macaque.
Presenter
Andrea Luppi, PhD, McGill University
Montreal Neurological Institute
Buguggiate
Italy
Neuroimaging has advanced our understanding of the human brain by allowing non-invasive examination of brain structure and function. Nevertheless, human MRI research has predominantly centred around group-averaged data, which limits the specificity and clinical utility that MRI can offer[1]. Precision neuroimaging facilitates individualized mapping of brain structure and function through the use of repeated and prolonged scans[1]. A dense sampling of fMRI allows for detailed and reliable characterization of individual brain states and heteromodal networks[2]. Structural MRI's specificity can be augmented by using multiple quantitative MRI sequences, providing microstructural parameters characterizing inter-regional heterogeneity and inter-individual differences. Harnessing ultra-high field (UHF) neuroimaging at magnetic field strengths of 7 Tesla, can further enhance spatial and temporal resolution and is often imperative for precise mapping of highly susceptible and deep structures[3, 4]. Several initiatives have generated open-source UHF datasets; however, these focused either on functional[4] or structural sequences[3]. Here, we describe a multimodal precision neuroimaging dataset that capitalized on multiple sessions 7T MRI.
Presenter
Donna Gift Cabalo, McGill University
McGill University
Montreal, Quebec
Canada
Despite major methodological advances in the exploration of the cerebral white matter (Axer et al., 2011; Beaujoin et al., 2019) and growing interest in short association fibers (SAF) (Guevara et al., 2020), the latter remain underexplored. The examination of these connections through the classical fiber dissection (Ludwig and Klingler, 1956) is significantly impeded by the fact that the procedure involves the removal of the cerebral cortex, leading to a smooth surface where the bundles are scarcely visible, and causing the loss of a substantial portion of the sulco-gyral anatomy. To address the methodological renewal necessary for the accurate analysis of these delicate and superficial structures, we present the novel technique for inside-out fiber dissection of the post-mortem human brain that approaches subcortical fibers from their deep aspect with the preservation of the cortex.
Cognitive functions such as memory, attention and language are critical for our survival and success as a species. They rely on cortical networks connected by bundles of axons (i.e., white matter) which, when disconnected, can lead to different disorders. While tremendous progress in our anatomical description of white matter has been achieved in the last 20 years [1], the relationship between brain connections and the emergence of cognitive functions remains elusive. This proposal aims to unveil the functional specialization of the white matter in the brain in a data-driven way [2].
Over the past several decades, neuroanatomy and neuroimaging research has revealed large individual differences in the size of the human visual cortex (Stensaas et al. 1974; Andrews et al. 1997; Dougherty et al. 2003). Further studies have documented covariance amongst the size of visual areas, and between the size of visual areas and properties of other visual structures (Benson et al. 2022; Miyata et al. 2022). We wondered whether there was also substantial variability in the grey matter tissue microstructure of the visual cortex across individuals, and how such measures covary throughout the multiple cortical maps.. Recent advances in structural neuroimaging provide opportunities for characterising tissue properties of cortical areas using MRI. The ratio of T1- to T2-weighted signal intensity (T1w/T2w) has become a widely used semi-quantitative measure of tissue microstructure of the brain (Glasser & van Essen, 2011; Berman et al. 2022). Here, we analysed the Human Connectome Project 7T retinotopy dataset (Benson et al. 2018), to evaluate individual differences and covariance of T1w/T2w amongst early visual areas V1, V2, and V3.
Presenter
Maiko Uesaki, National Institute of Information and Communications Technology Suita, Osaka
Japan