![]() ![]() Anatomical in vivo MRI investigations of the human subcortical auditory pathway so far have focused on thalamic nuclei ( Devlin et al., 2006 Moerel et al., 2015), and the identification of the acoustic radiations between the auditory cortex and medial geniculate nucleus of the thalamus with diffusion-weighted MRI tractography ( Devlin et al., 2006 Behrens et al., 2007 Javad et al., 2014 Maffei et al., 2018). To study the subcortical auditory system in living humans, MRI is the best available tool due to its high spatial resolution. However, to the best of our knowledge, postmortem MRI has not been utilized within the subcortical auditory system, although it has provided useful information about laminar structure in the auditory cortex ( Wallace et al., 2016). This points to 'magnetic resonance histology’ ( Johnson et al., 1993) as a promising avenue for identifying the small, deep subcortical auditory structures. More recently, Kulesza (2007) stained six human brainstems for Nissl substance, focusing on the superior olivary complex, finding evidence of a substructure (the medial nucleus of the trapezoid body) whose existence in the human auditory system has been debated for decades.Īdvances in post-mortem human MRI allow for investigating three-dimensional (3-D) brain anatomy with increasingly high resolution (100 µm and below). (1995) used myelin and Nissl cell body staining to investigate the timeline of myelination in human auditory brainstem development. Later investigations from the same group Moore et al. Moore (1987) stained both myelin and the cell bodies of subcortical auditory structures in four postmortem human brainstem samples and compared them to the analogous structures in cats (a common model for auditory investigations at the time). In this paper, we show that three human imaging modalities – histology, postmortem magnetic resonance imaging (MRI), and in vivo MRI at ultra high-field (7 Tesla) – can identify the structures of the subcortical auditory pathway at high spatial resolution (between µm).Īlthough MRI has become increasingly powerful at imaging deep brain structures, anatomical investigation of the human subcortical auditory pathway has been primarily conducted in postmortem tissue dissection and staining. This might be problematic because, while the organization of the auditory pathway is largely conserved across mammalian species ( Malmierca and Hackett, 2010 Schofield, 2010), the form and function of each structure may not be analogous ( Moore, 1987). However, due to methodological issues in human research, most of our understanding of the subcortical (thalamic, midbrain, and brainstem) auditory pathway arises from research conducted in animal models. Understanding the structure of the human subcortical auditory pathway is a necessary step to research its role in hearing, speech communication, and music. This work captures current MRI capabilities for investigating the human subcortical auditory system, describes challenges that remain, and contributes novel, openly available data, atlases, and tools for researching the human auditory system. Using diffusion MRI tractography, we revealed structural connectivity maps of the human subcortical auditory pathway both in vivo (1050 µm isotropic resolution) and post mortem (200 µm isotropic resolution). Further, a group functional atlas derived from the functional data locates these structures with a median distance below 2 mm. We measured functional MRI (fMRI) responses to natural sounds and demonstrate that the functional localization of subcortical structures is reliable within individual participants who were scanned in two different experiments. ![]() We created anatomical atlases based on state-of-the-art human histology (BigBrain) and postmortem MRI (50 µm). Wfe addressed these issues using a combination of histological data, post mortem magnetic resonance imaging (MRI), and in vivo MRI at 7 Tesla. Additionally, the elaborate three-dimensional (3-D) structure of the system can be difficult to understand based on currently available 2-D schematics and animal models. Studying the human subcortical auditory system non-invasively is challenging due to its small, densely packed structures deep within the brain.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |