Multimodal MRI reveals brainstem connections that sustain wakefulness in human consciousness.
Brian L Edlow, Mark Olchanyi, Holly J Freeman, Jian Li, Chiara Maffei, Samuel B Snider, Lilla Zöllei, J Eugenio Iglesias, Jean Augustinack, Yelena G Bodien, Robin L Haynes, Douglas N Greve, Bram R Diamond, Allison Stevens, Joseph T Giacino, Christophe Destrieux, Andre Van der Kouwe, Emery N Brown, Rebecca D Folkerth, Bruce Fischl, Hannah C Kinney
Science translational medicine May 1, 2024 DOI: 10.1126/scitranslmed.adj4303 via PubMed
Summary
AI-generated from the abstractA proposed subcortical arousal network, crucial for wakefulness, has been mapped in the human brain, revealing connections between key areas like the brainstem and hypothalamus. Utilizing data from three neurologically normal individuals' brains and advanced imaging techniques, this study identified pathways linking the default ascending arousal network with the cortical default mode network. Notably, the dopaminergic ventral tegmental area emerged as a central hub connecting these networks. This work enhances our understanding of how arousal and awareness integrate in human consciousness.
Study at a glance
| Characteristics | Observational study with ex vivo and in vivo neuroimaging and immunohistochemistry Peer reviewed |
|---|---|
| Sample size | 3 |
| Population | Postmortem human brains from neurologically normal individuals |
| Citations | 39 |
| Key finding | The proposed default ascending arousal network (dAAN) includes nodes in the brainstem, hypothalamus, thalamus, and basal forebrain, with the ventral tegmental area serving as a hub linking arousal and awareness networks. |
Abstract
Consciousness is composed of arousal (i.e., wakefulness) and awareness. Substantial progress has been made in mapping the cortical networks that underlie awareness in the human brain, but knowledge about the subcortical networks that sustain arousal in humans is incomplete. Here, we aimed to map the connectivity of a proposed subcortical arousal network that sustains wakefulness in the human brain, analogous to the cortical default mode network (DMN) that has been shown to contribute to awareness. We integrated data from ex vivo diffusion magnetic resonance imaging (MRI) of three human brains, obtained at autopsy from neurologically normal individuals, with immunohistochemical staining of subcortical brain sections. We identified nodes of the proposed default ascending arousal network (dAAN) in the brainstem, hypothalamus, thalamus, and basal forebrain. Deterministic and probabilistic tractography analyses of the ex vivo diffusion MRI data revealed projection, association, and commissural pathways linking dAAN nodes with one another and with DMN nodes. Complementary analyses of in vivo 7-tesla resting-state functional MRI data from the Human Connectome Project identified the dopaminergic ventral tegmental area in the midbrain as a widely connected hub node at the nexus of the subcortical arousal and cortical awareness networks. Our network-based autopsy methods and connectivity data provide a putative neuroanatomic architecture for the integration of arousal and awareness in human consciousness.