Scaling Principles of Thalamic Subregions Revealed by Thalamocortical Connectivity across Species
Poster No:
1634
Submission Type:
Abstract Submission
Authors:
Luqi Cheng1, Yufan Wang2, Yu Zhang3, Qian Wang1, Lingzhong Fan2, Tianzi Jiang2
Institutions:
1School of Life and Environmental Sciences, Guilin University of Electronic Technology, Guilin, Guangxi, 2Institute of Automation, Chinese Academy of Science, Beijing, China, 3Zhejiang Lab, Hangzhou, Zhejiang
First Author:
Luqi Cheng
School of Life and Environmental Sciences, Guilin University of Electronic Technology
Guilin, Guangxi
School of Life and Environmental Sciences, Guilin University of Electronic Technology
Guilin, Guangxi
Co-Author(s):
Qian Wang
School of Life and Environmental Sciences, Guilin University of Electronic Technology
Guilin, Guangxi
School of Life and Environmental Sciences, Guilin University of Electronic Technology
Guilin, Guangxi
Introduction:
The thalamus is a complex brain structure within the brain that serves as a crucial relay station, coordinating the flow of information from various cortical regions(Segobin et al., 2024). Certain thalamic regions are connected to primary sensory cortices, facilitating motor and sensory processing, while some other regions are connected to association cortices, contributing to higher-level cognitive functions(Chin et al., 2023; Rikhye et al., 2018). During evolution, the neocortex has undergone significant expansion, particularly in the frontal, temporal, and parietal cortices (Buckner & Krienen, 2013; Van Essen et al., 2019). Whether and how the regions connected to the distinct cerebral cortex in the thalamus have evolved and changed with the brain are not fully understood.
Methods:
Human T1w and diffusion MRI data from 40 subjects were from the HCP database (Van Essen et al., 2013). Chimpanzee T1w and diffusion MRI data from 46 subjects were from the National Chimpanzee Brain Resource. Macaque data from 8 subjects were obtained from TheVirtualBrain (Shen et al., 2019). The human thalamus is from the Harvard-Oxford structural atlases. The chimpanzee thalamus was segmented using Freesurfer. The macaque thalamus is derived from the SARM level 2 (Hartig et al., 2021). Five cortical targets were selected including frontotemporal, precentral, postcentral, posterior parietal, and occipital cortices. Five thousand streamlines were seeded from each of the thalamic voxel to estimate its anatomical connectivity with the five cortical region using probabilistic tractography. The resultant map records the number of the streamlines reading to each cortical region and normalized by diving the maximum value in that map. We subdivided the thalamic voxels into different subregions based on the maximum probability of their connections to the relative target regions. The whole brain grey matter and thalamus volumetric measurements were calculated using Freesurfer and log-transformed. Linear regression was performed to investigate the allometric relationship between the volume of each of the thalamic subregions.
Results:
Using connectivity-based parcellation, the thalamus was parcellated into five homologous subregions based on its connectivity with the cerebral cortex in humans, chimpanzees, and macaques(Fig. 1A[c]). The proportion of thalamic subregions to thalamic volume was relatively similar between species, except for frontotemporal and precentral thalamic subregion(Fig. 1B). The thalamic subregions primarily connected to the frontotemporal, precentral, and parietal cortices exhibited isometric scaling relative to the whole brain grey matter(Fig. 1C[a,b,d]), while subregions connected to the postcentral and occipital cortices displayed negative allometric scaling(Fig. 1C[c,e]). All the thalamic subregions not only demonstrated strong connections with their respective cortical targets but also exhibited extensive connectivity with other cerebral regions(Fig. 2A). Furthermore, the connectivity strength between the thalamus and the cerebral cortex displayed a gradient pattern, with the highest in humans, followed by chimpanzees, and the lowest in macaques(Fig. 2B).
·Fig.1. Connectivity-based parcellation of the thalamus for humans, chimpanzees, and macaque monkeys
·Fig.2. Connectivity profiles of thalamic subregions across species.
Conclusions:
In conclusion, connectivity-based parcellation is a powerful tool to reveal internal organizations of the brain structure and can be used for identifying homologous regions across species. Our results revealed that the internal structure of the thalamus exhibits inconsistent allometric scaling during evolution. Connections between thalamic subregions and the cerebral cortex showed a similar pattern, with connectivity strengthening during evolution. These findings provided new insights into the co-evolution of the thalamocortical system.
Modeling and Analysis Methods:
Connectivity (eg. functional, effective, structural)
Segmentation and Parcellation 1
Novel Imaging Acquisition Methods:
Diffusion MRI 2
Keywords:
ANIMAL STUDIES
Cross-Species Homologues
MRI
Structures
Thalamus
Tractography
WHITE MATTER IMAGING - DTI, HARDI, DSI, ETC
1|2Indicates the priority used for review
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Rikhye, R. V., Wimmer, R. D., & Halassa, M. M. (2018). Toward an Integrative Theory of Thalamic Function. Annual Review of Neuroscience, 41(Volume 41, 2018), 163-183.
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