Biology subjects

Yeh, F.-c.

Publications and source records attributed to Yeh, F.-c..

3 recordsLinked to original sources

bioRxiv2020

Redundancy Circuits of the Commissural Pathways in Human and Rhesus Macaque Brains

It has been hypothesized that the human brain has traded redundancy for efficiency, but the structural existence has not been identified to examine this claim. Here, we report three redundancy circuits of the commissural pathways in primate brains, namely the orbitofrontal, temporal, and occipital redundancy circuits of the anterior commissure and corpus callosum. Each redundancy circuit has two distinctly separated routes connecting a common pair of cortical regions. We mapped their trajectories in human and rhesus macaque brains using individual and population-averaged tractography. The dissection results confirmed the existence of these redundancy circuits connecting the orbitofrontal lobe, amygdala, and visual cortex. The volume analysis showed a significant reduction in the orbitofrontal and occipital redundancy circuits of the human brain, whereas the temporal redundancy circuit had a substantial organizational difference between the human and rhesus macaque. Our overall findings suggest that the human brain is more efficient in the commissural pathway, as shown by the significantly reduced volume of the anterior commissure which serves as the backup connections for the corpus callosum. This reduction of the redundancy circuit may explain why humans are more vulnerable to psychiatric brain disorders stemming from the corpus callosum compared to non-human primates. SignificanceWe report and describe the connection routes of three redundancy circuits of the commissural pathways in human and rhesus macaque brains and compare their volumes. Our tractography and dissection studies confirmed that the human brain has smaller redundancy circuits. This is the first time such redundancy circuits of the commissural pathways have been identified, and their differences quantified in human and rhesus macaque to verify the redundancy-efficiency tradeoff hypothesis. The findings provide new insight into the topological organization of the human brain and may help understand the circuit mechanism of brain disorders involving these pathways.

neuroscience↗

bioRxiv2020

In vivo Restricted-Diffusion Imaging (RDI) is sensitive to differences in axonal density in typical children and adults

BackgroundThe ability to dissociate axonal density in vivo from other microstructural properties of white matter is important for the diagnosis and treatment of neurologic disease, and new methods to do so are being developed. We investigated one such method-restricted diffusion imaging (RDI)-to see whether it can more accurately replicate histological axonal density patterns in the corpus callosum (CC) of adults and children compared to diffusion tensor imaging (DTI), neurite orientation dispersion and density imaging (NODDI), and generalized q-sampling imaging (GQI) methods. To do so, we compared known axonal density patterns defined by histology to to diffusion-weighted imaging (DWI) scans of 840 healthy 20- to 40-year-old adults, and, in a replication and extension, to DWI scans of 129 typically developing 7-month-old to 18-year-old children and adolescents. Contrast analyses were used to to compare pattern similarities between the in-vivo metric and previously-published histological density models. We found that RDI was effective at mapping axonal density of small (Cohens d= 2.60) and large fiber sizes (Cohens d= 2.84) in adults. The same pattern was observed in the developing sample (Cohens d= 3.09 and 3.78, respectively). Other metrics, notably NODDIs intracellular volume fraction (ICVF), were also sensitive to differences in axonal density across the longitudinal axis of the CC. In conclusion, the study showed that RDI is effective at measuring axonal density of small and large axons in adults and children, with both single- and multi-shell acquisition DWI data. Its effectiveness and availability to be used on standard as well as advanced DWI acquisitions makes it a promising method in clinical settings.

neuroscience↗

bioRxiv2020

Shape Analysis of the Human Association Pathways

Shape analysis has been widely used in digital image processing and computer vision, but they have not been utilized to compare the structural characteristics of the human association pathways. Here we used shape analysis to derive length, area, volume, and shape metrics from diffusion MRI tractography and utilized them to study the morphology of human association pathways. The reliability analysis showed that shape descriptors achieved moderate to good test-retest reliability. Further analysis on association pathways showed left dominance in the arcuate fasciculus, cingulum, uncinate fasciculus, frontal aslant tract, and right dominance in the inferior fronto-occipital fasciculus and inferior longitudinal fasciculus. The superior longitudinal fasciculus has a mixed lateralization profile with different metrics showing either left or right dominance. The analysis of between-subject variations shows that the overall layout of the association pathways does not variate a lot across subjects, as shown by low between-subject variation in length, span, diameter, and radius. In contrast, the area of the pathway innervation region has a considerable between-subject variation. A follow-up analysis is warranted to thoroughly investigate the nature of population variations and their structure-function correlation.

neuroscience↗