The Length and the Width of the Human Brain Circuit Connections are Strongly Correlated

TL;DR

This study reveals strong correlations between the length, width, and occurrence frequency of human brain connections, indicating that most frequent and strongest connections are short and wide, based on analysis of a large consensus connectome.

Contribution

The paper provides the first comprehensive analysis of correlations among edge length, width, and occurrence in a large human brain connectome, revealing fundamental organizational principles.

Findings

Most frequent connections have the largest fiber counts.

Shorter edges tend to have higher fiber counts.

Longer edges are less frequent and typically weaker.

Abstract

The correlations of several fundamental properties of human brain connections are investigated in a consensus connectome, constructed from 1064 braingraphs, each on 1015 vertices, corresponding to 1015 anatomical brain areas. The properties examined include the edge length, the fiber number, or edge width, meaning the number of discovered axon bundles forming the edge and the occurrence number of the edge, meaning the number of individual braingraphs where the edge exists. By using our previously published robust braingraphs at \url{https://braingraph.org}, we have prepared a single consensus graph from the data and compared the statistical similarity of the edge occurrence numbers, edge lengths, and fiber counts of the edges. We have found a strong positive Spearman correlation between the edge occurrence numbers and the fiber count numbers, showing that statistically, the most frequent cerebral connections have the largest widths, i.e., the fiber number. We have found a negative Spearman correlation between the fiber lengths and fiber counts, showing that, typically, the shortest edges are the widest or strongest by their fiber counts. We have also found a negative Spearman correlation between the occurrence numbers and the edge lengths: it shows that typically, the long edges are infrequent, and the frequent edges are short.