Relationship of Hemodynamic Delay and Sex Differences Among Adolescents Using Resting-state fMRI Data

Among the non-invasive neuroimaging techniques, resting-state functional magnitude imaging is the most widely used method for capturing whole brain activity. Functional connectivity enables us to extract brain networks which exhibit temporal coherence from resting-state fMRI data. However, there are some limitations to fMRI which limit the questions we can ask. The latency estimated from fMRI is a mixture of the sluggish hemodynamic delay and neural latencies. Due to the large spatially varying delays related to hemodynamics, the pattern and order of activities between brain regions in a very short period will be driven by hemodynamics in this case. In this study, we proposed a method to estimate the hemodynamic delays between brain regions. We performed cross-correlation between pairs of time courses and estimated the optimal lags such that the correlation is maximized. We applied our method to a large dataset of adolescents and investigated the differences between males and females on different lag measures. In addition, we proposed short and long-time delay graphs to visualize the differences between groups more easily. Our result suggests that the female subjects had shorter hemodynamic delay compared to the male group of the same age. Significant differences were identified both within and between domain regions, including the cerebellar, somatomotor, default mode, cognitive control, and visual domain.