Neuroscientists from the University of Arizona have potentially identified a neural biomarker of mood vulnerability following sleep loss. Their study found that white matter compactness in three important brain networks is related to resilience to mood degradation during sleep deprivation.

The findings were published in the journal NeuroImage.

“Exploring different neuroimaging techniques including functional, structural and white-matter diffusion properties has been my passion for the last 10 years,” said study author Sahil Bajaj, who will soon be the Director of Multimodal Clinical Neuroimaging Laboratory (MCNL) at Boys Town National Research Hospital.

“I had noticed that sometimes people, including me, get irritated if they do not get enough sleep. Lack of sleep is well known to lead to increased mood variability. There is also much evidence suggesting that individuals differ in their responses to sleep loss — some people are severely affected but others seem to be quite resilient and show little effect from sleep deprivation.”

“While most studies have focused on individual vulnerability to sleep loss with regard to simple attention and alertness, very little is known about what makes some people vulnerable to the mood degrading effects of sleep deprivation. The findings reported in previous studies raised my interest in exploring characteristics of the brain that may help in sustaining mood degradation following sleep deprivation.”

The researchers were particularly interested in the brain’s the default-mode network, central executive network and salience network. Previous research has indicated that interconnectivity among these three networks are characteristic of several major psychiatric and neurological disorders.

In the study, 45 healthy individuals underwent brain MRI with a specialized technique called diffusion tensor imaging (DTI). A few days later, the participants returned to the lab, where they stayed awake overnight and completed an assessment of their mood every hour between 7:15 p.m. and 11:15 a.m. the following morning.

The researchers found that participants with greater white-matter compactness tended to display a greater ability to sustain a positive mood during sleep deprivation.

“There are essentially two different types of tissue in our brains: grey matter, which is made up of the actual brain cells or neuron bodies, and white matter, which is made up of long insulated fibers that connect these brain cells together,” Bajaj told PsyPost.

“We found that it is the compactness of white-matter that is associated with greater resilience to mood degradation induced by 24 hours of sleep deprivation. Characteristics of grey matter do not seem to play a role in sustaining mood degradation following sleep deprivation. Very simply put, people with more compact white matter fibers seemed to be less likely to get ‘moody’ when sleep deprived.”

The study — like all research — includes some limitations.

“First, our data quality was of moderate resolution. More advanced types of scans will allow us to look at this in even more fine grained ways. Second, diffusion measures used in our study are known to be sensitive to several factors such as crossing white matter fibers, magnitude of myelination and viscosity which may hinder or facilitate water diffusion,” Bajaj explained.

“Therefore, there is possibility of more complex interpretations from our findings. Moreover, these findings involved simple correlations between brain measures and mood change, so identification of causal associations between mood variability following sleep deprivation and large-scale effective connectivity measures still needs to be addressed in future studies.”

“I would like to thank SCAN lab and in particular my advisor, and the Principal Investigator of the study, Dr. William D.S. Killgore — the director of SCAN lab at the University of Arizona — for all his help and support in completing this project among several others. More details about our lab can be found here: https://scanlab.arizona.edu/,” Bajaj added.

The study, “Vulnerability to mood degradation during sleep deprivation is influenced by white-matter compactness of the triple-network model“, was authored by Sahil Bajaj and William D.S. Killgore.