fNIRS Investigation of Brain Activity, Cognitive Function and Sleep Quality in Major Depression

Individuals with major depressive disorder (MDD) living with insomnia show significantly less activity in the prefrontal cortex during verbal fluency test (VFT) compared with those who do not, as shown in new data.¹

All brain regions, except the right dorsolateral prefrontal cortex (DLPFC), were significantly more active in patients with MDD and insomnia than in those without insomnia, suggesting sleep quality is an important indicator in functional near-infrared spectroscopy (fNIRS) screening.

As a common mental disorder that affects a significant portion of the global population, MDD is characterized by feelings of sadness, loss of interest in activities, and decreased cognitive function. Insomnia, a common symptom of MDD, has been found to affect prefrontal function and cognitive abilities.

The study cited previous data which have identified specific patterns of brain activation to counteract sleep and improve cognition in healthy individuals. However, the effects of insomnia on the prefrontal cortex of individuals with MDD and the patterns of activation to counteract sleep in this population largely remain unclear.

Investigators led by HuaSen Xu, Department of psychiatry, Affiliated Hospital to Guizhou Medical University, aimed to examine the impact of insomnia on the prefrontal cortex of patients with MDD and the patterns of activation to counteract sleep in this population, using fNIRS.

How Insomnia Impacts a Depressed Brain

The study population was evaluated alongside a control group of healthy patients with significantly higher oxygenated hemoglobin (oxy-Hb) values in the bilateral prefrontal cortex during a verbal fluency test than the group with MDD.

In the MDD group, oxy-Hb values in all brain regions, except the right dorsolateral prefrontal cortex, were significantly higher in the group of those with insomnia than in the group without insomnia. Conversely, the verbal fluency test performance was significantly lower in the group with insomnia than in the group without insomnia and the healthy group.

Scores from the Pittsburgh Sleep Quality Index (PSQI) demonstrated a positive correlation with oxy-Hb values in some left-brain regions, while the Hamilton Rating Scale for Depression (HAMD), as well as the Hamilton Rating Scale for Anxiety (HAMA) scores, showed no correlation with oxy-Hb values.

Sleep Quality, Depression and Cognitive Function

Investigators recruited 80 patients with major depressive disorder and 44 healthy controls. The changes in oxy-Hb concentration in the prefrontal cortex were assessed with fNIRS during the verbal fluency test of all participating individuals, which was used to assess cognitive ability.

The number of words created was recorded to evaluate cognitive function. Additionally, the PSQI was implemented to examine sleep quality, while the HAMD and the HAMA were used to evaluate the severity of depression and anxiety, respectively.

“Furthermore, there was a positive correlation between the severity of insomnia and left VLPFC activation levels, indicating that the left brain region, particularly the VLPFC, plays a crucial role in overcoming sleepiness in MDD patients; these findings may provide new ideas for the treatment of insomnia in MDD patients in the future,” they wrote.

References:

1. Xu, H., Wang, Y., Wang, Y.M. et al. Insomniacs show greater prefrontal activation during verbal fluency task compared to non-insomniacs: a functional near-infrared spectroscopy investigation of depression in patients. BMC Psychiatry 23, 217 (2023). https://doi.org/10.1186/s12888-023-04694-z