Cortical activation and functional connectivity in patients with chronic insomnia based on working memory tasks: a...

Working memory (WM) impairment has been found in patients with insomnia, and the frontotemporal region plays a central role in working memory. Therefore, changes in functional connectivity in the frontotemporal region may play an important role in WM impairment in patients of chronic insomnia, but little is known about the neural processes associated with WM dysfunction in patients with chronic insomnia. This study used functional near-infrared spectroscopy (fNIRS) to investigate differences in cortical activation and functional connectivity during a WM task between patients with chronic insomnia and healthy controls (HCs).

A total of 88 patients with chronic insomnia, as well as 84 HCs, were recruited. We used a WM task in which participants were asked to memorize and make choices based on the presented stimulation (graphics and colors). The WM task was divided into a block range set at baseline, a WM stimulation range set, a WM exploration range set, and a no WM (NWM) exploration range set. The oxygenated haemoglobin (Oxy-Hb) concentration in the frontotemporal lobe of the participants during the performance of the WM task was monitored using fNIRS, and brain functional connectivity and cortical activation in different brain regions were examined in patients with chronic insomnia.

Behavioral tasks showed that the accuracy of patients with chronic insomnia was significantly lower than that in the HCs. The fNIRS showed that during the WM stimulation phase of the WM task, the oxy-Hb values of bilateral medial prefrontal cortex (mPFC) and dorsolateral PFC (DLPFC) in patients with chronic insomnia were significantly lower than those in HCs, while no significant differences were found in other brain regions. The average connection strength between different channels in patients with chronic insomnia is lower than that in the HCs. Further functional connectivity calculations for different brain regions revealed that the HCs had significantly higher connection strengths between four pairs of brain regions than the patients with chronic insomnia.

This study found that patients with chronic insomnia exhibited decreased activation and abnormal functional connectivity in bilateral mPFC regions during the WM task, suggesting that chronic insomnia showed damage to relevant brain regions during WM processing, which provides an objective theoretical basis for explaining WM impairment in patients with chronic insomnia.