The Sleepless Brain: Neuroimaging Support for a Differential Diagnosis of Insomnia

One-tenth of the population suffers from insomnia, increasing their risk on other health problems such as depression. Self-reported sleep quality only was historically leading for insomnia diagnosis, but more recently a state of 24-hour hyperarousal has been associated with insomnia, either physiological (increased heart rate, higher frequency EEG) or predominant cognitive-emotional hyperarousal (worry, rumination, repetitive thoughts). Strong evidence shows that those suffering from insomnia with physiological hyperarousal are at higher risk of short and long term severe health problems such as inflammation and hypertension than the group without physiological hyperarousal. The neurophysiological basis of these insomnia phenotypes has however barely been investigated, although its results can have major consequences for how this limiting condition will be treated.

To support the development of a differential diagnosis of insomnia, structural and functional brain connectivity in insomnia patients with different levels of hyperarousal will be investigated and related to sleep variables. Investigators will compare the insomnia group to a normal sleeping control group. Investigators expect that the emotion processing circuit (amygdala-ventromedial prefrontal cortex) is a) more affected in insomniacs compared to normal sleeping controls and b) the directionality of this effect to depend on the level and type of hyperarousal in insomniacs. Further, investigators expect c) amygdala activity to be positive correlated with physiological hyperarousal level and d) prefrontal activity to be positively correlated with cognitive-emotional hyperarousal level. Investigators expect a higher physiological hyperarousal level to be reflected in affected afferent pathways of the amygdala towards the ventromedial prefrontal cortex and investigators expect higher cognitive-emotional hyperarousal to be related to affected efferent pathways from the ventromedial prefrontal cortex to the amygdala. Investigators expect sleep quality to play a mediating role in both types of hyperarousal and their brain activation patterns in insomnia patients and normal sleeping controls.

These data can lead to the definition of new insomnia phenotypes and to new customized and effective insomnia treatment, focused not only on improving sleep but also on changing dysfunctional hyperarousal levels that currently put insomniacs at risk of numerous severe health problems.