Mismatch negativity and personality traits in chronic primary insomniacs

The thalamo-(fronto)cortical circuit is involved in sleep regulation, and its dysfunction might contribute to the pathophysiology of chronic primary insomnia. To obtain more evidence of the involvement of the circuit, we studied 23 patients with chronic primary insomnia and 28 healthy volunteers via the assessment of mismatch negativity (MMN) elicited by tone intensity deviance, and of personality traits measured by Zuckerman's Sensation Seeking Scales, and Zuckerman-Kuhlman's Personality Questionnaire. In insomniacs, MMN amplitude at Fz was significantly larger; Depression, which was measured by Plutchik-van Praag's Depression Inventory, and Neuroticism-anxiety and Impulsivity scores were higher, while the Thrill and adventure seeking score was lower; MMN amplitude was positively correlated with Depression and with Impulsivity. In healthy subjects, MMN amplitude at Fz was positively correlated with Neuroticism-anxiety, but negatively with Experience seeking. The larger MMN and distinct personality traits suggest a hyperactivity in the thalamo-(fronto)cortical neuronal circuit in insomniacs, which is probably the result of weak thalamic gating mechanisms, or an imbalance of several neurotransmitter systems.