Symmetries of Vestibular Dysfunction in Major Epression

bstract—Depression is characterized by alterations in the ircadian secretion of hormones, sleep and motor activity, all f which are regulated by suprachiasmatic nuclei (SCN). The estibular system in the inner ear registers the amount of otor activity. To test the integrity of this motion sensitive ystem in depression, we studied the vestibulo-ocular reflex VOR) in depressive patients who were not taking medication nd healthy control subjects, which allowed us to investigate ach ear and its corresponding nerve centers. Ocular reflex ovement depends on vestibular nuclei activity, and we ound that at 30 °C stimulation the right vestibular system in epressive patients has approximately half the activity of the eft side. Significant asymmetry was not detected in control ubjects. We also found a significant decrease in the slow hase (16.92 9.13°/s) of the reflex in the depressed group as ompared with the control group (43.77 16.04°/s). The vesibular nuclei of the right and left sides are hypoactive. Speifically, the right vestibular nucleus is hypoactive in deressed people and can easily be measured using VOR. hese results support the abnormal asymmetries hypothesis f depression and suggest that these asymmetries also exist t the level of the brain stem or neuronal centers that are fferents to right vestibular nuclei, like SCN or raphe nuclei. 2006 IBRO. Published by Elsevier Ltd. All rights reserved.