Mice with vestibular deficiency display hyperactivity, disorientation, and signs of anxiety

Previous studies revealed that vestibular cues are crucial for exploration in the absence of visual cues. The working hypothesis of this study was, accordingly, that mice with vestibular dysfunction would become disoriented or unable to globally explore an unfamiliar environment. In 2- and 3-month-old mutant headbanger (Hdb) mice, stereocilia of hair cells are abnormally elongated, yet maintain partial staircase arrangement, suggesting some spared vestibular function at these ages. Here we tested a group of 3-month-old mutant Hdb and a group of non-mutant mice obtained from the same litters (Wt mice). Each individual mouse was introduced into a dark 120 cm x 120 cm arena and its behavior was followed for 10 min. Hdb mice were hyperactive and appeared to engage in local exploration, traveling in a restricted zone for a while and then shifting to travel in another zone. In contrast, Wt mice traveled across zones incessantly with fewer visits to recently entered zones. Thus, Hdb seemed to display local compared with the global exploration of Wt mice, indicating that they were less oriented in the global environment. In addition, Hdb exhibited numerous stretch-attends, which is suggested as a sign of elevated anxiety. Altogether, the three comorbidities of hyperactivity, anxiety, and disorientation can be presented as a syndrome associated with vestibular deficiency in this animal model, and serve in studying vestibular deficiency in humans. (C) 2009 Elsevier B.V. All rights reserved.