title: Sensory mismatch induces autonomic responses associated with hippocampal theta waves in rats.
abstract: Hippocampal (HIP) theta power increases during sensory mismatch, which has been suggested to induce motion sickness with autonomic abnormality (Zou et al., 2009 [29]). To investigate relationships between hippocampal theta rhythm and autonomic functions, theta waves in the HIP and electrocardiograms (ECGs) were recorded during sensory mismatch by backward translocation in awake rats. The rats were placed on a treadmill affixed to a motion stage that was translocated along a figure 8-shaped track. The rats were trained to run forward on the treadmill at the same speed as that of forward translocation of the motion stage (a forward condition) before the experimental (recording) sessions. In the experimental sessions, the rats were initially tested in the forward condition, and then tested in a backward (mismatch) condition, in which the motion stage was turned around by 180° before translocation. That is, the rats were moved backward by translocation of the stage although the rats ran forward on the treadmill. In this condition, proprioceptive information indicated forward movements while vestibular and visual information indicated backward movements. The theta (6-9 Hz) power was significantly increased in the backward condition compared with the forward condition. Spectral analysis of heart rate variability indicated that sympathetic nervous activity increased in the backward condition. These data (theta power and sympathetic nervous activity) were positively correlated. Furthermore, electrical stimulation of the HIP at theta rhythm (8 Hz) increased heart rate. These results suggest that sensory mismatch information activates the HIP to induce autonomic alteration in motion sickness.
authors.affiliation: System Emotional Science, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama 930-0194, Japan.
authors.forename: Michiyo
authors.initials: M
authors.lastname: Aitake
authors.forename: Etsuro
authors.initials: E
authors.lastname: Hori
authors.forename: Junpei
authors.initials: J
authors.lastname: Matsumoto
authors.forename: Katsumi
authors.initials: K
authors.lastname: Umeno
authors.forename: Masaji
authors.initials: M
authors.lastname: Fukuda
authors.forename: Taketoshi
authors.initials: T
authors.lastname: Ono
authors.forename: Hisao
authors.initials: H
authors.lastname: Nishijo
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001341:Autonomic Nervous System / Q000502:physiology*; D017776:Autonomic Pathways / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology; D004558:Electric Stimulation / Q000379:methods; D004562:Electrocardiography / Q000379:methods; D005080:Exercise Test; D005583:Fourier Analysis; D006339:Heart Rate / Q000502:physiology; D006624:Hippocampus / Q000502:physiology*; D008297:Male; D009039:Motion Perception / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013826:Theta Rhythm / Q000502:physiology*; D013997:Time Factors; D014722:Vestibule, Labyrinth / Q000502:physiology; D014851:Wakefulness; D014868:Water Deprivation / Q000502:physiology