Direct perturbation of neural integrator by bilateral galvanic vestibular stimulation.
Caloric vestibular stimulation (CVS) and galvanic vestibular stimulation (GVS) act primarily on the peripheral vestibular system. Although the electrical current applied during GVS is thought to flow through peripheral vestibular organs, some current may spread into areas within the central nervous system, particularly when the bilateral galvanic vestibular stimulation (bGVS) method is used. According to Alexander's law, the magnitude of nystagmus increases with eccentric gaze movement, due to the function of the neural integrator (NI); thus, if the information for vestibular stimulation corresponds to Alexander's law, the peripheral vestibular organ is stimulated. Therefore, it would appear that if CVS results comply with Alexander's law, and bGVS results do not, the sites stimulated by bGVS are not perfectly located in the peripheral vestibular area. In our experiments on normal human subjects, the magnitude of nystagmus under CVS increased with rising gaze eccentricity in the direction that the magnitude of the nystagmus increases, and this change was found to follow Alexander's law. However, in the case of nystagmus under bGVS, results did not follow Alexander's law. In addition, study of the influences of bGVS at different current intensities on nystagmus magnitude showed that bGVS at 5 mA distorted nystagmus magnitude more than at 3 mA, which suggests bGVS acts not only on the peripheral vestibular nerves, but also on some areas of the central nervous system, particularly the NI. According to our experiments, bGVS directly affects neural integrator function.
Biomedical Engineering Research Center, Asan Institute for Life Sciences, Asan Medical Center, Seoul, Korea.
Kihwan
K
Hong
Department of Digital Electronics, Dong Seoul University, Seongnam, Korea.
Hyeon-Min
HM
Shim
Institute for Information and Electronics Research (IIER), Inha University, Incheon, Korea.
Minsoo
M
Goh
Department of Otolaryngology-Head and Neck Surgery, Inha University Hospital, Incheon, Korea.
Seung-Yon
SY
Jang
Institute for Information and Electronics Research (IIER), Inha University, Incheon, Korea.|Department of Electronic Engineering, Inha University, Incheon, Korea.
Sangmin
S
Lee
Institute for Information and Electronics Research (IIER), Inha University, Incheon, Korea. stedman@inha.ac.kr.|Department of Otolaryngology-Head and Neck Surgery, Inha University Hospital, Incheon, Korea. stedman@inha.ac.kr.
Kyu-Sung
KS
Kim
D000328:Adult; D004558:Electric Stimulation / Q000379:methods*; D006801:Humans; D008297:Male; D009760:Nystagmus, Physiologic / Q000502:physiology*; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology*; D014725:Vestibular Nerve / Q000502:physiology
Alexander’s law; Bilateral galvanic vestibular stimulation; Caloric vestibular stimulation; Galvanic vestibular stimulation; Neural integrator; Nystagmus; Vestibulo-ocular reflex