Noisy vestibular stimulation improves autonomic and motor responsiveness in central neurodegenerative disorders

Abstract

The vestibular nerves are known to influence neuronal circuits in the medullary cardiovascular areas and, through the cerebellar vermis, the basal ganglia and the limbic system. By means of noisy galvanic vestibular stimulation (GVS), it might be possible to ameliorate blunted responsiveness of degenerated neuronal circuits of patients with multi system atrophy or Parkinson's disease, or both. We evaluated the effect of 24-hour noisy GVS on long-term heart rate dynamics in 7 patients with multi system atrophy and on daytime trunk activity dynamics in 12 patients with either levodopa-responsive Parkinson's disease or levodopa-unresponsive parkinsonism. Six of the latter patients were also examined for cognitive performance by means of a continuous performance test. Short-range or high-frequency fluctuations of heart rate were significantly increased by the noisy GVS compared with sham stimulation, suggestive of improved autonomic, especially parasympathetic, responsiveness. Long-range antipersistency of trunk activity patterns probed by an autocorrelation measure was significantly increased by the noisy GVS, suggestive of quickening of bradykinesic rest-to-active transitions. The mean reaction time of the continuous performance test was also significantly decreased by the noisy GVS, without significant changes in either the omission or commission error ratios, which is suggestive of improved motor execution during the cognitive task. In conclusion, the noisy GVS is effective in boosting the neurodegenerative brains of patients with multi system atrophy or Parkinson's disease, or both, including those unresponsive to standard levodopa therapy; it is also effective in improving these patients' autonomic and motor responsiveness.