| The outbreak of space motion sickness is very common in astronauts during space flight because the afferent impulses from vestibular otolith receptors are reduced when the astronauts are exposed to a new weightlessness environment. The symptoms of space motion sickness include cold sweat, nausea, vomiting, as well as loss of initiative and sensitivity to normally innocuous sensory stimuli and some attentional and cognitive disorders such as decreased concentration. These symptoms affect 75% of crewmembers and impair their average physical and mental efficiency. Until now no exploration have been done on the dynamic changes and adjustment characteristics of brain high function modulated by vestibular stimuli in space medicine. In this study we will deal with the dynamic changes of selective attention -one of the high brain function using event-related potentials (ERP) technique. The main purposes of this work are as follows: (1) To study the dynamic changes of the brain cognitive processing under different acceleration levels which stimulate the horizontal semicircular canal and differentiate the different effects between acceleration and deceleration action. (2) To explore the changes of brain cognitive processing modulated by off-axis rotation that stimulates vestibular otolith receptors and to compare the different influences between stimulation on semicircular canal and otolith. (3) To study the dynamic characteristics of human cardiovascular activitiesunder different acceleration levels, and to provide the evidences that the changes of cardiovascular activities under different vestibular stimuli have potential connection with the dynamic changes of the brain cognitive processing.The ERP were measured in normal young subjects under different vestibular stimuli using auditory selective attention paradigm. The auditory stimuli were the pre-recorded go/no go one syllable digit 2 to 9 in Chinese pronunciation in random interval that is about 1000ms. In the selective attention paradigm subjects were asked to respond as soon as possible when hearing the odd numbers (target signal) and to withhold when hearing the even numbers (non-target signal).The vestibular stimuli were designed according to the objectives in this study. (1) In order to analyze the dynamic changes of auditory selective attention and have a bird view of the cardiovascular fluctuations under different vestibular stimuli, four linearly related angular acceleration levels were used, that was 0.6/s2, 0.8/s2, 1.0/s2 and 1.2/s2. (2) To compare the difference nature of acceleration and deceleration effect, four corresponding angular deceleration levels were used, that was -0.6/s2, -0.8/s2, -1.0/s2 and -1.2/s2. (3) The constant low angular velocity rotation was given to differentiate the effects of pure rotation and acceleration on brain cognitive processing. (4) In order to clarify the influences of otolith stimulation on brain cognitive processing, the 50cm off-axis rotation was given.The main results are listed below.(1) Compared with control, the latencies of N1, P2 and P3 components in target event-related potentials (T-ERPs) were significantly shortened during 10/s constant rotation. The P20-50 mean amplitudes were significantly increased and the P3 amplitudes and mean amplitudes of T-ERPs and N2 amplitudes and mean amplitudes of non-target event-related potentials (NT-ERPs) were significantly decreased during 10/s constant rotation. These results demonstrated that pure rotation speeded the processing of target signaland the speeding effects began at the sensory period. The amplitude changes of ERP components were similar to the electrophysiological change of some central stimulant drugs such as ethanol and Ro 17-1588. It was suggested that 10?s constant rotation promoted and facilitated the brain cognitive processing. This kind of central stimulant effect was directly related to the activation of ascending reticular activating system when subjects were exposing to a constant angular velocity rotation environment.(2) Compared with con...
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