Abstract
Investigation of cerebral arterial circulation during cognitive testing was performed before and after prolonged isolation of 6 healthy subjects imitating a mission to space. The ultrasonic technique was used to measure linear blood velocity (LBV) in the medial cerebral artery (MCA) in the course of verbal and tactile testing. Analysis of MCA LBV both before and after isolation showed that at rest and during testing blood flow changes were equally wave-like; however, the amplitude made a significant increase at testing. It was found that LBV fluctuations occurred within the low-frequency band (LFB) and were consistent with the regular changes in tone of resistive vessels, primarily due to own myogenic activity. The wave-like LBV dynamics was observed over all testing time in all the subjects irrespective of central hemodynamics and respiration parameters. Analysis of LBV dynamics revealed a reliable seasonal (periodic) component supporting to the wave-like LBV fluctuations during testing. At large, prolonged isolation did not influence cerebral circulation much but for the reaction to the verbal testing after isolation completion when we registered a reliable rise of the LFB amplitude in left CMA due to activation of the left hemisphere resulting from specifics of communication in a small isolated group. We assume that the wave-like blood flow in cerebral vessels is an adaptive mechanism of autoregulation capable to meet the metabolic demand of the brain during cognitive testing and protect from local hyperthermia.
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