Cerebellar morphology and behavioural correlations of the vestibular function alterations in weightlessness.

• Vestibular changes in altered gravity and their morphological basis are discussed. • Behavioural correlations of vestibular abnormalities are provided. • Gecko and mice vestibular cerebellum in the Bion-M and Foton-M experiments are widely reviewed. • Bion-M1experiments provided evidence for the sensory compensation hypothesis. In humans and other vertebrates, the range of disturbances and behavioural changes induced by spaceflight conditions are well known. Sensory organs and the central nervous system (CNS) are forced to adapt to new environmental conditions of weightlessness. In comparison with peripheral vestibular organs and behavioural disturbances in weightlessness conditions, the CNS vestibular centres of vertebrates, including the cerebellum, have been poorly examined in orbital experiments, as well as in experimental micro- and hypergravity. However, the cerebellum serves as a critical control centre for learning and sensory system integration during space-flight. Thus, it is referred to as a principal brain structure for adaptation to gravity and the entire sensorimotor adaptation and learning during weightlessness. This paper is focused on the prolonged spaceflight effects on the vestibular cerebellum evidenced from animal models used in the Bion-M1 project. The changes in the peripheral vestibular apparatus and brainstem primary vestibular centres with appropriate behavioural disorders after altered gravity exposure are briefly reviewed. The cerebellum studies in space missions and altered gravity are discussed. [ABSTRACT FROM AUTHOR]