'Critical periods' in vestibular development or adaptation of gravity sensory systems to altered gravitational conditions?

摘要

A feature of sensory and motor systems is their susceptibility to modifications of their adequate physical and/or chemical stimuli during development. Studies in kittens deprived of the visual input have revealed that this susceptibility is restricted to a certain period of life (cf. [59]), which was called the critical (sensitive) period. Critical periods were also described for other sensory and motor systems including hearing, feeling, olfaction or walking (12, 25, 27, 33, 52, 57). They are characterized (1) by a sensitivity of the developing system to modifications of the adequate environment, preferably to stimulus deprivation, (2) by a clearly defined time window of this sensitivity and (3) by the irreversibility of anatomical, behavioral or physiological modifications induced by these altered environmental conditions. These criteria imply that developing animals have to be exposed to short- and long-lasting modifications of their environment at different periods of their life.