Electron microscopy examination of layers III-IV in the somatosensory cortex of rat's brain following 5- and 33-day and repeated 5-day exposure to 2 G revealed ultrastructural changes in dendritic spines, synapses, axon terminals and nervous cell body suggesting their functional activation and increase of the afferent input from hindlimb mechanoreceptors Hypertrophy of the acicular apparatus (AA) due to hypergravity, growth of AA destruction as a result of 33-day exposure and its ample evidence after repeated 5-day exposure lead to the conclusion that AA ultrastructure can be used for assessing afferent input into the brain cortex of animals exposed in a changed field of gravity.