Effects of gravity, hypergravity and microgravity on vestibular neurones of the crab.

Recordings were made from identified balancing system interneurones using implanted electrodes in crabs oscillated at 0.3 Hz during bouts of Parabolic flight. Repeatable non stabilized patterns of response firing were seen in head up and head down interneurones. During the hypergravity phases, the ratio of firing frequencies in the two directional categories of interneurones was altered showing that hypergravity produced effects normally seen during tilting of the crab, implying greater bending of the sensory thread hairs. During microgravity, firing levels remained low and constant or changed slowly towards initial firing levels.