ONTOGENY OF EQUILIBRIUM BEHAVIOR IN THE RAT, WITH SPECIAL REFERENCE TO THE INFLUENCE OF VISION AND TRAINING

Rats aged between 1 day and 3 weeks were placed on an horizontal mast rotating about its axis. The time during which they maintained their equilibrium without falling down was measured. Three categories of rats were used: normal (N) rats, reared in normal conditions of daylight and tested in light; visually-deprived (VD) rats, reared and tested in darkness; dark-tested (DT) rats, reared in normal conditions of daylight and tested in darkness. These rats were naive or non-naive and were grouped using either a single-litter procedure or a split-litter procedure; rotation rates were 10 and 20 revolutions per minute (rev/min) and sometimes 15 and 30 rev/min. The main results and conclusions are the following: (1) Whatever the rotation rate, the rearing and testing conditions and whether the rats were subjected to training (non-naive rats) or not (naive rats) one observed a period of time (the shift period) between Days 15 and 18 after which the scores sharply increased; it is concluded that the maturation of the equilibrium function depends neither on rotation rate nor on vision and is also independant, to a large extent, of training; (2) The scores reached by the animals were lower for high than for low rotation rates, especially when vision was excluded; (3) in N, VD and DT non-naive rats the scores were better than in naive rats; so, training helps the animals to maintain their equilibrium upon the rotating mast; (4) In naive VD rats the scores were very much decreased compared with those of N naive rats, while in naive DT rats they were much less decreased; so, the presence of vision during both rearing and testing conditions, but particularly during rearing, helps the animals to maintain their equilibrium; (5) In non-naive rats there is no significant difference between the scores obtained by VD and DT groups, so it seems that training masks the effects of the absence of vision during rearing. © 1979.