Abstract
Behavioral responses to visually moving stimulus in rats are not fully investigated. Here we determined the lowest velocity of motion stimulus effective for the shuttle box avoidance task. Four groups of male Wistar rats were trained to avoid electrical shocks from a grid floor using a different velocity of sin-wave gratings as a conditioned stimulus (CS; 40, 20, 1.5 or 0.5 deg/s). Sin-wave gratings with a spatial frequency of 0.5 c/deg was presented on a CRT display placed on the top of the shuttle-box, and moved for a 10 sec. The foot shocks were delivered at 10 sec after CS onset, unless the animal crossed the central barrier to move the adjacent compartment of the box. An inter-trial interval was random with a mean of 60 sec (45-75 sec). A daily session consisted of 50 trials. Avoidance rate increased as training proceeded in all four groups and reached at an asymptote level of 50-70% after 3-4th sessions. The 0.5 deg/s group showed a higher avoidance rate than those in the other groups after 3rd session. However, inter-trial responses (ITRs) in the 0.5 deg/s group were significantly higher than those in the other groups (5.6 vs. 3.0/trial), indicating that 0.5 deg/s group did not learn the task. At the 5th session ITRs were highest in 0.5 deg/s group (N=6) and lowest in 20 deg/s group (N=4). The ITRs in 0.5 and 40 deg/s groups (N=6 and N=4, respectively) were similar. These results suggest that rat can perceive motion most easily with a velocity of 20 deg/s, and can perceive motion with a velocity at least higher than 1.5deg/s. [Jpn J Physiol 55 Suppl:S157 (2005)]
