Figure 1.
A time reproduction task for rodents. (A) Experimental apparatus and task. A gerbil was placed on a treadmill surrounded by a projection screen. Trials started with a timed stimulus (black screen). Then a virtual corridor appeared and the animal had to reproduce the time interval by walking. If the reproduction was close to the stimulus duration (“in”), a food reward was delivered and the entire screen was set to green for 3–4 s before another trial was initiated; otherwise, the screen was set to white (“out”). (B) The range for positive feedback, i.e., the error-tolerance window, was narrowed/widened after each in/out response. (C) Stimulus durations for one session were randomly sampled from one of three discrete uniform distributions with seven values each. Upper and lower borders are given as numbers. These stimulus ranges differed only by their mean values (marked by a vertical black solid line and a number). Colors identify range and will be used throughout the article. (D) Time reproductions of an example gerbil. Individual reproduced values are given as small dots and averages for each stimulus as large dots connected by a solid line. Gray dashed line marks equality. Inset: Square roots of the average variance (i.e., the SD) vs those for average squared bias for the three stimulus distributions. The distance from the origin of the coordinate system is the RMSE. Along the dashed quarter circles, RMSE would be constant. (E) SD for each stimulus duration (SDs). (F) Average bias, i.e., response − stimulus, for each stimulus (BIASs).