Similarities in the development of place and cue navigation by rats in a swimming pool

The development of place and cue spatial navigation was evaluated in 18-, 19-, and 20-day-old males in the Morris water task (MWT). Past work has suggested that place and cue learning develop at different rates, suggesting that the two aspects of spatial navigation have different neural substrates. In the present study, a new training methodology was used in which animals received spaced training trials, drying and warming in between trials to maintain body temperature, and two probe trial-dependent measures to evaluate spatial memory performance. All ages of rats had lower latencies on the cue task than on the place task. Nevertheless, 18-day-old rats did not learn either task as measured by acquisition latencies and probe trial-dependent measures. The 19- and 20-day-old rats learned both the place and cue tasks as measured by acquisition latency and direct swims to the correct platform location on the probe trial, and both 19- and 20-day-old rats demonstrated a strong spatial bias to the former platform location on the place probe trial but not on the cue probe trial. The finding that developmental onset of place and cue spatial navigation is rapid and complete by day 19 is discussed in relation to contemporary theories of spatial navigation.