Chunking by Proximal Arm Cues Facilitates Rats′ Performance in the Radial Maze

Three experiments showed that training rats to chunk a 16-arm radial maze into striped and wire mesh (gridded) arms facilitates their spatial working memory for arm locations. Rats were trained to visit eight unblocked baited arms of a 16-arm radial maze (half-maze run) and then were exposed to the complete maze to sample the remaining eight baited arms (whole-maze run). The initially exposed eight arms were either all striped or all gridded on alternating trials for half the rats (Arm Cue Relevant, ACR group). The remaining rats (Arm Cue Irrelevant, ACI group) received a mixture of striped and gridded arms on their half-maze runs. Following this phase of segmented trials, all rats were exposed only to all 16 arms over a series of trials in the first two experiments. In the third experiment, the initial eight arms were either all striped or all gridded on alternating trials for all rats. During some second, whole-maze runs, however, all arms contained the same proximal cue. ACR rats made fewer reentries than ACI rats in all phases of all experiments. This difference was maintained over increasing delays between half- and whole-maze runs in the first experiment, changes in arm cue and blocking configurations in the second experiment, and removal of differential arm cues in the third experiment.