NAVIGATION THROUGH VECTOR ADDITION

During short foraging excursions away from their home, central place f oragers update their position relative to their point of departure by processing signals generated by locomotion. They therefore can home al ong a self-generated vector without using learned references, In roden ts(1-5) and other mammals(6,7), this path integration process (dead re ckoning) can occur on the basis of purely internal signals, such as ve stibular(8) or proprioceptive (re)afferences(6). We report here that h amsters are also capable of proceeding to a previously learned feeding site through vector information from locomotion only. The subjects co mpute(9) the direction and distance to the goal by subtracting their c urrent-position vector from the stored nest-to-goal vector. This compu tation pertains to locations per se and therefore occurs in absolute s pace, independently of landmark objects. If available, prominent visua l cues merely serve to confirm the path planned through the addition o f self-generated vectors, whereas visual as well as nonvisual referenc es confirm that the subject has arrived at the goal site.