Learnt sensori-motor mappings in honeybees: interpolation and its possible relevance to navigation

We investigated the ability of bees to associate a motor parameter with a sensory one. Foragers were trained to fly along a prescribed route through a large box which was partitioned into compartments. Access from one compartment to the next was through a hole in each partition. In two of the compartments, the back wall was covered with a grating of black and white stripes. Stripe orientations and the required trajectories differed in the two compartments so giving bees the opportunity to learn that one stripe orientation signalled the need to fly leftwards and the other rightwards.We videotaped the bees' trajectories through one of these compartments in tests with the grating on the back wall in one of four possible orientations. Flight trajectories to stripes in the training orientations were appropriately to the left or to the right implying that bees had linked a given flight direction to a given stripe orientation. With gratings oriented between the training values, flight directions were, under some conditions, intermediate between the training directions. This interpolation indicates that the training regime had induced a continuous mapping between stripe orientation and trajectory direction and thus suggests that trajectory direction is a motor parameter which is encoded explicitly within the brain. We describe a simple network that interpolates much like bees and we consider how interpolation may contribute to the ability of bees to navigate flexibly within a familiar environment.