Active antennal movement in cockroaches - towards understanding multimodal exploration

The long and highly mobile cockroach antennae are multifunctional sensory appendages incorporating two of the most fundamental senses – olfaction and touch. Previous laboratory experiments with cockroaches in unisensory tasks have demonstrated the animal’s ability to perform antenna-dependent tasks such as chemotaxis in presence of relevant odours, positive thigmotaxis (wall-following) when the antennae come in contact with a wall, ability to negotiate obstacles and to achieve tactile orientation. However, studies of multisensory capabilities mediated by the antennae are lacking. Here we employ an integrated experimental and computational approach to investigate how active antennal movement affects sensory acquisition in a multimodal environment. We characterize the relationship between antennal searching movement and the spatial and temporal properties of encountered odour concentrations, which will serve as the basis for a future extension to study olfactory-tactile integration.
When presented with a behaviourally relevant odour antennae exhibited systematic movements, and there appears to be a dynamic modulation of coupling between the left and right antenna. In order to gain insight into the coordination of antennal movements we employed an adaptive Hopf coupled oscillator model, with parameters fitted to kinematic data derived from high-speed recordings of antennal movement. In addition we mapped the structure of the odour plume that the antennae encountered and used the odour concentration map as driver signals for the model. A transfer function between the odour signal and the inter-oscillator coupling strength will subsequently be defined. We will use the model to predict how the neural coupling between the two antennae is modulated by the encountered odour concentration, and consequently the relationship between odour sensing and antennal movements. In vivo recordings from the animal’s olfactory neurons will allow us to determine how neural activity in response to a relevant odour varies with antennal movements, and will allow us to gain insight into the mechanisms that underlie active sensing in insects.