Meeting Abstract
The reduced hindwings of flies, known as halteres, are specialized mechanosensory organs that are essential for flight. Through arrays of strain-sensitive sensilla on their bases, halteres detect inertial forces associated with body rotation during flight (Nalbach 1993; Dickinson MH 1999). Previous studies have shown direct haltere inputs to both wing-steering and neck motoneurons (Fayyazuddin and Dickinson 1996; Chan and Dickinson 1996), but there is currently no evidence of haltere stimulus representation in the brain, where body rotation information could be integrated with other sensory inputs. As in the vertebrate vestibular system, the haltere system interacts with vision to control body and head movements. Behavioral work done in our lab has shown that halteres are important for mediating wing-steering responses to wide-field motion (Mureli & Fox 2015). This visual stimulus is also encoded in the central complex (CX), an associative sensorimotor integrating region in insect brains (Weir and Dickinson 2015). Whereas fast flight maneuvers require direct neural connections from haltere afferents to flight steering muscles, it is also possible that integration of visual and haltere information may take place in the brain which can be used in various tasks, such as longer-term planning. Using multichannel extracellular recording, we examined responses of CX cells to various haltere and visual motion stimuli. Some CX cells showed non-linear, speed-dependent responses to both haltere and visual input. We also quantified the modulation of these responses by simultaneous stimulation in both modalities. By showing how haltere information is represented and integrated in the central brain, we provide the first evidence of ascending input into the CX and demonstrate how multi-modal information can be used to support locomotor or other complex behaviors.
