A pinboard by
Akriti Chadda

PhD Student, The Hong Kong University of Science and Technology


My research focusses on studying the sensory role of abdomen in flight control in flying insects.

Flying insects have been intriguing neuroscientists and engineers for centuries because of their agility and manoeuvrability during locomotion. Much of the focus in these studies was on the sensory systems such as vision, olfaction and auditory signals. However, over the recent years, more research is being done in closing the loop, that is studying both the sensory and motor control in these insects. Although wings seem like the first point of interest in such a case, my research focusses on studying how the abdomen might be performing the dual role of both a sensor, and an actuator. For the same, we use the technique of neural electrophysiology which involves acquiring signals from the nervous system of the model organism while giving it a stimulus. More specifically, I study the hawkmoth, Manduca Sexta because they are extremely agile flyers and might give us great insights into better flight control algorithms. After exposing the ventral nerve cord of the moth, which is essentially an equivalent of the spinal cord in humans, electrodes are precisely inserted into the same. Following that, a motor stimulus is applied to the abdomen of the moth which is held in a custom made 3-D printed holder. There have been evidences of the wings serving the dual role of an actuator and a sensor, as well as an extensive literature available on the sensory roles of antennae and halteres in these insects. There is a lot of significance of my research in the aerial robotics industry where we are trying to look for novel ways to control these micro-air vehicles and make them fully autonomous, and the at the same time, extremely agile and manoeuvrable. Studying the insects and getting inspired by their flight control enables the progression of the field of 'bio-inspired robotics', aptly named so.


Biomechanical basis of wing and haltere coordination in flies.

Abstract: The spectacular success and diversification of insects rests critically on two major evolutionary adaptations. First, the evolution of flight, which enhanced the ability of insects to colonize novel ecological habitats, evade predators, or hunt prey; and second, the miniaturization of their body size, which profoundly influenced all aspects of their biology from development to behavior. However, miniaturization imposes steep demands on the flight system because smaller insects must flap their wings at higher frequencies to generate sufficient aerodynamic forces to stay aloft; it also poses challenges to the sensorimotor system because precise control of wing kinematics and body trajectories requires fast sensory feedback. These tradeoffs are best studied in Dipteran flies in which rapid mechanosensory feedback to wing motor system is provided by halteres, reduced hind wings that evolved into gyroscopic sensors. Halteres oscillate at the same frequency as and precisely antiphase to the wings; they detect body rotations during flight, thus providing feedback that is essential for controlling wing motion during aerial maneuvers. Although tight phase synchrony between halteres and wings is essential for providing proper timing cues, the mechanisms underlying this coordination are not well understood. Here, we identify specific mechanical linkages within the thorax that passively mediate both wing-wing and wing-haltere phase synchronization. We demonstrate that the wing hinge must possess a clutch system that enables flies to independently engage or disengage each wing from the mechanically linked thorax. In concert with a previously described gearbox located within the wing hinge, the clutch system enables independent control of each wing. These biomechanical features are essential for flight control in flies.

Pub.: 22 Jan '15, Pinned: 27 Jul '17

Integration of parallel mechanosensory and visual pathways resolved through sensory conflict

Abstract: The acquisition of information from parallel sensory pathways is a hallmark of coordinated movement in animals. Insect flight, for example, relies on both mechanosensory and visual pathways. Our challenge is to disentangle the relative contribution of each modality to the control of behavior. Toward this end, we show an experimental and analytical framework leveraging sensory conflict, a means for independently exciting and modeling separate sensory pathways within a multisensory behavior. As a model, we examine the hovering flower-feeding behavior in the hawkmoth Manduca sexta. In the laboratory, moths feed from a robotically actuated two-part artificial flower that allows independent presentation of visual and mechanosensory cues. Freely flying moths track lateral flower motion stimuli in an assay spanning both coupled motion, in which visual and mechanosensory cues follow the same motion trajectory, and sensory conflict, in which the two sensory modalities encode different motion stimuli. Applying a frequency-domain system identification analysis, we find that the tracking behavior is, in fact, multisensory and arises from a linear summation of visual and mechanosensory pathways. The response dynamics are highly preserved across individuals, providing a model for predicting the response to novel multimodal stimuli. Surprisingly, we find that each pathway in and of itself is sufficient for driving tracking behavior. When multiple sensory pathways elicit strong behavioral responses, this parallel architecture furnishes robustness via redundancy.

Pub.: 24 Oct '16, Pinned: 27 Jul '17