Bittu Kaveri Rajaraman
Associate Professor of Biology and Psychology
"I am interested in behaviour, neuroscience, ecology and evolution. I work on various puzzles in animal communication, sensation and cognition.
I work on understanding the relationship between signal production and signal reception systems involved in animal communication, especially when it comes to acoustic and vibratory communication in bushcrickets. I also look at the challenges of communication such as acoustic competition and masking, the difficulty in locating signalers, how ecological factors like predator pressure shape communicatory behaviour, and the structural and neurophysiological adaptations that overcome challenges in communication.
I have also worked on visual sensory systems in amphibia, zebrafish, mosquito larvae, and ants and have just started some interesting work on quantitative cognition in zebrafish.
Acoustic and vibratory communication: I am interested in the function and evolution of communication systems, mostly in bushcrickets which sing at night to attract mates. I am interested in the question of how characteristics of the song production and auditory systems are matched for effective communication, how listeners recognize the call produced by callers of their species and distinguish it from the songs of other species, how both singers and listeners deal with acoustic masking by noise, how listeners localize and figure out the direction in which to move to locate a caller, and vitally, how they deal with predators and parasites which eavesdrop on the communication cycle to find their targets. I have so far worked on some of these questions with respect to the bushcricket Onomarchus uninotatus, where the males and females perform a temporally precise multimodal duet where he sings and she vibrates out of phase, sending him a vibrational signal that he can localize. We have investigated the factors shaping this duet, from predator pressure to acoustic competition, and found interesting structural and behavioural matches between the tuning of the song and the auditory system. I am now interested in looking at these questions and others relating to how genes and neural circuits affecting calling and listening behaviour drive evolutionary change and speciation in some other species of Orthopterans. This kind of work holds promise in acoustic monitoring of species diversity in forests.
Numerical cognition: I am interested in the question of how mathematical cues are learned and processed, and in the question of whether logical inference emerges spontaneously or in the context of reward driven learning. I am also interested in the question of what kinds of computations neural hardwire can perform with relative ease. We look at this question relative to various ecological factors in two systems: zebrafish and semi-ferral dogs. We are training zebrafish in the lab on mathematical tasks to eventually study the neural basis of such cognition using calcium imaging in larval zebrafish. Our goal in studying this question in dogs is to explore the possibility of large scale citizen science based data collection on the question of mathematical cognition and inference in animals with whom humans have a relatively strong behavioural understanding, and who are wild enough to benefit from strong learning abilities. For now this is work that undergraduates carry out with dogs around the campus.
Visual cognition: I remain interested in visual cognition in multiple systems. I examined the parameters of weaver ant visual abilities for a series of theses, and am now also looking at mimicry of these ants by ant-mimicking spiders, along with a collaborator. I am particularly interested in the role of visual cognition in higher order visual tasks such as nest construction by these weaver ants, and in the possible effectiveness of mimicry by ant-mimicking spiders. I have also looked at the spatial frequency tuning of the switch between attractive appetitive and aversive responses in zebrafish, and done smaller projects on larval mosquito vision and the ocellar visual system of locusts, using immunohistochemistry and electrophysiology to trace visual neural circuitry."