OFF response paper published in Current Biology
Dr. Devineni’s postdoctoral study on temporal dynamics in the fly taste system was published today in Current Biology! This work was conducted at Columbia University with the help of two awesome former technicians, Julia Deere (now a PhD student at Rockefeller) and Christina Sun (now a medical student in the Sackler / Tel Aviv medical program).
Update: you can read a nice summary of the paper here by Marco Gallio and colleagues.
In this study, we show that different types of taste neurons in Drosophila display striking differences in their response dynamics. Most interestingly, individual bitter-sensing taste neurons in the fly’s proboscis respond strongly to bitter onset (an ON response) as well as bitter removal (an OFF response). The bitter OFF response is often larger than the ON response, and with repeated bitter taste the ON response disappears while the OFF response remains strong, suggesting that it plays an important role in bitter encoding. These results were surprising because many previous studies have monitored the activity of Drosophila taste neurons, but bitter OFF responses were never reported!
In the rest of the paper, we characterize the mechanism and functional implications of the bitter OFF response. We show that the bitter ON and OFF responses are likely generated by the same receptors, and we made a computational model of how this could occur. We also show that bitter OFF responses are propagated to downstream dopamine neurons that are involved in learning. When bitter is used as a reinforcement cue during learning, the presence of the OFF response alters the type of synaptic plasticity induced by the dopamine neurons.
There are still lots of open questions, like how these bitter response dynamics impact a fly’s behavior. Dr. Devineni spent many months trying to determine whether the OFF response drives specific behavioral responses, with little success, so we’re open to new ideas about how to address this! Please get in touch if you have questions or comments about this study.
