Speaker
Description
Odorants are detected by olfactory receptor neurons (ORNs) that project to the antennal lobe (AL), the first olfactory neuropil in the insect brain. In the AL, ORNs make synaptic contacts with: i) projection neurons (PNs), which in turn send olfactory information to other brain areas; and ii) local interneurons (LNs) that form a dense network of lateral inhibitory and excitatory interactions within the AL. Functional and computational studies indicate that this local network transforms sensory input, presumably to enhance perception of meaningful odors.
Here, we investigate the role of GABAergic local neurons in both learning-dependent plasticity in the AL and the ability of flies to perceive the presence of learned odorants in a mixture. For that aim, we performed aversive olfactory conditioning using a single odorant as a conditioned stimulus. Next we tested olfactory preference in a T-maze by exposing the flies to the conditioned odorant, or to the conditioned odor embedded in a mixture of different proportions with a novel odorant (distractor). We determined the proportion threshold that flies need to detect the learned odorant immersed in the mixture. Next, we demonstrated that blocking the activity of different groups of LNs in the AL impears the ability to detect the learned odorant embedded in mixtures. We then asked wheater aversive conditioning affects the representation of odorant mixtures in the AL. We recorded odorant evoked responses in PNs using calcium imaging, while concomitantly training animals with the same protocol used in the T-maze experiments. We were able to study odorant representation before and after training, and found that the representation of a binary mixture in the AL changes after the learning.
Finally, we are investigating whether this type of experience-dependent plasticity is conserved in an appetitive conditioning. For that, we paired a single odorant with sucrose and test attraction preference to a binary mixture that contains this odor. We then evaluated whether the detection of target odors in mixtures requires the activity of local neurons.
