Behavioral, physiological and computational characterization of olfactory sensory adaptation

GASCUE, F.; PÍREZ, N.; LOCATELLI, F. F.

CABA

Simposio; Fronteras en Biociencia 4; 2023

IBIoBA

The olfactory system is continuously exposed to an extraordinary array of chemical stimuli. To maintainsensitivity to meaningful odors, the system must be adjusted based on the animal’s experience. One ofthe main phenomena that contributes to this adjustment is sensory adaptation, which is defined as adecrease in sensitivity or response to a stimulus after sustained exposure to it and depends on theanimal´s immediate experience. In this work, we investigate the role and mechanisms involved inolfactory sensory adaptation using honey bees. We measured the activity of olfactory receptor neurons(ORNs) by means of electroantennograms and characterized temporal aspects of this phenomenon suchas induction, duration, and recovery time. Additionally, we analyzed whether adaptation depends onodor identity. Furthermore, to study the behavioral implications of adaptation for the animal, weconducted classical conditioning experiments, where we exposed bees to an odor before stimulatingthem with a mixture that contains the same odor. The results of this experiment showed thatadaptation reduces appetitive learning of the adapted stimuli, while facilitating learning of the othercomponents in cases where they would normally stay occluded. We also conducted calcium imagingexperiments to measure odor-induced signals in the projection neurons (PNs) of the antennal lobe, thefirst olfactory neuropil in the insect brain. This allowed us to observe how adaptation changes the neuralrepresentation of odors. Lastly, we developed a computational model of the olfactory system using anadaptive exponential integrate-and-fire model for ORNs and PNs. The model showed similar results tothose obtained experimentally, indicating that a decrease in the response of ORNs and PNs is sufficientto observe sensory adaptation without the need for further plasticity. Overall, our results emphasizethat sensory adaptation is critical in maintaining the olfactory system unsaturated and ready to detectchanges in the olfactory context.