Sensory adaptation modulates coding and perceptual quality of odor mixtures

Abstract

The sensitivity of the sensory systems must be dynamic in order to allow animals to adjust their behavior based on experience to optimize detection of relevant information while ignoring stimuli with no predictive value. In this context, one of the main phenomena that modulate the olfactory system is sensory adaptation. It is usually defined as a decrease in the sensitivity or response to a stimulus after a sustained exposure to it. Adaptation may occur in brief intervals of time and depends on the immediate prior experience. Here, we investigate aspects of the function and neurobiology of sensory adaptation in olfaction using the honeybee Apis mellifera. By means of electroantennograms we set stimulation protocols that induced sensory adaptation. We show that activation patterns that encode mixtures of odorants in the antennal lobe are drastically altered after sensory adaptation, favoring the representation of stimuli that are present at sub-threshold concentrations. We investigate the effects that sensory adaptation has on the perception of odorant mixtures and show that adapting animals to one of the components of a binary mixture, reduces the appetitive learning of the adapted stimulus and enhances the detection and learning of the non-adapted stimulus in cases in which it would stay normally occluded. These results suggest that olfactory sensory adaptation is critical to allow detection of minor components present in complex mixtures, emphasizing its role as a fundamental mechanism to improve sensitivity to discrete stimuli.