Role of antennal lobe inhibition in gain modulation and odor generalization across concentration

AYELEN NALLY; RAMON HUERTA; MARACHLIAN EMILIANO; FERNANDO LOCATELLI

Bordeaux

Congreso; Neurofrance 2017; 2017

Société des Neurosciences

Role of antennal lobe inhibition in gainmodulation and odor generalization across concentration.  EmilianoMarachlian 1,2,3, Ayelen Nally 1, RamonHuerta 4, Fernando Locatelli 1,3 1. Departamento de Fisiología, Biología Molecular yCelular, FCEyN , UBA, Argentina2. Departamento de Física, FCEyN , UBA, Argentina.3. IFIByNE- CONICET, Argentina4. Biocircuits Institute, UCSD, USA. Animals extractecologically relevant information from the environment and form an  internal image of the surroundings through amulti-sensory system. That sensory input must be compared with internal templatesto allow stimuli recognition and guide proper behavioral decisions. For thiscomparison the stimulus has to be encoded regardless of its intensity (in somerange) and unaffected by complex or noisy backgrounds. In addition, theneuronal convergence that takes place at the first level of sensory systems requiressignal adaptation. Therefore, the local inhibitory network at early sensory processingplays a fundamental role in sensory systems.In this work we use honeybees as model animal for studying odor generalization across intensities and tounderstand the neural computations that underlie this ability. Odors aredetected and primarily encoded by the olfactory sensory neurons (approximately60,000 that converge into 800 projection neurons organized in 160 glomeruli in theantennal lobe). Each specific odor activates a unique combination of receptorsthat provides the input for its internal representation. However odors presentedat different concentrations produce different activity patterns, mainly interms of the intensity of activation but also in the combination of receptors. Thequestion is how animals recognize the same odor across different concentrationsin spite of the different input patterns.Using different GABAblockers we describe the contribution of the local inhibitory network instabilizing odor patterns across intensity. We found that GABA-A and GABA-Bcomponents contribute differentially in terms of the intensity range of odorsand in the temporal profile of the activation. We perform calcium imaging to describeneural representation of high and low odor concentrations in the antennal lobeunder control of the GABAergic neurotransmission and without it. We describe alsobehavioral generalization across odor concentrations. Finally, the results areformalized in a computational model of the antennal lobe that provides detailof the inhibitory network and the role of GABA. The simplicity and robustness ofthe circuit suggests that similar versions might be involved in other sensorysystems and even at higher processing levels.