Role of inhibition in the antennal lobe: gain control and odor invariance across concentrations

EMILIANO MARACHLIAN; FERNANDO LOCATELLI; AYELEN NALLY; RAMÓN HUERTA

San Diego, California

Congreso; Society for Neuroscience; 2016

Animals need to extract information from complex and noisy environments. Even though the animals form their internal image of the surroundings through a multisensory system, each sense needs to be able to recognize (in some range) the identity of one stimulus regardless of its intensity and independently of complex or noisy background (if the stimulus is biologically relevant). Therefore the first processing level, where the sensory signal is adapted and organized, plays a fundamental role in sensory systems. In the olfactory system the chemical cues are detected and primarily encoded by the olfactory sensory neurons. Each specific odor recruits a particular combination of receptors that provides the input for its internal representation. The great neuronal convergence in the Antennal Lobe (approximately 60,000 olfactory sensory neurons converge into around 800 projection neurons organized in 160 glomeruli in the honey bee) requires a signal adaptation. In insects the first processing is done by the local inhibitory neurons located in the Antennal Lobe. Nevertheless the specific form in which the signal is adapted is not fully known. In this work we investigate the action of the different GABA components and their role in gain control and stabilization of neural activity patterns elicited by a range of odor concentrations. We use honey bees as model animal and perform calcium imaging to measure the neural representations from low to high odor concentrations in the projection neurons of the Antennal Lobe. With different GABA blockers we isolate and identify the specific contributions of GABA-A and GABA-B components. We also introduce math and computational models with which we confirm experiment interpretations, study the network contribution and evaluate the robustness of this mechanism for different input patterns. We show that the GABAergic neurons play an important role, stabilizing the pattern representation and regulating levels of activity, allowing animals to generalize the odor identity across concentrations. The simplicity of the system under study suggests that analogous versions could be involved in other sensory systems and even in higher levels of processing.