Spatially anisotropic lateral inhibition: Convergent circuit designs in the insect AL and vertebrate OB

Veronica Egger - Universität Regensburg
Silke Sachse - MPI for Chemical Ecology, Jena

Inhibitory neurons are present and active all over the nervous system and play an essential role in stabilizing and tuning responses of excitatory neural subnetworks. In the olfactory system, complex inhibitory circuits modulate the impact of sensory neuron input and mediate interactions between second order principal neurons. These pathways are assumed to regulate olfactory sensitivity depending on behavioural state, control the gain exerted by principal neurons, synchronize neural subnetworks along fast and slow rhythms of activity, and enhance the spatial contrast of odor coding via decorrelation of similar odor-evoked response patterns. The architecture of the underlying network anatomy is astonishingly similar across insects and vertebrates - a prime example of convergent evolution. Here we aim to clarify the cellular basis of defined inhibitory interactions across phylae, based on predictions inspired by findings in the respective tandem lab. More specifically, we will investigate the cellular basis and functional impact of anisotropic lateral inhibition which allows for directed interactions between individual glomerular channels that in the fly might be even hard-wired. To this end we will expand our promising functional data in the fly with respect to identification of the anatomical correlate, i.e. tracking down the local interneurons involved, and in the rat we will establish imaging of binary mixture coding in our semi-intact nose brain preparation similar to the fly, and reduce ansiotropic interactions via laser ablation. In rat, the main candidates for the cellular substrate of anisotropic inhibition are long-range interneurons in the glomerular layer which feature intriguing so far unknown circuit motifs and whose synaptic interactions will be studied in detail with whole-cell recordings, high-resolution imaging and uncaging techniques. We will also investigate the cellular substrate of recurrent and presynaptic inhibition in the fly, and ultimately aim to assign specific inhibitory interactions to defined interneuron types. Finally, we plan to integrate the results of these investigations into a new generic network model of the convergent olfactory system, in tight collaboration with other members of the priority program with computational and circuits expertise.