Location: HSB G-328, 10:30am (unless otherwise noted)
February 27, 2014
Elizabeth Hong, Ph.D. , Harvard University
Host: Stan Froehner
The specificity of synaptic inhibition is poorly understood in circuits where no systematic relationship exists between a neuron’s physical location and its tuning (“non-topographic” circuits). Here, we ask how inhibitory specificity arises in the Drosophila antennal lobe, a non-topographic circuit that comprises the first olfactory relay in the fly brain. GABAergic local neurons (LNs) in the antennal lobe mediate inhibition among olfactory channels (defined by glomeruli) and control the gain of afferent synapses. Surprisingly, we find that the recruitment of inhibition is untuned to odor identity: activating a single glomerulus elicits GABAergic interneuron activity in all glomeruli. However, inhibition is strongly target-specific: glomeruli differ dramatically in their sensitivity to inhibition, which is strongly correlated with their sensitivity to GABA. Notably, sensitivity to inhibition is independent of odor selectivity; an odor typically co-activates glomeruli having diverse sensitivities to inhibition, and thus to gain control. We propose odors are simultaneously processed by glomeruli subject to strong gain control, which should maximize coding efficiency, and weak gain control, which should preserve intensity information.