Abstract
Although odorant concentration-response characteristics of olfactory neurons have been widely investigated in a variety of animal species, the effect of odorant concentration on neural processing at circuit level is still poorly understood. Using calcium imaging in the silkmoth (Bombyx mori) pheromone processing circuit of the antennal lobe (AL), we studied the effect of odorant concentration on second-order projection neuron (PN) responses. While PN calcium responses of dendrites showed monotonic increases with odorant concentration, calcium responses of somata showed decreased responses at higher odorant concentrations due to postsynaptic inhibition. Simultaneous calcium imaging and electrophysiology revealed that calcium responses of PN somata but not dendrites reflect spiking activity. Inhibition shortened spike response duration rather than decreasing peak instantaneous spike frequency (ISF). Local interneurons (LNs) that were specifically activated at high odorant concentrations at which PN responses were suppressed are the putative source of inhibition. Our results imply the existence of an intraglomerular mechanism that preserves time resolution in olfactory processing over a wide odorant concentration range.
Highlights
How sensory information on physical or chemical quantities is processed in neuronal circuits is a fundamental question in understanding sensory systems
This implies that the dose-response curve of projection neuron (PN) calcium responses is modified downstream of the ORN-PN synapses at high odorant concentrations
Relationship between Calcium and Spike Responses In previous calcium imaging studies investigating PN concentration-response characteristics in insect antennal lobe (AL), calcium responses were mostly observed in dendritic regions [25,30,31,32,33]
Summary
How sensory information on physical or chemical quantities is processed in neuronal circuits is a fundamental question in understanding sensory systems. While odorant concentrationresponse characteristics of olfactory neurons have been well investigated in a variety of animal species [1,2,3,4,5,6,7], the effect of odorant concentration on changes of the representation of individual odorants from one processing level to the in olfactory circuits is not well understood. Odorant concentration is a key parameter for animals to localize odorant sources [12,13] In this behavioral task, the information concerning specific odorants of interest may mainly be processed by an intraglomerular circuit, in particular for odorants encoded by a labeled-line scheme such as pheromones. Concentration-response characteristics of MGC neurons have been investigated previously [6,17,18,19,20], mechanisms adjusting processing at circuit level depending on stimulus concentration remain to be elucidated
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
