Mechanismen der Verarbeitung zeitlich strukturierter olfaktorischer Stimuli
Molekulare Biologie und Physiologie von Nerven- und Gliazellen
Zusammenfassung der Projektergebnisse
Intensity fluctuations inherent to natural odour plumes are generated by turbulent airflows in which they are carried. Odour plumes therefore hold a rich temporal structure of odour concentration variation. These temporal dynamics contain information about the distance an odour plume has travelled, as well as location and nature of an odour source. Thus, in order to identify naturally complex odours, in a first step the olfactory system faces the challenge to separate odour sources and possibly attribute different chemicals to different sources. During the DFG Research Fellowship “Mechanisms of processing temporally structured olfactory stimuli” the applicant Tobias Ackels studied whether mice can perceive and process these odour intensity fluctuations and thus allowing for odour scene segmentation when navigating through natural environments. The applicant and his collaborators established an experimental approach to measure odour concentrations of two odours simultaneously with high temporal bandwidth. Importantly, they could show that odours presented from the same source fluctuate with high correlation. When presented from two separate sources, almost no correlation was observed proving that correlated odour concentration fluctuation predicts mixing of odours and about the distance of the odour source itself. The design and construction of a high-speed multichannel odour delivery device allowed for precise and reliable odour stimulation carrying complex temporal information. This led to the investigation of the psychophysical limits for discriminating odour correlation structure using an automated behavioural system. These behavioural experiments bring evidence that mice can detect and discriminate the correlation structure of odours at frequencies over 40 Hz. Additionally, targeted multi-photon Ca2+ imaging experiments in olfactory bulb projection neurons revealed differential responses to the correlation structure of odours already in the output of the olfactory bulb rendering mammalian olfaction a high-bandwidth sense.
