Glomerular activity patterns of aliphatic aldehydes presented by the retronasal or orthonasal pathway. A: Response maps evoked by a homologous series of aliphatic aldehydes (C4 – C8) from a single mouse. The left-most panel shows the resting fluorescence image. Scale bar = 200 μm. Retronasal stimuli were delivered for 30 s at 300 ml /min (upper panels). Orthonasal stimuli were delivered for 10 s at 150 ml /min (lower panels). Percent dilutions in mineral oil are given in each panel. B: Overlay of retronasal and orthonasal response maps expressed in different color channels to indicate glomeruli responding to one or both airflow pathways (retronasal only: green, orthonasal only: red, both: yellow). C: Dot-plot representation of responses of the glomeruli numbered in panel B. Dots correspond to > 0.5% increase in response amplitudes. Black and gray filled circles show retronasal and orthonasal responses, respectively. D: Vapor pressure and log P of test aldehydes (log P = index of hydrophobicity).