Rapid Encoding and Perception of Novel Odors in the Rat

1. Rapid Encoding and Perception of Novel Odors in the Rat Wesson, D., Carey, R., Verhagen, J., Wchowiak, M. Novel odorants can be as rapidly discriminated as trained odorants. Little time is required for central processing to discriminate novel odorants and initial glomerular activation plays a major role in determining odor quality. Odor discrimination must require more than simple changes in spike rate.

2. Thirteen (13) head fixed female rats • Fitted with cannula • Trained to CS+ and CS- (lick/no lick) • Odors presented using custom computer-controlled olfactometer • ORNs loaded with calcium-sensitive dye • Optical window created over dorsal OB to record optical signals • Pressure recorded from intranasal cannula • Exploratory sniffing used as indicator of novel odorant • Nine sniffs within any 2 second block Methods

5. Similar odorants have similar ISI1 Dissimilar odorants also have similar ISI1

7. Tdetect – Latency between start of first inhalation and first optical signal in OB Tonset – Onset time of presynaptic calcium signal T90 – time until 90% of maximum amplitude of calcium signal T50 – time until half maximal activation of aggregate response averaged over all glomeruli

10. Rats can discriminate novel odorants as rapidly as trained odorants • Discrimination typically occurs after first inhalation • Inhalation is required for odor detection • Very little time is required for central processing during novel odor discrimination • Most time required for odor detection • Behavioral response elicited prior to full activation of glomeruli Conclusions