Fig. 1. Two-alternative odor choice task.
a Rats were trained in a behavioral box to signal a choice between left and right port after sampling a central odor port. The sequence of events is illustrated using a schematic of the ports and the position of the snout of the rats. b Illustration of the timing of events in a typical trial. Nose port photodiode and valve command signals are shown (thick lines). A trial is initialized after a rat pokes into a central Odor Port. After a randomized delay dodor a pure odor or a mixture of odors is presented, dependent of the task at hand. The rat can sample freely and respond by moving into a choice port in order to get a water reward. Each of these ports is associated to one of two odors—odor A ((R)-(−)-2-octanol) and odor B ((S)-(+)-2-octanol). Highlighted by the gray box, reaction time (RT) is the amount of time the rats spend in the central Odor Port after odor valve is on (i.e. discounting dodor). See Methods for more details.