Figure 1.

Experimental design. A, The Gabor patch, which was used as a stimulus in the visual testing sessions. Subjects had to indicate whether it was oriented vertically or horizontally. B, Sequence of events during each trial of the visual testing sessions. Subjects pressed a button to start the trial; after a delay they viewed the Gabor stimulus and then indicated their perceived orientation. C, The sequence of events in an olfactory session. D, The sequence of sessions that were typically performed across many days of testing.