FIG. 1.
Top: experimental design for analysis of figure-ground separation by anterior piriform cortex (aPCX) and mitral/tufted neurons. Each component and the binary mixture were given twice for 2 s with at least a 60-s interval to determine initial response magnitude. Then 1 component of the binary mixture (background odorant) was presented for 50 s. Forty seconds after the onset of background, the other (target) odorant was added for 2 s, essentially creating a 2nd binary mixture. Binary mixtures and target against background stimuli were created by dividing the airstream toward both odors, thus total flow rate of odorized air did not differ between component and mixture stimuli. Bottom: representative examples of mitral/tufted and aPCX neuron responses during single stimulus and background stimulation. While both the mitral/tufted and aPCX neuron increased firing rate when the target odorant was presented against background, because the aPCX neuron had stopped responding to the background, its response was more similar to the target alone. The mitral/tufted cell response magnitude was more similar to the binary mixture under this same condition. Mean waveforms for both cells are shown to the right.