Signal propagation from piriform cortex to the endopiriform nucleus in vitro revealed by optical imaging.

Optical signals were recorded from the posterior piriform cortex slices of guinea pigs stained with a voltage-sensitive dye to analyse spatio-temporal spread of neural activity evoked by electrical stimulation of afferent fibers. After propagation of activity along layers II and III, an isolated island of activity appeared deep to the layer III and moved caudally. Histological inspection revealed that the area where the island appeared corresponded well to the endopiriform nucleus. The present results provided an evidence for one of the main outflows of olfactory information from the posterior piriform cortex.