MULTISITE OPTICAL-RECORDING OF THE RAT PIRIFORM CORTEX ACTIVITY

OPTICAL signals were recorded in the in vivo rat piriform cortex (PC) in response to olfactory bulb (OB) electrical stimulations delivered a t 4 different sites. Afferent activity had a relatively wide (26.6% of the recorded area) but nonhomogeneous distribution on the PC surface. The different patterns of afferent activity observed in response to t he 4 OB stimulations were intermixed with an overlap of only 38.5%. Th is activity was redistributed to the whole PC by intrinsic association fibres. The increase in the delay (from 4 ms to 12 ms) between affere nt and redistributed activities along the antero-posterior axis indica ted that the rostral to caudal association fibre system originating in the anterior PC was mainly responsible for the redistribution.