receiving the olfactory centripetal fibers and those sending the centrifugal
fibers to the olfactory bulb (OB) were investigated electrophysiologically in
the carp telencephalon.
Evoked potentials were recorded in the granule cell layer of the OB when electrical shocks were systematically applied to various areas in the telencephalon. The evoked potentials resulted from the activation of the centripetal fibers were distinguished from those resulted from the activation of the centrifugal fibers by their polarity and latencies. Thus, the pathways of the both fiber systems could be traced.
It was revealed that 1) the centripetal fibers of the lateral olfactory tract (LOT) ran, at precommissural level, in the ventrolateral part of the ipsilateral telencephalon (i-TEL) and projected to an extensive area in the caudoventral part of the i-TEL, 2) the centripetal fibers of the medial olfactory tract (MOT) ran, at precommissural level, in the ventromedial part of the i-TEL and projected to an extensive area in the caudoventral part of the i-TEL, 3) a part of both LOT and MOT centripetal fibers projected to the contralateral telencephalon through the anterior commissure, and 4) the areas, in which the centrifugal fibers existed, considerably overlapped with the projection areas of the centripetal fibers.