AN EVOKED POTENTIAL STUDY OF OLFACTORY PATHWAYS IN THE CARP

(1)    The projection areas of mitral-cell axons in the lateral (LOT) and medial (MOT) olfactory tract and (2) the pathways of the centrifugal fibers to the olfactory bulb(OB) were studied in the carp, Cyprinus carpio.  Evoked potentials were recorded in the internal cell layer of the OB when electrical shocks were applied to various sites in the telencephalon, the preoptic area, and the diencephalon.  At the precommissural level, mitral-cell axons in the LOT projected to the ventrolateral part of the ipsilateral telencephalon (i-TEL) and those in the MOT to the ventromedial and ventrolateral part of the I-TEL.  At the postcommissural level, mitral-cell axons in the LOT, as well as those in the MOT, projected to an extensive area in the ventral part of the I-TEL.  Mitral-cell axons in both the LOT and the MOT also projected to the contralateral teltencephalon.  Furthermore, the bilateral preoptic area and the nucleus posterior tuberis(NPT) in the diencephalon received mitral-cell projections from both the LOT and the MOT.  Centrifugal fibers existed in the telencephalon, the preoptic area and the NPT, which considerably overlapped with the projection areas of mitralcell axons.  These results parallel those obtained from anatomical studies.


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