Premium
Parallel involvement of perirhinal and lateral entorhinal cortex in the polysynaptic activation of hippocampus by olfactory inputs
Author(s) -
Liu Ping,
Bilkey David K.
Publication year - 1997
Publication title -
hippocampus
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.767
H-Index - 155
eISSN - 1098-1063
pISSN - 1050-9631
DOI - 10.1002/(sici)1098-1063(1997)7:3<296::aid-hipo5>3.0.co;2-j
Subject(s) - perirhinal cortex , dentate gyrus , neuroscience , hippocampal formation , entorhinal cortex , hippocampus , chemistry , olfactory system , olfactory memory , perforant pathway , temporal lobe , psychology , central nervous system , perforant path , olfactory bulb , epilepsy
It has previously been shown that olfactory input to the hippocampus (HPC) is mediated polysynaptically via the lateral entorhinal cortex (LEC), the site of origin of the lateral perforant pathway (LPP). Because previous anatomical studies have shown that olfactory projections also terminate in perirhinal cortex and that this latter region projects directly to the hippocampus, we investigated the role of perirhinal cortex (PRC) in the mediation of the olfactory‐hippocampal potential in the rat. Single‐pulse stimulation of the lateral olfactory tract (LOT) resulted in a long onset latency (12–20 ms) evoked response in the dentate gyrus of the ipsilateral hippocampal formation. LOT‐HPC potentials were rapidly and completely abolished following the microinfusion of procaine into the LPP, suggesting that they are ultimately mediated via this pathway. In support of this finding, a current source density analysis indicated that the LOT‐HPC response was generated by a current sink at the outer molecular layer of both dorsal and ventral blades of the dentate gurus. Electrolytic and ibotenic acid lesions of PRC produced a significant decrease in the amplitude of LOT‐HPC potentials when testing was conducted 4–7 days postlesion. Lesions of LEC produced similar effects and combined lesions of LEC and PRC resulted in an almost complete eradication of the potential, suggesting that parallel entorhinal‐hippocampal and perirhinal‐hippocampal pathways are involved. These data suggest, therefore, that a portion of the olfactory input to the hippocampus is mediated via polysynaptic connections routed through perirhinal cortex. Because recent research has suggested that PRC plays an important role within the temporal lobe memory system, this connectivity may be important for olfactory memory processes. Hippocampus 7:296–306, 1997. © 1997 Wiley‐Liss, Inc.