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A new subdivision of anterior piriform cortex and associated deep nucleus with novel features of interest for olfaction and epilepsy
Author(s) -
Ekstrand Jeffrey J.,
Domroese Mark E.,
Johnson Dawn M.G.,
Feig Sherry L.,
Knodel Susan M.,
Behan Mary,
Haberly Lewis B.
Publication year - 2001
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.1178
Subject(s) - piriform cortex , neuroscience , anterior olfactory nucleus , biology , olfactory bulb , cytoarchitecture , nucleus , olfactory system , anatomy , olfactory tubercle , hippocampus , central nervous system
The anterior part of the piriform cortex (the APC) has been the focus of cortical‐level studies of olfactory coding and associative processes and has attracted considerable attention as a result of a unique capacity to initiate generalized tonic‐clonic seizures. Based on analysis of cytoarchitecture, connections, and immunocytochemical markers, a new subdivision of the APC and an associated deep nucleus are distinguished in the rat. As a result of its ventrorostral location in the APC, the new subdivision is termed the APC VR . The deep nucleus is termed the pre‐endopiriform nucleus (pEn) based on location and certain parallels to the endopiriform nucleus. The APC VR has unique features of interest for normal function: immunostaining suggests that it receives input from tufted cells in the olfactory bulb in addition to mitral cells, and it provides a heavy, rather selective projection from the piriform cortex to the ventrolateral orbital cortex (VLO), a prefrontal area where chemosensory, visual, and spatial information converges. The APC VR also has di‐ and tri‐synaptic projections to the VLO via the pEn and the submedial thalamic nucleus. The pEn is of particular interest from a pathological standpoint because it corresponds in location to the physiologically defined “deep piriform cortex” (“area tempestas”) from which convulsants initiate temporal lobe seizures, and blockade reduces ischemic damage to the hippocampus. Immunostaining revealed novel features of the pEn and APC VR that could alter excitability, including a near‐absence of γ‐aminobutyric acid (GABA)ergic “cartridge” endings on axon initial segments, few cholecystokinin (CCK)‐positive basket cells, and very low γ‐aminobutyric acid transporter‐1 (GAT1)‐like immunoreactivity. Normal functions of the APC VR ‐pEn may require a shaping of neuronal activity by inhibitory processes in a fashion that renders this region susceptible to pathological behavior. J. Comp. Neurol. 434:289–307, 2001. © 2001 Wiley‐Liss, Inc.