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Intrinsic association fiber system of the piriform cortex: A quantitative study based on a cholera toxin B subunit tracing in the rat
Author(s) -
Datiche Frédérique,
Litaudon Philippe,
Cattarelli Martine
Publication year - 1996
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/(sici)1096-9861(19961209)376:2<265::aid-cne8>3.0.co;2-1
Subject(s) - piriform cortex , cholera toxin , laminar organization , anterograde tracing , olfactory system , retrograde tracing , anatomy , biophysics , neuroscience , synapse , axoplasmic transport , cortex (anatomy) , protein subunit , fiber , biology , chemistry , central nervous system , biochemistry , endocrinology , organic chemistry , gene
By using retrograde and anterograde transport of the B subunit of cholera toxin (CTb), we examined quantitatively the association fiber systems, i.e., the collaterals of pyramidal cell axons, that reciprocally connect both the rostral and the caudal parts of the piriform cortex (PC). Well‐defined CTb injections were obtained in layers Ib or II‐III of the rostral and the caudal parts of the PC. Using precision counting, we determined the proportion of cellular profiles in layers II and III that gave rise to association fibers and thus demonstrated a predominance of rostrocaudal fibers over the caudorostral ones. Our data also support a precise laminar organization of the PC in which the rostrocaudal fibers originated mainly from layer II and the caudorostral fibers primarily from layer III. Cholera toxin injections into layer Ib produced a peak of labeled profiles 2 mm from the site, indicating that a large proportion of the association fibers from layer II travel for at least 2 mm and then synapse in layer Ib. At either end of the PC, the association projections are concentrated laterally. The functional significance of these anatomical features is discussed with respect to olfactory processing, propagation of the activity within the PC, and the possible role of intrinsic fibers in olfactory memory. © 1996 Wiley‐Liss, Inc.