Abstract

The density and distribution of labeled cortical cells was examined following discrete deposits of retrograde tracers into the superior colliculus (SC) of neonatal and adult rats to study the topographic order of SC afferents from the cortex during the initial phase of axon ingrowth. Small deposits of red and green latex microspheres (0.02-0.05ul) were placed into the SC of rats ranging in age from birth to adulthood using glass micropipettes (tip diameter 25-35um). The animals, following a 48hr survival period, were deeply anesthetized and perfused with normal saline followed by a 10% formal-saline solution. The brains were sectioned coronally at 50um, and the location and density of labeled cortical neurons plotted for computer reconstruction. Labeled corticocollicular cells were first observed following injections on postnatal day three (P3) which confirms the work of others. Between P3-P7 the number of cells increased substantially. In all ages studied (> P5) an area of densely labeled cortical cells was observed in a restricted portion of the primary visual cortex corresponding retinotopically to the location of the SC deposit site. Concurrently, there was an extensive areal distribution of labeled corticocollicular cells in other cerebral cortical areas. This was further investigated by examining the distribution of cortical cells following superficial and deep injections into the SC. Injections into the superficial laminae of the neonatal rat SC labeled cells principally in primary visual cortex, while deeper injections resulted in an increase of labeled cortical surface area including more labeled cells in extrastriate cortex as well as in somatosensory, motor and cingulate cortices. These exuberant nonvisual corticocollicular projections decreased by P19-P21 establishing the adult pattern.

In summary our data suggest: (1) Substantial topography is present during the early ingrowth of projections from primary visual cortex to the superficial laminae of the SC. (2) Exuberant projections observed during early neonatal periods primarily terminate in the deep laminae and not in the superficial laminae of the SC.

LLU Discipline

Anatomy

Department

Anatomy

School

Graduate School

First Advisor

Michael A. Kirby

Second Advisor

Paul J. McMillan

Third Advisor

John W. Patrickson

Degree Name

Master of Science (MS)

Degree Level

M.S.

Year Degree Awarded

1991

Date (Title Page)

3-1991

Language

English

Library of Congress/MESH Subject Headings

Superior Colliculus -- cytology; Superior Colliculus -- physiology; Rats -- physiology

Type

Thesis

Page Count

2 xi; 93

Digital Format

PDF

Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.

Collection

Loma Linda University Electronic Theses and Dissertations

Collection Website

http://scholarsrepository.llu.edu/etd/

Repository

Loma Linda University. Del E. Webb Memorial Library. University Archives

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