The long-term goal of this project is to describe and understand the postnatal development of the structural and functional properties of the neurons of the mammalian retina. An understanding of the mechanisms underlying normal development is a necessary prerequisite for understanding the deleterious effects of abnormal visual input like those following strabismus or congenital cataracts. The present project has two specific aims. The first is to describe the functional development of kitten retinal ganglion cells (RGCs) during the period when synaptogenesis occurs and transient morphological features are expressed. This will be accomplished by using metal microelectrodes to record spatial frequency response functions (SFRFs) of single RGCs whose functional types have been identified by application of a battery of physiological tests in the context of multivariate cluster analysis. The SFRFs will be used to derive estimates of the spatial extent and sensitivity of the receptive field center and surround mechanisms. The RGCs will be recorded in retinas obtained from 0 - 2 and 2 - 4 week-old kittens and adult cats and will be maintained in the superfused retina-eyecup preparation.
The second aim i s to study directly structure-function relationships of single physiologically identified RGCs during this same developmental period. For this purpose the receptive field organization of single functionally identified RGCs will be quantified while recording extracellularly with micropipettes filled with horseradish peroxidase (HRP). The RGC will then be impaled by the micropipette and its morphology visualized by intracellular iontophoresis of HRP. Relevant morphological features will be quantified in 3-dimensional reconstructions for comparison with observed functional properties. Correlations will be sought between 1) dendritic field and RF center diameters, 2) degree of dendritic stratification in the innerplexiform layer and RF center type (on, off, on-off) and 3) the presence of exuberant dendritic processes (spines, hairs) and supernormal spatial contrast gain.
| Tootle, J S (1993) Early postnatal development of visual function in ganglion cells of the cat retina. J Neurophysiol 69:1645-60 |
