HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Simon, E. J. Search for Related Content PubMed PubMed Citation Articles by Simon, E. J.

1. Two classes of luminosity horizontal cells have been identified in the retina of the turtle by intracellular recording. These cells differ in the area of retinal surface over which they are sensitive to light. For moderate light intensities the maximum response amplitude of `type I' cells increases progressively as the radius of a circle of light is enlarged to over 750 µm. Responses of `type II' cells instead reach maximum amplitude with circular illumination of about 300 µm radius.

2. Both types are maximally sensitive to red light and have similar action spectra.

3. The cells from which these responses originated were identified by intracellular marking with Procion Yellow dye. Both types were located in the inner nuclear layer. Type I cells had asymmetric, thick, tuberous processes and no apparent discrete somata. Type II cells had thin processes radiating symmetrically from rounded cell bodies.

4. The different properties of the two types of cells can be simply explained assuming that the cells of type I are coupled by low-resistance electrical junctions while in cells of type II the junctional resistance is higher.

5. Since type I and type II cells differ both morphologically and physiologically, they may have different functions.