CHAPTER 13 



Electrical Phenomena in Vision^ 



LORRIN A, RiGGS 



Brown University, Providence, Rhode Island 



Introduction. The resting potential. The electroretinogram: Evidence from primitive 

 eyes — The vertebrate electroretinogram — The human electroretinogram — Conclusions with 

 regard to the retinal action potential. Optic nerve impulses: Visual responses of primitive 

 eyes — Responses of vertebrate eyes — Conclusions tvith regard to the responses of optic 

 nerve fibers — Responses of the optic tract, geniculate body, and cortex — The sequence of 

 events from retina to cortex. Electrical .stimulation of the visual system: Visual effects 

 of electrical stimulation — Physiological effects — Polarization of the eyeball — Polarization 

 of individual retinal units — Effects of light on electrical excitability. Summary and 

 conclusions. References. 



INTRODUCTION 



The sense of sight is generally given credit for being our most impor- 

 tant source of information about the outside world. It is not surprising, 

 then, to find that vision, more than any other sense, has been studied 

 intensively by physiologists, psychologists, chemists, physicists, ophthal- 

 mologists, and many others. Textbooks on vision (e.g., those of Hartley, 

 1941; Davson, 1949; Hartridge, 1950; Ogle, 1950; Wright, 1947) reveal 

 that there is now a large mass of factual material on the subject, but it 

 is at once apparent that some of the most elementary facts are still 

 unknown. We seem to be in the anomalous position of having a more 

 extensive coverage of complex phenomena such as form and distance dis- 

 crimination, contrast effects, apparent motion, and visual illusions than 

 of the more basic processes by which sensory cells respond to light and 

 generate impulses in the conducting mechanisms of the nervous system. 

 We are not sufficiently acquainted with the properties of individual reti- 

 nal receptors to state the processes underlying visual acuity, color vision, 

 or brightness discrimination. 



The author of this chapter is strongly of the opinion that new progress 

 in this field must largely depend upon an analytical approach in which 

 the separate events are studied in receptor cells, retinal neurons, optic 

 nerve fibers, and projection and association areas in the higher centers 



' This chapter was prepared under Contract N7onr-358, Task Order II, NR-140-359, 

 between the Office of Naval Research and Brown University. 



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