INHIBITORY INTERACTION IN THE RETINA 

 AND ITS SIGNIFICANCE IN VISION* 



H. K. Hartline, F. Ratliff and W. H. Miller 

 The Rockefeller Institute, New York 



The importance of nervous inhibition in sensory processes has become in- 

 creasingly evident in recent years. But it was nearly one hundred years ago 

 that Ernst Mach (1865) first recognized the possible significance of reci- 

 procal retinal inhibition in accentuating contours and borders in the visual 

 field. More recently, Bekesy (1928) pointed out a similar possible role of 

 inhibition as a "sharpening" mechanism in the auditory system. These 

 speculations, based primarily on indirect evidence from psychophysical 

 experiments have since been borne out by the direct observation of neural 

 activity made possible by the development of modern electrophysiological 

 techniques, especially when applied to the study of the activity of single 

 cellular units. As a few examples of the numerous modern studies that show 

 the diverse roles that neural inhibition plays in the physiology of sensory 

 systems we may cite Granit's work on the interplay of excitatory and inhibit- 

 ory influences in the vertebrate retina (for reviews see Granit, 1947 and 1955); 

 the observation of inhibition in the auditory pathways by Galambos and 

 Davis (1944), and Mountcastle and Powell's (I960) studies of inhibition in 

 the cutaneous system. 



The interaction of nervous elements and the interplay of excitatory and 

 inhibitory influences can mold particular patterns of neural activity in specific 

 pathways. Less specific interactions also have an important integrative action 

 in sensory systems. Thus in the visual system, inhibitory influences exerted 

 quite indiscriminately on one another by neighboring receptors and neurons 

 in the retina have the effect of enhancing contrast in the visual image. If each 

 element in the retinal mosaic inhibits the activity of its neighbors, to a degree 

 that is greater the more strongly it is excited, then brightly lighted elements 

 will exert a stronger suppressing action on dimly lighted neighbors than the 

 latter will exert on the former. As a consequence, the disparity in the activities 

 in the pathways from the two regions will be exaggerated, and brightness 

 contrast will be enhanced. If the inhibitory interaction is stronger for near 



* This work was supported by a research grant (B864) from the National Institute of 

 Neurological Diseases and Blindness, Public Health Service, and by Contract Nonr 1442 

 (00) with the Office of Naval Research. 



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