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A'Q - BioMedSearch

A'Q - BioMedSearch

A'Q -

THE RESPONSES OF LIMULUS OPTIC NERVE FIBERS TO PATTERNS OF ILLUMINATION ON THE RECEPTOR MOSAIC* BY FLOYD RATLIFF AND H. K. HARTLINE (From The Rockefeller Inslitute) (Received for publication, December 18, 1958) ABSTRACT The inhibition that is exerted mutually among receptor units (ommatidia) of the compound eye of Limul~ is less for units widely separated than for those close to- gether. This diminution of inhibition with distance is the resultant of two factors: (1) the threshold of inhibitory action itwrextse.s with increasing distance between the units involved; and (2) the coefficient of inhibitory action decreases with increasing distance. The discharge of nerve impulses from ommatidia at various distances from one another may be described quantitatively by a set of simultaneous linear equations which express the exdtatory effects of the illumination on each ommatidium and the inhibitory interactions between each ommatidium and its neighbors. The values of the thresholds and coefficients of inhibitory action, which appear as parameters in these equations, must be determined empirically: their dependence on distance is somewhat irregular and cannot yet be expressed in an exact general law. Neverthe- less the diminution of inhibitory influences with distance is sufficiently uniform that patterns of neural response generated by various patterns of illumination on the receptor mosaic can be predicted qualitatively. Such predictions have been verified experimentally for two simple patterns of illumination: an abrupt step in intensity, and a simple gradient between two levels of intensity (the so-ealled Mach pattern). In each case, transitions in the pattern of illumination are accentuated in the corre- sponding pattern of neural response. One of the significant features of the pattern of stimulation on the receptor mosaic of a sense organ is the locus of transitions from one level of intensity to another. Such transitions may be accentuated, in the patterns of neural activity generated by the sense organ, by neural interaction among the receptor units which make up the receptor mosaic. For example, in the lateral eye of Limzd~ the receptor units (ommatidia) are interdependent: the discharge of impulses * This investigation 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. Reproduction in whole or in part is permitted for any purpose of the United States government. 1241 J. GIN. P]~sIOI,., 1959, Vol. 42, No. 6 The Journal of General Physiology

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