Light adaptation is a gain-control process that endows photoreceptors with large dynamic range. In invertebrates, this process appears to be mediated by a negative feedback that sets the amplitude of the isolated photon responses (bumps) by modulating an enzyme's rate of catalysis. This paper reports measurements of the feedback dynamics of Limulus from the responses to small modulations in light intensity. The responses show a noise that apparently arises from the random arrival of photons. We use a dynamic noiseanalysis technique to extract the cells's frequencyresponse transfer function for bump amplitude. Its ratio to the transfer function for the summed response of the cell has a simple form at low frequencies. This indicates that the origin of the feedback responsible for the adaptation is at a stage temporally close to the final conductance response. Moreover, the form of the transfer function suggests feedback by a chemical agent which is removed by a single enzymatic-like stage at low light intensity and by several such stages in parallel but with a spread of time constants at high intensity.
This is a preview of subscription content, log in to check access.
Buy single article
Instant access to the full article PDF.
Price includes VAT for USA
Subscribe to journal
Immediate online access to all issues from 2019. Subscription will auto renew annually.
This is the net price. Taxes to be calculated in checkout.
Brodie SE, Knight BW, Ratcliff F (1978) The response of the Limulus retina to moving stimuli: a prediction of Fourier synthesis. J Gen Physiol 72:129–166
Dodge FA, Knight BW, Toyoda JI (1968) Voltage noise in Limulus visual cells. Science 160:88–90
Fein A, DeVoe RD (1973) Adaptation in the ventral eye of Limulus is functionally independent of the photochemical cycle, membrane potential and membrane resistance. J Gen Physiol 61:273–289
Grzywacz NM, Hillman P (1988) Biophysical evidence that light adaptation in Limuus photoreceptors is due to a negative feedback. Biophys J 53:337–348
Grzywacz NM, Hillman P, Knight BW (1988) The quantal source of area supralinearity of flash responses in Limulus photoreceptors. J Gen Physiol 91:659–684
Grzywacz NM, Hillman P, Knight BW (1992) Response transfer functions of Limulus photoreceptors: interpretation in terms of transduction mechanisms. Biol Cybern 66:429–435 (this issue)
Lisman JE, Brown JE (1972) The effects of intracellular iontophoretic injection of calcium and sodium ions on the light response of Limulus ventral photoreceptors. J Gen Physiol 59:701–719
Lisman JE, Brown JE (1975) Effects of intracellular injection of calcium buffers on light adaptation in Limulus ventral photoreceptors. J Gen Physiol 66:489–506
Rice SO (1944) Mathematical analysis of random noise. Bell Telephone Sys J 23:282–332
Schnakenburg J (1988) Can quantum-bumps in photoreceptors be reconstructed from noise-data? Biol Cybern 59:81–90
Wong F, Knight BW, Dodge FA (1982) Adapting bump model for ventral photoreceptors of Limulus. J Gen Physiol 79:1089–1113
This work was supported by grants from the Binational Science Foundation (BSF) Jerusalem, Israel and the Israel Academy of Sciences and Humanities, by NIH grant EY 1428, and by NSF grant DMS 8505442
About this article
Cite this article
Grzywacz, N.M., Hillman, P. & Knight, B.W. The amplitudes of unit events in Limulus photoreceptors are modulated from an input that resembles the overall response. Biol. Cybern. 66, 437–441 (1992). https://doi.org/10.1007/BF00197724
- Light Intensity
- Transfer Function
- Time Constant