These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Linear transduction of natural stimuli by dark-adapted and light-adapted rods of the salamander, Ambystoma tigrinum.
    Author: Vu TQ, McCarthy ST, Owen WG.
    Journal: J Physiol; 1997 Nov 15; 505 ( Pt 1)(Pt 1):193-204. PubMed ID: 9409482.
    Abstract:
    1. We examined signal, noise and response properties of salamander rod photoreceptors by measuring: (a) the circulating current of rods which were adapted to darkness and to a wide range of backgrounds; (b) contrasts of natural environments; (c) the effect of adaptation on the linear response range of rods; and (d) the behaviour of rods responding to dynamically modulated stimuli having a range of contrasts found in nature. 2. In the dark, the circulating current contained two noise components analogous to those described in toad. A discrete noise component consisted of events occurring at a rate of 1 event per 32 s (21 degrees C) and had a variance of 0.036 pA2. A continuous noise component contributed 0.022 pA2 to the dark current, roughly equal to the discrete noise variance. 3. Exposure to a wide range of steady backgrounds (suppressing up to 80% of the circulating current), elicited a sustained fluctuating photocurrent having a power spectrum which resembled those of single photon responses and was consistent with the linear summation of single photon events; this indicates that the primary source of noise in the current is caused by the light. 4. Eighty-nine per cent of the contrasts (C) measured in natural environments had magnitude of C < 50%, where C = magnitude of I - Imean/magnitude of Imean. The linear response range elicited by brief flashes expanded with brighter backgrounds, well-encompassing flash contrasts of 100%. 5. Dynamically modulated stimuli and incremental flashes having contrasts similar to those in natural scenes elicited small currents which deviated by a few picoamps about the mean and the transfer functions computed from each type of stimulus-response pair closely corresponded to one another. These results indicate that in natural environments, rods behave as linear small-signal transducers of light.
    [Abstract] [Full Text] [Related] [New Search]