Premium
Retinal origins of the temperature effect on absolute visual sensitivity in frogs.
Author(s) -
Aho A C,
Donner K,
Reuter T
Publication year - 1993
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1993.sp019608
Subject(s) - rana , retinal , q10 , retina , anatomy , chemistry , biophysics , biology , biochemistry , neuroscience , respiration
1. The absolute sensitivity of vision was studied as a function of temperature in two species of frog (Rana temporaria, 9‐21 degrees C, and Rana pipiens, 13‐28 degrees C). 2. Log behavioural threshold (measured as the lowest light intensity by which frogs trying to escape from a dark box were able to direct their jumping) rose near‐linearly with warming with a regression coefficient of 1.26 +/‐ 0.03 log units per 10 degrees C (Q10 = 18). Threshold retinal illumination corresponded to 0.011 photoisomerizations per rod per second (Rh* s‐1) at 16.5 degrees C. 3. The effect of dim backgrounds on jumping thresholds suggested ‘dark lights’ of 0.011 Rh* s‐1 at 16.5 degrees C and 0.080 Rh* s‐1 at 23.5 degrees C, corresponding to Q10 = 17. 4. Response thresholds of retinal ganglion cells were extracellularly recorded in the isolated eyecup of R. temporaria. The thresholds of the most sensitive cells when stimulated with large‐field steps of light were similar to the behavioural threshold and changed with temperature in a similar manner. 5. The decrease in ganglion cell 'step’ sensitivity with warming consisted of a decrease in summation time (by a factor of 2‐3 between 10 and 20 degrees C) and an increase in the threshold number of photoisomerizations (a decrease in ‘flash’ sensitivity, by a factor of 2‐5 over the same interval). No effect of temperature changes on spatial summation was found. 6. Frequency‐of‐response functions of ganglion cells indicated an 11‐fold increase in noise‐equivalent dark light between 10 and 20 degrees C (mean values in four cells 0.009 vs. 0.10 Rh* s‐1). 7. The temperature dependence of ganglion cell flash sensitivity could be strongly decreased with dim background illumination. 8. It is concluded that the desensitization of dark‐adapted vision with rising temperature is a retinal effect composed of shortened summation time and lowered flash sensitivity (increased numbers of photons required for a threshold response) in ganglion cells. The desensitization bears no simple relation to the apparent retinal noise increase.