Adaptation to changes in higher-order stimulus statistics in the salamander retina.
Adaptation in the retina is thought to optimize the encoding of natural light signals into sequences of spikes sent to the brain. While adaptive changes in retinal processing to the variations of the mean luminance level and second-order stimulus statistics have been documented before, no such measurements have been performed when higher-order moments of the light distribution change. We therefore measured the ganglion cell responses in the tiger salamander retina to controlled changes in the second (contrast), third (skew) and fourth (kurtosis) moments of the light intensity distribution of spatially uniform temporally independent stimuli. The skew and kurtosis of the stimuli were chosen to cover the range observed in natural scenes. We quantified adaptation in ganglion cells by studying linear-nonlinear models that capture well the retinal encoding properties across all stimuli. We found that the encoding properties of retinal ganglion cells change only marginally when higher-order statistics change, compared to the changes observed in response to the variation in contrast. By analyzing optimal coding in LN-type models, we showed that neurons can maintain a high information rate without large dynamic adaptation to changes in skew or kurtosis. This is because, for uncorrelated stimuli, spatio-temporal summation within the receptive field averages away non-gaussian aspects of the light intensity distribution.
Institute of Science and Technology Austria, Klosterneuburg, Austria.
Gašper
G
Tkačik
Indian Institute of Science Education and Research-Kolkata, Mohanpur (Nadia), India.
Anandamohan
A
Ghosh
Department of Neurobiology, Weizmann Institute of Science, Rehovot, Israel.
Elad
E
Schneidman
Faculty of Natural Sciences, Department of Life Sciences and Zlotowski Center for Neuroscience, Ben Gurion University of the Negev, Be'er Sheva, Israel.
Ronen
R
Segev
D000200:Action Potentials / Q000502:physiology / Q000528:radiation effects; D000221:Adaptation, Ocular / Q000528:radiation effects*; D000818:Animals; D008027:Light; D016014:Linear Models; D017711:Nonlinear Dynamics; D010775:Photic Stimulation; D012160:Retina / Q000502:physiology* / Q000528:radiation effects*; D012165:Retinal Ganglion Cells / Q000502:physiology / Q000528:radiation effects; D055351:Retinal Neurons / Q000502:physiology / Q000528:radiation effects; D013223:Statistics as Topic; D014562:Caudata / Q000502:physiology*