Relative modulation sensitivities of the red and green color mechanisms

The sensitivities of the human green and red cone mechanisms to sinusiodally flickering light were found to be near equal and independent of field size and estimation method. No wavelength dependency of modulation sensitivity was found. An observer who lacks the red cone pigment (protanope) did not show unusually high flicker sensitivity to green light of 525 nm. The modulation transfer function for the normal observer measured with a green flickering test on a red background is identical to that on a green background when the backgrounds have been equated for the green cones by the protanope. The same is true for the contrast transfer function of the normal observer when determined with a green grating on the red and green backgrounds equated by the protanope.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22781/1/0000336.pd

Visual masking: past accomplishments, present status, future developments

Visual masking, throughout its history, has been used as an investigative tool in exploring the temporal dynamics of visual perception, beginning with retinal processes and ending in cortical processes concerned with the conscious registration of stimuli. However, visual masking also has been a phenomenon deemed worthy of study in its own right. Most of the recent uses of visual masking have focused on the study of central processes, particularly those involved in feature, object and scene representations, in attentional control mechanisms, and in phenomenal awareness. In recent years our understanding of the phenomenon and cortical mechanisms of visual masking also has benefited from several brain imaging techniques and from a number of sophisticated and neurophysiologically plausible neural network models. Key issues and problems are discussed with the aim of guiding future empirical and theoretical research

Ganglion Cell Adaptability: Does the Coupling of Horizontal Cells Play a Role?

Background: The visual system can adjust itself to different visual environments. One of the most well known examples of this is the shift in spatial tuning that occurs in retinal ganglion cells with the change from night to day vision. This shift is thought to be produced by a change in the ganglion cell receptive field surround, mediated by a decrease in the coupling of horizontal cells. Methodology/Principal Findings: To test this hypothesis, we used a transgenic mouse line, a connexin57-deficient line, in which horizontal cell coupling was abolished. Measurements, both at the ganglion cell level and the level of behavioral performance, showed no differences between wild-type retinas and retinas with decoupled horizontal cells from connexin57-deficient mice. Conclusion/Significance: This analysis showed that the coupling and uncoupling of horizontal cells does not play a dominant role in spatial tuning and its adjustability to night and day light conditions. Instead, our data suggest that anothe