Prolonged Inner Retinal Photoreception Depends on the Visual Retinoid Cycle.

Unlabelled: In addition to rods and cones, mammals have inner retinal photoreceptors called intrinsically photosensitive retinal ganglion cells (ipRGCs), which use the photopigment melanopsin and mediate nonimage-forming visual responses, such as pupil reflexes and circadian entrainment. After photic activation, photopigments must be reverted to their dark state to be light-sensitive again. For rods and to some extent cones, photopigment regeneration depends on the retinoid cycle in the adjacent retinal pigment epithelium (RPE).

Melatonin Suppression by Light in Humans Is More Sensitive Than Previously Reported.

The retina drives various non-image-forming photoresponses, including circadian photoentrainment and pupil constriction. Previous investigators showed that in humans, photic suppression of the clock-controlled hormone melatonin is most sensitive to 460-nm blue light, with a threshold of ~12 log photons cm(-2) s(-1). This threshold is surprising because non-image-forming vision is mediated by intrinsically photosensitive retinal ganglion cells, which receive rod-driven synaptic input and can respond to light levels as low as ~7 log photons cm(-2) s(-1).

The rat retina has five types of ganglion-cell photoreceptors.

Intrinsically photosensitive retinal ganglion cells (ipRGCs) are inner retinal photoreceptors that mediate non-image-forming visual functions, e.g. pupillary constriction, regulation of pineal melatonin release, and circadian photoentrainment.

Bias-free double judgment accuracy during spatial attention cueing: performance enhancement from voluntary and involuntary attention.

Recent research has demonstrated that involuntary attention improves target identification accuracy for letters using non-predictive peripheral cues, helping to resolve some of the controversy over performance enhancement from involuntary attention. While various cueing studies have demonstrated that their reported cueing effects were not due to response bias to the cue, very few investigations have quantified the extent of any response bias or developed methods of removing bias from observed results in a double judgment accuracy task. We have devised a method to quantify and remove response bias to cued locations in a double judgment accuracy cueing task, revealing the true, unbiased performance enhancement from involuntary and voluntary attention.

Bias corrected double judgment accuracy during spatial attention cueing: unmasked stimuli with non-predictive and semi-predictive cues.

The present experiments indicate that in a 7-AFC double judgment accuracy task with unmasked stimuli, cue location response bias can be quantified and removed, revealing unbiased improvements in response accuracy for valid cues compared to invalid cues. By testing for cueing effects over a range of contrast levels with unmasked stimuli, changes in the psychometric function were examined and provide insight into the mechanisms of involuntary attention which might account for the observed cueing effects. Cue validity was varied between two separate experiments showing that non-predictive (14.

Involuntary attention enhances identification accuracy for unmasked low contrast letters using non-predictive peripheral cues.

There is controversy regarding whether or not involuntary attention improves response accuracy at a cued location when the cue is non-predictive and if these cueing effects are dependent on backward masking. Various perceptual and decisional mechanisms of performance enhancement have been proposed, such as signal enhancement, noise reduction, spatial uncertainty reduction, and decisional processes. Herein we review a recent report of mask-dependent accuracy improvements with low contrast stimuli and demonstrate that the experiments contained stimulus artifacts whereby the cue impaired perception of low contrast stimuli, leading to an absence of improved response accuracy with unmasked stimuli.