Divergent photic thresholds in the non-image-forming visual system: entrainment, masking and pupillary light reflex

Light is the principal cue that entrains the circadian timing system, but the threshold of entrainment and the relative contributions of the retinal photoreceptors—rods, cones and intrinsically photosensitive retinal ganglion cells—are not known. We measured thresholds of entrainment of wheel-running rhythms at three wavelengths, and compared these to thresholds of two other non-image-forming visual system functions: masking and the pupillary light reflex (PLR). At the entrainment threshold, the relative spectral sensitivity and absolute photon flux suggest that this threshold is determined by rods. Dim light that entrained mice failed to elicit either masking or PLR; in general, circadian entrainment is more sensitive by 1–2 log units than other measures of the non-image-forming visual system. Importantly, the results indicate that dim light can entrain circadian rhythms even when it fails to produce more easily measurable acute responses to light such as phase shifting and melatonin suppression. Photosensitivity to one response, therefore, cannot be generalized to other non-image-forming functions. These results also impact practical problems in selecting appropriate lighting in laboratory animal husbandry.

Download Full-text

The pupillary light reflex in normal and innate microstrabismic cats, II: Retinal and cortical input to the nucleus praetectalis olivaris

Visual Neuroscience ◽

10.1017/s0952523800004454 ◽

1989 ◽

Vol 3 (2) ◽

pp. 139-153 ◽

Cited By ~ 26

Author(s):

C. Distler ◽

K.-P. Hoffmann

Keyword(s):

Electrical Stimulation ◽

Visual Field ◽

Ganglion Cells ◽

Occipital Cortex ◽

Pupillary Light Reflex ◽

Binocular Summation ◽

Cortical Input ◽

Light Reflex ◽

Pupillary Light ◽

Upper Visual Field

AbstractThe anatomical substrate of the pupillary light reflex was investigated in normal and innate microstrabismic cats using anatomical methods as well as electrical stimulation. The bilateral retinal input to the nucleus praetectalis olivaris (NPO), the pretectal relay station in the subcortical pupilloconstrictor pathway, was identified to come from the ventral retina where the upper visual field is represented. Orthodromic electrical stimulation revealed that retinal information is transmitted to on-tonic neurons in the NPO mainly via slowly conducting axons probably originating from W- and X-type retinal ganglion cells.For the first time, a direct cortical input to on-tonic neurons in the NPO could be demonstrated. This cortical input originates from caudolateral parts of the occipital cortex. Putative input structures are those subdivisions of areas 19 and 20a where the upper part of the visual field is represented.A direct, predominantly contralateral projection with a weak ipsilateral component from NPO to the nucleus of Edinger-Westphal, and an interhemispheric connection between the NPOs could be demonstrated. With respect to the anatomical connections as described in this study, no differences between normal and innate microstrabismic cats could be found.The results are discussed with respect to the binocular summation of the pupillary light reflex and its reduction in subjects with impaired binocular vision.

Download Full-text

Delayed response of human melanopsin retinal ganglion cells on the pupillary light reflex

Ophthalmic and Physiological Optics ◽

10.1111/j.1475-1313.2011.00846.x ◽

2011 ◽

Vol 31 (5) ◽

pp. 469-479 ◽

Cited By ~ 31

Author(s):

Sei-ichi Tsujimura ◽

Yuta Tokuda

Keyword(s):

Retinal Ganglion Cells ◽

Ganglion Cells ◽

Pupillary Light Reflex ◽

Delayed Response ◽

Retinal Ganglion ◽

Light Reflex ◽

Pupillary Light

Download Full-text

The influence of intrinsically-photosensitive retinal ganglion cells on the spectral sensitivity and response dynamics of the human pupillary light reflex

Vision Research ◽

10.1016/j.visres.2009.10.012 ◽

2010 ◽

Vol 50 (1) ◽

pp. 72-87 ◽

Cited By ~ 122

Author(s):

David H. McDougal ◽

Paul D. Gamlin

Keyword(s):

Retinal Ganglion Cells ◽

Spectral Sensitivity ◽

Ganglion Cells ◽

Pupillary Light Reflex ◽

Retinal Ganglion ◽

Response Dynamics ◽

Light Reflex ◽

Pupillary Light

Download Full-text

How Does Light Regulate Mood and Behavioral State?

Clocks & Sleep ◽

10.3390/clockssleep1030027 ◽

2019 ◽

Vol 1 (3) ◽

pp. 319-331

Author(s):

Milosavljevic

Keyword(s):

Retinal Ganglion Cells ◽

Animal Studies ◽

Ganglion Cells ◽

Pupillary Light Reflex ◽

Current Understanding ◽

Behavioral State ◽

Retinal Ganglion ◽

Visual Responses ◽

Light Reflex ◽

Pupillary Light

The idea that light affects mood and behavioral state is not new. However, not much is known about the particular mechanisms and circuits involved. To fully understand these, we need to know what properties of light are important for mediating changes in mood as well as what photoreceptors and pathways are responsible. Increasing evidence from both human and animal studies imply that a specialized class of retinal ganglion cells, intrinsically photosensitive retinal ganglion cells (ipRGCs), plays an important role in the light-regulated effects on mood and behavioral state, which is in line with their well-established roles in other non-visual responses (pupillary light reflex and circadian photoentrainment). This paper reviews our current understanding on the mechanisms and paths by which the light information modulates behavioral state and mood.

Download Full-text