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A Path to Sleep Is through the Eye(1,2,3).

Morin LP - eNeuro (2015)

Bottom Line: The visual input route is a practical avenue to follow in pursuit of the neural circuitry and mechanisms governing sleep and arousal in small nocturnal mammals and the organizational principles may be similar in diurnal humans.Photosomnolence studies are likely to be particularly advantageous because the timing of sleep is largely under experimenter control.Moreover, the experimental designs and associated results benefit from a substantial amount of existing neuroanatomical and pharmacological literature that provides a solid framework guiding the conduct and interpretation of future investigations.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Psychiatry and Graduate Program in Neuroscience, Stony Brook Medicine, Stony Brook University , Stony Brook, New York 11794.

ABSTRACT
Light has long been known to modulate sleep, but recent discoveries support its use as an effective nocturnal stimulus for eliciting sleep in certain rodents. "Photosomnolence" is mediated by classical and ganglion cell photoreceptors and occurs despite the ongoing high levels of locomotion at the time of stimulus onset. Brief photic stimuli trigger rapid locomotor suppression, sleep, and a large drop in core body temperature (Tc; Phase 1), followed by a relatively fixed duration interval of sleep (Phase 2) and recovery (Phase 3) to pre-sleep activity levels. Additional light can lengthen Phase 2. Potential retinal pathways through which the sleep system might be light-activated are described and the potential roles of orexin (hypocretin) and melanin-concentrating hormone are discussed. The visual input route is a practical avenue to follow in pursuit of the neural circuitry and mechanisms governing sleep and arousal in small nocturnal mammals and the organizational principles may be similar in diurnal humans. Photosomnolence studies are likely to be particularly advantageous because the timing of sleep is largely under experimenter control. Sleep can now be effectively studied using uncomplicated, nonintrusive methods with behavior evaluation software tools; surgery for EEG electrode placement is avoidable. The research protocol for light-induced sleep is easily implemented and useful for assessing the effects of experimental manipulations on the sleep induction pathway. Moreover, the experimental designs and associated results benefit from a substantial amount of existing neuroanatomical and pharmacological literature that provides a solid framework guiding the conduct and interpretation of future investigations.

No MeSH data available.


Related in: MedlinePlus

A, Retinal projections, retinorecipient nuclei, and second order afferents to the VLPO. Black pathways, First-order retinal projections to basal forebrain, thalamic, and visual midbrain nuclei (thick black outlines in both A and B). Red pathways, Second-order projections afferent to the VLPO from retinorecipient nuclei. Projection density roughly corresponds to arrow line thickness. B, Connections between forebrain nuclei that may be providing second- or third-order retinal input to the sleep regulatory system. Solid red pathways, Virally traced projections from the SCN with at least one known synapse (red circles). Broken red pathways, Possible routes from the SCN to the VLPO involving a probable, but not identified, synapse (large broken red circles). Solid black pathways, Projections to ORx cells (after Yoshida et al., 2006; there is no similar information for MCH cell innervation). Dotted black pathways, Other projections to and from sleep-regulatory nuclei. Note: All nuclei identified in the figure are innervated by both ORx and MCH cells (see Table 1). See Table 2 for anatomical abbreviations and the text for references. These schematics are not intended to exclude any other possible arrangement of connections between the visual and sleep systems.
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Figure 3: A, Retinal projections, retinorecipient nuclei, and second order afferents to the VLPO. Black pathways, First-order retinal projections to basal forebrain, thalamic, and visual midbrain nuclei (thick black outlines in both A and B). Red pathways, Second-order projections afferent to the VLPO from retinorecipient nuclei. Projection density roughly corresponds to arrow line thickness. B, Connections between forebrain nuclei that may be providing second- or third-order retinal input to the sleep regulatory system. Solid red pathways, Virally traced projections from the SCN with at least one known synapse (red circles). Broken red pathways, Possible routes from the SCN to the VLPO involving a probable, but not identified, synapse (large broken red circles). Solid black pathways, Projections to ORx cells (after Yoshida et al., 2006; there is no similar information for MCH cell innervation). Dotted black pathways, Other projections to and from sleep-regulatory nuclei. Note: All nuclei identified in the figure are innervated by both ORx and MCH cells (see Table 1). See Table 2 for anatomical abbreviations and the text for references. These schematics are not intended to exclude any other possible arrangement of connections between the visual and sleep systems.

Mentions: Photosomnolence involves light detection by both classical photoreceptors and ipRGCs, with the latter funneling information from all photoreceptor types to the brain (Hattar et al., 2006; Göz et al., 2008; Güler et al., 2008; Hatori et al., 2008; Tsai et al., 2009; Morin and Studholme, 2011; Muindi et al., 2013). Retinal projections (Fig. 3A) from all types of ganglion cells are present in about 46 different mouse brain regions, including 12 in the hypothalamus (Morin and Studholme, 2014b). Many of the retinorecipient nuclei, especially those in the subcortical visual shell of the midbrain and thalamus, are reciprocally interconnected (Morin and Blanchard, 1998). In addition, there is a strong relationship between the intergeniculate leaflet (IGL) and SCN, not only because of their robust connection through the geniculohypothalamic tract, but because the two nuclei project to nearly all the same hypothalamic locations (Morin, 2013a). Except for the olivary pretectal nucleus, there are no direct retinal projections to brain stem regions associated with sleep regulation. Therefore, it is most likely that the critical input pathway for photosomnolence involves a relay in one or more of the hypothalamic nuclei to the sleep regulatory system, with the SCN being the prime candidate.


A Path to Sleep Is through the Eye(1,2,3).

Morin LP - eNeuro (2015)

A, Retinal projections, retinorecipient nuclei, and second order afferents to the VLPO. Black pathways, First-order retinal projections to basal forebrain, thalamic, and visual midbrain nuclei (thick black outlines in both A and B). Red pathways, Second-order projections afferent to the VLPO from retinorecipient nuclei. Projection density roughly corresponds to arrow line thickness. B, Connections between forebrain nuclei that may be providing second- or third-order retinal input to the sleep regulatory system. Solid red pathways, Virally traced projections from the SCN with at least one known synapse (red circles). Broken red pathways, Possible routes from the SCN to the VLPO involving a probable, but not identified, synapse (large broken red circles). Solid black pathways, Projections to ORx cells (after Yoshida et al., 2006; there is no similar information for MCH cell innervation). Dotted black pathways, Other projections to and from sleep-regulatory nuclei. Note: All nuclei identified in the figure are innervated by both ORx and MCH cells (see Table 1). See Table 2 for anatomical abbreviations and the text for references. These schematics are not intended to exclude any other possible arrangement of connections between the visual and sleep systems.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4596090&req=5

Figure 3: A, Retinal projections, retinorecipient nuclei, and second order afferents to the VLPO. Black pathways, First-order retinal projections to basal forebrain, thalamic, and visual midbrain nuclei (thick black outlines in both A and B). Red pathways, Second-order projections afferent to the VLPO from retinorecipient nuclei. Projection density roughly corresponds to arrow line thickness. B, Connections between forebrain nuclei that may be providing second- or third-order retinal input to the sleep regulatory system. Solid red pathways, Virally traced projections from the SCN with at least one known synapse (red circles). Broken red pathways, Possible routes from the SCN to the VLPO involving a probable, but not identified, synapse (large broken red circles). Solid black pathways, Projections to ORx cells (after Yoshida et al., 2006; there is no similar information for MCH cell innervation). Dotted black pathways, Other projections to and from sleep-regulatory nuclei. Note: All nuclei identified in the figure are innervated by both ORx and MCH cells (see Table 1). See Table 2 for anatomical abbreviations and the text for references. These schematics are not intended to exclude any other possible arrangement of connections between the visual and sleep systems.
Mentions: Photosomnolence involves light detection by both classical photoreceptors and ipRGCs, with the latter funneling information from all photoreceptor types to the brain (Hattar et al., 2006; Göz et al., 2008; Güler et al., 2008; Hatori et al., 2008; Tsai et al., 2009; Morin and Studholme, 2011; Muindi et al., 2013). Retinal projections (Fig. 3A) from all types of ganglion cells are present in about 46 different mouse brain regions, including 12 in the hypothalamus (Morin and Studholme, 2014b). Many of the retinorecipient nuclei, especially those in the subcortical visual shell of the midbrain and thalamus, are reciprocally interconnected (Morin and Blanchard, 1998). In addition, there is a strong relationship between the intergeniculate leaflet (IGL) and SCN, not only because of their robust connection through the geniculohypothalamic tract, but because the two nuclei project to nearly all the same hypothalamic locations (Morin, 2013a). Except for the olivary pretectal nucleus, there are no direct retinal projections to brain stem regions associated with sleep regulation. Therefore, it is most likely that the critical input pathway for photosomnolence involves a relay in one or more of the hypothalamic nuclei to the sleep regulatory system, with the SCN being the prime candidate.

Bottom Line: The visual input route is a practical avenue to follow in pursuit of the neural circuitry and mechanisms governing sleep and arousal in small nocturnal mammals and the organizational principles may be similar in diurnal humans.Photosomnolence studies are likely to be particularly advantageous because the timing of sleep is largely under experimenter control.Moreover, the experimental designs and associated results benefit from a substantial amount of existing neuroanatomical and pharmacological literature that provides a solid framework guiding the conduct and interpretation of future investigations.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Psychiatry and Graduate Program in Neuroscience, Stony Brook Medicine, Stony Brook University , Stony Brook, New York 11794.

ABSTRACT
Light has long been known to modulate sleep, but recent discoveries support its use as an effective nocturnal stimulus for eliciting sleep in certain rodents. "Photosomnolence" is mediated by classical and ganglion cell photoreceptors and occurs despite the ongoing high levels of locomotion at the time of stimulus onset. Brief photic stimuli trigger rapid locomotor suppression, sleep, and a large drop in core body temperature (Tc; Phase 1), followed by a relatively fixed duration interval of sleep (Phase 2) and recovery (Phase 3) to pre-sleep activity levels. Additional light can lengthen Phase 2. Potential retinal pathways through which the sleep system might be light-activated are described and the potential roles of orexin (hypocretin) and melanin-concentrating hormone are discussed. The visual input route is a practical avenue to follow in pursuit of the neural circuitry and mechanisms governing sleep and arousal in small nocturnal mammals and the organizational principles may be similar in diurnal humans. Photosomnolence studies are likely to be particularly advantageous because the timing of sleep is largely under experimenter control. Sleep can now be effectively studied using uncomplicated, nonintrusive methods with behavior evaluation software tools; surgery for EEG electrode placement is avoidable. The research protocol for light-induced sleep is easily implemented and useful for assessing the effects of experimental manipulations on the sleep induction pathway. Moreover, the experimental designs and associated results benefit from a substantial amount of existing neuroanatomical and pharmacological literature that provides a solid framework guiding the conduct and interpretation of future investigations.

No MeSH data available.


Related in: MedlinePlus