group of neurons in the intergericulate nucleus stained
with the immediate early gene, FOS, when the rat is
exposed to an abrupt shift from darkness to light.
changes in lighting conditions have a profound effect on behavior,
regardless of whether these changes in illumination occur during
the day or the night. What components of the visual system are involved
in mediating the effects of acute changes in lighting on sleep patterns?
In collaboration with Dr. Ruth Benca, we explored this question.
Our initial findings indicate that the superior colliculus and pretectum
are involved. In particular, removal of the pretectum eliminates
the characteristic REM sleep triggering response that is seen in
albino rats following a light-to-dark transition. Using FOS immediate
early gene expression, we have localized neurons in small regions
of the pretectum that are active during acute light-dark transitions.
Some pretectal nuclei are particularly responsive at midnight, others
at midday, suggesting that the illuminance detection system is linked
to the circadian system. We next asked the question: does rearing
rats in continuous dark or continuous light have an impact on sleep,
or on the response to acute changes in lighting conditions? Preliminary
findings from dark-reared rats show a reduced retinal input to subcortical
visual structures. Interestingly, these rats show no changes in
overall sleep and wakefulness. However, they do show enhanced REM
triggering in response to light-dark transitions, suggesting that
disturbances in illumination during development have lasting effects
on aspects of sleep-wake behavior. We hope these studies will lead
to a better understanding of how light affects normal individuals
as well as those with seasonal depression, and pre-term infants
that have been exposed to continuous illumination in hospital settings.
Related to This Topic:
A.M., W.H. Obermeyer, M. Behan and R.M. Benca. 1998 Effects
of superior colliculus-pretectal lesions on sleep: a novel
site for mediating light induced sleep-behaviors. Proc. Natl.
Acad. Sci. 95: 8957-8962. [Abstract] [Full
A.M., R.B. Miller, W.H. Obermeyer, M. Behan and R.M. Benca.
1999 The pretectum mediates rapid eye movement (REM)
sleep regulation by light. Behav. Neurosci. 113:755-765. [Abstract]
J.R., Stoffel R.T., Quimby, D.L., Obermeyer, W.H. Benca,
R.M. and M. Behan, 2002. Fos immunoreactivity in rat subcortical
visual shell in response to illuminance changes. Neuroscience
J.R., Fahy, J.L., Obermeyer, W.H., Behan, M. and Benca, R.M,
2004. Sleep responses to light and dark are shaped by early
experience. Behav. Neurosci. 118:1262-1273 [Abstract]
M.D., Benca, R.M. and M. Behan. 2006. Retinal projections to the
subcortical visual system in congenic albino and pigmented rats.
Neuroscience. 143: 895-904. [Abstract]
Prichard, JR., Benca, R.M., and M.Behan. 2007. Light-dependent retinal
innervation of the rat superior colliculus. Anat. Rec. 290:341-348.
J.R., Dabney, C., Fleming, M., Benca, R.M., Behan, M. 2009. Light-rearing
alters retinal input and immediate early gene responses to light
in the ventral hypothalamus in the rat. Sleep Research Society.