Dim artificial light at night alters immediate early gene expression throughout the avian brain

Artificial light at night (ALAN) is a pervasive pollutant that alters
physiology and behavior. However, the underlying mechanisms triggering
these alterations are unknown, as previous work shows that dim levels of
ALAN may have a masking effect, bypassing the central clock. Light
stimulates neuronal activity in numerous brain regions which could in turn
activate downstream effectors regulating physiological response. In the
present study, taking advantage of immediate early gene (IEG) expression
as a proxy for neuronal activity, we determined the brain regions
activated in response to ALAN. We exposed zebra finches to dim ALAN (1.5
lux) and analyzed 24 regions throughout the brain. We found that the
overall expression of two different IEGs, cFos and ZENK, in birds exposed
to ALAN were significantly different from birds inactive at night.
Additionally, we found that ALAN-exposed birds had significantly different
IEG expression from birds inactive at night and active during the day in
several brain areas associated with vision, movement, learning and memory,
pain processing, and hormone regulation. These results give insight into
the mechanistic pathways responding to ALAN that underlie downstream,
well-documented behavioral and physiological changes.